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Weather Discussion => Forecasting => Topic started by: lfmusiclover on February 18, 2009, 01:22:25 PM

Title: Ask The Weather Expert!
Post by: lfmusiclover on February 18, 2009, 01:22:25 PM
Got a weather question? Ask our very own meteorologist, Patrick! He is our newest member, he has a Master's degree, and has graciously allowed us to start this thread. So if you've got a question, he's got an answer!

Also, I know that Kyle (wxmancanada) and Chuck also have degrees and expertise in weather, so if either of you would like to interject your knowledge, feel free!
Title: Re: Ask The Weather Expert!
Post by: TWCToday on February 18, 2009, 03:14:13 PM
This isnt really weather related but related to meteorology.  I am about to enter my senior year of high school. What classes should I take to better prepare myself if I want to enter the field of meteorology?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 18, 2009, 03:32:02 PM
Hi, Martin!  Meteorology is a heavy application of mathematics and physics.  So, I would strongly urge you to take some form of a calculus class to prep yourself for college calculus courses.  If you're not up to the calculus level yet, finish off any remaining math subjects that you haven't completed such as algebra II and trigonometry.  I would also take physics as that will introduce you to simple concepts and laws of motion that you'll need to know before advancing into more difficult subjects in college.  If your school doesn't offer physics, then try a chemistry class as there are a few relevant applications to the weather.  I had to take one semester of chemistry, two semesters of physics, and four semesters of calculus just to meet the requirements!  Anything that you can do now before college to build up your base of knowledge in these subjects is a big plus. ;)  Good luck, and remember that even when it gets stressful from these classes during college, your passion about the weather is what will help you prevail! B)
Title: Re: Ask The Weather Expert!
Post by: TWCToday on February 21, 2009, 01:30:00 AM
Thank you so much for that information!!! It difficult to get straight answers on subjects like this. Thankfully I only require two courses to get my advanced diploma next year so it gives me the option to take the classes that will best help me in the future. I will defiantly peruse A.P Physics and A.P Calculus next school year. Thanks for the useful information and support! :happy:
Title: Re: Ask The Weather Expert!
Post by: Mike M on February 21, 2009, 02:16:15 PM
As much as I want to be a weather forecaster, I can never get myself into an AP or even a Level 2 course. I've never even taken algebra 1 yet since it's not available in my appropriate level. Hopefully I'll end up taking it and other important math courses before I graduate in two years.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 21, 2009, 03:23:08 PM
Mike, you don't have to worry.  Just focus on getting your background in math and science established while you're in high school.  You can start calculus and/or physics at the college level, but you just need to get your basics solidified before you start.  If you ever run into any trouble with major concepts, don't hesitate to ask! ;)
Title: Re: Ask The Weather Expert!
Post by: Localonthe8s on February 21, 2009, 03:49:12 PM
I hate math...but I want to be a met at the same time rofl
Title: Re: Ask The Weather Expert!
Post by: Anistorm on February 21, 2009, 03:55:58 PM
I too want to be a meteorologist, but my question is this: I know Meteorology covers almost every field of science, but is it necessary to take as many science classes as I can? (for example, I'm currently taking Astronomy)
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 21, 2009, 04:28:40 PM
To Victor:  I'm aware that math is the one big deterrent for many wanting to enter this field, but if you start taking Meteorology classes in college, you'll soon learn how important math is to describing the weather.  My best advice is this:  As you take each math class, think about how the subjects you're learning could directly be applied to the weather.  I can help you here if needed as I found that many students would get excited when they see how certain math principles could help them understand the weather in ways they never realized before.

To Ana:  Chemistry and Physics are the two main sciences that Meteorology covers, so you should definitely pursue these classes first.  The only two other sciences I can think of that could be helpful are Astronomy and Earth Sciences.  Since you already got Astronomy now, plan the rest of your schedule with these thoughts and the requirements of your high school in mind.  You'll never take Biology again after high school, so that's something to look forward to! :lol:

Good luck to both of you! B)
Title: Re: Ask The Weather Expert!
Post by: Anistorm on February 21, 2009, 06:01:42 PM
Well, here's a little correction, I'm in college now.
Well, I guess I was thinking pretty clearly when choosing Astronomy for my spring semester in college. I'm looking forward to Earth and Space Science in the summer session. Patrick, I appreciate your meteorological advice!
Title: Re: Ask The Weather Expert!
Post by: TWCToday on February 21, 2009, 06:08:26 PM
Would A.P Environmental Science be a good course to take as well?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 21, 2009, 06:19:04 PM
To Ana:  Oops!  Sorry about that.  I couldn't tell from your age on your profile whether you were a senior in high school or a freshman in college.  You're all set.

To Martin:  It's an okay choice, but I'd rank it behind Calculus and Physics.  Do you like learning about environmental issues such as global warming, the ozone hole, and pollution?  If you do and already have Calculus and Physics lined up, then go ahead.
Title: Re: Ask The Weather Expert!
Post by: TWCToday on February 21, 2009, 06:38:54 PM
To Martin:  It's an okay choice, but I'd rank it behind Calculus and Physics.  Do you like learning about environmental issues such as global warming, the ozone hole, and pollution?  If you do and already have Calculus and Physics lined up, then go ahead.
Yea I only need two courses next year to get my advanced diploma so with those courses Im also taking A.P Calculus and A.P Physics. So I have about 4 slots to fill. Just getting some ideas. B) Environmental issues aren't top of my list in my mind but if its at all helpful I may take it for the heck of it.
Title: Re: Ask The Weather Expert!
Post by: Anistorm on February 21, 2009, 06:55:34 PM
To Ana:  Oops!  Sorry about that.  I couldn't tell from your age on your profile whether you were a senior in high school or a freshman in college.  You're all set.
That's allright. It happens to me all the time.
Title: Re: Ask The Weather Expert!
Post by: twcfan68 on February 23, 2009, 08:40:13 AM
Wow, Hi Patrick! I would like to ask you a question. Do you believe that global warming may be the cause of stronger, more frequent tropical storms and hurricanes? Because many meteorologists hypothesize that warmer ocean waters could be a cause of this, and I was wondering if you also believed that.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 23, 2009, 11:05:53 AM
Hi, twcfan68!  We're in the active phase of a well-documented natural cycle that fluctuates tropical activity roughly every 20 years, which is one reason why we're seeing a lot of tropical activity lately.  However, current research seems to indicate that global warming could result in stronger but fewer tropical storms and hurricanes.  Warmer water certainly provides more energy, but there are so many other factors involved.  For example, we're finding that El Nino conditions in the Pacific weaken tropical activity in the Atlantic, but periods of normal to La Nina conditions in the Pacific strengthen tropical activity in the Atlantic.  El Nino and La Nina conditions drastically change the winds throughout the atmosphere worldwide, and we already know that the winds matter as too much wind shear (the change of wind speed and direction with height) tears the storms apart.  Scientists feel there will be more El Nino periods in the future due to global warming as that's been the trend lately, which would reduce the number of active Atlantic seasons.  Another point I should mention is that stronger storms would take up more warm water to where it would take longer for the ocean temperature to recover and be able to support the next storm.

With so many of these competing factors present, that's why I agree with the current research perspective of stronger but fewer tropical storms and hurricanes on average.  This topic is still under heavy research as predicting the strength and activity of a tropical season is extremely difficult, and we don't know how much global warming will offset the effects we'll experience when we enter the inactive phase of that natural cycle I described beforehand in the next ten years.  You gave a really hard question, but I hope that I answered you well enough so that you can appreciate the complexity of this issue! ;)
Title: Re: Ask The Weather Expert!
Post by: twcfan68 on February 23, 2009, 11:25:44 AM
Wow, thank you so much for the detailed information. I'm sorry, I didn't know it was that complicated, but thank you so much for your insight.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 23, 2009, 11:51:33 AM
Wow, thank you so much for the detailed information. I'm sorry, I didn't know it was that complicated, but thank you so much for your insight.
It's okay!  If there's anything I can tell all of you on TWCT about the weather, it's that the weather is far more complicated than what we all realize.  What I have in my signature now sounds crazy but is very true.  There are still many unsolved mysteries in this field despite the great leaps in progress we've made over the last 50 years.  Thus, we'll be continuing to explore the weather more to figure out these unsolved mysteries, and we'll be calling upon all of you as part of the future generations of meteorologists to help us! B)
Title: Re: Ask The Weather Expert!
Post by: jtmal0723 on February 23, 2009, 04:18:40 PM
Here's one I thought about emailing TWC about answering, but maybe Patrick can explain it better. What exactly is a "front" and what are the differences between a cold front and a warm front? I could never properly differentiate the two.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 23, 2009, 04:48:49 PM
Hi, Jesse!  A front is simply the boundary between two different air masses.  For example, a cold and dry air mass coming from Canada could clash into a warm and moist air mass coming from the Gulf of Mexico, which happens very often over the Central Plains.  Where the two air masses literally clash at each other is the front.

Now, the difference between a cold front and a warm front is determined by which air mass is winning the battle at the front.  A cold front means that the cold air is literally forcing the warm air upwards like a plow.  The cold air would be advancing forward in this case, and it would look like this picture:
(http://www.physicalgeography.net/fundamentals/images/coldfront.GIF)

In a warm front, the warm air is advancing forward as it's forcing the cold air backward, and it would look like this picture:
(http://www.physicalgeography.net/fundamentals/images/warmfront.GIF)

Another key difference between the two fronts pertains to the steepness and strength.  Cold fronts are steeper going up in the vertical and stronger than warm fronts.  It's far more effective for the heavier cold air to plow up the lighter warm air rather than the other way around where the warm air is trying to push the cold air back.  In both cold and warm fronts, the lighter warm air with its moisture is forced upward to create clouds and precipitation.  The steeper slope of a cold front allows for greater rising motion and heavier precipitation than a warm front.

There's your quick lesson on fronts.  There is more to this topic than what you see here as there can be more than two air masses involved, and there are also special situations that allow for two other kinds of fronts.  Hope this helps, Jesse! ;)

Note:  The two images above come from a nice e-book by PhysicalGeography.net
Title: Re: Ask The Weather Expert!
Post by: jtmal0723 on February 23, 2009, 04:53:33 PM
Awesome explanation! Thanks!  B)

So basically in a stationery front, neither mass is winning, correct?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 23, 2009, 04:58:01 PM
Awesome explanation! Thanks!  B)

So basically in a stationery front, neither mass is winning, correct?

Right, the winds would be blowing parallel along the front, so nothing forces the boundary to move.  It's literally a stalemate, which is a dangerous situation for flooding.  By the way, I hope all of you saw the note to indicate where you can find the e-book and browse through more of these figures.
Title: Re: Ask The Weather Expert!
Post by: beanboy89 on February 27, 2009, 11:14:00 AM
Patrick, you're probably gonna slap me for this, but here goes... :P

My original intention in college was to be a meteorologist. After going a year and taking some introductory courses, like chemistry, earth sciences, and precalculus, I soon realized that I was in way over my head. I was never strong at math (in high school, I got up to algebra 2 and geometry), and I just barely got by with my precalculus class. I can tell anyone first-hand that you need to be strong with math to be a meteorologist. I can not imagine myself ever being able to get through things like calculus 2 and 3, which are required for the meteorology degree.

I don't want to discourage anyone from choosing meteorology here, but I just wanted to share a personal experience.

Although, now I've found a place in geography. I hope to become an environmental geographer. I'm currently taking a physical geography class, and we've covered basic atmospheric phenomenon like pressures, clouds, and fronts. In fact, that image above looks like something that came right from my physical geography class. I really enjoy geography, and best of all, it's very light in math. B)
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 27, 2009, 01:15:16 PM
Billy, I won't slap you too hard. :P  I realize that mathematics is a difficult subject, and I continually remind myself that I'm very fortunate here.  When I went to Penn State to pursue my bachelor's degree in Meteorology, several of my classmates couldn't keep up with the math and eventually switched to Geography.  The bottom line is that you can pursue any major within the earth sciences if you still want to work with the weather and not have the heavy math requirements.  Naturally, you won't be able to understand why the weather works without the deep mathematics, so be aware of your interests and your abilities.  My best advice for everyone here who really wants to learn about the weather is to at least try out the Meteorology major and give it a chance.  If you later find that the math is too much to handle, then switch out to an alternative earth science major.  Most colleges don't force you into deciding about your major permanently until the end of your sophomore year.

By the way, Billy, those above images about cold and warm fronts came from an e-book from PhysicalGeography.net, so it shouldn't shock you that they look familiar if you've had a physical geography class! :lol:
Title: Re: Ask The Weather Expert!
Post by: ruhgster on March 03, 2009, 09:17:58 AM
I'd like to add to the discussion about classes to take.  If you are interested in meteorology, I would highly recommend considering taking some computer programming in college if it is not required.  If it is available, I'd highly recommend taking a class in FORTRAN, and/or learning it and IDL on your own, as well as some basic shell scripting.  FORTRAN was requiered for my Meteorology degree, and they now require IDL knowledge along with it, and honestly with my job now I am using my programming skills much more than my meteorology knowledge.  Having this knowledge can open your doors to many more oppurtunities in the meteorology field.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on March 03, 2009, 01:05:52 PM
Many colleges now do require one computer programming class in the Meteorology major.  I actually had to learn some forms of FORTRAN and shell scripting when doing the research for my Master's thesis, so take Ruhgster's point seriously!
Title: Re: Ask The Weather Expert!
Post by: ruhgster on March 03, 2009, 02:19:49 PM
Even though FORTRAN is an old language that not many people use any more, it is still widely used in the meteorological community because it is very efficient at running calculations of large amounts of data.  I work with a few meteorological models, and they are all mostly FORTRAN based, with some scripting to tie it all together.  IDL is good for visualizing stuff (making graphs, maps, etc).  I have found it much easier to work with than Excel if you know what you are doing with it.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on August 31, 2010, 04:53:31 AM
I'm bringing this thread back from the dead to remind you all that I'll still take weather questions here as I've seen a demand for it recently. :happy:
Title: Re: Ask The Weather Expert!
Post by: Charismatic Applesauce on September 04, 2010, 12:14:24 AM
When is a storm considered a tropical depression? Tropical storm?

P.S. This should be made a sticky.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on September 04, 2010, 04:25:18 AM
A tropical depression has winds of 38 mph or less, and it's not named but only assigned a number.  A tropical storm has winds ranging from 39 to 73 mph, and it's strong enough to earn a name.  Both systems have to be tropical cyclones with well-defined centers and closed circulations at the surface.  They just can't be tropical waves that are only troughs of low pressure, which are not closed in circulation.  Hope that helps!
Title: Re: Ask The Weather Expert!
Post by: Eric on September 04, 2010, 10:06:33 AM
A tropical depression has winds of 38 mph or less, and it's not named but only assigned a number.  A tropical storm has winds ranging from 39 to 73 mph, and it's strong enough to earn a name.  Both systems have to be tropical cyclones with well-defined centers and closed circulations at the surface.  They just can't be tropical waves that are only troughs of low pressure, which are not closed in circulation.  Hope that helps!

Worthy of a textbook!  Ever since I became interested in the weather in the late 1980s, tropical cyclones were, by far, my favorite area of study.  In fact, I would have become a meteorologist if I had... well... even the most elementary understanding of mathematics.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on September 05, 2010, 02:03:13 PM
Worthy of a textbook!  Ever since I became interested in the weather in the late 1980s, tropical cyclones were, by far, my favorite area of study.  In fact, I would have become a meteorologist if I had... well... even the most elementary understanding of mathematics.
Thanks for the compliment!  I try my best with all these explanations to make it clear for you all who have not had advanced mathematics or physics but keep things scientifically accurate.  Math alone does wipe out about half of all incoming students in Meteorology as they don't realize how much it's needed to describe everything.
Title: Re: Ask The Weather Expert!
Post by: Eric on September 05, 2010, 03:38:05 PM
Worthy of a textbook!  Ever since I became interested in the weather in the late 1980s, tropical cyclones were, by far, my favorite area of study.  In fact, I would have become a meteorologist if I had... well... even the most elementary understanding of mathematics.
Thanks for the compliment!  I try my best with all these explanations to make it clear for you all who have not had advanced mathematics or physics but keep things scientifically accurate.  Math alone does wipe out about half of all incoming students in Meteorology as they don't realize how much it's needed to describe everything.

That pesky math...  To this day, I'm still a little upset that I wasn't able to pursue meteorology as a career because my math skills are utterly terrible... on a good day.  But, life goes on, I suppose.
Title: Re: Ask The Weather Expert!
Post by: TWCToday on September 06, 2010, 12:28:07 PM
What is weather? :P And I want my answer in song form!
Weather Dude Nick Walker (http://www.youtube.com/watch?v=JIWU4UVtPts#noexternalembed)
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on September 07, 2010, 12:13:34 AM
What is weather? :P And I want my answer in song form!
Where in the world do I even begin?  I'm going to pass on this one. :P
Title: Re: Ask The Weather Expert!
Post by: Eric on September 07, 2010, 01:07:25 AM
What is weather? :P And I want my answer in song form!
Weather Dude Nick Walker ([url]http://www.youtube.com/watch?v=JIWU4UVtPts#noexternalembed[/url])


What are you asking him for?  I'm the poet here!   :wave:
Title: Re: Ask The Weather Expert!
Post by: wxmediafan on September 07, 2010, 09:23:20 AM
I cannot believe that I haven't come across this thread before!  Great idea.

Back to the computer class and meteorology.  Yes, for my meteorology degree I am required to take computer programming, which I am currently enrolled in. 

I noticed earlier that Patrick had mentioned that many meteorology students decide not to follow through because of the math.  This was me circa 2009 :P.  My high school absolutely failed in preparing me for college.  I was so overwhelmed with my college algebra class that I just wanted to quite, because my advisor was throwing out Statisitcs and Trig and Calculus.  So, once I changed my major midway 1st semester last year, I quickly found out it was a horrible idea by the beginning of the next semester.  I got a job at a television station, and I got to experience the behind the scenes of making a forecast and presenting it on air, and I just got such a rush being able to see this happen, and I knew I couldn't give up my dream JUST because of math.  I told myself I'll get through it.  The Physics scared me as well.  Right now I am enrolled in Physics and Trig, and so far, so good. 

My advice:  DON'T give up just because of math.  It is very overwhelming at first, but if youtruly want it, you can have it :D
------

Anyway.. Tornadoes *generally*, if my minds serves me right, move in a northeast direction.  My guess of this is moving along the front if one is present.  Is his a good conclusion, or is there more?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on September 08, 2010, 12:41:17 AM
If you really love weather and want a career in this field, your interest will help you prevail in these hard classes.  Many concepts may not make sense initially, but it'll change once you begin to connect the dots and apply everything you've learned to explain how the weather works.

Kyle, you have to account for the atmospheric flow at all levels from the large-scale winds aloft around fronts to the small-scale winds within the storm.  Your conclusion alone doesn't explain the fact that tornadoes can travel in any direction and even change directions suddenly while on the ground.  While it's true that tornadoes move from southwest to northeast most often, it's not something you should assume for all as the small-scale flow within a storm environment can vary dramatically and alter the tornado's path.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on September 08, 2010, 07:42:34 AM
If you really love weather and want a career in this field, your interest will help you prevail in these hard classes.  Many concepts may not make sense initially, but it'll change once you begin to connect the dots and apply everything you've learned to explain how the weather works.

Kyle, you have to account for the atmospheric flow at all levels from the large-scale winds aloft around fronts to the small-scale winds within the storm.  Your conclusion alone doesn't explain the fact that tornadoes can travel in any direction and even change directions suddenly while on the ground.  While it's true that tornadoes move from southwest to northeast most often, it's not something you should assume for all as the small-scale flow within a storm environment can vary dramatically and alter the tornado's path.

That's true, I always assumed the samething, but the tornado that hit us went in the opposite direction, northwest to southeast. :yes:
Title: Re: Ask The Weather Expert!
Post by: Jonathon on September 08, 2010, 07:46:54 PM
What way do hurricanes move?
Title: Re: Ask The Weather Expert!
Post by: Eric on September 08, 2010, 08:58:56 PM
What way do hurricanes move?

They move wherever the steering currents and wind patterns take them.

If you mean which way they rotate, tropical cyclones and all low pressure systems in the northern hemisphere rotate counterclockwise, and in the southern hemisphere - clockwise.
Title: Re: Ask The Weather Expert!
Post by: Mr. Rainman on September 22, 2010, 10:44:37 AM
Hello, Patrick. I've got a question for you that I haven't been able to get a straight answer on for several months. My dream job is to work for the National Weather Service, specifically the Storm Prediction Center in Norman. However, these economic times have gotten me worried that finding a job anywhere for the National Weather Service will be tough. I graduate from college in the Spring of 2015. This leaves two questions.

1.) What do you think are the chances of finding a job with the NWS during this time period?
2.) Do you think University of North Dakota Grand Forks is a good meteorlogical school?

And, just because I'm slightly confused:

3.) I know the SPC issues various watches and warnings, but after they do, is it up to the local NWS offices whether to let the watches expire early or be extended?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on September 22, 2010, 04:26:06 PM
Here's some answers that I hope will help you:

1)  It's not easy right now as it took me a year to land my NWS job after completing my Master's degree.  Meteorology is a really competitive field regardless of the economy, so you need good grades and skills outside of education that make your resume stand out in the job interview.  Seriously consider volunteering or internships with the NWS as that's how I was able to succeed.  You can also ask them about how to join a student program called SCEP where you apply to the NWS while you're still in college and become a part-time employee with priority over others in accepting a full-time job once you finish your degree.

2)  I haven't heard much about their program to really know, but I would think it's okay.  If you're seriously thinking about working for SPC, Oklahoma is your best choice as they specialize in severe weather.  You can always start at a different school like the one you mentioned and transfer there when ready.  You should talk to other people in the field for their opinions as well, and it would be wise to perform searches on all Meteorology schools within your geographical and financial limits.

3)  SPC makes the decisions on whether to let watches expire early or be extended.  However, you should know that SPC does contact all local NWS offices and asks them for their input on the situation.  So, even though SPC makes the final call, there is collaboration with this process.
Title: Re: Ask The Weather Expert!
Post by: Mr. Rainman on September 22, 2010, 04:38:50 PM
You work for the NWS? What office and what is your position?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on September 22, 2010, 05:31:38 PM
You work for the NWS? What office and what is your position?
I've sent you a PM with more information.  I want to keep this thread open to everyone for weather questions.  You can ask me more about personal stuff in a message.
Title: Re: Ask The Weather Expert!
Post by: Mr. Rainman on September 22, 2010, 06:03:39 PM
Whoops. Sorry about that. Thanks for letting me know.
Title: Re: Ask The Weather Expert!
Post by: Mr. Rainman on October 25, 2010, 11:26:39 PM
Patrick, The Weather Channel just used a term called "bombogenesis," a word I can barely understand, let alone pronounce. What, exactly, is bombogenesis?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on October 26, 2010, 01:21:46 AM
Bombogenesis (pronounced "bomb-o-genesis") is the term for a mid-latitude cyclone that rapidly deepens and intensifies at an extreme rate.  A low has to drop at least 24 mb in a 24-hour period to qualify, which means a deepening rate of at least 1 mb per hour.  Atmospheric conditions have to be almost ideal to allow for air to converge into the low, rapidly ascend, and escape out of the low much faster than the air coming in at the surface to replace it for the pressure to drop so quickly.  The more proper term for the formation and intensification of any cyclone is cyclogenesis, but bombogenesis is just the extreme version of it.
Title: Re: Ask The Weather Expert!
Post by: Eric on October 26, 2010, 01:26:36 AM
Bombogenesis (pronounced "bomb-o-genesis") is the term for a mid-latitude cyclone that rapidly deepens and intensifies at an extreme rate.  A low has to drop at least 24 mb in a 24-hour period to qualify, which means a deepening rate of at least 1 mb per hour.  Atmospheric conditions have to be almost ideal to allow for air to converge into the low, rapidly ascend, and escape out of the low much faster than the air coming in at the surface to replace it for the pressure to drop so quickly.  The more proper term for the formation and intensification of any cyclone is cyclogenesis, but bombogenesis is just the extreme version of it.

 :clap:  Thanks - that's an excellent definition!
Title: Re: Ask The Weather Expert!
Post by: Mr. Rainman on January 18, 2011, 11:55:49 AM
More questions yet again!

1.) I've recently been told that when there is a 50% chance of rain, it means that 50% of your area or county is going to get some rainfall. Is that right, or does it really imply that there is a 50% chance that the entire county or area will see rainfall?

2.) Since tornado season is starting to crawl up, what are some ideal signals from models that signify the potential for tornadoes? I know high CAPE is one thing, but are there any other key signals?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on January 18, 2011, 01:36:40 PM
Here are your answers:

1.)  Probability of precipitation refers to the chance that a certain point will receive measurable precipitation.  It does not have anything to do with how much of your area will get it.  When you're told that you have a 50% chance of precipitation today, it means that there's a 50% chance that you will get measurable rainfall (at least 0.01") or measurable solid precipitation (at least 0.1") during the day.  Furthermore, it only refers to you at a point, not your entire area.

2.)  When you're looking at the models, you look for lots of moisture (high dewpoints and a good flow at 850 hPa bring moisture from somewhere like the Gulf of Mexico), wind shear (winds changing with direction and speed as you go up), CAPE as you said, and boundaries (fronts, drylines, sea breezes, etc.).  Using observed data like soundings, hodographs, surface data, radar, and satellite is a better choice over the models if you want to really gauge severe weather potential.  The models can't handle convection well enough yet, but they can help you see when a certain setup favorable for severe weather may happen.

Hope this helps!
Title: Re: Ask The Weather Expert!
Post by: Donovan on January 18, 2011, 03:24:58 PM
I am wanting to go to college to get a degree in meteorology and loves science, my problem comes with the math. I am great at math when my teacher is wanting to help and see me succeed. The problem is the past 2 years, my teachers have been terrible with explaining things and do not really care and just want a paycheck. I was wondering if you have ever had a problem with this and maybe could help me to find a solution. Thanks.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on January 18, 2011, 10:24:35 PM
You should try to form study groups with your classmates, find a tutor, or perhaps think of taking a couple math classes in college before going on to Calculus courses.  If you're able to just get everything through Trigonometry completed before college, then you're fine.
Title: Re: Ask The Weather Expert!
Post by: Donovan on January 26, 2011, 01:04:08 AM
You should try to form study groups with your classmates, find a tutor, or perhaps think of taking a couple math classes in college before going on to Calculus courses.  If you're able to just get everything through Trigonometry completed before college, then you're fine.
What should I do if my school doesn't have Trigonometry? I'm set up to take it like this: Algebra 1, Geometry, Algebra 2, then Calculus.  And thanks for the advice, my teacher this year is excellent at explaining things.(Got new classes last week).
Title: Re: Ask The Weather Expert!
Post by: Anistorm on January 26, 2011, 01:10:43 AM
I think you have to take Advanced Math/Pre-Calculus in order to jump right into Calculus.
Title: Re: Ask The Weather Expert!
Post by: Donovan on January 26, 2011, 01:28:47 AM
I think you have to take Advanced Math/Pre-Calculus in order to jump right into Calculus.
Some of our administrators at school said the new plan they were developing I guess was just to jump right into Calculus. They were supposedly cutting the funds of Pre-Cal and just combining the two into one.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on January 26, 2011, 04:12:44 AM
What should I do if my school doesn't have Trigonometry? I'm set up to take it like this: Algebra 1, Geometry, Algebra 2, then Calculus.  And thanks for the advice, my teacher this year is excellent at explaining things.(Got new classes last week).
Trigonometry is actually not too long a class.  If you're good with right triangles and the sine, cosine, and tangent functions, you'll probably be okay.  You can always take it in college if you have no choice and need the course.
Title: Re: Ask The Weather Expert!
Post by: Mike M on January 27, 2011, 10:12:39 PM
I know this is silly but... just WHY do I have to get all the snow? Frankly, I'm tired of it, and the removal of summer/spring break days... :hammer:
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on January 27, 2011, 10:36:54 PM
I know this is silly but... just WHY do I have to get all the snow? Frankly, I'm tired of it, and the removal of summer/spring break days... :hammer:
Mike, unfortunately, we're in a pattern that has been persistent for a couple months now.  The upper level flow continues to bring storms up the coast towards you, and nothing has changed this pattern yet.  The atmosphere can get stuck in blocking patterns and repeat over and over the same weather situations until something breaks it.  I can't tell you when it'll happen though as predicting when blocks start or end in weather is a really difficult task.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on January 27, 2011, 10:38:31 PM
I know this is silly but... just WHY do I have to get all the snow? Frankly, I'm tired of it, and the removal of summer/spring break days... :hammer:

Be happy that the cold the European model was showing two days ago has backed off quite a bit. or else you would think we were living with Santa Claus.  :P

From Jan 25th (12z runs)

Just to throw some numbers around at what it was showing from WED/THU next week.BTW I believe these were highs...not completely sure.
Atlanta, GA 7 degrees (Wed) -4 degrees (Thu)
Minneapolis, MN -15 degrees/ -8 degrees
Tampa, FL 50 degrees/ 21 degrees
NE WVA area -4 degrees/ -18 degrees
Title: Re: Ask The Weather Expert!
Post by: Zach on January 28, 2011, 05:21:39 AM
Yeah, Tampa has had a pretty intense winter this year (although 2010 was still more intense).. I actually enjoy it (usually i sweat my :censored: off for 10 months of the year :P)
Title: Re: Ask The Weather Expert!
Post by: Mike M on February 02, 2011, 10:50:33 PM
Mike, unfortunately, we're in a pattern that has been persistent for a couple months now.  The upper level flow continues to bring storms up the coast towards you, and nothing has changed this pattern yet.  The atmosphere can get stuck in blocking patterns and repeat over and over the same weather situations until something breaks it.  I can't tell you when it'll happen though as predicting when blocks start or end in weather is a really difficult task.
Is that why I haven't seen any days where we would have 60+ degree weather for short time this year as well as last year?
Title: Re: Ask The Weather Expert!
Post by: Donovan on February 02, 2011, 11:19:59 PM
Do you know if temperatures will rise over the next month, or will they stay cold/frigid?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 03, 2011, 07:33:23 AM
Is that why I haven't seen any days where we would have 60+ degree weather for short time this year as well as last year?
I'm afraid so, Mike.  We've been stuck with a persistent upper-level trough over the East for a while with very few breaks at times, which has kept us cold.  No upper-level ridge has yet been able to sit overhead of us for a period of time.

Do you know if temperatures will rise over the next month, or will they stay cold/frigid?
It's hard to predict out to a month for obvious reasons.  The models are showing a cold spell for next week, but I would think as time goes on that temperatures will slowly warm up as the angle of the Sun gets higher in the sky through February.  It's just going to take a while.
Title: Re: Ask The Weather Expert!
Post by: Donovan on February 03, 2011, 08:18:16 PM
Does an upper level low bring precip? If so do they always or just when the dew-point is high enough?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 03, 2011, 09:06:29 PM
An upper-level trough usually brings unsettled and cooler weather over the long term.  You'll often see disturbances spin around the trough, so you get more precipitation if you're on the periphery of it.  If you're right under the core of the trough, it'll just be really cold.  Ridges and troughs aloft are strongly connected to the mean temperature throughout the atmosphere in that area.
Title: Re: Ask The Weather Expert!
Post by: Mr. Rainman on February 19, 2011, 12:28:29 AM
Hi, again.

There's been debate over a certain youtube video floating around about the type of cloud this plane is flying over in Australia. Based on what looks like "bursting tops," I'd say these are fully developed CB Incis clouds. What do you think?

Here's the link:
Cabin Crew announcement approaching thunderstorm flying at 40,000 feet (http://www.youtube.com/watch?v=Q8XwqvkfNjI#)
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 19, 2011, 02:57:44 AM
I'm pretty sure that plane went through the top portion of a cumulonimbus cloud, and it was probably a pretty intense thunderstorm if the flight level is correct.  The turbulence shown in the video makes sense.  Mature cumulonimbus clouds will have overshooting tops when the updrafts in the cloud finally reach their equilibrium point in terms of buoyancy, and the momentum from rising up so much takes them just over that point.  You could see the anvil spreading out towards the end.
Title: Re: Ask The Weather Expert!
Post by: Donovan on February 24, 2011, 08:31:23 PM
During the course of this week the forecast went like this from both local tv met and weather.com for FRIDAY.

Monday-Wednesday
Weather.com:T-Storms 70%
Local TV Met: Few showers 20%

Wednesday/Thursday Morning:
Weather.com: Sct. Storms 40%
Local Met: 30%

Thursday Night:
Weather.com: T-storms/wind 60%
Local Met: Sct Showers 40%.

I was wondering who to believe since they both don't agree. Is their any particular reason that this happens?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 25, 2011, 04:48:30 AM
The forecasts on weather.com can be too pessimistic with precipitation.  Remember, TWC is trying to forecast for the whole country.  Your local meteorologist is only forecasting for your area, and he should know more about the geography and the local weather patterns.  In your case, the local meteorologist thinks the chances are not as good for rain compared to the weather.com forecast.  So, put them to the test by verifying their forecasts to what actually happens.  On average, the local meteorologist ought to do a better job if he really knows your area well.
Title: Re: Ask The Weather Expert!
Post by: P71nnacle on February 25, 2011, 09:54:29 PM
I have a minor in Meteorology, so I kind of am a semi-expert in the field  :happy: I was asked today what the ideal conditions for freezing fog would be....my initial response was that it was far easier to do it in the mountains than around sea level because of more consistent cloud cover and cooler temps, but I wonder if in marine climates, if advection fog would be able to freeze the water more easily because of its higher dewpoint temperature. What do you think? (Like I said, it's a little bit more complicated of a question.  :thumbsup:
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 26, 2011, 04:49:49 AM
I have a minor in Meteorology, so I kind of am a semi-expert in the field  :happy: I was asked today what the ideal conditions for freezing fog would be....my initial response was that it was far easier to do it in the mountains than around sea level because of more consistent cloud cover and cooler temps, but I wonder if in marine climates, if advection fog would be able to freeze the water more easily because of its higher dewpoint temperature. What do you think? (Like I said, it's a little bit more complicated of a question.  :thumbsup:
Sea salt is an ice nuclei, so you can get the supercooled water droplets to freeze on to them.  The major issue is that you have the warmer water below you.  You can't cool as efficiently in marine climates due to the higher moisture content, so freezing fog is more common over higher elevations.  But if you can keep everything below freezing at the surface, you can still get freezing fog in marine climates.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on June 18, 2011, 10:38:40 AM
I have a question pertaining to derechoes. Would the line of thunderstorms moving SSE into Tn (and eventually in my neck of the woods) be considered one? I know they travel very long distances w/o weakening and "bow out" causing tremendous amounts of damaging winds, but the problem is I don't know where this line of storms originated from before they got to KY so I can't say for sure how long they have been going. I do know they have caused wind damage, but regular squallines can do that as well. I provided a picture of it on radar circled in red. There's another one right on the heels of it I circled in blue. This brings up another question: Will it weaken from the one already in front of it since I'm sure it will stablize the air or will it be able to hold together and possibly provide a round two for us?  The SPC mesoscale discussion mentioned they would likely issue a Severe Thunderstorm Watch for TN N. AL, and N. GA within the hour for these storms because of higher CAPE and instability here. They didn't mention whether this was a derecho or if it will evolve into one later which is why I was hoping to get some thoughts and opinions on it. :happy:
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on June 18, 2011, 02:04:45 PM
These two features are mesoscale convective systems.  If you ever see "MCS" in a forecast discussion or hear someone on TV mention it, that's the acronym for this system.  A MCS is simply an organized cluster of thunderstorms.  Usually, each MCS has its own circulation as clearly shown in your picture.  They can form anywhere from the mid-latitudes to the tropics, and some tropical waves that potentially become hurricanes may start out as a MCS.  In the United States, they develop most often during late spring through summer in the northern Great Plains and migrate eastward.

The two MCSs shown here aren't bowing out and producing large swaths of 70-110 mph winds, which is what you need for derechos.  These MCSs are actually propagating southeastward if you watch them on satellite, and it looked like the second system was stronger and had more unstable air to its south.  Wind is most likely the biggest threat in regards to severe weather.  Hope that helps!
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on June 18, 2011, 05:14:33 PM
Yes, Patrick it did help.  :happy: Well the first line I thought was coming for us went well east into the Carolinas, but the second one is entering NW GA now and out of nowhere storms start firing immediately around Atlanta. Gotta love those pop up storms.

Title: Re: Ask The Weather Expert!
Post by: Donovan on June 18, 2011, 05:21:56 PM
Yes, Patrick it did help.  :happy: Well the first line I thought was coming for us went well east into the Carolinas, but the second one is entering NW GA now and out of nowhere storms start firing immediately around Atlanta. Gotta love those pop up storms.
I hope some of these get to the Charleston Area. We are in drought conditions. My lawn is brown, no notable rainfall in weeks. Deficit about 10-12" for the year now.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on July 21, 2011, 06:20:10 PM
Is there a difference between a Subtropical and Extra Tropical Storm?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on July 21, 2011, 06:56:58 PM
Is there a difference between a Subtropical and Extra Tropical Storm?
Yes, an extratropical storm has no tropical characteristics whatsoever.  Tropical characteristics include a warm-core and symmetric system with an upper-level ridge involved.  Our low pressure systems with cold and warm fronts in the mid-latitudes are extratropical as they are cold-core and asymmetric systems with upper-level troughs involved.

Subtropical storms are actually the hybrid breed between extratropical and tropical storms.  They have characteristics of both types, but they'll usually transition fully into one type later in a few days.  If a subtropical storm reaches winds of 74 mph or greater, then it's classified a hurricane by definition and deemed to be completely tropical.

As you can tell, atmospheric systems can freely transition over from one type to another provided that the given background conditions are right.  Hope this response answers your question!
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on July 21, 2011, 07:45:08 PM
Is there a difference between a Subtropical and Extra Tropical Storm?
Yes, an extratropical storm has no tropical characteristics whatsoever.  Tropical characteristics include a warm-core and symmetric system with an upper-level ridge involved.  Our low pressure systems with cold and warm fronts in the mid-latitudes are extratropical as they are cold-core and asymmetric systems with upper-level troughs involved.

Subtropical storms are actually the hybrid breed between extratropical and tropical storms.  They have characteristics of both types, but they'll usually transition fully into one type later in a few days.  If a subtropical storm reaches winds of 74 mph or greater, then it's classified a hurricane by definition and deemed to be completely tropical.

As you can tell, atmospheric systems can freely transition over from one type to another provided that the given background conditions are right.  Hope this response answers your question!

That helped me understand the difference a lot better. Thanks!  :)
Title: Re: Ask The Weather Expert!
Post by: gt1racerlHDl on August 15, 2011, 10:38:11 AM
when the clouds are moving in one way does this usually mean what the wind direction is and how fast the wind speed is?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on August 15, 2011, 05:50:02 PM
when the clouds are moving in one way does this usually mean what the wind direction is and how fast the wind speed is?
Yes, this method will work pretty well for a normal cloud, but it'll only tell you the winds at the cloud's height.  When we deal with thunderstorm clouds, things get a little tricky.  Some storms can build in different directions compared to the wind based on the storm-scale environment.  You could see the wind moving one direction, but the storms could be building the opposite direction to where it appears that the overall storm isn't moving.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on August 21, 2011, 02:18:19 PM
I've heard that when hurricanes make landfall, the heaviest precip can shift to the NW side. Is that true?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on August 21, 2011, 02:35:06 PM
I've heard that when hurricanes make landfall, the heaviest precip can shift to the NW side. Is that true?
It depends on the background environment around landfall.  If a hurricane is interacting with an upper-level trough or a front to its northwest as it makes landfall, you will get enhanced lift and precipitation on that side.
Title: Re: Ask The Weather Expert!
Post by: Trevor on August 21, 2011, 02:36:57 PM
This got me thinking...over in the Tropical Storm Irene topic, Tavores brought up the fact that sometimes, when the pressure goes down, the wind speeds go up. Is this always the case?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on August 21, 2011, 02:53:54 PM
This got me thinking...over in the Tropical Storm Irene topic, Tavores brought up the fact that sometimes, when the pressure goes down, the wind speeds go up. Is this always the case?
Pressure drops in a tropical storm when updrafts from thunderstorms force the air up to the top of the troposphere where the jet stream winds and outflow aloft can push the air away, which means there is less air in that initial column.  So, it creates a deeper low.  The atmosphere doesn't like having differences in anything, so the winds will increase around it to force more air into that deepening hole.  As you can tell, it's a race between two competing processes.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on August 23, 2011, 10:25:16 AM
I have another question pertaining to hurricanes. I've also heard that strong hurricanes, let's say Cat. 3 and above have a tendency to create their own environments conductive for them to stay healthy and can also deter away from their projected paths. I think Katrina was an example of this where instead of making a sharp turn north into the FL panhandle as projected, it continued west and turned north towards LA/MS. If that's true could the same be said for Irene as a possibility?

EDIT: Oh and there's one more thing, I've also heard that strong hurricanes can pump heights of ridges to their north which in result can force said hurricane to go more west. Is that true also?
Title: Re: Ask The Weather Expert!
Post by: Localonthe8s on August 23, 2011, 12:10:34 PM
Could 2 hurricanes make US landfall at the same time? Like, say in the Atlantic, one cat 3 hits TX/LA and another Cat 2 or 3 hits Long Island both around the same day. Could that happen?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on August 23, 2011, 03:30:33 PM
I have another question pertaining to hurricanes. I've also heard that strong hurricanes, let's say Cat. 3 and above have a tendency to create their own environments conductive for them to stay healthy and can also deter away from their projected paths. I think Katrina was an example of this where instead of making a sharp turn north into the FL panhandle as projected, it continued west and turned north towards LA/MS. If that's true could the same be said for Irene as a possibility?

EDIT: Oh and there's one more thing, I've also heard that strong hurricanes can pump heights of ridges to their north which in result can force said hurricane to go more west. Is that true also?
Yes, everything you said is true.  If a hurricane is strong enough and the background conditions surrounding it are right, a hurricane will build its own upper-level ridge due to all the warm air being pumped upward.  However, you have to consider the wind shear and the presence of any upper-level troughs nearby as they will obviously compete against this process.

Could 2 hurricanes make US landfall at the same time? Like, say in the Atlantic, one cat 3 hits TX/LA and another Cat 2 or 3 hits Long Island both around the same day. Could that happen?
Yes, there's nothing stopping the atmosphere from multiple hits at the same time.  During the 1893 and 1998 Atlantic hurricane seasons, there were four hurricanes occurring simultaneously.  In the 1971 and 1995 Atlantic hurricane seasons, there where five named storms (tropical storms and hurricanes) occurring simultaneously.  There are even historical records suggesting that two hurricanes have struck the United States only a day apart during at least two different seasons.  So, it could happen.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on August 23, 2011, 04:14:50 PM
I have another question pertaining to hurricanes. I've also heard that strong hurricanes, let's say Cat. 3 and above have a tendency to create their own environments conductive for them to stay healthy and can also deter away from their projected paths. I think Katrina was an example of this where instead of making a sharp turn north into the FL panhandle as projected, it continued west and turned north towards LA/MS. If that's true could the same be said for Irene as a possibility?

EDIT: Oh and there's one more thing, I've also heard that strong hurricanes can pump heights of ridges to their north which in result can force said hurricane to go more west. Is that true also?
Yes, everything you said is true.  If a hurricane is strong enough and the background conditions surrounding it are right, a hurricane will build its own upper-level ridge due to all the warm air being pumped upward.  However, you have to consider the wind shear and the presence of any upper-level troughs nearby as they will obviously compete against this process.

Thank you Patrick.
Title: Re: Ask The Weather Expert!
Post by: TWCCraig on April 25, 2012, 06:55:58 PM
Could someone please explain this, someone who knows a good amount of meteorology. Now, we just had pretty decent thunderstorm, not much thunder or lightning, it was mostly a heavy rain shower; it turned it a to be beautiful when it became a sun shower with double rainbows. Anyway, could someone tell me why did the barometric pressure increase during the shower, and then decreased after it ended. Normally, I would think it should decrease because of an updraft. Could a downdraft cause this? Here's the data from the shower:

Title: Re: Ask The Weather Expert!
Post by: Austin M. on April 25, 2012, 10:27:36 PM
Could someone please explain this, someone who knows a good amount of meteorology. Now, we just had pretty decent thunderstorm, not much thunder or lightning, it was mostly a heavy rain shower; it turned it a to be beautiful when it became a sun shower with double rainbows. Anyway, could someone tell me why did the barometric pressure increase during the shower, and then decreased after it ended. Normally, I would think it should decrease because of an updraft. Could a downdraft cause this? Here's the data from the shower:


Are you sure the time data on the barometer was correct? That definitely should be lower during the thunderstorm, primarily in the beginning to middle (if MY barometer is correct, it goes down at the beginning/before).
Title: Re: Ask The Weather Expert!
Post by: TWCCraig on April 25, 2012, 11:05:21 PM
Could someone please explain this, someone who knows a good amount of meteorology. Now, we just had pretty decent thunderstorm, not much thunder or lightning, it was mostly a heavy rain shower; it turned it a to be beautiful when it became a sun shower with double rainbows. Anyway, could someone tell me why did the barometric pressure increase during the shower, and then decreased after it ended. Normally, I would think it should decrease because of an updraft. Could a downdraft cause this? Here's the data from the shower:


Are you sure the time data on the barometer was correct? That definitely should be lower during the thunderstorm, primarily in the beginning to middle (if MY barometer is correct, it goes down at the beginning/before).
My the time data on my barometer is correct. I even checked some other personal weather stations in the area and they showed the same thing; a sharp increase in barometric pressure. This definitely not a problem with my barometer. I'm still curious to find out what caused it. My best guess would be a downdraft from rain cooled air, as the cooler air comes down from the cloud above, it creates more pressure on the air below and the air is colder and more dense, those two reasons could have lead to the increase in the pressure.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on April 25, 2012, 11:07:16 PM
Craig and Austin, the barometric pressure should drop before a storm arrives, because you're in the updraft region where air is rising away from the column above you into the approaching storm.  Once you're in the rain, you're in the downdraft of the storm, which will place more air over you.  Furthermore, the falling precipitation will cool the air and increase the density of the air, which also increases the air pressure.

Your barometer is simply recording what's known as a mesolow ahead of the storm and the mesohigh within it.  There will also be a wake low (another mesolow) behind the storm as the air is no longer being forced downward and gradually decreasing in density as it gets drier and warmer.  The bottom line is that thunderstorms create mesoscale highs and lows all around them.  This fact has greater consequences on the development of new storms, where storms will move, and much more.  If you take college classes in Meteorology, you will learn that we can use mesohighs and mesolows to explain the formation of splitting supercells.  Hope that helps. ;)
Title: Re: Ask The Weather Expert!
Post by: Mike M on May 28, 2012, 01:57:33 PM
My NWS office has issued an Excessive Heat Warning for today and tomorrow, however the heat index values are only supposed to reach the low 90s here, which barely even meets advisory criteria here. :blink: Warnings are only typically issued here if heat indices are supposed to exceed 100 degrees. In fact at this hour, the heat index is only 87!
Is time of year also put into consideration when these warnings are issued?

I have a feeling my office "abuses" the excessive heat warning sometimes... :thinking:
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on May 28, 2012, 02:29:02 PM
Although criteria are given to help each NWS office decide when to issue the various watches, warnings, and advisories, a local office has the right to issue anything based on impact.  In your instance, your NWS office may be thinking it's a really unusual heat wave for this time of year that could catch people off-guard.  After all, your area is running way above normal right now in both heat and humidity, and you're not thinking of taking serious heat precautions in May like you would in July and August.  Thus, they put out this warning simply to raise awareness for the public.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on May 28, 2012, 02:40:49 PM
They did the same thing in Indy, but there they were expecting the heat index to hover close to 100 along with some areas reaching record highs.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on June 20, 2012, 10:23:48 AM
I find this to be very baffling every summer, but anyone knows why is it that during heatwaves (short or long term) it seems the Northeast and MidAtlantic is always about 10 degrees or more hotter than many areas in the South? Like today for example, I see many areas could get very close to 100, yet down here I probably won't crack 90. In fact, the highest temperature we'll probably hit over the next week is 92 before slipping back into the 80s. :blink: :unsure: Does it have anything to do with the position of the highs?
Title: Re: Ask The Weather Expert!
Post by: Zach on June 20, 2012, 10:49:05 AM
I'm no weather expert, but I am going to assume that it's an effect of La Nia, just like last year. Patrick, feel free to correct me if I am wrong, though. :P
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on June 20, 2012, 06:00:31 PM
I find this to be very baffling every summer, but anyone knows why is it that during heatwaves (short or long term) it seems the Northeast and MidAtlantic is always about 10 degrees or more hotter than many areas in the South? Like today for example, I see many areas could get very close to 100, yet down here I probably won't crack 90. In fact, the highest temperature we'll probably hit over the next week is 92 before slipping back into the 80s. :blink: :unsure: Does it have anything to do with the position of the highs?
The center of this upper level ridge is directly over the Mid-Atlantic, while the surface high pressure is off the North Carolina and South Carolina coasts in a classic Bermuda High position.  Look at the latest model initializations to see everything for yourself.  The highest heights and equivalently the warmest temperatures aloft are over the Mid-Atlantic due to where the upper level ridge is located.  Furthermore, the Mid-Atlantic and the Northeast are experiencing southwest winds from the clockwise flow of the surface high to the southeast, which will advect warmer air from the southern Plains.  Those two factors combine to a heat wave in these places.

However, you are seeing winds more from the east due to the surface high being to your northeast.  Those winds will advect cooler air from the ocean.  Thus, your high temperatures are not climbing as high due to the fact you have more moisture in the air.  Moister air cannot heat or cool as quickly as drier air, because more energy goes into evaporation and condensation of water rather than heating or cooling of surfaces.  The positioning of the upper level ridges and troughs along with the corresponding surface highs and lows all dictate what kind of weather you will experience and what kind of air mass will be advected toward you by the resulting winds.

I'm no weather expert, but I am going to assume that it's an effect of La Nia, just like last year. Patrick, feel free to correct me if I am wrong, though. :P
It has nothing to do with La Nia or El Nio.  Those situations could cause long-term patterns to put the highs and lows in certain places more often.  However, we're back to neutral conditions now, so your assumption does not hold here.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on June 20, 2012, 07:18:19 PM
Thank you Patrick, I kinda figured that. It's just very interesting to see so many folks to the north sizzling near 100 while the warmest we've gotten is 86 today. We also had quite a few clouds today which is probably a result of the surface high off to our NE bringing in some low level moisture in the forms of clouds as you stated. :yes:
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on September 11, 2012, 07:36:53 PM
 :doublepost:

This might be a question(s) that can't really be explained and if you can't that's fine, but I'll ask them anyway. It's just something I'm curious about around here. Is there any reason as to why snowstorms move so swiftly (12 hrs or less) in the Southeast (specifically GA)? Why is it that other Southern cities all around us have MUCH higher single snowfall records than my hometown does?  Is it a climatology thing? I don't wanna come off bias asking this because of where I live, it's just I've noticed, we can never seem to get above 4 inches of snow no matter how near perfect the setup is for us. Lately, I consider a 6 inch snowstorm a significant storm for us because we rarely get that high. Before January 9-10, 2011 you had to go back to January 2002 for the last time we saw a 6 inch snowstorm and if you go by the weather records kept at the airport alone, before 2011 you have to go all the way back to March 24, 1983 when we saw 7.9 inches!

Believe it or not, Atlanta has never has a 1 foot snowstorm recorded in weather records. The highest we've had is 11.7 inches going back to the 1940s, yet places like Columbus, Macon, Birmingham and heck even Savannah have accumulated that much or more from a single storm.  :o The simple answer to all of this could turn out to just be terrible climatology, but I feel like it's has to be something else besides that.  :thinking:
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on September 11, 2012, 09:27:47 PM
Here's my attempt to answer your question, but I imagine there's more to your story as I haven't been in Georgia enough to explore your local weather patterns:  First, most of those cities you listed are closer to the coast and will get more moisture.  Atlanta seems to be stuck in between where storms finish picking up Gulf moisture and start tapping into Atlantic moisture if you imagine typical storm tracks.  Obviously, if you can't get enough moisture, you won't have big snowfall totals.

The other big key is the start of the Appalachian Mountains to your north.  If you have any winds coming from the north to northeast, you will get downslope flow off the mountains, which will make the air warmer and drier as the moisture is squeezed out over the mountains from upslope flow on the other side.  The other cities you listed do not have mountains nearby that could create this problem.

Hope that provides you a better idea for your area.  I'm sure there are plenty more, and you would have to watch approaching storms to see if you can spot more issues that inhibit your snowfall accumulations.
Title: Re: Ask The Weather Expert!
Post by: Lightning on September 11, 2012, 09:35:51 PM
:doublepost:

This might be a question(s) that can't really be explained and if you can't that's fine, but I'll ask them anyway. It's just something I'm curious about around here. Is there any reason as to why snowstorms move so swiftly (12 hrs or less) in the Southeast (specifically GA)? Why is it that other Southern cities all around us have MUCH higher single snowfall records than my hometown does?  Is it a climatology thing? I don't wanna come off bias asking this because of where I live, it's just I've noticed, we can never seem to get above 4 inches of snow no matter how near perfect the setup is for us. Lately, I consider a 6 inch snowstorm a significant storm for us because we rarely get that high. Before January 9-10, 2011 you had to go back to January 2002 for the last time we saw a 6 inch snowstorm and if you go by the weather records kept at the airport alone, before 2011 you have to go all the way back to March 24, 1983 when we saw 7.9 inches!

Believe it or not, Atlanta has never has a 1 foot snowstorm recorded in weather records. The highest we've had is 11.7 inches going back to the 1940s, yet places like Columbus, Macon, Birmingham and heck even Savannah have accumulated that much or more from a single storm.  :o The simple answer to all of this could turn out to just be terrible climatology, but I feel like it's has to be something else besides that.  :thinking:
Also, snowfall amounts can vary across a big metropolitan area like Atlanta. While Atlanta officially recorded 4 inches of snow during the March Blizzard of 1993, some suburbs had 10 inches of snow. The totals can vary from one place to another.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on September 11, 2012, 10:36:18 PM
Here's my attempt to answer your question, but I imagine there's more to your story as I haven't been in Georgia enough to explore your local weather patterns:  First, most of those cities you listed are closer to the coast and will get more moisture.  Atlanta seems to be stuck in between where storms finish picking up Gulf moisture and start tapping into Atlantic moisture if you imagine typical storm tracks. Obviously, if you can't get enough moisture, you won't have big snowfall totals.

The other big key is the start of the Appalachian Mountains to your north.  If you have any winds coming from the north to northeast, you will get downslope flow off the mountains, which will make the air warmer and drier as the moisture is squeezed out over the mountains from upslope flow on the other side.  The other cities you listed do not have mountains nearby that could create this problem.

Hope that provides you a better idea for your area.  I'm sure there are plenty more, and you would have to watch approaching storms to see if you can spot more issues that inhibit your snowfall accumulations.

Hmm, I didn't really take that part into consideration. That could be a large reason why during the February 12, 2010 Snowstorm places like Columbia, SC for example picked up 8 inches, they may have been closer to the Atlantic to receive additional moisture from there. Something I did neglect to mention was dry air, in the past couple of years where we have had snow storms, an Arctic Cold Front swept through, sometimes as early as just the day before. I know the more dry air, the longer it takes for the moisture to saturate the air to the surface thus cutting into snow totals, but in these cases the Gulf moisture was heavy, heavy enough that once the snow fell it stuck immediately it would have seemed like those heavy snowfall rates would have been able to combat that period of virga and bring significant amounts of snow, but apparently not. :no:

As far as the Appalachian Mountains, they can sometimes help us out with Cold Air Damming (or COLD Wedges as out local mets simply call them) ,but in those cases we need a stationary high to our NE (preferably around the interior NE/SE Canada) to flood the cold air down to us and since cold air can't go straight through mountains, it spills around on the NE side trapping it into the valley areas such as Atlanta for example. It could be argued in those type of events we would see more icestorms than snowstorms however because the cold air that gets trapped here is usually shallow in nature it can be overridden by warmer SW winds from the low pressure system to our South.

Going back to that question about storm duration, the only ones I know of that lasted more than 12 hours is the January 2, 2002 snowstorm we had (Technically this was like two storms in one, an ULL dug in south in concert with a developing Gulf low enhancing precip/snow across our area) ,the Superstorm of 1993 lasted about the same amount of time and I think the SnowJam of 1982 was about 18-24 hours.

Also, snowfall amounts can vary across a big metropolitan area like Atlanta. While Atlanta officially recorded 4 inches of snow during the March Blizzard of 1993, some suburbs had 10 inches of snow. The totals can vary from one place to another.

You're absolutely right about that, I live literally only about less than 10 minutes away (by car) from the Downtown Atlanta area on the NW side of town and we picked up a foot of snow, I got baby photos to prove that. The suburbs I believe picked up more than that because I know in the mountains of N. GA they picked up about 3 feet. Unfortunately, what bothers me is that I feel that 4 inches is a terrible representation of what the majority of the city actually saw. With the airport being on the southside, they do tend to see less snowfall totals than the northside does, that is something I have always observed. It makes the saying about the I-20 corridor being a battle zone for snow or ice/rain fairly valid, it really doesn't help that the city is literally divided along that interstate. 
Title: Re: Ask The Weather Expert!
Post by: gt1racerlHDl on September 12, 2012, 10:14:40 AM
Since i live along the coast could you tell me the difference between land breezes and sea breezes and how it affects the weather in areas like mine?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on September 12, 2012, 01:28:12 PM
A sea breeze occurs during the day when the land is warmer than the water, which will create a small low pressure over land and a small high pressure over water.  Since air wants to go from high pressure to low pressure, air will move onshore in this situation.  When a sea breeze goes past you, it will become cooler (anywhere from 5 to 15 degrees Fahrenheit) but more humid as you enter a marine air mass.  Showers and thunderstorms can develop or be enhanced on the leading edge of the sea breeze as it acts like a small frontal boundary to provide extra lift.  When any convection tries to go through the sea breeze, the more stable marine air at the lower levels eventually choke off the updrafts and suppress the storms.

At night, the entire process reverses due to the land cooling off so much to where the water is now warmer than the land.  Now, you get a small high pressure over land and a small low pressure over water, so air will move offshore in this case.  The cooling effects from the passage of the land breeze boundary would be felt over the ocean this time.  It's a lot harder to generate showers and thunderstorms on the leading edge of the land breeze due to the fact it's nighttime, but it could happen if conditions over the water are unstable.

Everything depends on having a significant temperature difference between land and ocean, or nothing will happen.  Sea breezes and land breezes can be enhanced by the prevailing flow, which would help them move further away from the shoreline.  Overall, they greatly affect your local temperature and wind patterns.  They also are important in determining thunderstorm chances during the warmer times of the year.  Thus, meteorologists have to greatly consider them when making forecasts for your area.  Look up some images on Google about lake and sea breezes, and you'll see each one is a circulation that creates the patterns I described above.  You'd need more advanced Meteorology classes to understand why it's true.  Hope this explanation helps you!
Title: Re: Ask The Weather Expert!
Post by: TWCCraig on September 12, 2012, 05:54:02 PM
Sorry to keep you busy in this thread, but can you explain to me what exactly is the difference between "stable" air and "unstable" air? I'm quite curious about this, I would also like to know how higher instability favors stronger thunderstorms. Thanks Pat.  :thumbsup:
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on September 12, 2012, 06:37:32 PM
Stable means if you displace something that it will always come back to you.  Unstable means it will never return.  In terms of the atmosphere, we are concerned about whether pushing air upward will cause it to come right back down or continue upward.  Thus, it all comes down to density as the atmosphere is like a fluid.  Colder air is more dense than warmer air as air molecules in cold air are closer together to create more mass in a volume.  Also, if two air masses have the same temperature, dry air is more dense than moist air as water vapor is lighter than the main components of dry air, which are nitrogen and oxygen.  A Chemistry class will reveal why it's true.

When you lift a bubble of air upward, it will naturally cool at certain rates depending on if the water vapor inside has condensed or not.  Those rates are something you will learn in advanced Meteorology classes.  However, the background environment temperature drops with increasing height at varying rates in the troposphere.  As the air bubble goes up, we check to see if it has become more or less dense than the surrounding environmental air.  If we lift a cold and dry air bubble, it will become more dense than the surrounding environment, which will cause it to sink back to the ground.  This setup happens in high pressure as more air is pushing down on you than can be taken away elsewhere, and the atmosphere is deemed as stable.  Blue skies are all that you will see as you can't lift anything upward to form a cloud.

However, if we lift a warm and moist bubble of air upward, it could reach a point where the surrounding environment has cooled off more than the bubble of air.  That bubble is now less dense and will continue to rise.  Eventually, the water vapor in it will condense and form clouds and precipitation.  This setup happens in low pressure as more air is lifting away from you than can be replaced, and the atmosphere is deemed as unstable.  If the atmosphere becomes really unstable, we create strong updrafts of warm and moist air that will fuel towering cumulonimbus clouds that become our thunderstorms.  Of course, instability is just one factor that determines the risk of severe weather, but you can't have any thunderstorms if you don't have any unstable air.

There's your lesson on atmospheric stability.  How to determine the state of the atmosphere's stability and quantify it from upper-air soundings will be something you will learn once you enter your first Meteorology classes.  Hope this explanation helps you! B)
Title: Re: Ask The Weather Expert!
Post by: TWCmatthew on September 28, 2012, 06:02:13 PM
Hey Patrick, I have a couple questions about microbursts.

Does higher 0-6km speed shear (or any strong winds in the atmosphere for that matter) tend to be bad for strong microburst formation? I know that stronger winds in the mid-levels helps the storm to move faster, and I believe that shear, combined with potentially greater instability, forms stronger cells that stay "alive" a long time and don't die quick enough to produce a vigorous downdraft, but could produce otherwise straight-line winds during its mature stage.

Also, is it better to have only a smaller amount of positive CAPE for microburst formation? I know that there has to be at least some positive buoyancy and limted (or no) negative buoyancy above the LCL for convection of any nature to form. But if there's too much CAPE, can the storm strengthen and sustain life for a longer period of time, and it may not die quick enough for rapid acceleration of rain cooled air toward the ground? However, I guess it would be hard for large CAPE to be present with a lot of dry air/negative buoyancy below the LCL aka DCAPE, unless mid level lapse rates are near dry adiabatic.

Sorry if I went a little too overboard. :P

Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on September 28, 2012, 11:44:49 PM
Matthew, microbursts have been reported in supercells and the beginning stages of bow echoes, which occur in highly-sheared environments.  So, the answer to your first question is actually no.  Having high wind shear can actually increase microburst formation as you can transport more momentum to the ground in a downdraft.  You can still produce vigorous downdrafts in highly-sheared environements, but it can be spread out over larger areas.  Microbursts are defined as powerful downdrafts in an area less than 2.5 miles in diameter.  Going larger than 2.5 miles in diameter would change the name to a downburst, but it's still the same physics just occurring over a larger area.

For your second question, I hope you now realize that there are two ways to make a microburst:  precipitation loading and downward momentum transport.  Microbursts can form at high CAPE values with a storm producing strong updrafts to lift moisture into a dry air layer aloft and strong downdrafts to force this rain-cooled air to the surface.  There are also microbursts that form without any precipitation as seen in dry thunderstorms, where the CAPE values could actually be quite small.  Those examples are wet and dry microbursts, respectively.  Hope this helps you, and there are lots of articles on microbursts as they are a popular research topic.
Title: Re: Ask The Weather Expert!
Post by: TWCmatthew on September 29, 2012, 10:33:29 AM
Thank you very much, Patrick! Great explanation.
Title: Re: Ask The Weather Expert!
Post by: TWCCraig on October 04, 2012, 05:26:14 PM
Hey Patrick,

You may not know the answer to this question, because it's mainly not a meteorological question, but, when I looked at today's airport observations at KISP, I noticed that the low temp was 66.2F according the observations. However, according to the NWS, the low was rounded up to 67F. I've always thought that the low gets rounded to the nearest degree, I don't understand why it would be rounded up in this case. The same thing also happened yesterday. Yesterday, the observations went down to 64.4F, but the actual low was 65F. I'm using this data from Wunderground. I noticed that on Wunderground, it has some observations between the standard 1-hour observations, those observations have the 66.2F reading which would make the low 66F vs. the NWS's 67F low. I noticed that on http://w1.weather.gov/data/obhistory/KISP.html (http://w1.weather.gov/data/obhistory/KISP.html) it doesn't have the observations between the hour so the low would round 67F. Are the observations between the hour considered invalid, because the NWS doesn't seem to take into consideration the in between hour observations.  :dunno:
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on October 04, 2012, 06:57:00 PM
Here's a really long answer, but I can perfectly explain this discrepancy as it's a weather reporting issue. :yes:  First, temperatures are always rounded to the nearest degree in Fahrenheit in the United States, but Celsius is the preferred unit worldwide.  Every temperature reading matters in determining the high and low, and your airport actually does it every second but only puts out a routine observation every hour, which is known as a METAR (Meteorological Terminal Aviation Routine) weather report.  You can rest assured that the high and low refer to the highest and lowest temperatures taken by the second each day.  Special METAR observations will also go out in between the hourly observations if changes in the weather that would threaten aviation like falling visibilities or a thunderstorm.  Weather Underground will show those special observations, but the official hourly observations are what you see on the NWS.  What you have uncovered is a flaw in Weather Underground, so let's explore why that site is wrong:

Here's what your METAR observation looked like at 4:21 AM (Z time is also UTC, which is currently 4 hours ahead of EDT, so it's 0821Z) when it was 66.2F according to Weather Underground:

Quote
KISP 040821Z 00000KT 2SM BR BKN003 OVC014 19/19 A3010 RMK AO2


The temperature is the first line before the slash in Celsius, which I have bolded.  It was 19C at that time.  If we convert to Fahrenheit, we get 66.2F, which is what Weather Underground uses.  But there's a huge problem here:  That 19C is just the temperature rounded to the nearest Celsius!  Remember, the worldwide standard is Celsius, so all airport observations reflect this fact and round to the nearest degree.  What you should consider is that 66F = 18.9C and 67F = 19.4C.  Thus, both of those temperatures in Fahrenheit round to 19C, so it could be either one of those!  Weather Underground fails to account for this possibility.  You're looking at one of the special observations above as it was issued off the hour due to the fog lowering visibilities during that time.  Now, let's look at the normal hourly observation back at 3:56 AM (0756Z):

Quote
KISP 040756Z 00000KT 3SM BR FEW002 OVC014 19/19 A3010 RMK AO2 SLP194 T01940194


Again, you see the same temperature in Celsius, but note the numbers I bolded.  The actual temperature in Celsius without rounding is 19.4C.  The zero out in front means that the temperature is positive in Celsius.  It would be a 1 if it was negative.  That temperature group only shows in the hourly observations.  Weather Underground sees this group and converts 19.4C directly to 66.9F, which rounds to 67F.  The NWS only uses that temperature group, so it will always be correct.  So, what was Islip's low this morning?  Every six hours (00, 06, 12, and 18 UTC), we get the high and low from the past six hours.  Here's your observation at 7:56 AM (1156Z):

Quote
KISP 041156Z 00000KT 2SM BR BKN008 OVC015 20/19 A3012 RMK AO2 SLP198 T02000194 10200 20194 51005


The numbers in bold are the high and low for the past six hours.  A 1 precedes the high, and a 2 precedes the low.  The high was 20.0C (again, 0 out in front as it's positive), and the low was 19.4C.  Thus, the low was 67F.  Unfortunately, Weather Underground looks at all the observations it gathered without considering the rounding issue I have explained above.  Thus, it wrongly thought the low was 18.9C, or 66F.  The NWS uses the six-hour groups above to determine the high and low, so it always gets the correct answer unless the weather station fails.

I hope this long explanation helps you, Craig!  The moral of the story is simple:  Look at the actual observations from the source itself.  The NWS is your best source for now, but you'll eventually learn how to read METAR reports when you take your first Meteorology classes.  There are tutorials online although it's quite complex at first until you understand the METAR code.  Once you have a grip on how it works, here's where you can look at METAR reports online by simply typing in your airport's ID (Islip, NY is KISP) and choosing how far back in time you want to go with the drop-down box (only goes back the past 36 hours):

http://aviationweather.gov/adds/metars/ (http://aviationweather.gov/adds/metars/)
Title: Re: Ask The Weather Expert!
Post by: Mr. Rainman on October 04, 2012, 07:16:52 PM
Excellent explanation, Patrick!  :biggrin:
Title: Re: Ask The Weather Expert!
Post by: Zach on October 04, 2012, 07:18:16 PM
Excellent explanation, Patrick!  :biggrin:
I certainly agree! Great job! :biggrin:
Title: Re: Ask The Weather Expert!
Post by: TWCCraig on October 04, 2012, 08:35:31 PM
Thanks a lot Patrick, very well explanation.  :twothumbs:
Title: Re: Ask The Weather Expert!
Post by: Localonthe8s on January 11, 2013, 01:41:38 PM
This is such a general question and it's not directed towards any specific member here but what do you think is your outlook for severe weather this season? Will it be just an average, uneventful year with a big outbreak or two and nothing else? Will it be much like last year where activity was strong during the early spring months but waned off after May? Or how about close to 2011?
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on January 11, 2013, 05:24:43 PM
This is such a general question and it's not directed towards any specific member here but what do you think is your outlook for severe weather this season? Will it be just an average, uneventful year with a big outbreak or two and nothing else? Will it be much like last year where activity was strong during the early spring months but waned off after May? Or how about close to 2011?
That's something you can't predict this far out.  Seasonal forecasts are just not accurate as so many factors come into play.  Furthermore, we're not in a La Nina or El Nino event, so I really can't tell you any preference for above or below normal with severe weather.
Title: Re: Ask The Weather Expert!
Post by: toxictwister00 on January 11, 2013, 05:58:41 PM
We'll have to see if a Nino or Nina episode makes a return by Spring and what potential effects it could have on Severe Wx Season. I'm not sure which one has the better chance of elevating the frequency of severe weather, but I'm naturally assuming it's La Nina.
Title: Re: Ask The Weather Expert!
Post by: WeatherWitness on January 17, 2013, 01:27:50 PM
So after the snowfall in Dallas the other day, and looking at the NWS daily weather summary for the day, does the precipitation report include snowfall?  I would think snowfall is considered precipitation, so it should be included, but I know they have a separate section for snowfall and precip.  I ask this because the snowfall report for DFW Airport was .3 inches, but the precip report was only 0.05 inches.  I read somewhere online where you need to divide by 10 to convert a snowfall total to a rainfall total, but it appears there was also rain from that day too.
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on January 17, 2013, 10:14:04 PM
So after the snowfall in Dallas the other day, and looking at the NWS daily weather summary for the day, does the precipitation report include snowfall?  I would think snowfall is considered precipitation, so it should be included, but I know they have a separate section for snowfall and precip.  I ask this because the snowfall report for DFW Airport was .3 inches, but the precip report was only 0.05 inches.  I read somewhere online where you need to divide by 10 to convert a snowfall total to a rainfall total, but it appears there was also rain from that day too.
When you have snow, you must melt what was collected in the gauge to get the liquid equivalent, which is reported as the precipitation.  However, you can never assume a 10:1 snow-liquid ratio!  It has been proven over and over that this ratio can vary widely with time and space.  Snow is generally drier as it gets colder, so the snow-liquid ratio increases.  Furthermore, you have to account for the microphysics involved in snow growth along with your moisture source.  Wet snow right near the freezing point can be down at 3:1.  At the other extreme, dry snow in the Rocky Mountains and lake-effect snow in the Northeast have reached up to 100:1.  The 10:1 ratio is just a common average that was thought to be a rule of thumb, but we have learned better thanks to modern research.  The liquid equivalent of 0.05" looks good to me as it gives a 6:1 ratio, and your area was just below freezing when it snowed at DFW. :yes:
Title: Re: Ask The Weather Expert!
Post by: TWCCraig on February 26, 2013, 05:17:05 PM
Quote
While that is true, we are in March now where our wavelengths are shorter than they are in December. Thus, you can more easily get away with having a ridge east of its ideal position.

-Dsnowx53 http://www.americanwx.com/bb/index.php/topic/39435-late-february-medium-and-long-range-discussion-thread/page-18? (http://www.americanwx.com/bb/index.php/topic/39435-late-february-medium-and-long-range-discussion-thread/page-18?)

Hey Patrick, can you explain what this meteorologist means when he refers to "wavelengths". I don't think he's referring to wavelengths like with solar radiation, something different. After a Google search, this is the best definition I could find:

Quote
The least distance between particles moving in the same phase of oscillation of a wave.

http://meteorology.geography-dictionary.org/Meteorology-and-Weather-Dictionary/WAVE_LENGTH (http://meteorology.geography-dictionary.org/Meteorology-and-Weather-Dictionary/WAVE_LENGTH)

To be honest, I don't clearly understand what that means. What does he mean when he refers to wavelengths being shorter in March than December? I wonder if he is referring to solar radiation. IDK   :wacko:
Title: Re: Ask The Weather Expert!
Post by: phw115wvwx on February 26, 2013, 05:28:56 PM
Craig, look at the pattern of upper-level ridges and troughs either in the forecast models or in the weather analysis maps.  Those are atmospheric waves.  A wavelength is the distance of a full wave (trough to trough, or ridge to ridge).  So, a shorter wavelength means the distance between an upper-level trough and an upper-level ridge is smaller.  These varying wavelengths result in completely different weather patterns.  You have to spend a whole chapter just on waves when you take Physics, and now you see why.  Nature, including weather, is full of them. :yes:
Title: Re: Ask The Weather Expert!
Post by: TWCCraig on February 26, 2013, 05:51:44 PM
Ooooooooh! Now I get it. I was thinking it was something more complicated than that. Thanks Patrick  :thumbsup: