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Author Topic: Ask The Weather Expert!  (Read 17039 times)

Offline Austin M.

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Re: Ask The Weather Expert!
« Reply #90 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).

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Re: Ask The Weather Expert!
« Reply #91 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.
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Re: Ask The Weather Expert!
« Reply #92 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. ;)

Offline Mike M

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Re: Ask The Weather Expert!
« Reply #93 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:
« Last Edit: May 28, 2012, 02:03:08 PM by Mike M »

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Re: Ask The Weather Expert!
« Reply #94 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.

Offline toxictwister00

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Re: Ask The Weather Expert!
« Reply #95 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.


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Re: Ask The Weather Expert!
« Reply #96 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?


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Offline Zach

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Re: Ask The Weather Expert!
« Reply #97 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 Niņa, just like last year. Patrick, feel free to correct me if I am wrong, though. :P
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Re: Ask The Weather Expert!
« Reply #98 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 Niņa, just like last year. Patrick, feel free to correct me if I am wrong, though. :P
It has nothing to do with La Niņa or El Niņo.  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.

Offline toxictwister00

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Re: Ask The Weather Expert!
« Reply #99 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:


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Re: Ask The Weather Expert!
« Reply #100 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:


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Re: Ask The Weather Expert!
« Reply #101 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.

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Re: Ask The Weather Expert!
« Reply #102 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.
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Offline toxictwister00

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Re: Ask The Weather Expert!
« Reply #103 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. 


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Offline gt1racerlHDl

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Re: Ask The Weather Expert!
« Reply #104 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?