Irene has weakened again as of the 5 PM advisory. Winds are 80 mph, as the hurricane continues its path to the NNE at about 13 mph. The NHC stated that in high-rise areas, wind speeds are increased by 20% upwards of 30 floors, and up to 30% or higher at 80-100 floors.
Assuming that Irene arrives in New York as expected (strong tropical storm), here are the wind speed forecasts by altitude.
Ground speed: 70 mph.
30 floors up: 84 mph.
80-100 floors: 91 mph or higher.