| Clark |
| (Meteorologist) |
| Tue Aug 21 2007 03:35 PM |
Re: Dean Makes Landfall in Mexico as a Category 5 Hurricane
|
Quote:
"178 KT AVERAGED OVER THE LOWEST 150 METERS OF THE SOUNDING."
Would be interesting to hear, what kind of things have to be taken into account, if you want to make an estimation of the surface wind with the help of this data!
145 kt by the NHC seems to be very conservative!?
It's the lowest 50-100 meters that have the strongest negative impact on the wind speeds experienced, largely due to frictional processes. Take a look at this graphic from the NHC's webpage illustrating the "normalized wind speed" taken from a composite of many dropsondes into hurricane eyewalls:
We're looking at a 20-25% decrease from 150m to the surface, particularly using the eyewall profile. It's 700mb that the 10% rule mentioned before applies to the most.