cieldumort
(Moderator)
Sat Sep 06 2008 04:37 AM
Re: how wind speeds are determined

Standard measuring elevation is 10 meters (33 feet). Wind speed at the lowest five feet above ground can run anywhere from 5% to even 80% less than the wind speeds at an unobstructed measuring station recording from a height of 33 feet.

Other things are at play, as well -

The description "sustained hurricane-force winds" is typically for winds at a 10 meter elevation - averaged over one minute. Within that minute the winds might actually be as little as, say, 40mph and perhaps as high as, say, 100mph, but at least 74mph, averaged-out.

Advisory wind speeds for tropical cyclones are not for the winds within the entire tropical cyclone, or even most of it. The advisory wind (NHC Advisory) represents the maximum sustained wind to be found at any point within the cyclone. In fact, most of the time better than 99% of any tropical cyclone will not be experiencing the maximum sustained wind speeds. Typically, you would have to be within the worst part of an eyewall to get them.. and your location's odds of that as an individual speck of sand in the sea of sand that represents all individual locations within a cyclone is almost infinitesimally small.

It is very likely that most other locations that are within the worst portions of a tropical cyclone will still experience maximum sustained winds which are impressive, but fall between 40% and 80% of the absolute max sustained.

Hope this helps!



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