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RE: Wind velocity

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There are conversion algebraic "approximations" only. You can be off by quite a margin depending on the velocity that is considered.

Exact solutions from fastes mile to 3 second gusts are an iterative process using the Durst Curve which is contained in the ASCE 7-02 page 296. The iteration closes fairly quickly (about 3 or 4 cycles). I developed a MathCAD template for conversions some years ago. I had Jon Peterka of CPP Labs verify my technique.

From that template I developed a series of tables for my own personal use
some years ago that converts various winds to 3 second gusts. I have converted Fujita Scale, Saffir Simpson Scale, Australian Cyclonic Scale. Beaufort Scale, World Meteorological Organization velocities, and Fastest Mile winds to 3 Second Gusts.

It is important to get the velocities correct because the pressures vary as a ratio of the velocities squared. A little mistake in velocity can be a huge mistake in pressure.
A Cat 3 hurricane is 1.5 times greater in velocity than a Cat 1. But a Cat 3 pressure is 2.25 times greater than a Cat 1.

Harold Sprague

From: "Javier Encinas" <jencinas(--nospam--at)>
Reply-To: <seaint(--nospam--at)>
To: <seaint(--nospam--at)>
Subject: Wind velocity
Date: Mon, 19 Sep 2005 13:08:31 -0400

What is the correlation between the "fastest mile" wind velocity and the "3-sec gust" wind velocity. For example, what is the equivalent of a 110 MPH fastest mile velocity using the 3-sec gust approach? Regards,

Javier Encinas, MSCE, PE

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