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# RE: Wind velocity

• To: seaint(--nospam--at)seaint.org
• Subject: RE: Wind velocity
• From: "Harold Sprague" <spraguehope(--nospam--at)hotmail.com>
• Date: Mon, 19 Sep 2005 18:40:12 +0000

There are conversion algebraic "approximations" only. You can be off by quite a margin depending on the velocity that is considered.
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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.
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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.
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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.
```Example:
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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.
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Regards,
Harold Sprague

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

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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,
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Javier Encinas, MSCE, PE
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