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### Wind Chill Formula

```
Date: 2/1/96 at 14:35:26
From: Anonymous
Subject: wind chill formula

Could you tell us the formula used for finding the wind chill?  We have
a chart, and we want to make connections in our Algebra class.  TG
```

```
Date: 3/12/96 at 0:19:28
From: Doctor Jodi
Subject: Re: wind chill formula

Hi there! Thanks for your question.  I'm glad to hear that you're
connecting algebra to other areas in your class!

Ken, one of the other doctors here, found the National Weather Service's
equation for calculating weather:

T(wc) = 0.0817(3.71V**0.5 + 5.81 -0.25V)(T - 91.4) + 91.4

T(wc) is the wind chill, V is in the wind speed in statute miles per
hour and T is the temperature in degrees Fahrenheit. From

http://www.usatoday.com/weather/wchilfor.htm

used.  Holly Devaul kindly forwarded our query to some meteorologists.

[snip]

Hi, - happy to oblige...here is the formula, from a weather software
application package known as GEMPAK:

Wind Chill T (in K) = 306.15 - (0.453843 * SQRT(Speed) + 0.464255
- 0.0453843 * Speed) * (306.15 - Temp [in K])

As you can see it is a bit complicated but this is the "official" NWS
formula.  I hope I typed it out correctly!

Note:  Speed (above) is in meters per second and Temps are in Kelvins.

This should be fun for units conversion freaks, since wind speed is
usually given in knots or miles per hour and temperature in the US is
measured in F!

Paul Ruscher

if you want to be even MORE esoteric, try this, developed by Siple and
Passel (1945):

H = (SQRT(100V) + 10.45 - V) x (33 - T)

where H = windchill in kilocalories per square metre of exposed flesh
per hour

V = wind speed in metres per second

and T = air temperature in C

I've never been a big fan of wind chill equivalent temperatures.  They
are largely meaningless and can note something they shouldn't, hence
the all too frequent confusions.  Wind and temperature combine to
produce a COOLING POTENTIAL, not a temperature.  Only one value need
be remembered here -- at about 1500 kcal/m2, exposed flesh will freeze.
At higher wind speeds and lower temperatures than those that combine
to create 1500, flesh will simply freeze more quickly.

Sincerely,

mark "more-than-you-wanted-to-know" cote

*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
Holly Devaul
Kids As Global Scientists
124 Education Building
Campus Box 249
Boulder, CO  80309-0249

303-492-3424
303-492-7090 (FAX)

Best luck with your project and let us know how it turns out!

-Doctor Jodi,  The Math Forum

```
Associated Topics:
High School Basic Algebra

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