Wind Chill FormulaDate: 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 Meanwhile, we asked Kids as Global Scientists about the formula they used. Holly Devaul kindly forwarded our query to some meteorologists. Here's their reply: [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 University of Colorado 124 Education Building Campus Box 249 Boulder, CO 80309-0249 303-492-3424 303-492-7090 (FAX) kgs@spot.colorado.edu http://stripe.colorado.edu/~kgshtml/Home.html Best luck with your project and let us know how it turns out! -Doctor Jodi, The Math Forum |
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