CHILL, a Windchill Temperature program by Joseph K. Horn

M. Edward Borasky posted two equations for the Windchill Index recently.  It
reminded me of the BURR (as in "Brrrrrr!!!") routine that was in the VOYAGER
program written by Dr. Robert Wilson for the HP-71 onboard the historic
round-the-world Voyager aircraft flight in 1986.  Here's that subprogram
rewritten in 48 RPL:

-------------- CHILL in --------------
%%HP:T(3)F(.);
\<< 3.4759 MAX 50 MIN 4.63 * 9 / SWAP 32 - 5 * 9 / \-> v t
'33-(10.45+10*\v/v-v)*(33-t)/22.03405' 9 * 5 / 32 + 1 RND \>>
-------------- CHILL out -------------

This takes a Fahrenheit temperature in level 2, and a wind speed in knots in
level 1.  The result is not a Windchill Index, but the "apparent temperature"
with the windchill factor already figured in.

So if you're skiing downhill on a 15 degree day with a 30 knot wind sanding
your face, this program says that it'll FEEL like it's 27.5 degrees below
zero!  Until frostbite sets in, of course.

What I find odd is that if it's cold and windy enough, the result can be far
below absolute zero.  But if absolute zero is when all molecular motion
ceases, how can it be windy?  And what would it mean to be "apparently" below
absolute zero?  Hm.

Also, 91.4 degrees seems to be a turning point; above that, and wind makes it
seem HOTTER, not cooler!  Seems to me that the magic number should be 98.6
("... when it's difficult to tell where you end and the night begins."); I'd
LOVE a breeze on a 92 degree day!

Wanna hear something outrageous?  In the Teacher's Edition of Addison Wesley's
"Algebra and Trigonometry" high school textbook (1988), page 305, it gives the
same formula for "windchill temperature" as used above, but it leaves the
units in the SI base: degrees Celsius, and windspeed in m/s.

But they stupidly thought that m/s means miles per second!  Here's what it
says:  "... where T is the actual temperature given in degrees Celsius and v
is the wind speed in mi/sec."  Wow, that's fast wind!

Problem 50 then asks the student to calculate the windchill temperature given
T=7 and v=8.  Let's see; 8 mi/sec = 28,800 mph, according to the HP 48.  At
that speed, the temperature would RISE due to air friction! You'd burn up in a
moment!  That's not what the books says, of course.

No wonder our kids are graduating from high school totally innumerate...

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                |  "Many are cold, but few are frozen."  |
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