From: utzoo!decvax!harpo!npoiv!npois!alice!rabbit!wolit
Newsgroups: net.misc
Title: Wind-chill factor
Article-I.D.: rabbit.595
Posted: Wed Jul  7 17:09:59 1982
Received: Fri Jul  9 00:53:45 1982

Well, here it is July in New Jersey (and elsewhere), so I guess it's a
good time to start a discussion of that old nemesis of
weather-watchers, the Wind-Chill Factor (hereafter, WCF).
This was brought on by a piece in net.auto, where some Honda-owner in
Wisconsn was bragging about how well his buggy started last winter
when the temperature was -20 and the WCF -80 or so.

As I understand these things, the WCF is only of concern to us
evaporation-cooled, warm-blooded beings.  A car, sitting outside all
night, is gonna be pretty much at the ambient temperature by morning,
no matter HOW hard the wind is blowing.  Unless you start dowsing it
with some volatile liquid, there's no way it'll get any colder.
Even then, it won't get below the wet-bulb temp, which is NOT the same
as the WCF.  The WCF basically tells you how bad you're gonna feel, 
by measuring how FAST you'll cool off.  

Now for the bad news:  All the WCF charts I've ever seen plot the WCF
as a function of the ambient, dry-bulb temperature, and the wind
speed.  Nowhere is the relative humidity taken into account.  It seems
to me that the RH should have some effect on how cold you feel, since
you'll cool off faster in dry air, because of evaporation, than you
will in moist air.  Any ideas on why there is no RH factor in the WCF?

Next winter, we'll talk about the Temperature-Humidity Index, and what
the Energy Factor number on your air conditioner means...

	Cheers,
	Jan Wolitzky
	(...rabbit!wolit)