Wind chill

[Zak]

It seems reasonable, to me, that measuring the heat loss from a heated
resistor could enable you to calculate windchill in the way the OP
suggested.

I'd suggest a sensor at body temperature, and measuring the power neede
to keep it warm.


Thomas

 

[Jim Thompson]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog


Just hold the bag. Your canine friend provides you with a lovely squishy
hand-warmer. (;-)

Yech :-( The only grass I have here is for the dogs, and the gardener
does the scooping ;-)

...Jim Thompson

 

[Spehro Pefhany]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog


Just hold the bag. Your canine friend provides you with a lovely squishy
hand-warmer. (;-)

Alas, the bag got a fair bit of snow in it as well, so it had the
opposite effect, what with the phase change and fast evaporative
cooling of the moist contents. Unusually, most of that accumulated
snowfall took place in very cold conditions, so the snow was very
powdery (crunchy underfoot). Typically it's more solid (the snow, that
is, Ms. Golden Retriever's contribution was solid enough).


Best regards,
Spehro Pefhany

 

[Jim Thompson]

I'd suggest a sensor at body temperature, and measuring the power neede
to keep it warm.


Thomas

You'll need to insulate matching typical clothing and/or skin thermal
resistance.

...Jim Thompson

 

[James Meyer]

Eh? Never been in Detroit this time of year have you ?

...Jim Thompson

Nope. Never been in Arizona at any time either.

Wind chill as a number that means anything is ridiculous. If you know
the air temperature and the wind speed you know enough. You don't need a
formula to tell you that the faster the wind blows, the more uncomfortable you
may become. And what about humidity? That's a large factor in how comfortable
or uncomfortable you may be.

Tell me the temperature, the wind speed, the humidity, the precititation
(if any), and I'll know what I need to wear and do to feel OK. I don't need a
fictitious wind chill number.

Jim "the other one" Meyer

 

[Don Klipstein]

And it has to be a naked person. It was developed by the military
to act as a baseline for cold-weather gear. Anyone wearing clothes
will find that a 10 degree wind chill is much warmer than a real
10 degrees.

So why is it so popular? It makes the weather report on your local
TV station more exciting. A REAL correction factor that tells you
how cold it will seem while you are wearing a good coat would be
far more useful, but instead they give the bogus numbers.

They did that a few years ago.

Before a few years ago, the windchill reported on the news was the one
for bare skin. And it took something like -30 degrees F on that scale to
achieve a windchill advisory. A really bad windchill that did not happen
most winters (in Philadelphia) was -40 degrees F and a day with both
strong wind and temperature slightly below zero managed around -50.

In recent years, they have been using a different windchill scale based
on wearing clothing. Now -10 achieves a windchill advisory. A recent day
(with a windchill advisory) when the windchill in Philadelphia got to
about -10 to -15 F felt the worst to me since a day in 1994 when the
windchill on the old scale was in the -40's F.

- Don Klipstein ([email protected])

 

[Spehro Pefhany]

You'll need to insulate matching typical clothing and/or skin thermal
resistance.

...Jim Thompson

Is the object to get something like the "official" numbers? If so,
then there *is* a mathematical formula- and the OP can just measure
the required variables, plug them into the official forumula and spit
out the number. That's easiest and probably best.

If the object is to get some new number that (perhaps better) reflects
how cold it "feels", that's something different. My favorite number,
although it's probably not very scientific, is the minutes (or
seconds) before exposed flesh freezes. ;-)

What's the equivalent in Phoenix? Minutes to fry an egg on the
sidewalk in midsummer? ;-)


Best regards,
Spehro Pefhany

 

[John Woodgate]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog

Unusually, most of that accumulated snowfall took
place in very cold conditions, so the snow was very powdery (crunchy
underfoot).

We had some of that a few years ago, and it was fine enough to get
through the vent grilles of our electric train motors, putting them out
of action. Some railway PR droid achieved immortality by describing it
to the media as 'the wrong sort of snow'.

My observation is that the flake size is inversely proportional to some
direct function of the difference between the air temperature and the
freezing point. We had a small snowfall here the other day with BIG
flakes. It melted within an hour.

 

[John Woodgate]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog

What's the equivalent in Phoenix? Minutes to fry an egg on the sidewalk
in midsummer? ;-)

No. Midwinter.

 

[Jim Thompson]

On Sun, 30 Jan 2005 16:05:04 -0500, Spehro Pefhany

[snip]

If the object is to get some new number that (perhaps better) reflects
how cold it "feels", that's something different. My favorite number,
although it's probably not very scientific, is the minutes (or
seconds) before exposed flesh freezes. ;-)

What's the equivalent in Phoenix? Minutes to fry an egg on the
sidewalk in midsummer? ;-)


Best regards,
Spehro Pefhany

I think that fried-egg-on-the-sidewak thing is an urban legend. It
takes a closed black car to get into the 160°F air-temperature range,
and I've heard numbers of around 140-150°F on good black asphalt...
not quite frying temperature... the demos I've seen on TV news show
whites looking like congealed snot, yech ;-)

...Jim Thompson

 

[Guy Macon]

Content-Transfer-Encoding: 8Bit

I took the dog for a walk at night a week or two ago- the wind was
~20-30mph and temperature -22°C (-8°F). Taking a glove off to use my
Maglite and bag the leavings, I wasn't across an open field diagonally
before all the feeling was out of my little finger in that hand. Wind
chill is real enough!

I really ought to mention that it has been between 72 and 75
degrees here in Los Angeles all week...

 

[Guy Macon]

They did that a few years ago.

Before a few years ago, the windchill reported on the news was the one
for bare skin. And it took something like -30 degrees F on that scale to
achieve a windchill advisory. A really bad windchill that did not happen
most winters (in Philadelphia) was -40 degrees F and a day with both
strong wind and temperature slightly below zero managed around -50.

In recent years, they have been using a different windchill scale based
on wearing clothing. Now -10 achieves a windchill advisory. A recent day
(with a windchill advisory) when the windchill in Philadelphia got to
about -10 to -15 F felt the worst to me since a day in 1994 when the
windchill on the old scale was in the -40's F.

Glad to hear that they are giving better answers. Mmmm. Let me check
to see when the last time I travelled to somewhere cold other than the
usual surf in the morning ski in the afternoon trick... Ah, Here it
is. Indiana, winter of 1997.

 

[keith]

On Sun, 30 Jan 2005 12:44:06 -0700, Jim Thompson wrote:

I always seem to have business back east at the worst-weather times of
the year... Pittsburgh on Wednesday :-(

Better than Pittsburgh last Monday. That must have been a depressing
place! ;-)

It's cold here today... a cold front with rain came thru yesterday
afternoon... it's only +60°F, +15.5°C, here ;-)

It's hotter than hell here today. It got to 27F (-2C for the
Canuckistanis here), and there was a big bright thing in the sky. We're
kinda wondering what it was, but it left about 5:00PM.

 

[Howard Eisenhauer]

Thanks to all who replied. After reading thru the various responses
I've reached the conclusion the simplest solution to the problem is to
stay inside .

Howard.

 

[Spehro Pefhany]

Content-Transfer-Encoding: 8Bit




I really ought to mention that it has been between 72 and 75
degrees here in Los Angeles all week...

Wait until all that stuff in _The Day After Tomorrow_ starts to
happen-- then you'll be singing a different tune. Destroying the
Capitol Records building was a nice touch.


Best regards,
Spehro Pefhany

 

[Keith Williams]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog


We had some of that a few years ago, and it was fine enough to get
through the vent grilles of our electric train motors, putting them out
of action. Some railway PR droid achieved immortality by describing it
to the media as 'the wrong sort of snow'.

I suppose you aren't prepared for "the wrong sort of snow". When you
get in your car and turn on the defroster and it snows *inside*, it's
"the wrong sort of snow" too. ...happens all the time, perhaps 30-40
mornings a year.

My observation is that the flake size is inversely proportional to some
direct function of the difference between the air temperature and the
freezing point. We had a small snowfall here the other day with BIG
flakes. It melted within an hour.

Sure. The colder the flakes the less they stick to each other making
for smaller "flakes" when they reach the ground. I always thought it
was "too cold to snow" when it got below 0F (-18C), but since I moved
to Vermont I'm repeatedly reminded at the folly of that observation. I
had never seen a foot of snow at -20F (-29C). I have now! Several
times.

 

[Keith Williams]

Nope. Never been in Arizona at any time either.

Wind chill as a number that means anything is ridiculous. If you know
the air temperature and the wind speed you know enough. You don't need a
formula to tell you that the faster the wind blows, the more uncomfortable you
may become. And what about humidity? That's a large factor in how comfortable
or uncomfortable you may be.

Wind chill was originally meant to express how rapidly uncovered flesh
would freeze. It's since been hijacked into a "touchy, feely" number
that does include humidity (e.g. Accuweather's "real feel").

Tell me the temperature, the wind speed, the humidity, the precititation
(if any), and I'll know what I need to wear and do to feel OK. I don't need a
fictitious wind chill number.

It's not fictitious. Though I agree, I listen to wind-speed far more.
At -30C (as it was last week), I was happy to hear that it was dead
calm (even the wind was frozen ;-).

 

[Jim Thompson]

On Sun, 30 Jan 2005 12:44:06 -0700, Jim Thompson wrote:



Better than Pittsburgh last Monday. That must have been a depressing
place! ;-)

I know, I was having great sport teasing the client's travel lady
about our mid-70's temperature.

It's hotter than hell here today. It got to 27F (-2C for the
Canuckistanis here), and there was a big bright thing in the sky. We're
kinda wondering what it was, but it left about 5:00PM.

Beware the "big bright thing in the sky", AKA the slush monster ;-)

...Jim Thompson

 

[Active8]

Is the object to get something like the "official" numbers? If so,
then there *is* a mathematical formula- and the OP can just measure
the required variables, plug them into the official forumula and spit
out the number. That's easiest and probably best.

Yes. It's in the JS code from that windchill calculator page that
was previously posted. I started to post it, but the line wrap
crapped it up.

Probably the best way as you said. Even the new formula isn't
perfectly linear and it says they've adjusted the wind speed for the
height above ground of the human face. That takes a lot of work out
of the project.

If the object is to get some new number that (perhaps better) reflects
how cold it "feels", that's something different. My favorite number,
although it's probably not very scientific, is the minutes (or
seconds) before exposed flesh freezes. ;-)

What's the equivalent in Phoenix? Minutes to fry an egg on the
sidewalk in midsummer? ;-)

LOL. My observation is that in winter, wind does more to make it
feel colder than a summer wind does to make it feel cooler - at
least during physical activity in the sun. The summer wind sometimes
appears to keep me from sweating, but IME that's just the air
keeping the skin dry That may lead you to believe it's not as hot,
but the whole time you're dehydrating. Normally, if you stop
sweating when you should be, you're headed for danger. If the wind
keeps the skin dry, you can't tell anything's changed until you
black out.

 

[keith]

I know, I was having great sport teasing the client's travel lady
about our mid-70's temperature.

I was referring to their non-show at the stadium the day before. The Pats
kicked their donkey, and at home. ...no snow even! Forget the 70F! It
was far colder there than the temperature would indicate, last Monday! ;-)

Beware the "big bright thing in the sky", AKA the slush monster ;-)

Naw! I gotta get my driveway cleaned off. Early January we had a
"little" wet snow on a Monday morning. By the time I got home in the
afternoon it had dropped 20F and was frozen solid. I'm just now getting
down to the black. ...Another few days and I may not need 4WD to get up
my short driveway.

Mud season is at least six weeks off. if we even have one this year.