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Calculating windchill...

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Calculating windchill...

Old 01-28-20, 02:42 PM
  #51  
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Originally Posted by u235 View Post
Wind chill is 100% a human factor and calculation. Splitting hairs you but... If that water you put outside was 70F, it would reach 35 faster in that wind compared to no wind so there is a wind factor but that's not a wind chill calculation. That faster cooling rate is what your body feels in the wind. Insulate that cup and it cools down slower, same as you wearing a jacket. It is all related.
We agree, and yes, it is splitting hairs.

IMHO & IME - proper clothing negates windchill factor.

OTOH - riding into the wind will always slow you down, and with the clothes to keep you warm, you will slow you down more as it gets colder. So windchill factor is more of a drag-factor ???
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Old 01-28-20, 02:45 PM
  #52  
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Originally Posted by AllWeatherJeff View Post
Ride 30 miles from home with a generous tailwind on a sub-freezing day. Then stop for 30 minutes to repair a rear flat tire. Now turn around and ride 30 miles home into the headwind. Now that your body has cooled down after the prolonged stop and the sweat trapped beneath your winter layers cools your body further still, you will very quickly become a believer in windchill.
That's true with or without wind (been there, done that).

I ride with Merino wool for this very reason, it's better at keeping you warm while wet.

Reference pic in my post - I'm experienced at riding in *real* winter conditions (please don't think you need to school me).
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Old 01-28-20, 03:02 PM
  #53  
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Oh, so you do believe in windchill?
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Old 01-28-20, 03:04 PM
  #54  
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Nope, I believe in dressing for the conditions. With the correct gear, windchill is not a factor.
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Old 01-28-20, 10:37 PM
  #55  
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I believe in dressing for conditions too. If there is a strong headwind in the lower temps, it makes a big difference as to what I wear. Or in some cases, if I even want to ride. With little or no wind, or even a tail wind, I can easily ride in much colder temps. I do believe in wind chill, I do believe in wind chill...
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Old 02-10-20, 08:25 AM
  #56  
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question for the scientists ... does windchill affect / aid surface freezing?

went for a ride Saturday at 31 degrees but it was very windy w/gusts over 20 mph. went thru a puddle & my mudflap wound up freezing solid in a funny reverse crescent shape. don't recall that ever happening before


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Old 02-10-20, 10:28 AM
  #57  
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Wind will remove temperature down to the air temp faster. On a sunny day, the road surface will heat water above freezing, splash on a bike (and parts) that's at air temp (below freezing) and you get some funny stuff.

This was a ride about 2 years ago in similar conditions, temps just below freezing with sun and strong winds.

Here's the bottom bracket:



And this funny little ice fender, the tire just barely clears this ice ... you couldn't design something with tolerances this close.

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Old 02-10-20, 11:46 AM
  #58  
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Originally Posted by rumrunn6 View Post
question for the scientists ... does windchill affect / aid surface freezing?

went for a ride Saturday at 31 degrees but it was very windy w/gusts over 20 mph. went thru a puddle & my mudflap wound up freezing solid in a funny reverse crescent shape. don't recall that ever happening before
The Toad is mostly correct, and that's the simple answer. The actual answer based on thermodynamics? It's more complicated than that.

Since windchill is mostly based on our perception of cold, or more accurately, on the rate of heat loss, it's not really accurate to apply the term 'windchill' to anything other than the human body.

What we feel as cold is due to the rate of heat loss to the environment. When a wind chill chart says that at 45F, with 10 mph wind, the windchill is 38F (just pulling numbers, I didn't check the chart). What that means is that 45F with 10mph wind is about the same feel (rate of heat loss) as 38F with no wind.

All these are based on the different modes of heat transport noted above in my post above, which are largely dependent on the temperature difference between the human body and the environment.

There's a fun experiment (pretty sure there's a video on youtube) that you can do. Go outside when the temps are in the low single digits with a cool glass of water and throw it up in the air. It will come down as mostly water and freeze. Do the same thing with a glass of hot water, and most of it will not even make it to the ground.
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Old 02-10-20, 01:58 PM
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reminds me: I live near the coast & we have fishermen. when listening to the NOAA weather radio, close to Boston or the cape, we get "marine" related forecasts. sometimes that includes "freezing spray" (ice buildup on vessels can be dangerous)

"Freezing spray is a serious concern for ocean voyagers because once the spray is airborne then, under the right conditions, it will freeze as soon as it contacts any surface. This will lead to ice accretion on every exposed portion of a vessel, including decks, superstructures, spars, shrouds and more. It may cause communication equipment to cease functioning and could lead to loss of function of mechanical parts. However the most serious impact of ice accretion is reduced vessel stability. The added weight of ice adhering to a vessel above the waterline will change the center of gravity of the vessel and make it much more susceptible to capsizing."

excerpted from
Freezing spray - Ocean Navigator - Web Exclusives 2015
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Old 02-10-20, 02:26 PM
  #60  
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That is the effect of what's known as supercooling. It's the same thing that causes freezing rain. In the midwest, ice storms from freezing rain is about as common as regular snow, but much more dangerous.

Nothing like having to chip through 1/4 ice covering your car just to get in. Then wait 20 mins while it warms up enough to start scraping the ice off..... I hated living in the midwest.

Pure water, if kept very still and undisturbed, can be cooled a few degrees below freezing and remain liquid. At that point, the slightest disturbance or slight impurity will cause it to freeze very quickly, almost instantly. It's pretty neat, actually....from a distance.

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Old 02-20-20, 10:45 AM
  #61  
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This thread was in my head while riding into the wind on the way to the store yesterday (12F into 13 mph wind) ...

The for-profit weather apps, channels, websites, etc .... they love extremes, it gets eyes and eyes means advertising revenue (I sell advertising, I know how this game is played). So windchill is a 'bigger' number than air temp and gets more eyes; in the summer it's heat index. Neither windchill nor heat index are worthless, but both are only a small part of the actual weather conditions and dressing to be comfortable while out riding.

Here are the things I will consider while picking gear for the ride:
  • Temp
  • Wind
  • Humidity
  • Precipitation
  • Cloud cover/sun
None of the 'feels like' stats reported by the 'weatherguy' factor the suns warmth or cold of rain; and these factors are bigger to my comfort than wind.
  • Sunny and 10F can be lovely and enjoyable; where 35F and cloudy with high humidity be miserable no matter how much wool you wear.
  • Sunny and 60F is summer kit weather (for this Toad); 60F with rain can leave you shiver uncontrollably if your stuck in the middle of nowhere (been there, done that)

FYI - the weather forecasting tool I use is NOAA hourly weather forecast graph:



For what it's worth, my riding includes temps as low as -28F and as hot as 102F (air temps).
I know a thing or two, because I've seen a thing or two.
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Old 02-21-20, 11:01 AM
  #62  
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So far, the coldest I've ridden in is ~10F, and that's in a velo, where I have good protection from the wind. In my defense, I'm an AZ boy at heart, and have no problem on long rides in 110-115F temps. I used to ride Tucson to Phoenix in the middle of August.

In my velo, I find myself wearing my lighter, non windproof, jacket because it breathes a little better. The only real bit of gear I had to add over my 2 wheel bike, where I was out in the wind, obviously, was a good set of winter bike shoes. Even in the velo, my feet would not warm up. Now I'm quite happy.

I got to work this morning, and there was an alert that came over the computer network that there was wind chill warning of less than 0F. I barely noticed the wind in my velo this morning.

And I agree that NOAA is the best web site for weather.
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