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Old 02-23-2011, 05:34 PM
 
Location: Somewhere in Texas
5,232 posts, read 11,682,466 times
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Quote:
Originally Posted by SouthernBelleInUtah View Post
You must not have experienced a dry cold - it makes a HUGE difference in how you feel. I wore a full-length down coat in New Orleans when it was 30 deg. and 90% humidity. I wear a fleece jacket here when it is 28 deg. and 20% humidity.
That sounds so, so nice.
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Old 02-23-2011, 06:02 PM
 
1,054 posts, read 1,835,658 times
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You must not understand how humidity works in the lower temperatures. In Nebraska, we experience long periods of dry air as well as gulf-fed air. Afterall, there is such a thing as clash of the air masses that involve warm/cool air as well as dry/moist air.

We get to be as dry as a desert here, then other times we get rather moist. When the air is cold, it has very limited ability to hold in moisture. The difference is felt in the summer and very, very little in the winter. As a matter of fact, moisture in the winter isn't even considered important for what is considered 'how cold it feels'. In the winter, only the phenonena of wind is considered.

The fact that you guys are comparing -5 to 30 and say moisture is the difference is completely delusional. Thirty degrees with 25 degree dew points versus thirty degree with -5 dew points has no bearing on how the air feels.

I about spit out my soda when reading that, lol.
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Old 02-27-2011, 12:02 AM
 
Location: Des Moines, IA
73 posts, read 146,712 times
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It is not delusional. I find that when I make ski trips out west that the dry air does make a significant difference in the real feel of temperatures. 30s in Iowa feel typically feel much colder than 30s in Utah or Colorado do. This might be an issue with central Iowa because we are the edge of those wonderful arctic air masses as well. We were in Big Cottonwood Canyon last winter and our temp gauge said -16 degrees... and it didn't even come close to that awful, biting cold we get in Iowa (I've felt colder 20 degree days here). I was outside for with flip flops and a t shirt for approximately two minutes grabbing a beverage and it didn't even bother me that much.

Maybe the mountains and world class skiing make me think I am less cold than I really am... I don't know but it sure feels different! I even dress very differently for skiing out west!
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Old 02-27-2011, 06:55 AM
 
Location: Somewhere in Texas
5,232 posts, read 11,682,466 times
Reputation: 2647
Quote:
Originally Posted by MitchMZ View Post
It is not delusional. I find that when I make ski trips out west that the dry air does make a significant difference in the real feel of temperatures. 30s in Iowa feel typically feel much colder than 30s in Utah or Colorado do. This might be an issue with central Iowa because we are the edge of those wonderful arctic air masses as well. We were in Big Cottonwood Canyon last winter and our temp gauge said -16 degrees... and it didn't even come close to that awful, biting cold we get in Iowa (I've felt colder 20 degree days here). I was outside for with flip flops and a t shirt for approximately two minutes grabbing a beverage and it didn't even bother me that much.

Maybe the mountains and world class skiing make me think I am less cold than I really am... I don't know but it sure feels different! I even dress very differently for skiing out west!
I totally agree with you. It's just as different as 95 degrees and dry and 95 degrees and humid. The latter is horrid!
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Old 02-27-2011, 12:33 PM
 
Location: 125 Years Too Late...
10,884 posts, read 10,579,688 times
Reputation: 9549
Quote:
Originally Posted by Canine*Castle View Post
I totally agree with you. It's just as different as 95 degrees and dry and 95 degrees and humid. The latter is horrid!
They are both horrid.


As for the cold, it does make a slight difference, but as someone else said, comparing -5 to 30 is stretching it way too far. There is no way that (in the absence of wind and/or sunshine) that you can compare -5 to 30. I'd doubt many of you have even experienced -5 in Utah (although there are places where it frequently reaches that low a temperature). I think the thing that many of you are experiencing is more related to sunshine than humidity. Compare the way you feel on an overcast day at 20 degrees to a sunny day at 20 degrees. The "Utah sun" has a profound effect on perceived temperatures. The humidity (although having a profound effect during the summer's high temps) has a very small (negligible) effect on perceived temperatures in winter.

If you don't believe me, look at what the meteorologists do with heat index. It isn't even computed with respect to humidity in temperatures lower than about 70 or 80 degrees (F) because it's negligible. On the other hand, the sunshine has a profound effect on perceived temps in both summer and winter. It can change the "apparent temperature" up to about 15 degrees.

Here are some calculations I did with typical relative humidity for Madison WI and SLC UT (using the meteorological matrix formula [4x4 matrix can also be multiplied out to a 16 term polynomial]):

---------temp: 90 --------- temp: 20
SLC July RH: 22% ----- Jan RH: 69%
Mad July RH: 70% ------Jan RH: 60%
Heat Index: SLC 87 deg --- SLC: 20 deg
Heat Index: Mad 106 deg --- Mad: 20 deg

As you can see, a big change in summertime temps and no change for wintertime temps. I'll lay odds that what you are feeling is the effect of our winter sunshine (and/or wind). To further my point, notice that the average relative humidity (and dewpoints) of SLC is actually higher than Madison. The concept of "humidity" is quite different in cold temps as compared to warm and hot temps, and plays a much smaller roll in perceived temps. Sunshine and wind are far, far more important in winter "heat index."

You have to understand what relative humidity and heat index actually does and how the air "holds" (the quotation marks are there because "holding" is a bit of a misconception) the H2O. The cooler the temperatures get, the less H2O the air can "hold." When you get down to, say, 20 degrees, the air can "hold" far less water than it can at 90 degrees. So when you get a relative humidity reading at 20 degrees, it's a percentage of a much smaller "100%" than at a temp of 90 degrees. So, when you see that SLC is at 69% RH in January, that's 69% of an already small percent of summertime RH maximum. The point is, at low winter temps (as compared to summer temps), there is much smaller variation from a "humid climate" to a "dry climate." The playing field is leveled (so to speak).

Also, remember that the "heat index" as computed by the weather people is based on our body's ability to perspire and effectively cool itself (which lessens in high-temp, high-humidity situations). That's not even an issue with cold temps.

Last edited by ChrisC; 02-27-2011 at 01:21 PM.. Reason: technical inaccuracy
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Old 02-27-2011, 01:46 PM
 
1,054 posts, read 1,835,658 times
Reputation: 699
Quote:
Originally Posted by ChrisC View Post
They are both horrid.


As for the cold, it does make a slight difference, but as someone else said, comparing -5 to 30 is stretching it way too far. There is no way that (in the absence of wind and/or sunshine) that you can compare -5 to 30. I'd doubt many of you have even experienced -5 in Utah (although there are places where it frequently reaches that low a temperature). I think the thing that many of you are experiencing is more related to sunshine than humidity. Compare the way you feel on an overcast day at 20 degrees to a sunny day at 20 degrees. The "Utah sun" has a profound effect on perceived temperatures. The humidity (although having a profound effect during the summer's high temps) has a very small (negligible) effect on perceived temperatures in winter.

If you don't believe me, look at what the meteorologists do with heat index. It isn't even computed with respect to humidity in temperatures lower than about 70 or 80 degrees (F) because it's negligible. On the other hand, the sunshine has a profound effect on perceived temps in both summer and winter. It can change the "apparent temperature" up to about 15 degrees.

Here are some calculations I did with typical relative humidity for Madison WI and SLC UT (using the meteorological matrix formula [4x4 matrix can also be multiplied out to a 16 term polynomial]):

---------temp: 90 --------- temp: 20
SLC July RH: 22% ----- Jan RH: 69%
Mad July RH: 70% ------Jan RH: 60%
Heat Index: SLC 87 deg --- SLC: 20 deg
Heat Index: Mad 106 deg --- Mad: 20 deg

As you can see, a big change in summertime temps and no change for wintertime temps. I'll lay odds that what you are feeling is the effect of our winter sunshine (and/or wind). To further my point, notice that the average relative humidity (and dewpoints) of SLC is actually higher than Madison. The concept of "humidity" is quite different in cold temps as compared to warm and hot temps, and plays a much smaller roll in perceived temps. Sunshine and wind are far, far more important in winter "heat index."

You have to understand what relative humidity and heat index actually does and how the air "holds" (the quotation marks are there because "holding" is a bit of a misconception) the H2O. The cooler the temperatures get, the less H2O the air can "hold." When you get down to, say, 20 degrees, the air can "hold" far less water than it can at 90 degrees. So when you get a relative humidity reading at 20 degrees, it's a percentage of a much smaller "100%" than at a temp of 90 degrees. So, when you see that SLC is at 69% RH in January, that's 69% of an already small percent of summertime RH maximum. The point is, at low winter temps (as compared to summer temps), there is much smaller variation from a "humid climate" to a "dry climate." The playing field is leveled (so to speak).

Also, remember that the "heat index" as computed by the weather people is based on our body's ability to perspire and effectively cool itself (which lessens in high-temp, high-humidity situations). That's not even an issue with cold temps.
Awesome breakdown. Humidity (affecting persperation) should not be considered for anything other than heat. Sunshine and wind are two that make more of a difference.
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Old 02-27-2011, 02:29 PM
 
Location: Salt Lake City
21,971 posts, read 22,145,963 times
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Quote:
Originally Posted by ChrisC View Post
They are both horrid.
LOL! The thing is, Chris, to you, 60 degrees is verging on too hot and to me, it's verging on too cold!
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Old 02-27-2011, 04:13 PM
 
Location: east millcreek
835 posts, read 1,793,677 times
Reputation: 529
Actually, humid air is a slightly better conducter of heat than dry air-therefore, your body will lose slightly more heat in a cold environment with higher humidities. However, I was probably
remembering my terrible childhood outdoors on the plains of Kansas during occasional winter fogs
(liquid and ice). I'm pretty sure that under these conditions the body looses much more heat than
when it is dry. Chris, are you sure that the equations you used above are applicable for cold conditions??? I do agree with you that the "sunshine factor" is a big player.
What it boils down to-pun intended-for me, is I will take a 5 below day here in Utah over a 30 degree day in Kansas.
Next week, maybe we can talk about Wind Chill, and how it is calculated while you are naked, and in the shade....?

Last edited by skibarbie; 02-27-2011 at 04:49 PM.. Reason: spelling
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Old 02-27-2011, 04:47 PM
 
Location: South Jordan, Utah
6,802 posts, read 7,372,937 times
Reputation: 2960
Quote:
Originally Posted by skibarbie View Post
Next week, maybe we can talk about Wind Chill, and how "they" it is calculated while you are naked, and in the shade....?
Make sure the pictures of this experiment get posted in the Pictures of Utah thread.
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Old 02-27-2011, 05:00 PM
 
Location: Salt Lake City
21,971 posts, read 22,145,963 times
Reputation: 10709
Quote:
Originally Posted by hilgi View Post
Make sure the pictures of this experiment get posted in the Pictures of Utah thread.
Hilgi! Shame on you!
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