Author Topic: Wet Cold vs Dry Cold  (Read 6408 times)

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Offline bcescape

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Wet Cold vs Dry Cold
« on: January 31, 2012, 09:26:55 PM »
Was hoping to tap into the expertise here.

I believe that where I live (pacific north north west) that a wet cold is colder because a) there is no sun out to warm you, b) windchill - it is always windy where I am. 

Was curious why many of us feel a 'wet cold' is colder than a 'dry cold'.

Offline Scalphunter

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Re: Wet Cold vs Dry Cold
« Reply #1 on: January 31, 2012, 09:34:34 PM »
Has to do with moisture content in the air. This is very noticable when in Seward at 20 below and then go to Fairbanks at 20 below. This is with all else being equal.


John

Offline GVaughn

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Re: Wet Cold vs Dry Cold
« Reply #2 on: February 01, 2012, 12:28:42 AM »
Having moved to Colorado 24 years ago from Califoenia (sea level to 5400 deet elevation), the difference between a given temp at seal level and 5400 feet was dramatic.  40 degrees at sea level can be bone chilling wjile 40 degrees here is quite tolerable.  The common explanation is that we have a dry cold and sea level has higher humidity and feels colder.  I am sure there is some trutg in that velief yet we have jigh humidity almost every dat and the cold stillfeels warmer.  At 5400 feet the air is much less dense and does not conduct heat as well.   We feek cold when heat is transferred away from our body.

I believe the real explanation is a matter of physics and the principles of heat conduction. Generally denser materials conduct heat (and cold) better than less dense materials.  The higher the barometric pressure, the denser the air and the better it conducts heat.  Adding moisture to the air (gumidity) increases the density of the air and conducts heat better than it does without the moisture.  This principal is easily observed; place a piece of bare wood and a china plate nest to each other in the fridge, wait an hour of so hen touch each ine - the wood will feel warmer than the plate.  The plate and the wood will be the same temp but because the plate conducts heat better it feels colder. The efect can be more dramatic with steel and a dry sponge. 

Probably did not explain this well but I know what I mean  ;).

Offline LFWX

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Re: Wet Cold vs Dry Cold
« Reply #3 on: February 02, 2012, 01:43:45 AM »
I believe every pilot (and race car driver) would disagree with the statement that "Adding moisture to the air (humidity) increases the density of the air".
Adding moisture to air decreases the density. It's the reason a dry line can be the focus of thunderstorms.
http://www.engineeringtoolbox.com/density-air-d_680.html
http://www.usatoday.com/weather/wdensity.htm
VIDEO: http://www.youtube.com/watch?v=KiyMlnAC098

Around my area a dry 32F day feels much colder than a snowy 32F day.
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Offline xykotik

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Re: Wet Cold vs Dry Cold
« Reply #4 on: February 02, 2012, 11:08:05 AM »


Facit solem suum oriri super bonos et malos et pluit super iustos et iniustos.

Springtime in Seattle...  March comes in like a lion and out like a wet lion.

Offline WeatherHost

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Re: Wet Cold vs Dry Cold
« Reply #5 on: February 02, 2012, 11:11:39 AM »
50, rainy/cloudy and windy will put a chill in me faster than 35, sunny/dry and calm.


Offline LFWX

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Re: Wet Cold vs Dry Cold
« Reply #6 on: February 02, 2012, 06:07:16 PM »
50, rainy/cloudy and windy will put a chill in me faster than 35, sunny/dry and calm.



True, add a little wind and all bets are off.
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Offline bcescape

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Re: Wet Cold vs Dry Cold
« Reply #7 on: February 06, 2012, 02:38:19 AM »
It seems accuweather calculates this with their Real Feel algorithm. I just learned about this today, was surprised how much colder their values were compared to windchill:

"The Real Feel temperature is a patented product developed by several of us at AccuWeather.  I am not familer with the general explanation.  But, I can tell you that we use the following variables to calculate the value:
Temperature
Dew point
wind speed
Sun angle for a given date
Solar intensity as defined from the solar index
percent of sky cover
precipitation and intensity
altitude

Each variable carries a weight for a given date and weather situation.  These weights are determined through various factors.  I cannot give you the formula since this is patented.   "
source Expert: Dan Kottlowski
http://en.allexperts.com/q/Accuweather-2546/Real-Feel-Temperature.htm

Any third party software get this fancy?


Offline xykotik

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Re: Wet Cold vs Dry Cold
« Reply #8 on: February 06, 2012, 10:16:44 AM »
"...The Real Feel temperature is a patented product developed by several of us at AccuWeather.  I am not familer with the general explanation.  But, I can tell you that we use the following variables to calculate the value:
Temperature
Dew point
wind speed
Sun angle for a given date
Solar intensity as defined from the solar index
percent of sky cover
precipitation and intensity
altitude

Each variable carries a weight for a given date and weather situation.  These weights are determined through various factors.  I cannot give you the formula since this is patented.   "
source Expert: Dan Kottlowski
http://en.allexperts.com/q/Accuweather-2546/Real-Feel-Temperature.htm

This guy is an "all-expert?"  Whether or not the "real Feel" system works, he either is not really associated with the accuwx mathemagicians, or at best doesn't know what he is talking about.  "Deleveloped by several of US at accuweather" but doesn't know how to explain it.  "Patented, so I can't tell you the formula."  Well, if it's patented, that won't take long to find.  Trade secrets are something different, that anyone with their name on a patent (as he implies) would know, hence this guy is a faker/poser. Seems like he should have given a link to his patented secret product that is so useful so they could make a buck.  Does he work for accuweather?  Shouldn't he at least be able to explain it?  Therefore, how can I trust him as an "expert?"

Sorry, I sound like a jerk, but there is a big difference between "In my humble opionion" or "as far as I know" and "I am all-expert and patented the method, but I don't know the general explanation."  Drives me nuts!


Facit solem suum oriri super bonos et malos et pluit super iustos et iniustos.

Springtime in Seattle...  March comes in like a lion and out like a wet lion.

Offline LFWX

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Re: Wet Cold vs Dry Cold
« Reply #9 on: February 06, 2012, 02:57:16 PM »
"...The Real Feel temperature is a patented product developed by several of us at AccuWeather.  I am not familer with the general explanation.  But, I can tell you that we use the following variables to calculate the value:
Temperature
Dew point
wind speed
Sun angle for a given date
Solar intensity as defined from the solar index
percent of sky cover
precipitation and intensity
altitude

Each variable carries a weight for a given date and weather situation.  These weights are determined through various factors.  I cannot give you the formula since this is patented.   "
source Expert: Dan Kottlowski
http://en.allexperts.com/q/Accuweather-2546/Real-Feel-Temperature.htm

This guy is an "all-expert?"  Whether or not the "real Feel" system works, he either is not really associated with the accuwx mathemagicians, or at best doesn't know what he is talking about.  "Deleveloped by several of US at accuweather" but doesn't know how to explain it.  "Patented, so I can't tell you the formula."  Well, if it's patented, that won't take long to find.  Trade secrets are something different, that anyone with their name on a patent (as he implies) would know, hence this guy is a faker/poser. Seems like he should have given a link to his patented secret product that is so useful so they could make a buck.  Does he work for accuweather?  Shouldn't he at least be able to explain it?  Therefore, how can I trust him as an "expert?"

Sorry, I sound like a jerk, but there is a big difference between "In my humble opionion" or "as far as I know" and "I am all-expert and patented the method, but I don't know the general explanation."  Drives me nuts!
Perhaps he misspoke "patented" for "trade secret"?
Perhaps he didn't personally help develop the "Real Feel" and the "us" was referring to all the employees at AccuWeather as a whole?
http://www.linkedin.com/pub/dan-kottlowski/26/9a3/490
http://thewatchers.adorraeli.com/tag/dan-kottlowski/
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Offline xykotik

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Re: Wet Cold vs Dry Cold
« Reply #10 on: February 07, 2012, 07:10:36 AM »
Quote
Perhaps he misspoke "patented" for "trade secret"?
Perhaps he didn't personally help develop the "Real Feel" and the "us" was referring to all the employees at AccuWeather as a whole?

Yeah, if so, then I am over-reacting to his self-puffery.  Media-types, I should expect it.

I am currently pursuing my first job change in over 20 years and was very careful to not overinflate or pad my resume, because it is an upper-tier support position in the field.  Even though it is an internal transfer and they have full access to all of my training records, certifications and performance reviews, I've had 5 interviews so far over the past month (make that six) with three different groups of managers and engineers, and they have been very thorough in making sure the candidates are not blowing smoke up their shady parts about their expertise.  So, it's a hot-button for me right now.


Facit solem suum oriri super bonos et malos et pluit super iustos et iniustos.

Springtime in Seattle...  March comes in like a lion and out like a wet lion.

Offline Salty

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Re: Wet Cold vs Dry Cold
« Reply #11 on: February 21, 2012, 11:55:28 AM »
It is indeed a patent:
http://www.google.com/patents?id=woQSAAAAEBAJ&pg=PA8&dq=accuweather+realfeel&hl=en&sa=X&ei=rctDT5qCI8j40gHL3qDyBw&sqi=2&ved=0CDgQ6AEwAg#v=onepage&q&f=false

Don't have time right now to read through all the formulas, but they're apparently all in there.

Offline SLOweather

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Re: Wet Cold vs Dry Cold
« Reply #12 on: February 21, 2012, 01:53:40 PM »
It is indeed a patent:

Oh, is that going to be fun to take apart!

Offline SLOweather

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Re: Wet Cold vs Dry Cold
« Reply #13 on: February 21, 2012, 02:58:51 PM »
I found one error so far... column 5, first full paragraph, "In step 220..." it refers to the second solar intensity parameter as ultra violet energy being measured in hectoJoules/meter. I believe it should be hectoJoules/meter^2 (square meter).

This is interesting.... In researching this, I ran across a US EPA paper regarding calculating an Experimental UV Index.

http://tinyurl.com/7x5rlo8

On page 2, it says that the calculation yields UV values in hectojoules per square meter, which "typically fall into a range between 0-15". That's pretty close to the "unitless" UV output of a Davis Vantage Pro 2 Plus station. The 2011 Davis catalog says it's 0-16, with a 5% (0.8) accuracy.

Offline xykotik

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Re: Wet Cold vs Dry Cold
« Reply #14 on: February 21, 2012, 03:07:29 PM »
It is indeed a patent:

Oh, is that going to be fun to take apart!

I'm glad you're doing it.  I'm one of those engineers that suck at math.  I'm more of an Archemidesian when it comes to calculation.


Facit solem suum oriri super bonos et malos et pluit super iustos et iniustos.

Springtime in Seattle...  March comes in like a lion and out like a wet lion.

Offline SLOweather

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Re: Wet Cold vs Dry Cold
« Reply #15 on: February 21, 2012, 03:34:12 PM »
I'm glad you're doing it.  I'm one of those engineers that suck at math.  I'm more of an Archemidesian when it comes to calculation.

Heh... I was looking up watts and converting them to hectojoules to see if the Davis solar sensor reading would be suitable for substituting in the formulas. The conversion is watts / 100 = hectojoules per second. That added time factor threw me for a minute. Then I remembered that watts = volts x amperes, and that an ampere (or amp) of current is defined as a flow of 1 coulomb (6.241 x 10^18) electrons per second. So, watt already has a time factor embedded in it. OTOH, joule is a unit of work with no time element.

Fun fun!

 

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