BajaNomad

Comfort Zone

comitan - 6-14-2009 at 02:32 PM

Interesting info on Relative Humidity and Dew Point. As it affects your Comfort Zone.

http://www.theweatherprediction.com/habyhints/190/

BajaBruno - 6-14-2009 at 03:58 PM

I wish I could say, having read that article, that I now have a good understanding of humidity vs dewpoint, but alas, I am still as confused as I ever was.

But, thanks for trying, Comitan. :o

comitan - 6-14-2009 at 04:06 PM

What I think I understand is that Dewpoint is a better basis than just Relative Humidity for a persons comfort level. A Dewpoint over 65F or 21C is very uncomfortable.

There is a comfort zone ----

beercan - 6-14-2009 at 04:14 PM

As a pilot I learned that the base of the clouds is the dew point .
On many summer bumpy days the bases are generally at 14, 16,000 feet AMSL. Get above that and the ride suddenly smooths out.

Ken Bondy - 6-14-2009 at 04:18 PM

Wiley, don't take it personally :) but that's probably the worst explanation of dewpoint and RH I have ever read. He doesn't explain what either one is, and the typo in the phrase "closeness the air is the saturation" will probably confuse almost everyone who reads it. Even if he got the words right "closeness the air is TO saturation" it is very awkward and doesn't fully explain the physics. There's no easy way to describe these terms other than directly: relative humidity is a measure of how much water vapor the air contains as a function of how much water it could contain at any particular temperature. At 50% RH the air contains half the water vapor it could contain at that temperature. How much water vapor the air can contain is a function of temperature. The warmer the air, the more water vapor it can hold. Dewpoint is the temperature at which the air becomes fully saturated (RH=100%). Cooled to the dewpoint, the air can't hold any more water vapor and the water vapor begins to condense (clouds form, windows fog up, etc.) On a cold day outside, warm air inside is cooled next to a window (which is cold). If the temperature of the air adjacent to the window reaches the dewpoint, it can't hold any more water vapor and the water vapor condenses into water droplets on the inside of the window. The same thing is happening on the outside of my scotch glass right now, which is probably why I didn't do a better job of explaining this :)

++Ken++

comitan - 6-14-2009 at 04:30 PM

Ken

Would it still be safe to assume that a Dewpoint over 65F be very uncomfortable and would it be a better way to to understand your comfort zone than just humidity because most weather sites give both? I'm trying to understand this because myself and everyone I know bases Comfort Zone on Relative Humidity.

BajaBruno - 6-14-2009 at 04:32 PM

Well, I see that although it hit 102 in La Paz, the dewpoint dropped to 60 (from 66) as the temps rose. So, semi-comfortable I guess, despite the temps. I'll look at the airport weather report with new enlightenment now... :spingrin:

http://weather.noaa.gov/weather/current/MMLP.html

Ken Bondy - 6-14-2009 at 04:56 PM

Quote:
Originally posted by comitan
Ken

Would it still be safe to assume that a Dewpoint over 65F be very uncomfortable and would it be a better way to to understand your comfort zone than just humidity because most weather sites give both? I'm trying to understand this because myself and everyone I know bases Comfort Zone on Relative Humidity.


Wiley

I think it is safe to say that the higher the dewpoint, the muggier and stickier it would feel. Dewpoint is the temperature at which the air is 100% saturated. So when RH reaches 100%, the air temperature IS the dewpoint. If the dewpoint is high, that probably relates to hot muggy air. But I think the same thing can be said about RH, which, like you say, is why most everybody bases comfort on RH. But RH and dewpoint are intimately related. Now the outside of my scotch glass is completely wet, so I better stop talking. But I am very comfortable :)

++Ken++

Dew Point

bonanza bucko - 6-14-2009 at 04:58 PM

I fly airplanes. If you are heading for a destination where the temperature is lowering to the dew point you need to expect fog and an instrument approach to the airport or a flight to an alternate airport.

If you take off early in the day and have a destination near the coast or a large body of water like the Great Lakes where the sun is going down and the temperature is falling to a dew point made higher by the water near by you had better have some extra fuel on board so you can "hold" for a while or go to the alternate.

Even when the temperature doesn't fall to the dew point there is always the heavy chance for haze and a hard to see horizon....that's what killed John Kennedy, Jr. He took off late in the day and wasn't ready for a hazy and dark horizon...and not experienced enough to let his auto pilot or artificial horizon keep him right side up....without that horizon your eyes and inner ear will tell you that you are straight and level when you are in a spiral ...to the left usually.

The dew point is a big deal....lots more interesting than humidity. The temperature and dew spread is like a measure of money in the bank.....makes you sweat if it's small.

Terry28 - 6-14-2009 at 09:23 PM

Ken, I teach weather as part of a wildland firefighting class...Your explanation of dewpoint is outstanding and should be understood by most if not all..........If I had a hat on I would take it off to you..