Extreme Dewpoint ob.! Crazy inversion!

[Austin Ivey]

I thought everyone would be interested to see the disparate observations in Los Alamos this morning .

The ob at 7,400 feet reads:
Air temp= 14.5F
Dewpoint= -8.0F

However, the ob at 10,360 feet reads:
Air temp= 24.1F
Dewpoint= -51.9F !

A spread of ~75F!!

I think that is the largest temp/dewpoint spread I have ever seen observed. The lab frequently calibrates all weather equipment so I do trust this ob.

See http://www.weather.lanl.gov/
for all the obs (PJMT is the one >10,000feet)

 

[B Ozanne]

Seems awfully dry, only .16%RH. I don't doubt that it is very dry there, but measuring the dew point is not an easy think to do. The best dewpoint measurements come from chilled mirrors or sling psychrometers...neither of which was on that radiosonde.

Conclusion: yes, it was likely very dry at that altitude, but be wary of dewpoint measurements.

Edit: oops, that ob is from a land based station, kills my radiosonde idea.

 

[Mike Peregrine]

The temperature inversion is what's interesting to me ... I love the crazy inversions that happen in the mountains. It seems illogical to rise in altitude and temperature at the same time, but it happens a lot in the Rockies in winter. I visited friends in Bozeman, Montana one time in February, which sits in a valley between ranges ... it was bitterly cold in town, but when we went up in altitude into Yellowstone, the temperature rose as well and it was totally comfortable once we were in the mountains ... there was like 8 feet of snow and we weren't wearing our jackets. Steam was rising out of every vent and stream, which added to the 'other-worldly' feel. What a place -

 

[Mike Umscheid]

The temperature inversion is what's interesting to me ... I love the crazy inversions that happen in the mountains. It seems illogical to rise in altitude and temperature at the same time, but it happens a lot in the Rockies in winter. I visited friends in Bozeman, Montana one time in February, which sits in a valley between ranges ... it was bitterly cold in town, but when we went up in altitude into Yellowstone, the temperature rose as well and it was totally comfortable once we were in the mountains ... there was like 8 feet of snow and we weren't wearing our jackets. Steam was rising out of every vent and stream, which added to the 'other-worldly' feel. What a place -

Shallow arctic airmasses are amazing. In fact, the record for the greatest temperature swing was recorded in the Black Hills I do believe of like 50 degrees in 2 minutes. Of course, these airmasses develop over the flat, low prairies of Canada just east of the Rockies and spill south in the right patterns with little zonal component deep tropospheric flow (downslope). You get a good one of these that's like 4500 to 5000 feet deep it could be like -10F at Rapid City and in the mid 30s in the higher elevations of the Black Hills, like near Custer. And "waves" of the cold air (much like waves on an ocean surface) atop the arctic layer can slam ya if you are right at the interface...and, hence, the potential for a ridiculous variation in temperature over the span of just a couple minutes.. or less!

Mike U

 

[Jeff Snyder]

This isn't entirely related to shallow cold airmasses, but here's a good example of the effects of winds on temperatures... Notice how areas that have calm winds are as much as 10-15F colder than other locales (even those 15-25 miles away) that even have 5mph winds, particularly in southeastern and central Oklahoma... You can see how easy it is to bust a low temp forecast, as an awful lot can depend upon whether winds go calm or stay light. In this case, there is another compication -- snow depth (as in some vs. none).