Thursday, November 30, 2017

Dreary But Mild Morning

It's a dreary morning with thick, high clouds (as was yesterday) above is 0730 am MST visible satellite image and just below is the 0800 am view of the Catalinas from campus. Because of the thick clouds, low temperatures were considerably milder than recent mornings: 55 F today vs yesterday's 44 F here at house (airport was 9 F warmer this morning). Second below shows the "official" TUS observations this morning - i.e., in the record it is clear. I show this mainly to emphasize some of the serious problems with the NWS automated surface observing system (ASOS).

I took a look the local KEMX radar data (at College of DuPage weather page - link to right), where access to various WSR-88D products is considerably better than at TUS website. Shown above is the fourth tilt reflectivity (3.5 degrees) that indicates a fairly uniform cloud deck around much of the radar. Comparing the echo with the range vs height diagram below indicates that the clouds are based around 15,000 ft with tops up around 20,000 ft - these heights are above the radar which is a bit above 5,000 ft MSL (indicating clouds based at a bit above 20,000 ft MSL). Interestingly, this is one of those times when the 88D is a better cloud observing system than is the ASOS at the airport.

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