Wednesday, July 02, 2014

Morning Upper-Air Data On 2 July 2014

Mike Leuthold has already done a discussion of the early WRF forecasts (from Maine no less!) and I will just take a look at some observations from this morning. The 500 mb chart (analysis and plot from Univ. of Wyoming weather page) shown above indicates several things: the 500 mb anticyclone has established itself near the Four Corners with east-northeast winds over southern Arizona and northern Sonora; any inverted troughs at 500 mb are weak and not well defined; and most importantly, temperatures at 500 mb are very cool (-8 to -9 C) over all of Arizona and New Mexico.

The TUS morning sounding (skew-T below from SPC) remains somewhat dry, with a deep, old boundary layer (BL) extending up to 600 mb (PW is a bit less than an inch). The SPC analyses indicate no CAPE, but I estimate some small amount of afternoon CAPE above 500 mb. This sounding would be supportive of downbursts.

The sounding from El Paso (above) is more moist and has a distinct outflow layer at surface related to the MCS shown in previous post.

Sounding below is for Empalme, Mexico (and is also from the Wyoming site - SPC and NCAR RAL are still not displaying the Empalme soundings). At Empalme there is a cool and moist surface layer with no CAPE. There is no distinct GoC surge signal present, but PW is approaching 2 inches. Inland over the foothills this air mass will have substantial CAPE this afternoon.

I have looked at the 12 UTC WRF-NAM forecasts for this afternoon and evening and they are much different than the early runs. The latest from WRF forecasts much reduced convection and less wind over Pima and Pinal Counties. The difference seems due to considerably less PW this afternoon in the latest model forecasts.

However, I think that this is probably a case where the early forecast may prove better than the 12 UTC forecast - there have been a number of such cases lately. I would rate the chances here at the house as quite good for outflows, winds, and dust late this afternoon. However, chances for rain in the gauge here at house are very low today.

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