Wednesday, August 01, 2018

July Ends With Day Of Total Suppression

July 31st was a day without deep convection (above CG flashes map ends at midnight last night - from Atmo and Vaisala) across southwestern New Mexico and most of Arizona. Thunderstorms were generally confined to the Rim Country and the White and Mogollon Mountains. When I ventured out yesterday afternoon, it was the first day since about the Fourth of July when I could not see a single Cb in any direction. If I'd been in a taller building, or on A Mountain, I probably could have seen storms very far to southwest and far to northeast.

The 500 mb analysis this morning (above from SPC) shows that the anticyclone center has inched eastward and is now over southern Utah. This has let the winds veer some over southern Arizona and get a bit south of east. There does appear to be cooler mid-level temperatures rotating around the anticyclone, which is good. The upper levels appear to be somewhat confluent over eastern Arizona, which is not good.

The morning sounding plot (above from SPC) shows PW back around an inch and a half, with the analysis indicating substantial CAPE. The wind profile is favorable for storms to try to come off mountains into lower elevations. However, the upper level winds from north could bring anvils from storms to north right across metro. Sounding also seems to indicate subsidence in a couple of layers below 500 mb - most significant from 600 to 700 mb. Thus, a very mixed bag of positives and negatives for storms today.

The models that I was able to look at this morning all forecast a return of thunderstorms to mountains and also parts of metro area. The timing ranges from mid to late afternoon in some forecasts, to storms from dark to midnight in others. The forecast skew-T below for TWC (from the 06 UTC WRF-GFS) is valid at 5:00 pm MST this afternoon. The forecast continues to indicate decent CAPE and little change from morning wind profile, but with dry air aloft from 400 to 600 mb. This sounding indicates to me that storms would need considerable outflow help to get into lower elevations. We start August still  watching and hoping for rain. 

I'll post a July summary a bit later today.

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