Wednesday, September 12, 2012

Quick Hitting Event Yesterday

Yesterday's storms and rains moved through the Tucson area during the early afternoon, and produced rainfall that was not as heavy as predicted. Here at the house the event was over by 2 pm MST, as it was across most of the Tucson metro area. I didn't hear thunder, but that doesn't mean there was none - rainfall here was 0.23". This morning 85 of the 93 ALERT stations reported rain during the past 24-hours; however, amounts were mostly light, especially compared to last few days. Only 5 stations had over half an inch and I found no reports that reached an inch anywhere in southeast Arizona. So, a widespread event but little in the way of heavy rains. Strongest storms on radar yesterday afternoon were to the east of Tucson, especially around the Benson area.

This morning there is lingering moisture in the lower troposphere and the morning sounding (TUS skewT above from SPC) indicates some CAPE mostly below 500 mb. Thus, buildups most likely on the mountains. The early WRF shuts everything down, except on the highest peaks. The WRF-GFS forecast skewT for Tucson (below) at 3 pm this afternoon indicates some surface-based CAPE, but also indicates that the dry air reaches down nearly to 700 mb. So, even though the trailing vorticity maximum with the weak 500-mb short-wave sinks across Arizona this afternoon, it will have little impact at lower elevations.

In the longer term, the weak short-wave leaves some circulation behind into the weekend, with perhaps some isolated showers lingering also. By Saturday, the morning NAM forecast indicates a substantial disturbance moving northward up Baja and the GoC (above graphic is 700 mb forecast valid at 5 pm MST next Saturday afternoon (September 15th).  The Baja disturbance is associated with TD Eleven-e (see NHC forecast below), which is forecast to become a TS but remain fairly far to the west. So, there are still some weather features of interest to watch through the weekend

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