Monday, August 11, 2014

Bit More CAPE Today

Considerably less thunderstorm activity yesterday in comparison to Saturday (CG flashes above through 11 pm last night - compare to the CG  plot in post below). Several showers developed over metro Tucson but thunderstorms remained on the Catalina and higher elevation areas. Here at the house there was a shower after dark and we received 0.07" of rain. Across the ALERT network 22 sites had light rainfall and there were two stations in the Catalinas with more than a quarter of an inch.

The morning skewT plot of TUS sounding (below) indicates a bit more PW and CAPE for today. A decent wind profile for organized thunderstorm systems continues, with steering flow today from east to southeast. So the situation is a bit more favorable for storms in the metro area; however, surface winds will be from the east, which always complicates the situation. 

The early WRF-GFS run went immediately awry, with forecasts of significant early morning storms. The early WRF-NAM forecast of composite radar echoes at 5 pm MST this afternoon (above) has storms mostly from south to southwest of Tucson along the Borderlands, but does develop an area of storms just west of Tucson metro area.

The model forecasts a significant surge of low-level moisture into the western portions of Arizona tomorrow in response to a weak short wave moving northward up the GoC. The PW forecast below is valid at 1 pm tomorrow afternoon.

The current NAM forecasts from 12 UTC this morning are much wetter than the early WRF. The 500 mb forecast above (valid at 12 UTC tomorrow morning) indicates the weak short wave about half way up the GoC. This feature is a piece of the inverted trough that moved across Mexico the last several days and the model forecasts indicate that it will be associated with significant thunderstorms tomorrow. The current NAM forecast of total rainfall through midnight tomorrow is shown below.

As always during the summer, the storm events today and tonight will play a big role in what actually transpires tomorrow.

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