Wednesday, August 21, 2013

Tough Forecast For Today


This morning heavy cloud cover persists over much of Arizona, with a few light showers also occurring. The cloudiness makes interpreting the model forecasts difficult. For example, both versions of the Univ. of Arizona WRF model have not forecast nearly enough cloud cover for this time (approx. 8 am MST - see above satellite image). So the models have way too much heating forecast this morning, and I'm not showing any out put from the forecasts.

The large-scale pattern remains complicated - below is 500 mb analysis from NAM for 12 UTC this morning. There is an inverted trough from south of Baja northeast toward the lower Rio Grande Valley, but it appears there is a weaker inverted trough over southeastern Arizona. The anticyclone is centered near the Four Corners, and the closed low continues to malinger off the central California coast.


This morning's sounding plot for Tucson (below) shows a classic "onion" sounding with dry low-levels beneath deep, saturated layers associated with the clouds and showers. So it's a bit of a contaminated sounding and it's hard to know what the afternoon will bring. The CAPE appears to be down considerably from yesterday, while the current vertical wind profile has strengthened and shows distinct easterly steering winds. So a mixed bag of pros and cons. We'll watch to see what afternoon brings.


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