Tuesday, October 20, 2015

500 mb Low Forecast To Move Right Over Tucson

Very strong thunderstorm situation setting up for parts of Arizona, as the 500 mb short wave closes off to our west this morning. Above is 500 mb analysis for 12 UTC this morning from NCAR RAL - note the very cold temperatures with this feature. Below is NAM 12 UTC analysis. The leading, weak vorticity maximum is moving rapidly northward and there is widespread morning thunderstorm activity occurring ahead of it. The strong max to the west will be associated with the closed low and is forecast to come directly overhead by tomorrow morning.

The morning skewT for TWC (from SPC - above) is again very unstable and the hodograph (below) is quite impressive for Arizona - somewhat of a classical severe storm situation, but well west of the Great Plains. The morning outlook from SPC (second below) indicates an unusually large area, for the Southwest, with a slight risk of severe thunderstorms.

The WRF models at 06 UTC from Atmo don't forecast storms affecting us until well after dark. The radar forecast above is from the NAM version and is valid at 5:00 am MST tomorrow morning. Not obvious to me that flow over the mountains won't get storms going sooner.The WRF rainfall forecast (below, valid through midnight tomorrow night) indicates heaviest Arizona rains to our north and northwest, but also forecasts a huge event for New Mexico.

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