Tuesday, December 21, 2010

Pacific Storm Event Advances Toward Southern Arizona



The unusual Pacific moisture plume (most recent PW image top from CIMSS) has resulted in extremely heavy rains and snows, especially in California. Rainfall totals in the LA Basin this morning are generally from around 4 to 8 inches. Snow amounts from the Sierras inland to the Wasatch have been very substantial and with high liquid content.
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The models generally agree that the final short wave of this event will move across Arizona tomorrow and tomorrow night, with highest precipitation amounts in the northwest and the RIM Country and a brush-by down here in the far southeast. The ECMWF is a bit slower and further south than the other models, and has a cutoff present at 500 mb as the system moves into the state. The WRF-GFS run at U of A Atmo this morning predicts a couple of bands of showers, and perhaps a bit of thunder, moving across Arizona at 9 pm tomorrow, Wednesday December 22nd (middle image is the forecast of radar composite reflectivity).
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Precipitation totals (bottom image) for the period from this past midnight through 6 am on Thursday morning are generally less than half an inch in southeast Arizona, except in the Catalinas, where the model again forecasts a very nice precip event. So we will now watch to see what actually happens.

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