Friday, May 06, 2016

NWS Operational Models This Morning

This morning's 12 UTC NAM analysis of the 500 mb level shows what a complex system will be crossing the Southwest during the next three days. Note that the NAM analysis indicates 6 vorticity maxima (indicated by the "Xs") circulating around the closed low, that is centered near Los Angeles.

Below are two NAM forecasts for 500 mb valid at 24-hours (12 UTC on Saturday, directly below) and at 48-hours (12 UTC on Sunday, second below). The forecasts indicate two distinct vorticity maxima will cross southeastern Arizona during this period.

As for the 06 UTC GEFS plumes for QPF, the forecasts for TUS (the airport, above) continue to be all over the place. Two things of note - the amounts at TUS  are very small and the operational member is the driest of the forecasts (as it also is out at Yuma). However, only two hours up I-10, the GEFS forecasts are quite different (below) - 100 % of the 21 members forecast measurable precipitation at Sky Harbor with amounts ranging from 1/10 to 6/10 of an inch. The timing is also much more distinct, with the Phoenix area main event forecast for tonight into Saturday morning.

The WRF forecasts also continue to indicate that the most significant showers and thunderstorms will occur to our west and north. There's not much to do now except to observe how all this evolves. But what a difference a few miles makes - assuming the models verify well.

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