Thursday, August 27, 2009

But It's A Dry Heat


This morning's strange stair-step sounding from Tucson is above - too dry realtive to GPS, but it illustrates the current dismal convective situation well.
Precipitable water over southern Arizona is right around 3/4" with depoints 30s to low 50s. No rainfall yesterday in ALERT network. The northern boundary of the moist, subtropical air has again been pushed down to around Guaymas. There was strong MCS activity last night in Mexico east of the southern reaches of the Gulf of California. This kind of activity will probably occur further north each of the next couple of nights.
The 500 mb anticyclone is centered over southwestern Utah this morning. There is warm, dry air in the southern and western quadrants of the high and cool, dry air in the northern and eastern quadrants of the high. Some cool advection over southeastern Arizona is likely, and the cool middle-level air, combined with a a hot boundary layer will produced isolated mountain storms today, increasing tomorrow, especially as more moist low-level air works westward in New Mexico. So it looks like several days of increased moisture recycling by mountain and, hopefully, northern Sonora storms. Mostly dry downburst conditions prevailing tomorrow. Saturday - too early to tell what the desert boundary layer might look like.
By Sunday afternoon and Monday, both the NAM and ECMWF forecast a disturbance or two moving northward from the subtropics and a likely return of moist low-levels to at least the southern portions of Arizona. Meanwhile, convective weather here at house could happen tomorrow, but mainly with wind and dust yet again.

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