Big Dry Out - How long Will It Continue?

Big Dry Out – How Long Will It Continue?

Today is the third day of the big dry out. No precipitation in the ALERT network on Sunday and Monday. The big question is whether or not there will be anymore precipitation in the local area before the end of July. The NAM indicates NOT.

Last night there were two large MCSs in Mexico – one peaked in northern Mexico, south of the New Mexico boot heel around 0800Z and the other is still active (see image for 1330Z above) over the southern Gulf of California. Some outflow from the northern MCS has pushed into far southeast Arizona, as indicated by the surface observations at Douglas and Rucker RAWS.

Precipitable water is down to less than an inch in southwest Arizona and ranges around an inch to an inch and a quarter over the rest of southern Arizona. In contrast, the Guaymas sounding indicates 2.1 inches this morning, so there is a very large gradient across northern Mexico.

Although the 500 mb anticyclone remains in an unfavorable location for storms, there are several things of interest in the data this morning. Surface pressures have been falling considerably over the lower Colorado River Basin – 24 hour falls of 2 to 3.5 mb from Tucson to Kingman and southwest of that line. There is a large pressure gradient up the Gulf of California and the trend should be for the higher moisture to try to come back to the north. A loop of the satellite water vapor imagery seems to indicate that this is happening.

The TWC morning sounding remains too dry, but only by about 0.3” this morning. The bad data in the lower part of the RRS soundings makes forecasting convection difficult (as per comments on last evening’s post). But, the Phoenix and Tucson soundings appear to indicate that storms are possible over higher elevations of eastern Arizona and along the borderlands this afternoon and evening. Will be keeping a close eye on the very unstable, subtropical air mass over northern and northwestern Mexico.