Drying Out Continues

Storms mostly on mountains yesterday (Tuesday August 25, 2009) but with a few drifting toward the south out over lower elevations. Thundered here at the house around 4:30 pm and again around 7:00 pm, but we only had some spits of rain. The storm shown above was west of the house at sunset and it was very active with frequent incloud lightning, but I didn't see any CGs. DM weather forecaster H. Green reported a storm with heavy rain and 1/2" hail at 5:30 pm - he was out at west Ajo Way and Kinney Road. The strongest storm (as indicated by radar) in eastern Pima County was moving south off the Tucson Mountains at that time. Only 10 of the 93 ALERT gauges measured rainfall yesterday.

Dewpoints continue on a downward trend, with 60s hanging on only in southwest Arizona at Yuma and Gila Bend. Precipitable water has fallen to values around three quarters to an inch. The 500 mb anticyclone has shifted south with its center over the central Gulf of California this morning. It will shift north over Southern California and then over southern Nevada during next 36 hours. The steering flow will become very favorable for moving storms toward the low deserts; however, the subtropical low-level air has been pushed down into Mexico again. So we'll be in a down mode with only some mountain storms to east and south until some feature acts on the GoC to push the moist air back north. Right now the only things in sight would be falling pressures over the lower Colorado Basin and MCSs moving out over GoC.

In the longer term the ECMWF keeps the subtropical air to the south through the weekend before bringing some subtropical disturbances north toward the Southwest. So, a not very exciting end to August as things appear now.