Things Looking Up - August 4, 2012

We have been away for 36 hours, and I've just gotten my first look at any weather info since early Thursday morning. We sneaked away to the cool, Pacific air in San Diego - which was a very nice change.

This morning the Tucson upper-air sounding (above from SPC) remains dry and stable, with an old boundary layer aloft to about 600 mb. Winds aloft are quite weak, except in the upper-troposphere. The morning values of PW (below is early WRF-GFS am forecast of PW valid 6 am today) are low across most of southern Arizona with values right around an inch, but a bit higher in Cochise County.

The early run of Atmo's high-resolution WRF-GFS model (above valid 4 pm MST this afternoon) forecasts of composite radar echoes indicate only activity today remaining to the east, primarily in Cochise County.

However, there are several interesting features that are about to come into play. The NAM 500 mb analysis at 12 UTC this morning shows a strong short wave over the Northern Plains. There is a strong cold front with this feature that is pushing down the Front Range currently - it may come into play here in southeastern Arizona tomorrow night.

The old short-wave trough that's hung up over the lower Colorado River Basin has been picked up by another that's swinging around the trough west of California - this feature will be moving slowly north across California, essentially out of play. But, the analysis indicates there's an inverted trough over the mouth of the Gulf of California (GoC - the data plots this morning don't verify nor negate this analysis). So it's important to watch to see if this feature is actually down there. The current cloud images and water vapor loop tend to support its presence. There was also a large MCS last night, inland along the southern end of GoC.

The new NAM 500 mb forecast this morning moves the IT northwestward along Baja (24-hour 500 mb forecast valid 12 UTC 5 Aug. is shown below). Thus, it appears that this feature, in conjunction with any MCS activity in southern Sonora and Sinaloa tonight, will push mT air up the GoC and into Arizona by tomorrow morning. So this is an upturn. There may be enough storm activity in Cochise County and northeastern Arizona this evening and early tonight to push outflows across the Tucson area, which would also be positive. So, even though it looks like another hot day here, there are a number of interesting features to watch.

Finally, the Atlantic has become active again with two named tropical storms - Ernesto (forecast to eventually move into the GoM as a hurricane), and Florence.