Hot And Dry But ........

The heat is back with the high yesterday at TUS hitting 105 F. This heat helping build the middle-level anticyclone northward, which will allow some moisture return for the rest of the week. Yesterday there was a brief increase in moisture from the southeast and some afternoon storms developed on the Rincons and east portions of the Catalinas. Four ALERT stations in those areas measured small amounts of rain before the storms moved off to the northeast.

Nocturnal and early morning storm activity over the Gulf of California has shifted northward today (Tuesday August 13th). Water vapor image at 5 am MST (above) shows moderate MCS heading toward the central GoC. Lightning strikes for 12-hours ending also at 5 am (below) shows a swath of dense CG activity beginning near the Continental Divide and continuing east-southeastward into the GoC.

Low-level moisture has inched northward up the GoC, as per the CIRA blended precipitable water product from 6 am this morning, shown above. The inverted trough over the southern GoC has produced stronger winds that are pushing mT air back toward the Southwest. The PW at Hermosillo began increasing yesterday and has now gone over 2 inches, after being less than an inch at this time yesterday. The 7 am MST observation at Hermosillo this morning indicates a temperature of 86 F but with a dewpoint of 75 F, up 38 F from yesterday.

The early runs, at Atmo, of the WRF-GFS and WRF-NAM both push increased moisture northward up the lower Colorado River Basin tonight and on through Thursday. The models forecast some afternoon storm activity along the southeastern borders of the state today. Tomorrow the GFS version forecasts storms over eastern Pima County tomorrow afternoon, while the NAM version keeps activity to the south of here. Both models forecast increased storms activity for the Tucson area on Thursday afternoon. Improved rain chances  for the second half of week will be most welcome.