PW Now Very High

Yesterday was mostly a down day, with the storms that occurred again tending to hug the mountains. At 6 pm MST only 3 ALERT stations had had rainfall. This morning, after several periods of nighttime showers, the count was up to 13 stations (only 14% coverage) with light amounts. Here at the house there was light rain at sunrise (9 July 2013) and the early morning showers had produced 0.01". The high temperature at the airport yesterday was 105 F and was likely the final day in the 100+ stretch of 38 consecutive days.

Very large nocturnal MCS (water vapor image above is from 4 am MST) over Sonora and southern Arizona has produced several outflows. The most significant outflow has interacted with the push of GoC moisture caused by TS Erick and surged into all of southwestern Arizona. At 5 am MST Yuma reported south winds up to 38 mph with a dewpoint of 69 F. This morning's TUS sounding (see below) is now VERY moist with PW of 1.85 inches! Significant CAPE is present also, but the wind profile remains somewhat disorganized. Obviously substantial cloud cover is at play today.

The water vapor image at top also shows a large inverted trough over and south of the Texas Big Bend and this feature is forecast to move across northern Mexico today - another complexity in the overall situation. The early run of the WRF-GFS forecasts another MCV to emerge later this morning and be over central Pima County at 9 am (see above forecast of composite radar echoes). So, many diverse factors present today - making the forecast very difficult.

The early WRF-GFS appears to forecast suppression during the afternoon hours due to clouds and a cooled BL from the surge. The model forecast develops strong storms after dark - above is forecast of radar echoes valid at 11 PM MST tonight. The model forecasts substantial rainfall to occur by 6 am (see below) tomorrow morning (Wednesday, with heaviest amounts along the Borderlands and to the north and west of Tucson.

The situation is very difficult and complicated; it will be much easier to observe the weather today that it will be to forecast it.