Saturday, July 05, 2008

Storms in Tucson on the Fourth of July

While the central and south parts of the state were very active yesterday with several severe storm reports, the nearby mountains here were suppressed relative to the day before. The boundary layerby late afternoon was only well-mixed in moisture up to 600 mb. This layer required substantial lift for its CAPE to be released.

A strong cluster of storms near Green Valley produced a deep outflow that was visible on the KEMX base scans. It passed TUS at 6:46 pm when winds shifted to the south with gusts to 38 mph. Thunderstorms were developing along this outflow as it moved north across the city. We had thunder and light to moderate rain here at house from about 7:00 to 7:40 pm with total rainfall of 0.35". The lightning was quite spectacular with CG bolts jumping out to the north of the cells through clear sky. Quite a dangerous situation.

Significant moisture remains in place but winds aloft over southeastern Arizona are becoming nearly light and variable in the NAM forecasts through midnight. My guess is that this afternoon's well-mixed, in moisture, boundary layer will have theta w of about 24C - a very favorable value for moderate CAPE and heavy storms. But the situation will probably be like yesterday and the air mass over the deserts will require a good kick from outflows from storms at higher elevations. Timing will depend on heating and how quickly storms develop over higher elevations. Also appears as if the northwestern half of state will have an active day.

No comments:

Post a Comment