Thursday, June 30, 2011

Strange Events Of Last 24 Hours

Thunderstorms yesterday afternoon tended to stay over the highest elevations and also to remain off to east of Tucson. There were several severe storm warnings in Cochise County; storms developed on the Santa Ritas and Rincons near Tucson. The 0000 UTC sounding from TWC appeared to have no CAPE, but it was too dry wrt GPS data, leaving the true situation a bit of a mystery. At 8 pm I observed frequent lightning from the southeast to the north-northeast and figured that that was that.

Shown above are the composite radar chart for 8:45 pm (MST) and the IR satellite image for 8:30 pm. These both seem to indicate that storms have once again avoided Tucson. However, it is of some interest that the RAWS station at Guthrie had 0.25" of rain along with a gust to 61 mph - so that, along with a nearly coincident gust to 64 mph at the Douglas-Bisbee airport, we had the first severe thunderstorm reports in southeast Arizona for summer 2011.

However, this morning at 4 am we were sitting on the front porch watching the rain and lightning flashes, and listening to rumbling thunder - quite a surprise to everyone. At top, just above, is the 3 am NWS Tucson base scan radar from NCAR RAP - still not much around of obvious interest. However, a convective complex in northern Sonora had again generated a northward moving outflow. This outflow moved into the Tucson area and storms developed at low elevations in the associated convergence zone. Thus, at 4 am (bottom) much of the Tucson area was experiencing thunderstorms and light rains. There was early morning wind damage and trees down just southwest of the airport with these storms.
Here at the house we had 0.11"; 28 of 93 ALERT gauges had rain; TUS had only 0.03" but Atmo had 0.22". Heaviest amounts were with the stronger cells, mostly northwest of the airport. However, Manning Camp in the Rincons had 0.83" and Rincon RAWS had 1.18" (these were the late afternoon/evening storms) and DEQ at Country Club (between the airport and DM AFB) had 0.75". So quite a surprise early morning event here. Obviouly, there were problems with the WRF forecasts for this event, and I'll try to do a postmortem later today.

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