Model Forecasts Very Different Today

Skew-T plot of the 00 UTC sounding from TUS is shown above. The sounding had only a sliver of CAPE due to the warm temperatures above 550 mb. The sounding fits well with what was observed last evening. Storms tried to move off the Catalinas and Rincons around 7 to 8 pm, but with little CAPE they weakened over the metro area. Here at the house there was some in-cloud lightning and rumbling thunder with light anvil/debris showers. There was a fairly strong gust front from the east at about 35 to 40 mph around 7:45 pm MST. Total rain from the decaying storms was only 0.05" here. Across the ALERT network 44 sites (48%) had rain, most of which fell over the east part of network and after 5:30 pm yesterday afternoon. There were 9 stations with amounts of 0.25" or greater and highest total was 0.43" at two sites. The plot of lightning strikes for 24-hours ending at 6 am this morning shows a few strikes in the east part of the metro area, but with more strikes in higher elevations of Cochise County and much more activity to the north and across New Mexico.

This morning's sounding plot for Tucson (above) indicates cooling through that warm layer that kept things fairly suppressed yesterday - so, a key question is whether this cooling and substantial increase in CAPE will actually persist through the afternoon. PW continues very high with values of 1.75" and greater across all of southern Arizona. But winds aloft are light and from the east - so little meaningful steering flow. The 500 mb anticyclone continues to have two distinct circulation centers (one over Nevada and one over west Texas) with a weak trough/deformation zone between that stretches from south Baja northeastward to eastern Colorado. There is just a single anticyclone at 250 mb and it is nearly overhead.

The early WRF GFS (above) forecasts a mostly down day over much of southern Arizona, including all of Pima County. The WRF GFS forecast does not develop much CAPE across Pima County this afternoon. However, the latest NAM (below) forecasts a big storm and rain day for all of southeast Arizona.Both forecasts show rainfall though midnight tonight. Plenty of complexities, including abundant morning clouds, continue and it will be interesting to see what the new WRF forecasts show.