A New Month - Will It Bring More Rain Than July?

Many thunderstorms across southeast Arizona yesterday, as per CG flash plot for 24-hours ending at 11 pm last evening (from Vaisala and Atmo). Yet another minimum over metro Tucson with most storms occurring at higher elevations. Several thunderstorms here at house but only sprinkles of rain; finally there was a bit of debris cloud rain after dark but only 0.02".

Across the ALERT network highest rainfalls were over over the Catalinas and eastern portion. From 5:00 am to 5:00 pm MST yesterday 29 sites had rain, with the heavy amounts restricted to the Catalinas - 1.26" at Sabino Creek/Marshall Gulch. from 5:00 pm through 5:00 am this morning 40 sites had rainfall, with heaviest amounts over the Catalina and metro-east sectors - Mt. Lemmon had 1.02".

There were several severe wind reports in the east part of the Phoenix area, with some decent reports of rainfall up there finally. There was a landspout-type tornado near Safford, similar to that photographed by Mike Olbinski on Tuesday near Marana -see earlier post below..

This morning's TWC sounding data from campus is shown above from SPC. There continues to be a fair amount of CAPE, even though there has been decreasing PW. Although the wind speeds have picked up aloft, there continues to be little directional shear, producing a profile that is not favorable for storms over many parts of the metro. The GPS time series from ERSL below indicates PW continuing to fall with values now estimated around 1.40 inches. The 12 UTC blended PW analysis from CIRA (second below) seems to indicate that the drier air is coming in from the south-southeast, with best PW values over southwestern part of Arizona. The CAPE may be decreasing during the day due to this weak dry intrusion.

The 06 UTC forecasts from the WRF model runs at Atmo both indicate thunderstorms over eastern Pima County this afternoon. The WRF-NAM forecast for rainfall through 11 pm this evening (first below) keeps amounts light over low elevations, with most storms on the mountains. The GFS version (at bottom) is much wetter, with a forecast for significant storms and rains in the Tucson area. Both models appear too wet and unstable, very much more so for the GFS version. So, the WRF-NAM will likely be closer to what actually happens this afternoon.