Sunday, August 19, 2012
Upturn In Storm Activity Likely Today
Conditions remain very moist across southern Arizona - 12 UTC sounding for TUS is above. The winds are mostly northerly, with perhaps a bit of northeasterly steering flow around 500 mb. CAPE is not impressive, but perhaps a bit improved wrt yesterday. The forecast CAPE for this afternoon, however, is impressive, with values around 2000 J/Kg. The 500 mb plot for 12 UTC this morning (below) indicates that the anticyclone is centered over southern Utah this morning. The most important thing to note on this chart is that cooler air is coming around the east side of the anticyclone (-9C at GJT and -8C at ABQ - DEN missing in action) and being advected our way. This type situation usually provides southeastern Arizona with an active storm day.
The WRF-GFS does forecast a significant increase in thunderstorms across central and eastern Pima County today - above is forecast of composite radar echoes at 5 pm MST. So, hopefully the Atmo, high-resolution model has picked up the trend correctly again today. Will need to check the 12 UTC WRF forecast runs.
Both the early WRF-GFS (above) and the NWS 12 UTC run of the NAM model (below) forecast widespread rainfall totals by midnight tonight. Both models have the heaviest rain amounts for the Southwest over central Pima County. So it appears that there may be better storms to watch today. Last decent rain amount here at the house was 5 days ago - even though PW has been very high.
Posted by Bob Maddox at 8:10 AM