Wednesday, July 19, 2017

More Of Same?

Heavy thunderstorm over the Catalinas early yesterday afternoon shown above from campus at a bit before 2:00 pm MST. The anvil from this storm spread out over much of metro area, suppressing low-elevation storms. There was a nice display of mammatus overhead as this happened (below). This storm may have produced thunder here at house but I didn't hear any; if there were some spits of rain, I also missed those - so zip for rainfall here.

The plot above shows detected CG flashes for 24-hours ending at 6:00 am this morning. Note the elongated suppressed zone from metro Tucson to Phoenix - with storms staying mostly over higher terrain. The ALERT rainfall (below), for same period, shows that the NWS mountain forecast zone was very active, while reverse was true for the low-elevation zone, which was basically skunked. The storm shown above produced some rain amounts of over 2 inches.

The morning sounding data from TWC remains similar to last several days, except that winds above 700 mb have increased substantially relative to yesterday. The surface cool layer is also deeper, which damps the SPC CAPE analysis above. The winds are nearly uni-directional from the east-southeast with little speed shear through 150 mb. This gives some hope that storms my move faster than the anvils, providing more favorable conditions for lower elevations. The 11:00 am forecast TWC sounding (below - from the 06 UTC run of the WRF-GFS at Atmo) indicates decreasing wind speeds at upper-levels, which would be good, if that actually happens. Mixed layer CAPE in the forecast sounding is over 1500 J/kg.

The WRF-GFS initiates storms very early, and composite radar forecast below is valid at 1:00 pm. These storms run off rapidly to the northwest impacting Pinal County and the Phoenix area later in afternoon. The shear profile is better than yesterday, indicating the chance for organized storms and severe winds is higher today. Finally, the WRF-NAM forecast is similar, although winds above 500 mb bring in drier air and storm developments are about three hours later than in the GFS version. Regardless, looks like today could be considerably more interesting than yesterday.

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