Friday, July 22, 2022

Don't Rush!


Heavy clouds with nice coloring over the Catalinas at about 5:30 am MST this morning.

Yesterday I demonstrated that it's not wise to rush a forecast. I ended previous post with thoughts that it might be a big storm day. However, the plot of detected CG flashes (below from Atmo and Vaisala) for 24-hours ending at 1203 UTC this morning (5:03 am MST) shows that thunderstorms completely avoided Pima County. Only report of rainfall across the entire ALERT network was 0.04" near Tubac - the most southern site in the network.



Now for today. Plot above is for the 12 UTC 250 mb level, which shows that the upper-tropospheric anticyclone is centered over the Colorado River, south of Las Vegas. There appears to be a slight bit of difluence over our region. During the next few days the anticyclone will shift eastward, while several upper-tropospheric, inverted troughs move westward along the Borderlands.


The morning sounding from TWC/TUS (above) continues to have considerable CAPE and moisture well-mixed up to above 700 mb. However, substantial lift is still required to trigger low elevation storms. Note also that wind speeds are considerably weaker today through the troposphere. 

Total PW this morning is 1.52", while yesterday morning it was 1.82". However, PW fell during the day yesterday and was only 1.38" in the 00 UTC sounding data. 

The 06 UTC WRF-GFS runs at Atmo are forecasting storms and precipitation this afternoon across eastern Pima County -forecast below shows the model's total precipitation forecast through midnight tonight.



These two panels are from the NWS Forecast office website - above is weekend outlook highlighting potential for severe thunderstorms, and below is the morning forecast for the airport - note the high POPs of 70 % for several periods.



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