Tuesday, October 23, 2018

Morning Storms - More This Afternoon?

This about as active as it got yesterday afternoon in the metro area. The models did much better than I did in forecasting the suppression that would dominate. I thought that there'd be at least some storms in eastern Pima County - this morning's ALERT plot shows only goose-eggs across entire network. So, I have to chalk another one up for the models.

The 00Z sounding last evening (below) shows PW about the same as yesterday morning, substantial CAPE, but a well-mixed in moisture BL that reached to only 850. The Cu above are based about 700 mb, but couldn't build through the much drier air aloft.

Second below shows detected CG flashes (from Vaisala and Atmo) for 24-hours ending at 6:30 am this morning. There was considerable thunderstorm activity over Cochise County. The white to pinks show early morning activity that has developed to our southeast.

The morning skew-T plot from SPC for TWC (above) is similar to yesterday's (previous post), but with a bit more moisture in mid-levels - morning clouds in this layer indicate that the moistening is probably continuing above 700 mb.

Composite radar above is for 7:00 am MST, showing the Cochise County storms and also a storm just east of the Rincons. The 12 UTC 500 mb analysis from the NAM model is below - main part of short wave is over southern California and just west of Baja. However, there appears to be a weaker, leading wave from near Phoenix down to northeastern Sonora. The NAM amplifies this leading wave during the day, as it moves the storms southeast of here into New Mexico, with coverage and intensity increasing. 

I looked at the 06 UTC WRF forecasts and the 12 UTC WRF-RR - the NAM version from midnight had the most accurate forecast of the convection for 7:00 am. Interestingly, the WRF-NAM amplifies the storm activity to our southeast and moves it into New Mexico during the afternoon. However, the NAM version has much less activity over eastern Pima County this afternoon than do the two other WRF versions, which forecast significant and intense thunderstorms locally. The forecast of composite radar echoes at bottom is valid at 6:00 pm this afternoon. 

The two key forecast questions for today: will the morning activity develop northwestward into our area?, and how much thunderstorm activity will there be as the final portion of the 500 mb short wave moves across southern Arizona later today and tonight?

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