Tuesday, June 23, 2015

Brief Look At Conditions Today - June 23rd

The large-scale setting is a classic summer pattern (above is 500 mb analysis for 12 UTC this morning from NCAR RAL) with the mid-level anticyclone centered well northeast of here. The subtropical easterlies feature a complex cyclone over north-central Mexico, with two inverted troughs extending north and also east-northeast from the cyclone. These will be difficult features for the models to forecast accurately, but portions of the northern-most inverted trough will brush southern Arizona by Thursday. Note that mid-level temperatures are fairly warm to our east, which will limit low-elevation CAPE, at least in the short-term.

The morning sounding for TWC (from SPC) is shown below - and CAPE is indeed quite limited, even though PW remains close to an inch. The BL is very deep with convective cloud bases likely to be up around 500 mb - an excellent setting for more strong winds.

Forecast of PW this evening at 7:00 pm (above from 06 UTC run of the WRF-NAM) indicates dry, hot desert air butting heads with outflow and moisture just to our east. Note that weak southerly flow over GoC continues to advect moisture into southwest Arizona, while easterly winds over the Big Bend and southern New Mexico continue to push moisture westward. Add a number of mesoscale outflows into the mix, and we should see low-level moisture increase substantially tomorrow and Thursday.

The WRF-NAM forecasts more heavy thunderstorms for the White Mountains and then Cochise County this afternoon and evening. Forecast of composite radar echoes above is valid at 7:00 pm MST. The storms produce strong to severe outflows that eventually move westward across much of Pima County - forecast below of 10-m winds is valid at 9:00 pm this evening. So, today looks to be another teaser, with storms and anvils visible again but impacts most likely to be wind and dust down here in the desert.

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