Thursday, July 05, 2018

East Winds And then Storms By Weekend?

The SPC morning skew-T plots of the upper-air data from El Paso (above) and Tucson (below) are worth a look this morning. The PW at El Paso is above an inch, while that at Tucson has dropped a bit since yesterday morning and is now under an inch. Both soundings have almost no CAPE (best is at El Paso with a bit under 200 J/Kg for the forecast afternoon sounding). CAPE has been impacted by the warmer temperatures in middle-levels, where the 500 mb temps have increased by about 4 C since yesterday. The sounding to our east does show the strengthening easterly winds that models have been predicting.

The forecast for 10-m winds above (from the 06 UTC run of the WRF-GFS at Atmo) is valid at 6:00 am MST tomorrow morning. Such strong easterlies in lower-levels  are a summer forecast challenge since the downslope from here to Continental Divide in New Mexico is usually very hostile for convection. The model forecasts of these strong winds tonight and tomorrow have led to an NWS high wind advisory for the metro area after 3:00 am MST early tomorrow (note - wind advisory criteria here at lower elevations are sustained winds of 30 mph with higher gusts).

The WRF-GFS has continued to forecast very strong winds below 700 mb for the Sonoita sounding (below valid at 4:00 am tomorrow morning). The forecast wind speeds are very impressive and, if they verify, I would expect winds at the Mt. Hopkins RAWS site to gust to speeds of 65 to 75+ mph during the night tonight. 

As for thunderstorms and rainfall - the GEFS plumes for QPF at TUS seem to keep delaying storms. The 06 UTC plumes above don't really do much at the airport out through the 11th of July. The two QPF forecasts below (from the 06 UTC WRF-GFS run) are for total rainfall. Top is for period ending at 6:00 am on Sunday morning, while that at bottom is for period ending the same time on Monday morning. If these verify, it looks as if Sunday is the better day for thunderstorms - but mostly storms with light rains and strong outflow winds, with continuing threat of lightning ignited wild fires.

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