Friday, October 07, 2016

Backdoor Front Appraoches Today

Very interesting situation as backdoor front from the southern High Plains will move westward across southern Arizona this afternoon and evening. Graphic above is 12 UTC 850 mb analysis from NCAR. Most prominent feature is, of course, Hurricane Matthew, but also of note is the front over Texas, extending well into New Mexico. A fairly large pool of moisture is moving southwestward with this front. The 7:00 am MST surface plot below (also from NCAR) shows the front to have reached Deming and Truth-or-Consequences already. The increase in moisture tomorrow and threat for thunderstorms involves both this backdoor front and the weak 500 mb short wave forecast to move across Baja and Arizona tomorrow.

The forecast skewT above, valid at 2:00 pm tomorrow afternoon, is from the 06 UTC WRF-GFS run at Atmo last night. This is a very impressive sounding, with substantial CAPE and a pronounced veering wind profile. Were it to verify, there would likely be severe thunderstorms. Which, indeed, the model is forecasting for eastern Pima and Pinal Counties - forecast of composite radar echoes below is valid at 4:00 pm. The exact location of storms when a backdoor front is a player can be very difficult to forecast - so we'll have to watch how the details play out.

The strong push of east winds will also likely result in another period of high winds from the east at the Mt. Hopkins RAWS this afternoon and especially tonight. My estimate is that winds could reach 50 to 60 mph at that site - about double what the current NWS grid point forecast indicates there.

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