Sunday, August 07, 2016

Next Three Days Should Be Very Interesting

This morning's upper-air sounding from TWC (skewT above from SPC) remains very moist below 500 mb with PW of 1.57" and moderate CAPE. Wind profile remains a bit of a mish-mash with the westerlies between 300 to 500 mb. Drier air has encroached across the northern GoC and just into southwestern Arizona - shown below are both the MIMIC PW analysis for 10 UTC and the CIRA blended PW for 11 UTC. (The MIMIC product is from CIMSS at University of Wisconsin and the CIRA analysis is from Colorado State University.) Basically, amounts of around 1.25 to 1.50 inches appear to be hanging on across much of southern Arizona - so a battle of dry vs wet today. The 06 UTC WRF runs were very similar to yesterday's with the NAM version forecasting isolated storms in eastern Pima County and the GFS version keeping the activity further east.

For the next three days TD-11E comes quickly into play (note that if/when 11E becomes a TS it will be Javier - a similarly named storm impacted the Tucson area significantly back in 2004). The NHC morning outlook above with IR imagery shows that 11E currently has a very large MCS to its north that is near the mouth of the GoC. The pressure gradient up the GoC appears to on the order of at least 5 mb this morning and MCS pressure rises will easily trigger a new GoM surge of the mT air back into Arizona. Forecast track of the eventual storm below indicates that the surge, which could occur as early as early tomorrow, may be followed by the moisture directly associated with the storm.

At the bottom is a forecast of PW from the 06 UTC WRF-GFS on the 5.4 grid - valid time is 5:00 pm MST Tuesday afternoon the 9th. By that time the surge has reached north to Las Vegas and PW is quite high over all of southern Arizona. Both the NAM and GFS WRF versions forecast a big storm day for our area Tuesday afternoon and evening. Tomorrow will be a difficult forecast day as the larger-scale setting evolves rapidly.

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