Thursday, September 29, 2011

Just Looked Off To The Northeast!

First - Hilary has weakened rapidly and  become a remnant low already this morning - far off to the west of lower Baja (and far off the early predicted tracks, with latest NHC forecast below). It appears that the middle and higher level moisture is initially heading east toward Mexico.  However, low-level moisture to the north and east of Hilary is pushing northward - that which comes up the GoC will likely move mainly up the Colorado River Basin, while the best push actually moves north up the west coast. That said, let's look off to the northeast this morning.


Below is the 1500 UTC surface plot from the CoD weather pages. There is a strong cold front pushing rapidly down the Front Range of the Rockies. This front currently extends from Wisconsin, southwestward into the Texas Panhandle and northeastern New Mexico, and then back up the Front Range and westward across southern Wyoming. The front is heading south as the long stagnant, large 500 mb cutoff over the Great Lakes finally pulls off to the east and northeast.


The 1500 UTC visible image above (also from CoD) shows there is some cloudiness along and behind the front. There is also a large arc of cloudiness from northeastern Mexico, across the Big Bend and westward to northern Sonora. The NAM forecast from this morning's run for 850 mb (below - valid at 1200 UTC tomorrow morning) indicates that the cold front will have pushed westward across southeastern Arizona by Friday morning.


The early run of the Atmo WRF-GFS (which did quite well again yesterday) indicates little in the way of storms today; however, the model forecasts increasing activity tomorrow and Saturday. When I ran loops of the model forecast 700 mb RH, I was puzzeled at first by the strong increases forecast to come into Arizona from the southeast. However, it appears that moisture increases for the weekend will be strongly influenced by the backdoor front and moisture from northern Mexico. Hilary may still have some role in the weekend weather, but not at all like appeared possible a couple of days ago. So it goes!

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