Thursday, August 20, 2009

Nearly A Repeat Discussion


Very suppressed day yet again yesterday with only storm activity to the east and along the border. No rainfall measured in eastern Pima County network.
The complicated situation discussed yesterday continues today with a few additional wrinkles.
The vorticity maximum over central Gulf of California was actually suppressed to the south and is now over the southern Gulf (see 15Z water vapor image above) with a secondary lobe extending northeastward through the Big Bend country of Texas.
The large 500 mb anticyclone is over northern Nevada this morning and as shifts southeastward today it appears that there'll be some dry advection from the north around 700 mb. This will serve to minimize CAPE again and keep activity pushed to the south.
A back door front from the Plains will likely stall out around the New Mexico/Arizona border and not be a player over southeastern Arizona.
The upper-level deformation zone is now over the border lands. It is forecast to shift north and weaken dramatically, leading to very strongly difluent flow aloft over most of Arizona by tomorrow evening.
The NAM continues to forecast the inverted trough over the southern Gulf to move to the north-northwest, bringing the subtropical air mass northward into the Southwest by Saturday. The 500 mb wind speeds forecast by the model seem excessively strong, but as the vort max, the cutoff low west of San Diego, and the building anticyclone make a squeeze play, gradients will increase substantially. If the model is slow, as often the case, then there's good potential for a big storm day tomorrow and if not tomorrow, then an interesting weekend is likely in store.

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