Sunday, August 03, 2008

Sunday Morning Postmortem

Well my guess for yesterday afternoon was about as bad as I can do. Obviously the negatives dominated the local area around Tucson - only 7 of the 91 Alert gauges had rain yesterday, and the highest amount was 0.59 way down south at Tubac.

So what went wrong - I think that it was mainly related to the dry air in the upper-troposphere curling across southeast Arizona and keeping there from being much activity to the east - as per the WRF forecast. Although there were more storms to the east than the WRF indicated, they were not widespread and didn't produce any significant, organized outflows. With the GoC surge and increasing low-level moisture, the Tucson sounding at 00Z yesterday afternoon had substantial CAPE, but needed mesoscale convergence to kick it loose. That didn't happen.

As for today - moisture is way up as expected and there is substantial CAPE at both TUS and PHX this morning. El Paso is fairly stable so we have to assume that the air over the southeastern mountains is somewhat like the Tucson sounding. Morning wind shear from middle to upper levels is unidirectional but the NAM indicates that the wind profiles may improve by evening. Mainly a shear zone affecting southeast Arizona today and with no data from the south, it is hard to have much confidence in the model predicted winds aloft. So, there will be a lot of small and mesoscale interactions driving the evolution of storms today - good potential for more severe across all of southern Arizona and Phoenix could get hit by a strong, severe storm event. The chances are probably better for here at house today, but, even though it's not a binary call like yesterday, the shear profile could throw anvils over this part of town. So it's wait and see, as per many to most storm days down here.

The other wild card at play here is that there is a lot of strong morning storm activity out to the west of Tucson. If these storms continue to build produce early, cool outflows, that would complicate things greatly. I got a couple photos as sunrise showers moved by, producing an early morning rainbow. I'll post these to the blog later today.

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