Wednesday, July 08, 2009

Beat Up by the WRF

Yesterday was a tough day for an old-time forecaster, as the WRF forecast totally out did my assessment that the hot and hostile air in upper half of troposphere would dominate the low-level moist surge. If anything, there was more storm activity here in the southeast corner of the state than the model predicted. One small tower went up right overhead and gave us 0.02” in a minute or two and then it was gone. A storm out west of the Tucson Mountains produced a gust to 59 mph at Ryan Field. Nogales got hit with a serious storm that gave them a gust to 48 mph and over an inch of rain in a short period. The NWS forecasts were quite good yesterday, especially the early am update based on the new sounding data.

As for rain here in the extended metro area, the ALERT network shows spotty reports with the most concentrated measurable rain occurring in the south and southwest portion of the network. Nine of ninety three gauges had measurable precipitation before 6 pm and another 12 measured rain after 6 pm (21 of 93 with precip during past 24 hours).

This morning conditions were deathly clear at sunrise, quite a contrast to yesterday. Even though there is still CAPE in the morning soundings, the middle to upper troposphere is even more hostile today. The surge ended late yesterday afternoon and GPS precipitable water is trending down across southern Arizona. The anticyclone at 500 mb has shifted eastward and is now centered a bit northeast of Tucson near the Arizona/New Mexico border. Temps at 500 mb are an ugly -3 to -4C.

So, I’ll just recycle my discussion from yesterday and say that I expect storms today only over the higher terrain of the borderlands and far east. I’ll be very surprised if any of the gauges in the Pima County ALERT network catch any rain today.

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