Friday, August 02, 2013

Strange Day Yesterday

It was a strange day yesterday, with cloud cover hanging around most of the day. Thunderstorms developed by 11 am and intensified over Cochise County (above is regional radar from NCAR RAL at 11 am MST on the 1st). The storms to the east produced a fairly strong outflow that moved across the Tucson area around 1 pm. So, the low-levels were stabilized for most of area, although a couple of strong storms developed in the afternoon to the east and south. The ALERT network had only 9 stations with precipitation through 6 pm - Haystack Mountain on the far southeastern edge of the network reported 0.93". Here at the house a light shower around 1 pm left 0.09" in the gauge. By 8 pm MST (see WV image below) last evening activity continued down in Mexico, with abundant anvil cloud over southeastern Arizona.

Precipitable water has continued to creep upward over most of southern Arizona, due both to the outflow mentioned above and southerly from along the GoC. The Tucson morning sounding today (see skew-T plot above for 12 UTC) indicates 1.77" of PW, with a noticeable increase in low-levels. The sounding has increased CAPE at low elevations, relative to last several days. Winds, however, continue light and variable below 300 mb and a very weak trough is embedded within the larger anticyclone. This feature is over east Arizona at 500 mb. So, storms that form today may be more widespread and certainly have the potential to produce heavy rains and perhaps wet microbursts.

There are internet problems at Univ. of Arizona this morning and I can't reach any sites over there. The morning NAM forecasts another strange with storms and rain, centered almost over Tucson, beginning this morning and continuing through about 3 pm. I can't say that I have much confidence in that forecast, but based on the strange happenings yesterday, I can't totally discount it either. Observations will eventually tell what the day will bring.

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