Thursday, July 01, 2010

Battle Continues

Summary of yesterday - convection and a few thunderstorms again yesterday afternoon and evening. Limited CAPE and light winds kept most significant radar echoes at higher elevations. Nogales and Douglas recorded lightning from their single sensor systems and this may have been in-cloud signals? Closest CG strike I saw on the lightning maps was off near Benson, with most strikes over higher terrain far to the north and northeast. One station in Catalinas reported 0.04" and Keystone Peak (about 10 miles west of Green Valley) recorded 0.20". Only two RAWS stations reported rainfall - 0.04" at Columbine but an amazing 0.98" at Guthrie (if reading is correct). Guthrie is very near the New Mexico border where moisture amounts have been higher.
This morning - downslope flow continues and the low was only 85F. Moisture has continued to increase slowly. The morning sounding and GPS PW values are very close and TWC PW has crept just over 30 mm - which some use as a threshold to indicate that moisture has reached levels associated with the monsoon. CAPE this morning appears quite similar to yesterday's, as moisture increases are offset by warming in upper-troposphere. A narrow tongue of cooler 500 mb air extends southward over eastern Arizona with ominous warmer temepratures of 4 to 6C both to west and east. Tropospheric winds remain very light.
I've shown this morning's NAM forecasts for 06 UTC tonight in the three panels above. The models continue to indicate that the western US trough at 500 mb will dominate during the next several days and keep the subtropic flow regime suppressed to the south of Arizona. Thus, the key as to whether there will be a significant increase in low-level moisture for Fourth of July weekend will be over the southern half of GoC. If remnants of Alex can trigger significant convection on and west of the Sierra Madre Occidental, then a low-level surge may result. If, not then Pat Holbrook's assessment of too much troughiness in the west will prevail.

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