Wednesday, July 14, 2010

Brief Overview

Thunderstorm activity shifted a bit to the north late yesterday afternoon - see IR image at top, which indicates a small MCS in the Nogales area. These storms tried to shift north during the evening but core echoes tended to remain on the higher elevations. The 00Z TWC sounding indicated no CAPE at the sounding site - but sounding was 5 mm too dry; so exact situation is not known. Anvil covered the sky at sunset, and we observed lightning far to the southwest (probably around Kitt Peak) from a foothills restaurant about 8:30 pm. There were a couple of sprinkles at the house during the night (another trace event) and the skies were heavily clouded over with middle-cloud debris at sunrise (some light showers and virga around the Rincons). Still have not observed lightning, nor heard thunder, nor measured rain here at house so far this summer.
Rain amounts last 24-hours: Ft. Huachuca had 0.23" and Douglas had 0.27" while Nogales only measured 0.08". The Pima County ALERT network showed small amounts of rain at 7 of the 93 stations - only amount of significance being 0.24" at the Santa Cruz at Elephant Head Road. Four RAWS stations had decent rain amounts - Sasabe 0.37", Guthrie 0.48", Trail Cabin 0.77", and Stray Horse 1.07". So some decent rainfall but not widespread nor very heavy - best amounts at high elevations and along borderlands.
Conditions remain moderately moist with GPS PW amounts over lower elevations of southern Arizona holding around 40 to 42 mm. Thus, situation is fairly similar to yesterday, with some CAPE possible but also continued light/variable winds lower portions of troposphere. There are stronger southerlies up at anvil level (not a good flow pattern for house, unless something develops nearly overhead). This morning's NAM forecasts for this afternoon and tomorrow afternoon indicate more of the same (considerable cloudiness over the entire southeast half of state complicates things a bit). However, the NAM gradually shifts the 500 mb anticyclone westward and northward some so that easterly winds slowly increase over northern Mexico and the borderlands. Model indicates considerably increased storm activity for Friday afternoon. There is also a developing tropical disturbance in Pacific off Mexican coast that could come into play, so we should keep watch on low latitudes too.

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