Wednesday, August 24, 2011

Early Morning Showers Along The Borderlands

This morning there were light showers in the distance, surroundig Tucson from east to south to west - this was much as forecast by yesterday's early run of the WRF-GFS model. Visible satellite image below is from 1330 UTC. Douglas carried a sunrise thunderstorm on their observations. Yesterday storms in southeast Arizona made it as far north as the Tucson airport at lower elevations. The high cloud bases and light rain amounts led to some dusty outflows - outflow and dust here at house around 6 pm, with lightning visible from east to south after dark. No rain here, and only 8 of the ALERT gauges (mostly in far southern parts of network) had rainfall. I do see that the Carr RAWS station reported 0.61" - by far the largest amount at any gauge.

There is an inverted trough moving westward across the central and lower GoC - as forecast by the models yesterday. At 1330 UTC (IR image above) there was a very large MCS over the southern GoC, with some areas of light showers to its north, all the way to Arizona. Will this trough and associated convection be significant enough to trigger a new surge of low-level moisture into Arizona? The models hint that it will and that increased low-level moisture will spread into southern Arizona by morning tomorrow.

The Tucson morning sounding (above from Univ. of Wyoming) has PW of only 34 mm (the early run of Atmo's WRF-GFS forecasts this to drop into upper 20s this afternoon), and there will likely just be a sliver of CAPE present this afternoon. The wind field remains very chopped up through the troposphere - the strongest wind speed in the entire sounding is only 18 kts at 190 mb. Storm activity may even be down a bit today, as per the WRF-GFS forecast of rainfall through midnight (below) indicates. The latest run of the NAM is quite similar. Perhaps things will be a bit better tomorrow?

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