The water vapor image above indicates that the upper-level cyclone, that has been moving northwestward the last several days, is currently located near the southeast corner of Arizona. This feature is confined to the upper troposphere (not apparent at 500 mb), and thus should be a minor player in today's weather.
The NAM 200 mb analysis (above) at 1200 UTC this morning indicates a closed circulation. Regardless, the NAM forecast opens this circulation and minors it out rapidly to the north. There is a massive anticyclone over the central US at 500 mb with heights near 6000 m and very warm temperatures of -2 to -3C. Southeastern Arizona has been under the influence of the western portion of this anticyclone, with increasing middle-level moisture and a resumption of thunderstorm activity, particularly at higher elevations the last two days. Steering flow is from the southeast and the NAM forecast indicates westerly flow at thunderstorm anvil level by late afternoon. Thus, a good predicted wind shear, but minimal CAPE available at low elevations again. The U of A WRF model forecast from midnight indicates numerous thundershower echoes moving across the Tucson area during the late afternoon today, but with only light rainfall amounts - similar to yesterday.
This morning's Tucson sounding (above) has PW of about 1.4 inches and is in good agreement with the GPS data. There appear to be two elevated, residual boundary layers from yesterday. Lower levels reflect higher moisture from yesterday's storms, but surface cooling has been slight.
The times series of RAOB and GPS PW values for the last 5 days (above) shows the increase of moisture after the 16th due to moist advection at middle levels and storm recycling into lower elevations. The mT airmass remains to the south this morning. There has been continuing convective activity at the south end of the GoC with the result that the mT air has pushed northward up the GoC during the past 48 hours and now extends nearly to the north end. The passage of a distinct, 700 mb inverted trough across the lower GoC today could push the mT air into southwestern Arizona during the night.
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Thus, a complicated situation, but one that seems not to have everything coming into phase for widespread, intense thunderstorms. More storms at high elevations, strong winds and gusty outflows, and a few storms making it into lower elevations.
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