Friday, August 31, 2018

Trough In Westerlies Advancing


Perfectly clear skies at sunrise today - still fairly comfortable with some cool spots along the Rillito.


Plot of detected CG flashes for yesterday (above from Atmo and Vaisala for 24-hours ending at 11:00 pm MST last night) indicates a very suppressed day, even with the increase in PW to values just above 30 mm. The most activity was way off east over the Chiricahuas.


Morning skew-T plot for TWC upper-air data (above - from SPC, as are two analyses below) shows a very strange vertical wind profile and thermodynamics that appear to indicate considerable subsidence above 500 mb, with a nasty warm inversion up there. My subjective estimate of CAPE for late afternoon is for a sliver at best.


The 500 mb chart for 12 UTC (above) shows that the advancing trough in westerlies has nudged the anticyclone all the way east to Oklahoma/Texas. The 250 mb streamlines (below) help explain the upper-level winds at TWC, as quite strong west winds approach (note the 90 kt jet over central California). It appears that the trough is coming into the west considerably stronger than the models have been predicting, which is not good for our chances for storms and rain over the long weekend.



The early WRF forecasts for today keep southeast Arizona quite suppressed. The 06 UTC WRF-NAM is most active for tomorrow, although it still keeps most storm activity to our north and east. The above sounding forecast (from that run for TWC) indicates that west winds dominate, while warm middle level air continues with its nasty inversion. I again estimate just a sliver of CAPE for this sounding with considerable capping above.

The forecast from that model run for total precipitation through midnight tomorrow night (below) keeps most activity along the eastern quarter of Arizona. So it goes.


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