I'll try to cover the most important features that I see affecting southern Arizona through the weekend - I'll resist to the temptation to speculate about the futures of Hurricane Danielle and TS Earl in the Atlantic.
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Top image shows the rain and storms continuing to increase over south-central Arizona. I see the NWS has amended its forecast to increase the rain POPs to 50% for today and tonight. The morning NAM forecasts a nice rain event in south-central Arizona during the day today, but nothing at all during the night - which seems very suspect!
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Middle image shows the Tucson morning sounding from the SPC, indicating moderate CAPE aloft in the 800 to 700 mb layer, where winds have a more southerly fetch. The problem with the sounding is that it appears to be seriously too moist wrt GPS observations, which indicate the sounding data have almost 7 mm too much PW. It is virtually impossible to do anything but make guesses about where the sounding data are too moist - regardless, I'll guess that the surface to 800 mb layer is drier than indicated. My guess is based on the ongoing convection and the indicated layer of elevated instability that seem to fit the observed data above 800 mb.
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Bottom image is this morning's 500 mb analysis from NCAR RAP. It indicates that the weak 500 mb cyclone, or inverted trough, is located out to the west of Tucson this morning. If someone wants a challenging exercise - try to draw a streamline analysis for the observed data! The active convection appears to be occurring in the eastern sector of this feature. The morning NAM forecasts the weak vorticity maxima to drift slowly eastward during the day, ending up nearly overhead by midnight (which is what makes the dry nighttime forecast somewhat suspect). Tomorrow the feature opens up with weak westerly winds as the Pacific trough digs southward.
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The upper-troposphere (300 and 250 mb) appears to be very difluent today over southeastern Arizona.
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It appears that the northward push of deep moisture associated with TS Frank (see previous post) will be picked up ahead of the Pacific trough, making for a potentially stormy weekend.
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Finally, the NAM forecasts indicate that the inverted trough, currently near the Louisiana and Texas border, will intensify into a TD or TS. The model moves this feature westward into northeastern Mexico by 84 hours.
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So, plenty of ingredients for an interesting four days!
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