Yesterday was more active in far eastern Pima County than I expected, and definitely more so than the models predicted. Above is visible image from 2315 UTC yesterday afternoon (4:15 MST). Storms had developed along the San Pedro Valley and in the Borderlands. The north-south line of storms along the San Pedro came westward and made it into far eastern sections of the metro area (see regional radar at 0100 UTC from NCAR below). Not great areal coverage across all of southeast Arizona. But, 30% of the ALERT gauges measured rainfall and 20% of the Greater Tucson gauges had rain - so, NWS POPs were right on for the local area yesterday. Five ALERT gauges had more than 1/2 an inch. We had distant thunder and a dusty outflow with wind gusts of 40 mph or so here at house - no rain as usual. DM AFB had thunder and dust and a gust to 46 mph. Atmo had 52 mph at its rooftop anemometer. So, except for the mountains and far east side, it was mostly a duster.
Tucson's morning sounding from SPC is shown above. As has been so typical this summer - winds are light and variable below 400 mb. Any storms that might occur today would stick to mountains, have anvils heading off to east, and be gusty again because of the very deep boundary layer and high cloud bases. Other things of note: low-level moisture and PW is down a bit this morning wrt yesterday; the layer from 400 to 250 mb has warmed 2 to 4C - this is in the westerly flow from the Pacific. So several negatives again, but with no counter-balances that I can see.
The WRF-GFS and the NAM both forecast that today will be quite suppressed with only some storms off in the far southeast corner of the state. Above is the WRF-GFS forecast for 3pm MST this afternoon - the forecast field is 850 mb Td. So models are forecasting more drying this afternoon on the northwest winds from the low desert (note that at 0000 UTC last evening the 850 Td was 8C here at Tucson but -7C at Phoenix!). So, sounding trends and models both say hot and dry for this Saturday, September 3rd.
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Tropics are very active and most interesting - too much to go into in this post - but take a look at what this morning's NAM does with TS Lee at 84-hours.
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