Wednesday, September 28, 2022

Limited Low-Level Moisture



Red skies this morning over the Rincons at about 6:10 am MST.

Down at bottom is visible satellite image of Hurricane Ian, which is nearing landfall on the southwestern Florida coast. Ian is currently a high-end Cat 4 storm, or perhaps a Cat 5.

Plot of detected CG flashes (above from Atmo and Vaisala) for 24-hours ending at 0133 am this morning. Thunderstorm activity over southeastern Arizona was much reduced relative to Monday, with only activity in central and western portions of Pima County.

The sounding from TWC/TUS this morning (above) is similar to yesterday's. There is little to no CAPE. PW of about an inch, and light winds below 200 mb. A significant increase in low-level moisture would be needed for there to be CAPE for afternoon storms.

There is a layer between 700 and 800 mb with stronger southeasterly winds, so there is a chance of gusts to around 30 mph again today. Highest gust at TUS yesterday was 33 mph.

Forecast above (from the 12 UTC run of the WRF-RR at Atmo) indicates rainfall across Pima County will be similar to yesterday - mostly south to west of our area.

In contrast, the NWS has issued the graphic below, indicating moderate chances for heavy to severe storms in eastern Pima County. The POPs for the airport are currently 30 percent in the morning forecast. I find this outlook a bit puzzling, given the morning sounding.



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