Wednesday, September 08, 2021

Tropical Storm Olaf



Last evening a large MCS developed over much of Sonora and moved westward into the GoC - IR image above is from 1:00 am MST this early morning. Yuma reported a gust to 45 mph at 4:57 am from the south. Since there was no significant gradient of Td, this was not a surge, but a rather strong flux (V dot Q) of moisture into southwestern Arizona.

Further south, TS Olaf has formed south-southeast of the end of Baja. Olaf (below at 1530 UTC) is forecast to move northwest and then turn westward before reaching northern Baja. This trajectory should, however, keep the flow of moisture continuing into the lower Colorado River Basin. Plot of total precipitable water is shown for 14 UTC (second below).



At 500 mb (above for 12 UTC) this morning the very large anticyclone is centered somewhere over eastern Nevada. The morning TUS/TWC sounding below shows deep, and quite strong, east-northeasterly steering flow. CAPE is significant for the lifted near-surface parcel. But, if BL mixes out to about to about 600 mb, there will be just a sliver of CAPE left. This is what morning model forecasts indicate. The 12 UTC WRF-RR run forecasts only isolated storms along the Borderlands of western Pima County - forecast below shows that model's forecast of precipitation through midnight tonight. So, a promising situation may bring only storms visible off to our distant southwest. 


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