Monday, September 11, 2017

Quick Look September 11th

A sad day in history made even sadder for those suffering from the impacts of hurricanes Harvey and Irma.

High-based cumulus over the Catalinas yesterday at 3:00 pm MST (above) was about as active as it got yesterday, which was a seriously suppressed day. The plot of 24-hour CG flash density (below, ending at 6:30 am this morning - from and Vaisala) shows that all of southern Arizona had no thunderstorm activity yesterday. Unusual though is the degree of thunderstorms and lightning affecting southern California, which was associated with the persistent cyclone off-shore.

The TWC sounding plot above (from SPC) has PW around an inch, with perhaps a sliver of CAPE during afternoon. Some stronger easterly winds continue in low-levels, as dry air in New Mexico pushes against more moist air out to our west. The warm-air inversion just below 500 mb appears quite formidable also.

At 500 mb (above also from SPC) the huge cyclone, associated with now Tropical Storm Irma, has pushed the western anticyclone westward. this trend will continue as the anticyclone shifts toward the Four Corners and then is nudged southward as the Pacific cyclone shifts northeastward. The anticyclone eventually ends up over northern Mexico. This leads to a Fall-type pattern with a large trough over the West by 00 UTC on 16 September, as per ECMF 120-hour forecast below.

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