Stratospheric cooling over Alaska motivated a tropospheric "ridge bridge" across Alaska to the polar region motivating cross-polar flow of arctic air into an emerging polar vortex over the Midwest U.S. resulting in a frigid arctic outbreak for the U.S.

In one of today's Climate Impact Company market reports, noted was the vast sharp warming of the ocean water off the West Coast of South America. Indicated is a potential weakening of the Humboldt Current. If so, this is one diagnostic suggesting La Nina's demise is ahead.

A cold blast of arctic air will surge into the Great Plains midweek rapidly charging to the Gulf of Mexico and moderating into the East. A primary concern is the extremely tight pressure gradient between a 1060 MB arctic high over Montana Thursday and a 980 MB low over Michigan Friday which will cause wind gusts from 55 to 70 mph (or more) in the Upper Midwest, Midwest, Great Lakes region and into the Northeast Thursday into Friday. The immediate Atlantic Seaboard is also at risk for very high wind on Friday.

Last week, the Nino SSTA regions were warmer. Three of the four Nino SSTA regions remain within the La Nina threshold. The Nino34 SSTA is -0.9C which is moderate strength La Nina but slightly warmer than the previous week.