The pre-Christmas 2022 arctic outbreak in the U.S. was caused by a sudden combination of stratospheric factors over the polar region and North America just-after mid-December. This type of arctic air catalyst can occur quickly and is difficult to forecast in the medium-range and certainly 3-6 weeks out. Suddenly, arctic air evolves fast in Northwest/West Russia the next 7-10 days expanding across Eurasia (although moderating) in the 11-15-day period. This type of an event can easily regenerate over North America the second half of winter.

The 2020-22 La Nina has produced wide variation in ENSO diagnostics. Multi-variate ENSO index has consistently indicated a La Nina climate while Nino34 SSTA, the conventional ENSO phase diagnostic, has been choppy and subsurface upper ocean heat has varied widely during the 3-year period.

Latest 1-2 week outlooks indicate a dry and hot pattern developing across Argentina to far Southeast Brazil. In Northeast Argentina, a large area of deep layer soil moisture deficits is present. The combination of the forecast and deep layer soil moisture condition will lead to an Argentina flash drought by the middle third of January.

Causal of the recent polar vortex event into the U.S. was the combination of persistent high latitude blocking high pressure related to the warming influence of the upper atmospher caused by farther north open water during winter, warm water zones of the Northeast Pacific and western North Atlantic basins whose attendant upper air patterns force susceptibility of polar vortex events in North America and cross-polar flow of frigid Siberian arctic air making this polar vortex event even stronger.