Given the tendency for Covid-19 spread with established cold weather regimes in high population areas the importance of cold weather monitoring has (of course) increased. The 15-day outlook for Europe identifies an established cold weather risk which could be enhanced by developing snow cover and supported by a super negative Scandinavia Index pattern centered on days 6-10 ahead!

Agreement between both the GFS ENS and ECM ENS on stratospheric warming over northwestern portions of North America is indicated. Stratospheric warming indicates potential for arctic air development at ground level as the stratosphere warms and expands and the weather atmosphere beneath (troposphere) contracts and cools. Developing arctic air in 15 days can be difficult to project by operational models. However, the caveat 2 and caveat 3 version of the mega-cluster ensemble indicates arctic air is present and possibly heading for the U.S.

Today’s North Atlantic oscillation (NAO) forecast intensifies into the strong negative phase for next week signaling a high latitude blocking pattern forcing a Northeast U.S. storm featuring extreme intensity. Both the GFS and ECM project 970 MB low-pressure which could produce another intense wind event for the northern Mid-Atlantic and New England States for early-to-middle of next week, just before the Thanksgiving Holiday.

Inevitable is the likelihood of the feared polar vortex pattern in January 2022. Why? Simply stated, there is precedent for persistent high-amplitude high-pressure ridge areas forming over large regions of much warmer than normal SSTA during the past 10 years in the winter season. Implied by the International Multi-Model Ensemble (IMME) are high-amplitude high-pressure ridge areas across very warm regions of SSTA just east of the Dateline and across western and central North Atlantic. In-between the two ridge areas, the atmosphere (always looking for balance) compensates by allowing a cold upper trough (polar vortex) to form over central North America.