-WPO/-EPO climate signals regained recognition during the 2013-14/2014-15 “polar vortex” winter seasons in North America and again on single events such as last February’s ERCOT freeze. This time around, -WPO and -EPO (-EPO climatology shown) reach moderate intensity (-1.0 to -1.5) which typically produces a chilly pattern during autumn over west-central/central North America.

Right now, snow cover is coming on strong and is above normal in aerial coverage across Northeast Eurasia. This zone is the most likely location to gather early season cold air masses including arctic air. Additionally, the widening snow cover and increased arctic air source region risk in this location implies China is a target for increased risk of unusual cold once we’re well into November and December which is a significant problem given their energy crisis.

A comparison between rankings from the past 20 years for the winter 2021-22 forecast vs. 2020-21 observed of gas population weight HDD is issued. The cold risk for the U.S. is on the front half of winter trending milder than last year for late winter.

New to the forecast is a developing heavy rainfall regime developing in the East/Southeast centered on the 6-10-day period according to ECM. Most of the rainfall is mid-to-late period as a Pacific trough arrives and regains strength while entraining Gulf of Mexico moisture. Heavy rain causing flash flooding is possible from the Tennessee Valley to the Mid-Atlantic States and Southeast also featuring severe thunderstorms during October 27-29.