Zooming over the Euro-Atlantic sector, the extended forecast starts picking up on this signal as November is now in sight.
It's been 11 years since the North Atlantic Oscillation (NAO) had a daily value of -2σ or lower during December.The streak may end next week!The following Decembers had NAO values ≤-2: 1961-63, 1970, 1976-78, 1997 & 2008-10.Cutting to the chase, here's how Northern Hemisphere snowfall looked during previous episodes of a strong negative NAO (≤-2) in December.Above normal snowfall was favored along the U.S. East Coast, Midwest & across Europe.During previous episodes of a strong negative NAO (≤-2) in December, temperatures had a tendency to be below normal across the central & eastern U.S., Canada & throughout Europe The December 2022 -NAO event looks similar to the major historical episodes, but every event is different!We live in a warmer climate now and it will be interesting to see how this traditionally cold mid-latitude teleconnection manifests itself in our sensible patterns.The block party may not stop in December! In the January following the 11 strong -NAO Decembers, there was a higher incidence of the -NAO pattern: the NAO was negative in 62% of January days.This favored a continuation of colder than average mid-latitude temperatures.