Comparing DEC-2013 and DEC-2022 cold outbreaks; 2022 stronger (if snowy).
Fig: 1-2: The 500 MB height analysis for Dec. 8-14, 2013, and the attendant U.S. temperature anomalies.
Fig: 3-4: Projected 500 MB heights for the December 2022 arctic outbreak and attendant surface temperature according to ECM ENS calid Dec. 22-27, 2022.
Discussion: The December 2022 arctic outbreak is forecast stronger intensity and of longer duration the December 2013 arctic episode. During the week of Dec. 8-14, 2013, an Alaska “ridge bridge” inspired arctic outbreak into the U.S. featured a frigid polar vortex across central and eastern Canada. According to NCDC/PSD analysis, the 500 MB heights were <510 DM (Fig. 1). The attendant U.S. chill produced MUCH BELOW normal temperatures in the Great Basin and Upper Midwest (Fig. 2).
Interestingly, the peak cold of the upcoming arctic outbreak is forecast in the 11-15-day period which ECM ENS projects a less intense 522 DM 500 MB height across Ontario (Fig. 3) which is >12 DM higher than the 2013 event. Despite the higher 500 MB heights, the surface temperature forecast is MUCH BELOW normal across a much larger area (Fig. 4) than the 2013 event.
The larger aerial coverage of stronger cold for the 2022 event also expected to last longer occurs due to a projected more expansive snow cover (Fig. 5) than in 2013. The snow cover will need to be as expansive as forecast by GFS ENS for the aerial coverage and intensity forecast of the cold outbreak to verify.
Fig: 5: The GFS ENS snow depth forecast in 15 days across North America.