Why The Colder Medium-range Forecast: -EPO/-WPO climate signals, the signals too watch for winter 2021-22
Fig. 1: Beginning Sunday and lasting through November 4th a moderately intense negative East Pacific oscillation develops.
Fig. 2: At the end of the -EPO regime, a moderate-strength -WPO follows.
Fig. 3-4: The OCT/NOV moderate-strength -WPO/-EPO temperature climatology for North America.
Fig. 5: The ECM ENS 6-10-day temperature anomaly forecast.
Fig. 6-7: The ECM ENS <32F and <24F risk for days 6-10.
Fig. 8: PJM-West is targeted for high-demand HDD November 1-7.
Discussion: The 6-10-day forecast trended colder today due in-part to agreeable moderate negative phase of both the West Pacific/East Pacific oscillation forecasts (Fig. 1-2). -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 reach moderate intensity (-1.0 to -1.5) which typically produces a chilly pattern during autumn over west-central/central North America (Fig. 3-4). Consequently, support for cold Central U.S. forecasts centered on the 6-10-day period by all models (ECM ENS version shown in Fig. 5). Cold weather risk is ahead featuring <32F into the southern Great Plains to central/northern Appalachian States (Fig. 6) and <24F into the central Plains and Midwest States (Fig. 7). If snow cover was present these readings would be much colder. Hardest-hit HDD region is the PJM-West sector peaking late next week (Fig. 8).