New Forecasts Made on October 21：
In this week’s forecast, we are forecasting a new event, named as STRAT_D, to occur during the period of 11/29-12/06. STRAT_D looks to be a strong event. Thus, the associated cold air outbreaks are expected over both North American and Eurasian continents.
Follow up on Forecast Made in Previous Week:
The STRAT_A (10/16-10/22), first forecasted on 24 September to occur between 10/21 and 10/28, had peaked at 10/18. Therefore, our original forecasts whose lead time was nearly one month long were accurate, though the timing turned out to be slightly earlier than we originally forecasted. As we forecasted, STRAT_A had brought cold temperatures to large area of North America north of 30°N (peaked at 10/18). In the next few days, STRAT_A will continue to bring cold temperatures and stormy conditions to Eurasia.
STRAT_B (11/01-11/06), first officially forecasted on October 7, is still expected to occur in the first week of November (the expected peak day is around 11/03). STRAT_B is a relatively minor event. Therefore, STRAT_B will cause cold air surges mainly over the mid-latitude region of Eurasia. Northeastern region of North America is also expected to experience cold temperature conditions, although less severe than the cold conditions over Eurasia.
STRAT_B1 (11/10-11/15), first officially forecasted on October 15, is going to take place as expected. As we forecasted last week, STRAT_B1 is a short event right after STRAT_B, which will continuously bring cold air surges and cool the large area of North America and Eurasia, especially North America, in the end of the second week and first few days of the third week of November.
STRAT_C (11/21-11/25), first forecasted on October 7 to occur in the third week of November (11/16-22) and then revised on October 15 to occur in 11/21-28, is expected to occur in 11/21-25. We downgrade the intensity of STRAT_C in this week’s forecasts. But since it is closely following STRAT_B1, we still expect STRAT_C to bring fresh cold air into much of the area of mid-latitudes, particularly over North America. STRAT_C will likely cause interruption of pre-holiday travel.
Due to the relay of consecutive STRAT events, B, B1, and C, we expect a 2-to-3-week long below-normal temperature condition for North America since the beginning of the second week of November. This makes the November of 2015 a cold winter month in term of the monthly mean temperature anomalies.