New Forecasts Made on October 30:

No new event is forecasted in this week.

 

Follow up on Forecast Made in Previous Week:

 

STRAT_B (11/01-11/06), as first officially forecasted on October 7, is around the corner. It has two peaks, one at 10/30 and the other one at 11/4. As we forecasted consistently, STRAT_B is a relatively weak event of poleward mass transport into the polar stratosphere, whose peak intensity is expected to be less than 0.7 trillion tons per day, much weaker than the peak intensity of STRAT_A (0.85 trillion tons per day). Therefore, the associated cold air surges are expected to be not severe. According to the one-week forecasts of surface air temperature from CFS models, the first peak of STRAT_B will mainly affect North America, leading to moderately cold temperatures over most regions of North America. The return of warm air temperatures looks to be quick and we can expect relatively warm Halloween night, as we have been forecasting since October 7. The second peak of STRAT_B is expected to bring cold temperatures into Eurasia and west coast of North America within few days.

 

Note that right before STRAT_B, during the period 10/25-10/29 when intensity of the air mass transport into the polar stratosphere was below normal, Eurasia experienced a cold event. This cold event merely coincides with the peak of cold air mass transported out of the polar region in the lower troposphere at 10/26, indicating that this cold event is induced by shallow synoptic waves rather than deep and large-scale waves. This was the reason why we would not be able to forecast this round of cold air surge events 20-40 days in advance.

 

STRAT_B1 (11/10-11/15), first forecasted on October 15, is still going to take place on time. This relatively weak event will mainly affect North America, pushing large areas of North America back into below-temperature regions in the second of week of November from a short warming period since Halloween. This is consistent with the latest mid-range forecasts of surface air temperature from CFS models.

 

STRAT_C (11/21-11/25), first officially forecasted on October 7 to occur in the third week of November, is possible to grow into a twin-peak event based on this week’s forecasts. Despite the intensity of STRAT_C is not strong, it is expected to cause temperature dropping over mid-latitudes, particularly over North America, which will likely cause interruption of holiday travelers.

 

STRAT_D (12/02-12/08), as first forecasted on October 21, remains highly robust and is going to peak at 12/04. Based on the updated information, we’d like to narrow down the time range from 11/30-12/08 to 12/02-12/08 in this week’s forecasts. We think STRAT_D is going to be a potentially large event and bring major cold air outbreaks to both continents, but particularly to North