What we do: We are making sub-seasonal forecasts for time periods of high probability of cold air outbreaks in Eurasia and North America 30-40 days in advance. We issue such forecasts on a weekly basis and this website is updated around Thursday each week.
New Feature: Maps of probability of cold surface temperature anomalies over both North America and Eurasia continents in the vicinity of forecasted stratospheric PULSE events
New Forecast Made on December 24:
No new forecast is made this week.
Follow up on Forecast Made in the Previous Weeks:
STRAT_D (12/11 – 12/18), whose main peak was first forecasted on 11/20 and minor peak was added on 12/03, has been materialized. The first (minor) peak of STRAT_D occurred on 12/11 with a net air mass transport into the polar stratosphere about 0.5 trillion tons per day, and the second (main) peak occurred on 12/16 with up to 0.9 trillion ton per day of air mass transport. The first peak of STRAT_D was associated with the winter storm Caly, which swept through the North American continent and bring heavy snow. The second peak of STRAT_D on 12/16 affected both continents: almost 80% of area over mid-latitudes of North America was below normal while cold was felt mainly over northern latitudes of Eurasia, as we forecasted. Associated with the main peak, the winter storm Decima brought extreme below-normal temperature to Western United States and heavy snow to the Northeastern United States.
STRAT_D1 (12/24 – 12/31), first forecasted on 11/25 and later revised on 12/03, is still expected to be a long-lasting, twin-peaked event. The first peak of STRAT_D1 is expected to occur on 12/26, and the second peak is going to occur around 12/31. Both peaks will transport up to 0.7 trillion tons air mass per day into the polar stratosphere. Based on the map of probability of below-normal surface temperature, cold surges associated with STRAT_D1 will mainly take place over northern latitudes of the Eurasian continent and western half of North America, which may affect the holiday travel （see maps).
STRAT_E (01/08 – 01/13), first forecasted on 12/03, is still expected to occur on time. We believe STRAT_E is going to be a strong event with a peak net mass transport into the polar stratosphere around 0.7 trillion tons per day on 01/13. The map of probability of below-normal surface temperature shows high likelihood for strong cold air outbreaks to take place over the North American continent and northern latitudes of the Eurasian continent (see maps).
STRAT_F (01/23 – 01/28), first forecasted on 12/10 with a 45-day lead. STRAT_F is still expected to occur on time. It looks to be a twin-peaked, strong event with a peak net mass transport into the polar stratosphere about 1.2 trillion tons per day. We expect strong cold air intrusions over the North American continent, especially over Canada and west coast of the United States during the last week of January. The northern part of Eurasia (north of 45N) is also expected to experience below-normal temperatures (see map forecasts).
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