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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 February 24:

No new forecast is made this week.


Minor Stratospheric Warming Event (02/23 – 02/26)

The minor stratospheric warming event we forecasted on 02/18 started on 02/23. The STRAT_G event significantly weakened the polar vortex and the (unexpected or unforecasted) strong stratospheric PLUSE event that was right after the STRAT_G broke the polar vortex few days after its peak, which had an intensity of 1.2 trillion tons per day. This minor SSW event is causing a temporary relocation of the polar stratospheric vortex off the Arctic.

Follow up on Forecast Made in the Previous Weeks:

STRAT_H (02/23 – 02/28), first forecasted on 01/21 to take place between 02/23 and 02/28 with a peak on 02/27, is happening. We believe STRAT_H is a moderate “aftermath” event after the minor stratospheric warming event caused by the PULSE event on 02/19. The peak net mass transport into the polar stratosphere for STRAT_H is about 0.7 trillion tons per day. Associated with STRAT_H, West coast and mid-west of the United States are experiencing below-normal temperature, bringing heavy snow to regions in mid-west; while in China, regions below 45°N are now suffering from abnormally cold weather, and snow are reported in some areas where snow is not common.

STRAT_I (03/08 – 03/12), first forecasted on 02/11, is expected to take place on time. STRAT_I is also a moderate event, with a peak intensity of 0.6 – 0.7 trillion tons per day. Associated with STRAT_I, the majority of the area above 45°N in both North American and Eurasian continents will experience below-normal temperatures.

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