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 18:
No new forecast is made this week.
Minor Stratospheric Warming Event (02/19 – 02/23)
It appears that a minor stratospheric warming event may occur around 02/19 after a (unexpected or unforecasted) strong stratospheric PLUSE event that is right after the STRAT_G event. This minor SSW event would cause a temporary relocation of the polar stratospheric vortex off the Arctic.
Follow up on Forecast Made in the Previous Weeks:
STRAT_G (02/11 – 02/15), first forecasted on 01/07, has peaked on 02/15. STRAT_G transported about 0.9 trillion tons of air mass per day, significantly weakened the recovering polar vortex. Associated with STRAT_G, the winter storm Pluto is affecting the New England area, bringing heavy rainfall and snow. Meanwhile, the northern latitudes of the Eurasia is experiencing below normal temperature. However, due to the extremely warm polar surface air temperature condition that is partially caused by the series of events associated with the week-long collapse of the polar vortex, the polar air mass transported out of polar region near surface associated with STRAT_G was not able to impact areas south of 45°N in both continents. Similarly, the (unexpected) PLUSE event on 02/19 will have limited impact to surface temperature in both continents due to the currently anomalously warm surface air temperature over the Arctic region. Nevertheless, the PULSE even right after the G, which is going to transport over 1.2 trillion tons of air on its peak date, would break up the polar vortex again, causing a minor stratospheric warming event as we mentioned above.
STRAT_H (02/23 – 02/28), first forecasted on 01/21, is still expected to occur between 02/23 and 02/28 with a peak on 02/28. 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, we expect strong cold air surges over the North America and up to 70% of the area will be anomalously cold during the last week of February.
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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