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 10:
STRAT_F (01/23 – 01/28)
This week we are forecasting a new event with 45 lead days, named as STRAT_F. It is expected to occur between 01/23 and 01/28. STRAT_F looks to be a strong event with a peak net mass transport into the polar stratosphere about 1.0 trillion tons per day. We expect strong cold air intrusions over the North American continent during the last week of January. The northern part of Eurasia is also expected to experience below-normal temperatures (see maps).
Follow up on Forecast Made in the Previous Weeks:
STRAT_D (12/11 – 12/18), first forecasted on 11/20, and later revised on 12/03, is happening. STRAT_D turns out to be a moderate event with twin peaks, transporting a net air mass into the polar stratosphere about 0.5 trillion tons per day now, and is expected to peak again on 12/17 with a 0.6 trillion ton per day of air mass transport, which is the peak we originally forecasted on 11/20. The winter storm Caly, which is associated with our first peak of STRAT_D, is mainly affecting Northwestern United States, bringing heavy snow and imposing hazard conditions to people there. It is going to sweep through the continent in the next few days. We expect nearly 80% area plunging below normal temperatures. But the cold is not over yet. The second peak of STRAT_D on 12/17 will affect both continents, especially North America, leading to more than 80% and 55% of area occupied by below-normal temperature for mid-latitude regions of North America and Eurasia, respectively
STRAT_D1 (12/24 – 12/27), first forecasted on 11/25, and later revised on 12/03, is still expected to be a long-lasting, twin-peaked, but relatively weak event. STRAT_D1 is expected to 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, STRAT_D1 will mainly affect the Eurasian continent, causing below normal temperature conditions up to 60% of area, while the United States will not be affected.
STRAT_E (01/08 – 01/13), first forecasted on 12/03, is still expected to occur between 01/8 and 01/13 with a peak on 01/08. We believe STRAT_E is going to be a very strong event with a peak net mass transport into the polar stratosphere over 1.0 trillion tons per day. The map of probability of below-normal surface temperature shows high likelihood for strong cold air outbreaks to take place over the entire Eurasian continent, as well as the Western and Southeastern United States.
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