Climate Fact: Jet Stream Secrets

Could lessons from its 44-year climatology improve our forecasts of cold snaps?

Jet streams are the air traffic controllers of Earth’s weather. These fast-moving “rivers of air” meander through the atmosphere’s landscape, pushing around mountains and valleys of high and low pressure. The jet stream’s position can be a great clue for predicting some types of extreme weather.  An international team of scientists showed that when the average position of the Polar Jet falls below 44°N in winter months, the chances of an extreme cold snap nearly double for the Mountain West and triple across Europe. And these odds remain in place for nine days – even if the jet stream moves! Even more amazingly, these odds quadruple in Europe for the most severe, record-breaking cold snaps that represent the coldest one percent of all recorded temperatures from 1957 to 2001. However, when the Polar Jet inches northward between 44°N and 53°N, the odds of a European cold snap actually decrease and the U.S. remains unaffected. These jet stream secrets could be strong, medium-range forecasting tools for meteorologists since these results are derived from almost 50 years of observational data.

The Polar Jet Stream. Video courtesy of NASA.

(Source: Mahlstein, I., O. Martius, C. Chevalier, and D. Ginsbourger, 2012. “Changes in the odds of extreme events in the Atlantic basin depending on the position of the extratropical jet.” Geophysical Research Letters, 39:L22805, doi:10.1029/2012GL053993)

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