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The polar vortex—it sounds like a post-apocalyptic blue hole of swirling ice. But it’s just a low-pressure system of cold air. There are two polar vortices that exist in the stratosphere about six miles above Earth’s north and south poles. Temperature differences—cold air over the poles, warm air over the equator—are what drive all weather on Earth. A polar vortex event is no different, except that the storms are really cold.
The word “vortex” refers to the counterclockwise flow of air (from west to east). When the vortex is strong, it’s stable, acting like a temperature fence to keep the cold air close to the pole and the polar jet stream, a narrow band of westerly air currents, flowing in a relatively smooth circle along 50°–60°N/S latitude. The polar vortex over the North Pole is stable most of the year, but in the winter, the fence often weakens and expands, sending cold air southward to Siberia, Europe, and the USA with an increasingly variable jet stream path.
The January 2019 polar vortex event was exceptionally newsworthy not for how low the temperatures got (though some areas of the US Midwest experienced temperatures on par with an average winter in Antarctica) but for how widespread it was. Subzero temperatures (in Fahrenheit) are a fairly common occurrence in North Dakota and Minnesota, but not so much in Iowa, Illinois, Indiana, Ohio, and Pennsylvania.
What a lot of people—scientists and anyone who has to pay a heating bill in the Midwest—want to know is what causes the polar vortex to push southward, and when.
Saildrone operates a fleet of unmanned surface vehicles collecting an unprecedented amount of in-situ data, from wind speed and direction to relative humidity, pressure, and CO2, and surface temperature, in the Atlantic, Pacific, Southern, and Arctic oceans (the North Pole is not on land but situated on a sheet of floating ice in the Arctic Ocean that expands and shrinks with the seasons). The collected data informs Saildrone’s weather forecasting tool, which is generated by information from the world’s leading weather models.
Extreme temperatures, high or low, can make outdoor activities uncomfortable and sometimes even dangerous. Saildrone Forecast features hour-by-hour weather forecasting including wind, rain, snow, clouds, and temperature—and accurately predicted the January 2019 polar vortex event in the Midwest several days in advance—to make it easy to determine what activities are appropriate and what gear is required. Weather information is presented in a series of map layers that can be toggled on or off depending on your needs.
The Saildrone Forecast temperature layer provides absolute and relative temperature scales that can be toggled on and off with a single tap. Zoom out to view the entire US and you may see temperatures ranging from 70°F (20°C) in California to 0°F (-18°C) in Minnesota; zoom in to view Minnesota only, turn on the relative temperature scale, and you’ll see a colorful visualization of regional microclimates.
There is some evidence that rising ocean temperatures, disturbances in the jet stream, and increasing carbon dioxide in the atmosphere could make the polar vortex over the North Pole more unstable, causing it to expand southward more often causing more frequent or severe polar vortex events in inhabited areas of the Northern Hemisphere. Saildrones can’t keep the polar vortices over the poles, but the data collected in the oceans can help us better understand what causes them to shift, and when those shifts will occur.
Saildrone Forecast is available in the App Store for iOS and at forecast.saildrone.com.
