jet stream, cold front, polar vortex, July | The Old Farmer's Almanac

When Jet Streams Wiggle

Photo Credit
NASA, the Space Station
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It’s a bird; it’s a plane—no—it’s a polar vortex! AAAAAGH!


The jet stream wiggled far to the north in the West and dropped south in the Midwest, bringing cool weather. Source: European Ensembles (ECMWF MODEL)

Relax; during the third week of July, we had a cold front. It was a bit stronger than normal and reduced July temperatures between 10˚–30˚F. Around the Great Lakes, it almost felt like autumn. Actually, it was refreshing, but some people needed to slip on a sweater. If you lived in the sweltering West, you were envious.

However, in the headlines a scary polar vortex was going to slam the Midwest. Anyone who remembers last winter’s polar vortex had a moment’s pause. Was frost going to hit the garden? Were the crops going to die? Were we going to be buried in snow?

This July’s weather pattern was compare (erroneously) to last winter’s polar vortex. (Source: NASA)

No, we were hit by a cliché!

Look, it’s hard for comfortable summer weather to get any attention. This summer, weather reporting is competing with lots of scandals. Northern Canadian temperatures are really hot, but sweating Inuit or Eskimos don’t make headlines. However, the jet stream is dipping unusually far south in the Midwest. The last time this happened, it was the frigid Polar Vortex, and it was fun to be a weatherman last winter. Some weather people warned that the Polar Vortex was coming back and made headlines.

Actually, it is only a wiggly jet stream. The jet stream winds form on the boundary between cool atmosphere and warm atmosphere. Normally they tend to surge north, then south, then north again. However, early this month, Japan was hit by a category 4 super typhoon. Typhoon Neogori then swirled north and pushed a lot of hot, humid air unusually far north. The jetstream veered unusually far north, so California and Western Canada were hot. Then it plunged south, and the Midwest got a cold front.

The eye of Super Typhoon Neogori, the storm that shoved the weather patterns around. Source: NASA, the Space Station

Notice, this was not a real polar vortex, just a “ridge” or southern drop of the jet stream. It was a cool front, a bit stronger than normal. But for a few days, a wiggly jet stream sure collected some scary headlines!