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Washington Voices

Weather: High pressure system sent polar vortex south

Thu., Jan. 16, 2014

I’ve been receiving a number of questions asking about the so-called “polar vortex” of Arctic air that has contributed to some of the coldest weather in decades across much of the country.

The polar vortex is also known as a polar cyclone, polar low or a circumpolar whirl. It’s a massive low pressure system that is often stationary and located near the North Pole. There are actually two of these systems, one near Baffin Island, southwest of Greenland, and the other over northeastern Siberia. The polar vortexes also surround the polar high which is usually directly over the North Pole.

Early last week, the polar vortex moved 1,200 miles farther south when compared to its normal winter position. One reason why this massive low pressure system moved was due to a strong high pressure system that built in over the western U.S. The high built so far to the north that much colder air from Canada moved down the ridge and also forced the polar vortex to move southward and push the frigid air into the U.S., especially east of the Rockies.

Fayetteville, Ark., plunged to an all-time record low of minus 3 degrees on Jan. 7. Farther to the north, it was a brutal minus 15 degrees in Chicago and a dangerously cold minus 41 near Jordan, Mont., on Jan. 4 and 5. Temperatures near the Great Lakes ranged from minus 20 to minus 35 degrees with wind chills near minus 50 last week.

By contrast, California is seeing one of the driest periods in recorded history. Wells are going dry as there is also very little snow in the Sierra Nevada. The long-range computer models continue to have the strong high pressure system located over the western U.S. at least through next week, which would mean little or no rain for California and the Southwest and just occasional showers in our region.

However, toward the end of the month, the high may weaken to allow moisture into California with rain and snow across the Inland Northwest.

As far as snowfall totals for the rest of the season, it looks like we’ll have some snow mixing in with occasional rain in the lower elevations as we now have, according to some scientists, a weak and warmer El Niño sea-surface temperature pattern.

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