C-C-C-COLD-D-D-D!
Dec 16, 2016
Blame Russia. No – we aren’t being political. We’re talking about the Siberian Express. It’s sort of a cold war of weather, when the frigid Arctic weather in eastern Russia zips through the USA. While scientists argue about the La Niña in the tropics, (it’s flickering on and off), our weather is being hammered by the polar air mass from Russia.
In winter, the Arctic air mass is the big dog for shaping weather.
Several scientists, including Judah Cohen of Atmospheric and Environmental Research, have warned that the recent giant build-up of Arctic cold and snow in Siberia signaled a potential problem for the US. Siberia is the refrigerator of the Northern Hemisphere and many were concerned that this cold could be carried to the US by “Siberian Express” jet stream winds, like we saw in 2012.
Cold weather built up in Siberia and is now being carried to Canada and the US.
The polar jet stream winds whip around the Arctic, trapping the cold air north. If it weakens, the cold air escapes south. This is called an Arctic Oscillation (AO) and when it is positive the winds are strong. When the AO is weak, cold air plunges deep into North America. Usually the air blasts along the east of the Rockies, blasting the Great Plains and portions of the Midwest.
A positive AO keeps the cold in the Arctic
A negative AO lets the cold escape into the US
Right now, the AO has weakened. Huge weather patterns, shaped by shifting air pressure or even large volcano blasts can affect the AO. Currently we have seen a moderately large (10 km or 6 miles high) volcano eruption in Kamchatka Russia and a weather pattern called a negative North Atlantic Oscillation (NAO) weakening the polar jet stream. It opened the door and the cold Arctic air poured in and made itself at home. Most experts expect the NAO to become positive by next week. Hopefully they are right.
The polar vortex is hitting parts of the US with temperatures 20 -- 30° colder than average. Source: NASA
Meanwhile, in the tropics, the weak La Niña conditions reformed. Don’t expect the tropical weather patterns to save us this winter. Instead, most experts expect a weak La Niña to bring some dry weather to California and the Gulf and leave Texas alone. Almost all experts agree the drying La Niña will be gone by spring planting.
Just remember, no matter what happens to the La Niña, the big dog this winter is the Arctic Oscillation.
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