“This split of the polar vortex will shift the upper atmospheric pattern such that the coldest airmass is located in western North America as well as over parts of Europe. This will allow for a ridge of high pressure to amplify in the eastern US, bringing unseasonably warm conditions next week,” said Ed Vallee, Long-Range Meteorologist and President of Vallee Wx Consulting.
The Weather Channel describes the atmosphetic impact for the Northern Hemisphere, as this unique weather event splits the polar vortex into two smaller vortices: one over western Canada and another over Europe.
- A split of the polar vortex occurred this week due to warming in the stratosphere
- This is likely to result in cold temperatures in Europe
- Although a disruption of the polar vortex is sometimes associated with cold weather in the eastern U.S., that is not always guaranteed
Further, from the Weather Channel:
“Across the Arctic, where the polar vortex typically stays locked, the stratosphere has warmed. This typically kicks into motion a polar vortex disruption like we are seeing. The stratosphere is a layer of the upper atmosphere above which most of our weather occurs – known as the troposphere – and where most of the polar vortex resides.” (Shown Below: The polar vortex has split into smaller vortices, one over Europe, and the other over northwestern North America.)
The one vortex over Western Europe and much of Eurasia will send the region into a dangerous deep freeze for the second half of February into early March. A disruption of the polar vortex has sent March 18 U.K. natural gas contracts soaring on the session, advancing +3.6% to 51.540.
During the same timeframe, the vortex over western Canada could bring spring-like conditions for the Eastern U.S. in the second half of February through early March. Temperatures for the next few weeks could be 20 to 25 degrees Fahrenheit above average for this time of year. Highs in the 70s Fahrenheit are possible from Washington, D.C. to New York City, which would be a significant change from the arctic conditions experienced earlier in the winter season. In the Western U.S, it is an entirely different story, particularly in the Northern Rockies, which could see measurable snowfall and frigid arctic air for the next two weeks.
A disruption of the polar vortex has sent US March 18 natural gas contracts crashing -22% in February to December 2017 lows. A breach below 2.50 would indicate a deeper correction, as much as -15% to 2.172 area where the .764-fib resides (measured from the March 2016 low to December 2016 high).
“Models are indicating very impressive early Spring warmth across the eastern U.S. next week… the West/Rockies will have some cold air to deal with, however,” said Michael Ventrice, a Meteorological Scientist for the Weather Company.
What’s all this talk about a Sudden Stratospheric Warming (SSW)?
Mashable explains that the primary polar vortex exists in the stratosphere, which is the layer of the atmosphere where most of the weather occurs. An SSW event refers to a rapid warming of the stratosphere at high latitudes, up to 122 degrees Fahrenheit in a matter of days, some six to nine miles above the earth’s surface. Mashable said, “an SSW event, took place in early-to-mid February, and this has caused the splitting of the stratospheric polar vortex.”
“Someone once asked why they call them “sudden” stratospheric warmings,” said Anthony Masiello, a private weather forecaster.
Mashable further explains how the SSW broke apart the polar vortex into two and what it means for the weather in your region:
Sudden stratospheric warming events occur when large atmospheric waves send energy upward, into the stratosphere, setting in motion a complex process that results in the temporary breakdown of the polar vortex. This February’s stratospheric warming event was particularly extreme, possibly setting records for how sharply temperatures spiked in the upper atmosphere.
The polar vortex split isn’t the only factor favoring a cold snap in Europe, warmup in the Eastern U.S., and cool down in the West. There’s also a cycle of atmospheric pressure over the North Atlantic Ocean, known as the North Atlantic Oscillation (NAO), that can increase the odds of colder and snowier weather in some of these areas.
Computer models are projecting the NAO will become strongly negative during the next few weeks in response to the polar vortex split and stratospheric warming event, and this also favors cold and snow in Western Europe. (It also ups the odds of similar weather in the eastern U.S., but that may not happen right away.)
“A significant PV [polar vortex] disruption is often followed by widespread cold temperatures across northern Eurasia and the Eastern US. However the cold is more certain across northern Eurasia following these type of PV disruptions,” meteorologist Judah Cohen, who specializes in seasonal weather forecasting and tracking the polar vortex for AER, a Verisk Analytics company, wrote on his blog.
The negative mode of the NAO typically features an area of strong high pressure over Greenland, which blocks the progression of weather systems moving in from the southwest, and causes the jet stream to plunge southward over Europe, allowing cold air to flow in from the Arctic and Scandinavia. Sudden stratospheric warming events tend to cause the NAO to switch into negative mode shortly after they occur.
The rest of February should feature a colder than average Western U.S., coupled with a milder than average East Coast. However, the negative NAO phase could bring a return of winter weather to the East in early March, depending where exactly that Greenland block sets up. There’s often a delay between when the polar vortex is disrupted, and when the cold air arrives in parts of the U.S., if at all.
Snow lovers will be watching upcoming forecasts anxiously because the deeper into March we go, the less likely widespread snows along the East Coast become.”
In summary: the polar vortex has split, here’s what that means for us: