WASHINGTON — A pattern flip that could send extreme cold air spilling into the region this winter may take shape. The polar vortex, which traps cold air near the North Pole, may experience a disruption that will allow some of the cold air to escape. Right now the chances are very small, but some of the long range weather models are picking up on a trend. Even if the polar vortex experiences a disturbance, impacts will not be felt until late January or February, if at all.
The polar vortex trends
Think of the polar vortex as a pool of very cold air, surrounded by winds circulating around the North Pole.
Right above the polar vortex, we have the stratospheric polar vortex, about 10 to 30 miles above the North Pole, essentially the top of the world. It's the warming near the stratospheric polar vortex that could have ripple effects on our weather. It can cause the polar vortex to wobble and spill cold air.
Scientists at Climate.gov, who track the polar vortex, found only a minor chance for stratospheric warming. Laura Ciasto, a meteorologist with the Climate Prediction Center with an expertise in long range forecasting and the role of the stratosphere in forecasting, is monitoring the trend.
In a blog post, Ciasto said the GEFS model (Global Ensemble Forecast System) found that only 13% of individual forecasts indicate major sudden stratospheric warming.
However, when looking at the European model or ECMWF (European Centre for Medium-range Forecast) she found that those models also show a minor warming, but more of those individual forecasts hint at a major warming.
"Even when the polar vortex is only slightly weakened, particularly for a prolonged period, additional small wobbles can further destabilize the vortex and break it down completely," Ciasto said.
At this point the impacts are not completely clear, but it's definitely a phenomenon that will be closely watched. Seasonal outlooks with the Climate Prediction Center show a trend for above average temperatures in the DMV and for the northern half of the U.S. However, a disruption in the polar vortex could cause a cold air outbreak.
Warming the stratosphere
Disruptions in the stratosphere can cause sudden stratospheric warming event or "SSW" event.
These SSW events are caused by disruptions in the stratosphere. Just as there are waves at the beach, there are large atmospheric waves of air on the planet. Those atmospheric waves can crash, just like the ones in the ocean. As they do, they transfer large amounts of energy that can cause warming and alter the circulation around the polar vortex. This could allow cold air that is normally trapped to spill out into the United States
Usually, the highest impacts of a disrupted polar vortex are felt in the North Atlantic in the eastern United States or northern Eurasia, according to experts at Climate.gov.
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