Since word of a looming polar vortex event hit the street, some meteorological purists – including the National Weather Service - have pushed back hard.
They say vortex isn’t responsible for the spell of autumn-like weather spilling into the eastern U.S. this week, at the peak of summer.
They say those promoting the polar vortex are misleading the public and making a scientifically dubious connection.
If I hear a meteorologist call this a polar vortex, I may just shoot myself #NotAPolarVortex— EnriqueWx (@enriqueh0891) July 11, 2014
But, in reality, this is a textbook case of polar vortex influence on mid-latitude weather and, frankly, the reasoning of these polar vortex doubters is flawed. I’ll explain why using three graphics.
Some, including the National Weather Service Weather Prediction Center, have claimed the air mass spilling into the U.S. isn’t polar in origin, but rather has its roots from the northeast Pacific.
That’s only half right, as the animation below makes abundantly clear:
Two deep pools of cold air at high altitudes - yes, one from the northeast Pacific but also one from high in the Arctic - combined over Canada to generate this cold air outbreak. You can plainly see the evolution of these cold pools, as marked with “x”s above.
To see the polar origins of this air mass even more clearly, consider this graphic showing the air mass trajectory (i.e. where the air is coming from) posted on Slate.com by meteorologist Eric Holthaus.
The flow of air doesn’t get much more polar than this graphic portrays. Furthermore, if it was solely a northeast Pacific air mass affecting the U.S. this week, we would *not* have temperatures 10 to 30 degrees colder than normal (the Pacific ocean isn’t that cold!).
So I’ve demonstrated the air streaming in has some polar origins, but is it from the polar vortex? Absolutely – as this third and final graphic (below) helps illustrate.
The graphic is an animation of high altitude (roughly 30,000 feet) winds from the vantage point of the North Pole. The blue streaks circling the North Pole are the strongest winds and represent the proverbial polar vortex. Notice how one of the blue and green streaks – over which I superimposed stars - breaks off over North America. That’s effectively a spoke or filament of the polar vortex diving south and transporting this unseasonably chilly weather into the continental U.S.
Don’t just take my word for it. Consider Greg Postel, a severe weather expert at The Weather Channel with a Ph.D. in dynamic meteorology from the University of Wisconsin, buys into the polar vortex influence. Consider this Twitter conversation he had with Mashable’s Andrew Freedman:
The Weather Channel’s Stu Ostro also refers to what’s coming our way as a “spoke of the tropospheric circumpolar vortex”.
Some meteorologists may object to the use of the term polar vortex because the vortex is a “planetary-scale” feature the encircles the entire North Pole (the South Pole too) whereas, in reality, it’s just pieces of it that’s filtering into the U.S rather than the whole thing. But I don’t think media references to the vortex intend to imply the whole thing is devouring the Lower 48.
In my view, discussing the polar vortex’s significant role in mid-latitude cold air outbreaks is a great way to engage the public in the intriguing dynamics of meteorology. Some critics are being too literal about its definition and/or burying their heads in the sand, blinding themselves from a fascinating weather reality.