Eideard

Photo by Julie Denesha/Getty Images

Record snowfall, killer tornadoes, devastating floods: There’s no doubt about it. Since Dec. 2010, the weather in the USA has been positively wild. But why?

Some recent news reports have attributed the phenomenon to an extreme “La Niña,” a band of cold water stretching across the Pacific Ocean with global repercussions for climate and weather. But NASA climatologist Bill Patzert names a different suspect: “La Nada.”

“La Niña was strong in December,” he says. “But back in January it pulled a disappearing act and left us with nothing – La Nada – to constrain the jet stream. Like an unruly teenager, the jet stream took advantage of the newfound freedom–and the results were disastrous…”

“By mid-January 2011, La Niña weakened rapidly and by mid-February it was ‘adios La Niña,’ allowing the jet stream to meander wildly around the US. Consequently the weather pattern became dominated by strong outbreaks of frigid polar air, producing blizzards across the West, Upper Midwest, and northeast US.”

The situation lingered into spring — and things got ugly. Russell Schneider, Director of the NOAA-NWS Storm Prediction Center, explains:

“First, very strong winds out of the south carrying warm, moist air from the Gulf of Mexico met cold jet stream winds racing in from the west. Stacking these two air masses on top of each other created the degree of instability that fuels intense thunderstorms.”

Extreme contrasts in wind speeds and directions of the upper and lower atmosphere transformed ordinary thunderstorms into long-lived rotating supercells capable of producing violent tornadoes.2
In Patzert’s words, “The jet stream — on steroids — acted as an atmospheric mix master, causing tornadoes to explode across Dixie and Tornado Alleys, and even into Massachusetts…”

All this because of a flaky La Niña..?

And of course there’s this million dollar question: “Does any research point to climate change as a cause of this wild weather?”

“Global warming is certainly happening,” asserts Patzert, “but we can’t discount global warming or blame it for the 2011 tornado season. We just don’t know … Yet.”

Not that non-scientists won’t leap to negative conclusions as a result.

Not that anti-scientists won’t leap to stupid conclusions as a result.