From the Sarasota Herald Tribune:
Arctic blasts like those that plagued Florida in 2009 and 2010 could become the norm in coming decades.
The culprit is something weather experts call "blocking," which occurs when high pressure locks in place and forces the jet stream to go around it.A blocked jet stream — the current of air that drives weather eastward around the northern hemisphere — can steer far south bitterly cold air that is usually confined to the Arctic.Some blocking is likely again in the Atlantic this year, sending Florida at least a few blasts of cold air, one researcher predicts. And it may happen more in the future, leading to more cold winters.
"It wouldn't happen every year, but it would be more common," said Anthony Lupo, an atmospheric scientist at the University of Missouri.Meanwhile, weather experts with the National Oceanic and Atmospheric Administration say a Florida drought is almost certain this winter. But the agency did not make a temperature forecast, partly because of the uncertainty over that Arctic air.Common weather patterns periodically make the jet stream shift. La Niña, for example, a phenomenon driven by cooler-than-normal seas in the equatorial Pacific Ocean, makes the jet stream move north. La Niña winters, such as this one, can sometimes result in slightly warmer Florida temperatures.But La Niña also helps to set up a bubble of high pressure over the eastern Pacific. That high pressure blocks the jet stream, forcing it to shunt Arctic air south into central Canada and the United States....MORE