Frigid winter on LI? Blame it on La Niña

As if you had any doubts, yes, we're experiencing a colder and snowier winter than usual.

The National Weather Service in Upton says average temperatures for the past two months have been "remarkably" below normal - by about 4 degrees.

And we've had 20.5 inches of snow in January on top of December's 14.9. The average winter brings a total of 32 inches, so we've already surpassed that by more than 3 inches. And February, usually the snowiest month, is yet to come.

Blame it on a La Niña weather pattern that is bringing above-normal moisture in from the Pacific Ocean combined with a North Atlantic Block that is holding colder air from the north over us. And don't expect the pattern to change for at least a couple more weeks, meteorologists say.

"Once you get cold and snowy over a big part of North America early in the winter, which the [post-Christmas] blizzard did, it tends to make the next month or month and a half at least very snowy and cold," said News 12 Long Island chief meteorologist Bill Korbel. "Because there's more snow, it's colder, and because it's colder, there's more snow until there's a huge pattern shift. This pattern that has set up has been particularly stubborn."

The result is record cold for the region - the high Tuesday on Long Island was in the upper teens. Usually, the normal low temperature would be in the mid-20s.

Tim Morrin, a Weather Service meteorologist, said the agency defines meteorological winter as December through February. "We are a little bit over halfway through that and we have been persistently colder than normal," he said. In December the average temperature at Islip was significantly below normal, 4.2 degrees. "We consider that remarkable." More than 2 degrees is considered a significant variation.

SEE PHOTOSSnowstorms that buried LI over the past 100-plus years

In January so far, the average temperature has been 27.6 degrees, which is 3.5 degrees below normal, "again quite noteworthy," Morrin said. He expects the pattern of cold and snowfall to continue for at least two to three more weeks, which is as far out as any prediction can be made with some certainty. More snow is predicted for Tuesday and Wednesday.

The reason for the severe weather, Morrin said, is "we have been in a consistent La Niña pattern, which means the water temperatures in the equatorial Pacific are cooler than normal. El Niño is the opposite."

Either abnormality changes the jet stream and wind flow at lower elevations. La Niña pushes the jet stream farther south, making conditions more stormy with more precipitation, but usually milder temperatures, he said. But a blockage is disrupting the jet stream near Greenland.

"So what happens is the storms, rather than coming up from Texas to the Great Lakes with us on the warm side of the track, are blocked, keeping the cold air locked in place," Morrin said.