The Rutgers snow lab says this January saw the sixth-widest snow cover in the Northern Hemisphere; the United States had an above average snow cover for the last few months. But that’s a misleading statistic, Robinson said, because even though more ground is covered by snow, it’s covered by less snow.
And when those big storms finally hit, there is more than just added moisture in the air; there’s extra moisture coming from the warm ocean, Robinson and Oppenheimer said. And the air is full of energy and is unstable, allowing storms to lift yet more moisture up to colder levels. That generates more intense rates of snowfall, Robinson said.
‘‘If you can tap that moisture and you have that fortuitous collision of moist air and below-freezing temperatures, you can pop some big storms,’’ Robinson said.
Pennsylvania State University climate scientist Michael Mann points to the recent Northeast storm that dumped more than 30 inches in some places. He said it was the result of a perfect set of conditions for such an event: arctic air colliding with unusually warm oceans that produced extra large amounts of moisture and big temperature contrasts, which drive storms. Those all meant more energy, more moisture and thus more snow, he said.