Did you know that originally weather services said that Hurricane Sandy would die off when it left the Caribbean Sea?
A pattern called the “Greenland High” was creating winds that would shear off the top of the storm. Instead, the extraordinarily hot waters of the Atlantic kept Sandy alive and the shearing winds pushed Sandy straight into New Jersey.
The same winds that steered Sandy into the East Coast will be helping to shape the weather in early winter. Source: NOAA
Sandy is gone. The “Greenland High” however will be coming back and helping to shove more wet weather into the East Coast early this winter. No, not hurricanes, winter storms with snow, that white stuff that we didn’t see last winter.
Let’s explain. The hot waters of the Atlantic are still unusually warm off the Northeast coast. They were unusually warm all spring and summer and it will take a while to cool off. This means that when cold continental air hits this hot marine air, you get wet energetic storms. We saw this with Sandy, which was horrendously damaging despite only reaching Category 1 in wind power. It acquired energy from the cold front that was hitting the East at the same time. (See that line of clouds in the satellite picture? That’s the cold front that blended with Sandy to make a hybrid “Frankenstorm.) We will see this wet crash of warm and cold air until the Atlantic finally cools.
Secondly, when you get a hot Atlantic, it creates a weather pattern called a negative North Atlantic Oscillation (NAO). As I have mentioned in previous blogs, the North Atlantic Oscillation acts like a crossing guard. When it is positive, it lets cold storms leave North America and cross the Atlantic. When it is negative, it blocs the storms. The cold fronts remain in North America.
Warm Atlantic waters tend to encourage the development of negative NAOs and blocking Greenland High air pressure. Source: NOAA
This Halloween we had a negative NAO. It blocked Sandy from drifting out into the Atlantic. It created an atmosphere pattern with the Greenland High that turned shearing winds into steering winds and steered Sandy into the East Coast.
History suggests that Negative NAOs are more common when the Atlantic is warm. So expect the same blocks that affected Sandy to affect many of this winter’s storms. They will form Nor’easters and linger on the East Coast. This doesn’t mean that early winter would be astonishingly cold but it will be snowy.
So it looks like you will be able to build some snowmen this winter.
NOTE: I always try to write an upbeat blog. However, it hurts to see the damage that Sandy has done. My best wishes to everyone trying to recover.
Evelyn Browning Garriss, historical climatologist, is a longtime writer for The Old Farmer's Almanac. She is also editor of The Browning World Climate Bulletin and has advised farmers, businesses, and investors worldwide on upcoming climate events and their economic and social impact for the past 21 years.