What the heck is a nor’easter, anyway?

A nor’easter is a strong low-pressure system that typically affects Mid-Atlantic and New England states. It is a cyclonic storm, defined by powerful winds that circle counterclockwise around a region of low atmospheric pressure.

A storm is called a “nor’easter” when winds over coastal areas blow from the northeast. Such storm systems can occur at any time, but are most frequent, and strongest, between September and April. The storms usually develop between Georgia and New Jersey, within 100 miles of the coastline, and generally move north or northeast.

Intense nor’easters can produce heavy snow and rain, gale-force winds approaching 60 miles per hour, rough seas, coastal flooding and beach erosion.

Meteorological conditions on the East Coast are often ideal for the development of nor’easters. Cold arctic air travels south across the plains of Canada and the U.S. and eastward toward the Atlantic Ocean via the jet stream, while, at the same time, warm air from the Gulf of Mexico and the southern Atlantic moves northward. The coastal waters remain relatively mild during the winter thanks to the Gulf Stream, and this helps warm the cold winter air over the water. Areas where arctic air over land clashes with warm air over the ocean are where nor’easters are born.

Compiled by Deirdre Krasula from www.nws.noaa.gov and noaa.gov, the Web sites of the National Oceanic and Atmospheric Administration.