DMV StormWatch

DMV StormWatch

Storm forecasts, updates, news and information including school delays & closings.


Nor-easters, What It Is and Why It's Dangerous

So What is a Nor'easter?

The densely populated region of the Northeast Megalopolis, encompassing cities like Boston, New York City, Philadelphia, and Washington D.C., faces heightened vulnerability to this type of storm due to its proximity to the coastline.

Nor'easters can bring about significant impacts, including heavy rain or snow, strong winds, coastal flooding, and rough seas in the affected areas. Additionally, they have the potential to induce severe weather conditions in southern regions.

Key Nor'easter Facts:

  • The presence of snow is not a prerequisite for identifying a nor'easter; instead, it hinges on the prevailing winds. As long as the winds originate from the northeast, a weather system can be classified as a nor'easter, with the term commonly applied to robust winter storms along the Northeast coast.
  • These storms are most prevalent and intense between September and April, although they can occur throughout the year.
  • Typically, they form within a 100-mile stretch east or west of the East Coast, between Georgia and New Jersey, before moving east or northeastward.
  • Their peak intensity often occurs near New England or the Maritime Provinces of Canada.

Nor'easter Development:

The formation and strength of nor'easters are influenced by temperature differentials and geographic location.

A contrast in temperature between warm air over the water and cold air over land provides the necessary instability and energy for nor'easter development. Warmth is sourced from the Gulf Stream, a swift Atlantic Ocean current originating in the Gulf of Mexico, extending to Florida's tip, and following the U.S. eastern coastline northward. This current helps maintain relatively mild coastal waters throughout winter, warming the cold air above and causing it to rise. Cold air is ushered in by the polar jet stream, transporting frigid air southward from Canada into the U.S. and then eastward toward the Atlantic Ocean.

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