by Kathleen Hesketh

Created on: March 15, 2009

Though tornadoes and hurricanes are well known for their destructive force, few people understand the deadly nature of the nor'easter. Named for the counterclockwise direction of wind flow around an area of low pressure, these storms are capable of bringing high winds, heavy precipitation and strong wave action to the eastern seaboard of the United States.

Low Pressure Forms

Ben Franklin was the first to notice that northeast winds usually followed precipitation that began in the south and moved northward up the coast. This is the typical pattern of the nor'easter. According to Robert E. Davis in his article "Nor'easter", written in Volume 81 of the American Scientist, nor'easters begin life like all storms, arising from an unstable atmosphere. This instability is often the result of frontal activity, where a cooler air mass meets the face of a warmer air mass, and the difference in temperature causes the atmosphere to destabilize. The resulting area of low pressure is nature's way of trying to stabilize an unstable situation.

According to Davis, a nor'easter also needs the presence of a strong jet stream to develop. The jet stream acts as a catalyst by moving mass away from the heart of the low pressure system, causing surface pressure to drop. This results in an intensifying low. When driven by prevailing west winds out over the Atlantic, a nor'easter can develop.

The Storm Track
Once a low pressure area has been driven over the Atlantic, it moves northward following the coastline. The exact track determines the effects it has on the land. If the low stays over water, the clockwise rotation of the storm brings the warmer air off the ocean onto shore. Here it meets with colder air. The low acts like a blender, spinning warm and cold air and becoming stronger. This causes high winds which bring about strong wave action. Moisture from the ocean feeds the storm, falling mostly in the form of snow or ice. When the low tracks farther inland, the effects of the storm are usually less severe, with decreased amounts of precipitation and less of a storm surge.

Nor'easters continue to follow the coastline toward Maine and the Canadian Maritimes. As they exit an area, strong winds on the back of the storm hit the region from the north and east, giving the storm its name. These winds can be heavy and sustained, causing blowing and drifting snow, wide spread wind damage and power outages.

Worst Nor'easter storms
The largest number of nor'easter storms recorded occurred between

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