Nor'easter
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Nor'easter: Here's my layman's try at a Nor'easter definition. A Nor'easter is counter-clock wise turning cyclone (a storm system circulating around a center) as opposed to a hurricane which turns right in the northern hemisphere. Nor'easters are spawned by a very curvy Jet Stream that dips far south allowing cold arctic air to meet warm air. The warm air rises over the cold, creating instability up high and an area of low pressure below. Larger temperature differences create greater turbulence. Once the system is formed, the earths rotation causes the air to circle around the center (similar to when you drain the water out of your bath-tub). This creates the northeast wind, hence it's name nor'easter. They typically form near the Bahamas or north of Cuba, along the Appalachians or off Cape Hatteras. The Jet Stream plays a very important role also in the strengthening of the storm. As the incoming air rises around the center, the Jet Stream whisks it away further increasing the speed of the incoming air. The faster the air moves the faster the barometric pressure drops. Weather forecasters call a 24 millibar drop in 24 hours "The Bomb".  Normal Jet Stream winter pattern is to follow the coast and consequently drags the storm northeast ward. Some time a High further north blocks its path and so it churns over the ocean for a long time sending beach-eating waves onshore. During the October to April nor'easter season February is the busiest month. Researchers say the biggest ones occur in October, January and March. What nor'easter don't achieve in wind-speed as compared with hurricanes, they achieve in duration (up to a week) and size (up to 1000 miles or more in diameter).

WIND SPEED/SEA HEIGHT RELATIONSHIPS

 

Wind Speed Sea Conditions
0-3 KTS SEA LIKE MIRROR
4-6 KTS RIPPLES, LESS THAN 1 FT
7-10 KTS SMOOTH WAVELETS, 1-2 FT
11-16 KTS SMALL WAVES, 2-4 FT
17-21 KTS MODERATE WAVES, MANY WHITECAPS, 4-8 FT
22-27 KTS LARGE WAVES, SPRAY, 8-13 FT
28-33 KTS HEAPED SEAS, FOAM FROM BREAKING WAVES, 13-20 FT
34-40 KTS HIGH WAVES, FOAM BLOWN IN WELL MARKED STREAKS, 13-20 FT
41-47 KTS SEAS ROLL, SPRAY MAY REDUCE VISIBILITY, 13-20 FT
48-55 KTS VERY HIGH WAVES, WHITE SEAS, OVERHANGING CRESTS 20-30 FT
56-63 KTS EXCEPTIONALLY HIGH WAVES, 30-45 FT
OVER 63 KTS AIR FILLED WITH FOAM, SEA COMPLETELY WHITE, OVER 45 FT

THIS CHART  IS BASED ON CRITERIA USED BY THE WORLD METEOROLOGICAL ORGANIZATION.  MARINERS SHOULD REALIZE THAT THESE VALUES ARE REACHED AFTER WINDS HAVE BLOWN STEADILY OVER A LARGE AREA FOR AN EXTENDED PERIOD OF TIME.  ALSO, THE VALUES GIVEN ARE AVERAGE OBSERVED WAVE HEIGHTS, NOT THE HIGHEST THAT MAY BE SEEN FOR A GIVEN WIND SPEED.

Home Page Up One Level Hurricane vs Nor'easter History of Nor'easter
Revised: January 14, 2004

  J. Banck
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