What Is a Nor'easter? The East Coast's Biggest Winter Storms
A nor'easter is a storm that tracks up the US East Coast with its strongest winds blowing from the northeast onshore — that wind direction, not where the storm comes from, gives it the name. They are the East's heavyweight storms: the blizzard of 1888, the 1993 "Storm of the Century," and most of Boston's and New York's record snows were nor'easters.
The recipe
They form where cold continental air meets the warm Gulf Stream, usually between Georgia and New Jersey, from late fall through early spring. The temperature contrast feeds explosive strengthening: when a storm's central pressure drops 24 millibars or more in 24 hours, meteorologists call it bombogenesis — a "bomb cyclone." Many of the worst nor'easters bomb out just offshore, close enough to throw heavy snow, damaging coastal flooding, and hurricane-force gusts at the coast.
Why snow forecasts bust
The all-important rain/snow line often sets up within 50 miles of I-95. A 30-mile shift in storm track moves that line across ten million people — the difference between 2 inches of slush and 20 inches of snow. This is why forecasters talk in ranges and why consecutive model runs matter more than any single map (the same lesson as hurricane spaghetti models).
When a nor'easter is underway, its warnings cluster into a single East Coast event on our winter storm tracker, and coastal flood products appear alongside the winter ones.
FAQ
Why is it called a nor'easter?
For the northeast wind that blows onshore ahead of the storm along the coast — not because the storm comes from the northeast. Most nor'easters actually approach from the south or southwest.
What is bombogenesis?
Rapid intensification of a mid-latitude storm — a central pressure drop of at least 24 millibars in 24 hours. A storm that does it is informally a 'bomb cyclone,' and many major nor'easters qualify.
Can a nor'easter be as strong as a hurricane?
In wind, sometimes yes — intense nor'easters produce hurricane-force gusts and severe coastal flooding. They differ in structure: nor'easters are cold-core storms powered by temperature contrast and are far larger than hurricanes, spreading their energy over a wider area.