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NYC Hazards: Coastal Storm Basics

There are two types of coastal storms that typically affect New York. In New York City, OEM — working in close collaboration with the National Weather Service, the National Hurricane Center and state and federal officials — monitors any hurricanes or tropical storms that develop in the Atlantic Basin:

Nor'easters

Nor’easters are intense storms that can cause heavy snow, rain and oversized waves that can cause beach erosion and structural damage. Wind gusts associated with these storms can exceed hurricane force in intensity.

Unlike tropical cyclones (which include tropical depressions, tropical storms and hurricanes), nor'easters contain a cold core of low barometric pressure. Their strongest winds are close to the earth's surface and they often measure several hundred miles across. Additionally, nor'easters can produce low-level storm surge, putting areas along the immediate coastline at risk of coastal flooding.

Nor’easters may occur at any time of the year but are most common during fall and winter months (September through April). Evacuations are unlikely for nor’easters, but the City may open shelters during severe storms to offer people relief. Learn more about winter storm preparedness

Tropical Cyclones

A tropical cyclone is an organized rotating weather system that develops in the tropics. While tropical cyclones begin as a tropical depression, meaning the storm has sustained winds below 38 mph, it may develop into a tropical storm (with sustained winds of 39 to 73 mph) or a hurricane (with winds of 74 mph and higher).

Tropical cyclones contain a warm core of low barometric pressure and can produce heavy rainfall, powerful winds and storm surge.

While generally less dangerous than hurricanes, tropical depressions, and tropical storms can still be deadly. Heavy rains, coastal flooding and severe weather, such as tornadoes, pose the most significant threat.

Hurricanes

No storm combines duration, size, and wind speed more destructively than a hurricane. With sustained winds of more than 74 mph, hurricanes can flatten homes, topple trees and turn loose objects into deadly projectiles. The storm's driving winds and torrential rains can cause massive and dangerous flooding in low-lying and poor-drainage areas. However, storm surge — the dome of seawater pushed forward by the oncoming storm — is the most serious hurricane-related hazard.

Hurricanes are categorized by intensity using the Saffir-Simpson Hurricane Scale.

Hurricane season lasts from June to November, when hurricanes are most likely to form in the Atlantic Ocean and the Gulf of Mexico. While hurricanes may strike at any time during hurricane season, New York City is most at risk between August and October. 

Coastal Storm Terminology:

  • NOR'EASTER: An intense storm that can cause heavy rain and snow, strong winds, and coastal flooding. Nor'easters have cold, low barometric cores 
  • TROPICAL CYCLONE: An organized, rotating, low-pressure weather system of clouds and thunderstorms that develops in the tropics
  • TROPICAL DEPRESSION: A tropical cyclone with sustained winds of 38 mph or less
  • TROPICAL STORM: A tropical cyclone with sustained winds between 39 mph and 73 mph
  • TROPICAL STORM WATCH: Issued when there is a threat of tropical storm conditions in 48 hours
  • TROPICAL STORM WARNING: Tropical storm expected within 36 hours
  • HURRICANE: A tropical cyclone with sustained winds of 74 mph or greater
  • HURRICANE WATCH: Issued when there is a threat of hurricane conditions in 48 hours 
  • HURRICANE WARNING: Issued when hurricane conditions are expected within 36 hours 
  • STORM SURGE: Water pushed toward the shore by the force of the winds swirling around the storm. Learn more about storm surge