What is the Hazard?
Most New Yorkers recognize that they have to battle high winds from time to time, but not all high wind events are caused by the same types of weather systems.
Hazardous high-wind events can occur from tight pressure gradients, strong frontal systems, nor’easters, hurricanes and severe thunderstorms, which may produce straight line winds or tornadoes. High wind events may or may not be accompanied by precipitation and can vary in geographic extent, intensity, and duration. For example, events can range from short bursts of high-speed winds, such as with a severe thunderstorm, to longer periods of sustained winds from events such as a hurricane. Severe thunderstorms typically have less than an hour of warning lead time, but nor’easters, tropical cyclones, and other types of high wind events usually have several hours to a few days of warning lead time.
Causes of High Winds
New York City is subject to various high-wind events (for the purposes of this profile, high winds are defined as winds exceeding 50-60 mph which align with NOAAs definition of damaging winds), which each have different characteristics. As Nor’easters and hurricane are discussed in greater detail in the Coastal Storms profile, for the purposes of this hazard profile, high winds are grouped into three categories below:
Types of High Wind Events
Severe thunderstorms, which are capable of producing large hailstones- also known as hail, damaging winds, and tornadoes, can pose serious threats to human life, safety, and property in New York City.
Thunderstorms are normally localized events. According to the National Weather Service (NWS), the average thunderstorm in the United States is 15 miles in diameter and lasts an average of 30 minutes. Non-severe thunderstorms have winds of less than 58 mph or less and can produce lightning, rain, and sometimes, small hail.
About 10 percent of thunderstorms in the United States are classified as severe, with winds of at least 58 mph and/or large hail of at least 1 inch in diameter. Severe thunderstorms happen when warm, moist air collides with colder air. As the warm air rises, the moisture condenses and builds up energy as it forms into a thunderstorm cloud. This pent-up energy releases as a violent thunderstorm. In severe cases, the storm’s structure creates a vertical updraft that can rotate for hours, leading to hazardous tornadoes, high winds and hailstones.
Hail are falling particles of ice. Hail develops as warm, moist air rises in the upper troposphere and cools below the freezing point. The water vapor then condenses into ice crystals. These ice crystals remain suspended by high-velocity updraft winds, growing larger, and eventually fall to the ground as hail, at speeds that can approach 100 mph or more.
Generally, the size of hailstones are correlated with the severity of the thunderstorm. In New York City, the diameter of hail typically ranges from 0.20 inches to 2.0 inches.
Severe storms with high winds lead to several hazards -- broken tree limbs, downed power lines, and flying debris, which can lead to power outages, transportation disruptions, damage to buildings and vehicles, and personal injury and death.
A tornado is a violently rotating column of air that has winds of 65 mph to over 300 mph. These short-lived storms generally appear as whirling funnel-shaped clouds extending from the base of a thundercloud down to the ground. Tornadoes are initially transparent with extremely strong winds – a danger because they cannot be easily seen. As they pick up debris and dust, and as their water vapor condenses, they acquire a grayish color.
Tornadoes are the most violent atmospheric phenomenon to occur over land, and over a small area, they are the most destructive. In a matter of seconds, tornadoes can uproot trees, demolish buildings, and turn harmless objects into deadly missiles. Predicting them can be difficult, so there may only be a few minutes for officials to warn people to seek shelter and take other precautions for their safety.
A tornado’s path of destruction can be more than 1 mile across and 50 miles long. Each year in the United States, an average of 1,200 tornadoes strike, causing around 60 to 65 fatalities and 1,500 injuries.
Not all high-wind events are associated with severe thunderstorms and tornadoes. Other types of windstorms that affect New York City are the result of complex interactions in the atmosphere. High winds are a byproduct of certain processes in the air -- for example, when atmospheric conditions push air from high to low pressure areas, and when strong cold and warm frontal systems interact.
Two other causes of high winds that are familiar to New Yorkers – hurricanes and nor’easters - are included in the Coastal Storm hazard profile.
High winds can create a range of hazards -- downed trees and power lines, flying debris, and building collapses. Any of these hazards may lead to power outages, transportation disruptions, damage to buildings and vehicles, and personal injury and death.
Flying debris is the primary cause of damage during a windstorm. Even if a building remains structurally sound, broken window glass can injure people inside and outside the building and allow the wind to cause extensive damage inside.
High Wind Attributes/Characteristics
Depending on the type of high wind event affecting New York City the National Oceanic and Atmospheric Administration (NOAA) uses two different scales to describe the event - Enhanced Fujita is used to classify the severity of tornadoes and Beaufort is used to classify the intensity of wind speed. Each associates higher numbers on the scale with higher levels of property damage. The size of hailstones and wind gust speeds can also be used to measure the severity of thunderstorms.
A severe thunderstorm produces wind gusts of 58 mph or more and/or hailstones of 1 inch or more in diameter.
Hailstone size varies widely, and the size correlates with the severity of the thunderstorm.
Hail Size and Related Damages
Source: Burt, Extreme Weather, 2007
Severe thunderstorms can also produce tornadoes. Prior to 2007, the NWS used the Fujita Scale (F-Scale) as the standard measurement to rate the strength of a tornado. Since February 1, 2007, NWS uses the Enhanced Fujita Scale (EF-Scale) as its standard measurement.
The EF-scale is more complex than the F-Scale and enables surveyors to assess tornado severity with greater precision. However, the F-Scale is still used to place the more recent high-wind events into the historical context.
NOAA’s chart compares these two scales and indicates the severity of damage associated with these rankings.
Enhanced Fujita Scale
|F-Scale||3-sec. gust speed (mph)||EF-Scale||3-sec. gust speed (mph)||Typical Damage|
|F0||45-78||EF0||65-85||Light damage. Some damage to chimneys. Branches broken off trees. Shallow-rooted trees pushed over, signboards damaged.|
|F1||79-117||EF1||89-109||Moderate damage. Peels surface off roofs. Mobile homes pushed off foundations or overturned. Moving autos blown off roads.|
|F2||118-161||EF2||110-137||Considerable damage. Roofs torn off frame houses. Mobile homes demolished. Boxcars overturned. Large trees snapped or uprooted. Light-object missiles generated. Cars lifted off ground.|
|F3||162-209||EF3||138-167||Severe damage. Roofs and some walls from off well-constructed houses. Trains overturned. Most trees in forest uprooted. Heavy cars lifted off the ground and thrown.|
|F4||210-261||EF4||168-199||Devastating damage. Well-constructed houses leveled. Structures with weak foundations blown away some distance. Cars thrown and large missiles generated.|
|F5||262-317||EF5||200-234||Incredible damage. Strong frame houses leveled off foundations and swept away. Automobile-sized missiles fly through the air in excess of 100 meters (109 yards). Trees debarked. Incredible phenomena will occur.|
Beaufort Wind Scale
|Force||Wind Speed (mph)||Terminology||Description|
|0||Less than 1||Calm||Calm, smoke rises vertically|
|1||1 - 4||Light air||Smoke drift indicates wind direction, still wind vanes|
|2||5 - 7||Light breeze||Wind felt on face, leaves rustle, vanes begin to move|
|3||8 - 12||Gentle breeze||Leaves and small twigs constantly moving, light flags extended|
|4||13 - 18||Moderate breeze||Dust, leaves, and loose paper lifted, small tree branches move|
|5||20 - 24||Fresh breeze||Small trees in leaf begin to sway|
|6||25 – 31||Strong breeze||Large branches in motion; whistling in telephone wires; umbrellas used with difficulty|
|7||32 – 38||Near gale||Whole trees in motion; resistance felt while walking against the wind|
|8||39 - 46||Gale||Twigs break off trees; wind impedes walking|
|9||47 – 54||Strong gale||Slight structural damage to chimneys and slate roofs|
|10||55 - 63||Storm||Seldom felt inland; trees uprooted; considerable structural damage|
|11||64 - 72||Violent storm||Very rarely experienced; widespread structural damage; roofing peels off buildings; windows broken; mobile homes overturned|
|12||73+||Hurricane||Widespread structural damage; roofs torn off homes; weak buildings and mobile homes destroyed; large trees uprooted|
Source: NOAA, 2013
High winds and severe weather frequently affect New York City. Based on the frequency of these events in the past, the hazards associated with high winds are highly probable in the future.
New York City estimates the probability of future high-wind events based upon the annual frequency of past severe thunderstorms. From 2000 to 2017, New York City’s Hazard History and Consequence Database indicates that the city has had 209 severe weather events, including events where there were high winds, hailstones, lightning, macrobursts, and tornadoes. Of the 209 severe weather events tallied in the Hazard History and Consequence Database, 24 events produced hailstones ranging from 0.25 inches to 2.75 inches in diameter. Generally, the reported hailstone size was small, but 15 events produced hailstones of more than 0.75 inches in diameter.
The probability of future severe storms and damaging winds in New York City is high and such events may happens multiple times on a local scale each year. By comparison, the recurrence interval for tornadoes and large hail in New York City is much lower.
Tornadoes in New York City are less common than severe thunderstorms, but they are still likely to occur in the future.
New York City’s first reported tornado was in 1974.Over the past 40 years, twelve tornadoes appeared in New York City, with eleven ranked at low severity levels of F0 or F1.
Reports of tornadoes have increased in New York City over the years. Seven tornadoes have been reported between 2007 and 2018, compared with only six reported in the previous 33 years. This increase in reported occurrences may be due to the greater precision of the Enhanced Fujita Scale.
Non-thunderstorm high-wind events happen very frequently in New York City -- including tropical cyclones, nor’easters, atmospheric conditions forcing air from high- to low-pressure areas, and interactions between strong cold and warm frontal systems.
Based on the historical record, New York City experiences at least one of these high-wind events per year.
New York City is located in an area of the United States that FEMA classifies as susceptible to all types of high winds events.
FEMA and the National Fire Protection Association's (NFPA) Model Manufactured Home Installation Standards categorize the United States into four wind zones: Zone I, Zone II, Zone III, and the highest wind zone, Zone IV. These wind zones portray the frequency and strength of extreme windstorms and are used to determine wind provisions for safe installation of manufactured homes.
As shown here, New York City is located in Zone II, which indicates that it is susceptible to winds in the 90- to 110-mph range. As noted in the New England detail on the graphic, New York City is also considered to be located in a hurricane-prone region.
U.S. Wind Zones
In the New York City metropolitan area, no single part of the city is more susceptible to high-wind hazards than another. This assessment is based on the historical record of where high-wind events have occurred.
Thunderstorms occur throughout New York City, but they do not necessarily affect all five boroughs simultaneously or produce high winds or hail that affect every location with the same severity. Some thunderstorms and their associated wind and hailstorms are extremely localized events.
A common misconception is that tornadoes do not occur in dense urban areas such as New York City. Scientists say that although tornadoes are rare, they could occur in any part of the city.
Since 1950, at least one tornado has occurred in each of the five boroughs, as shown on this map. Note that Manhattan’s August 1995 tornado is not plotted because accurate coordinates for this event are unavailable.
Between 1974 and 2013, New York experienced many non-thunderstorm high-wind events and severe thunderstorms, which produced damaging wind and tornadoes. Two events produced conditions so hazardous that they received Presidential Disaster Declarations.
For more information on high wind events, use the Hazard History and Consequence Database, an interactive tool developed for this website.