Hurricane Primer

Hurricane Category / Damage Primer

 

Hurricane Categories

CATEGORY	WIND SPEED	STORM SURGE	DAMAGE
1	74-95 mph           (64-82 kt)	4 - 5 feet	Minimal
2	96-110 mph         (83-95 kt)	6 - 8 feet	Moderate
3	111-130 mph       (96-113 kt)	9 - 12 feet	Extensive
4	131-155 mph       (114-135 kt)	13 – 18 feet	Extreme
5	over 155 mph      (135+ kt)	over 18 feet	Catastrophic

 

Damage Types

Wind: Hurricane-force winds can destroy poorly constructed buildings and mobile homes. Debris, such as signs, roofing material, siding, and small items left outside, become flying missiles in hurricanes. Winds often stay above hurricane strength well inland.

Storm Surge:?(A large dome of water often 50 to 100 miles wide that sweeps across the coastline near where a hurricane makes landfall.) The surge, topped by waves, is devastating. The stronger the hurricane and the shallower the offshore water, the higher the surge will be. Along the immediate coast, storm surge is the greatest threat to life and property.

Flood: Widespread torrential rains often in excess of 6 inches can produce deadly and destructive floods. This is the major threat to areas well inland.

 

Pre-Storm Concerns

CAT	EFFECTS	POSSIBLE EVACUATION
1	Low lying coastal roads inundated
2	Coastal roads and low lying inland escape routes blocked by rising water 2-4 hours before hurricane center arrives.	Some shoreline residences and low lying area residences
3	Low lying inland escape routes blocked by rising water 3-5 hours before hurricane center arrives	Low-lying residences within several blocks of shoreline
4	Low lying water 3-5 hours before hurricane center arrives	Massive evacuation of all residences within 500 yards of shore and single-story residences on low ground 6 miles or more inland.
5	Low lying escape routes inland cut off by rising water 3-5 hours before hurricane center arrives	Massive evacuation of residences on low ground 10 miles or more inland.

Category 1 - Minimal Damage

·    Damaged shrubbery and broken tree branches and poorly constructed signs.

·    Damage to trailers and unanchored mobile homes.

·    Some small boats torn away from their docks.

·    Some coastal flooding and minor pier damage.

 

Category 2 - Moderate Damage

·    Heavy damage to shrubbery and trees; some trees knocked down; extensive damage to poorly constructed signs.

·    Major damage to trailers and mobile homes.

·    Some roofing material, door, and window damage.

·    Heavy damage to piers; marinas flooded.

·    Many small boats in unprotected moorings torn away from their docks.

 

Category 3 - Extensive Damage

·    Foliage blown off trees; large trees and poorly constructed signs blown down.

·    Some mobile homes destroyed.

·    Damage to roofs, windows, doors, and small buildings.

·    Some structural damage to small residences and utility buildings

·    Small buildings and residences near the shore destroyed by flooding.

·    Large buildings next to shore damaged by waves and battering of floating debris; minor curtain wall (façade) failure.

·    Terrain continuously lower than 5 ft above mean sea level may be flooded inland 8 miles or more.

 

Category 4 - Extreme Damage

·    Shrubs and trees blown down; all signs knocked down.

·    Severe structural damage to houses and small buildings; extensive roof, window, and door damage

·    Some complete roof structure failure/collapse on small residences.

·    Mobile homes completely destroyed.

·    Major damage to lower floors of buildings near shore.

·    More extensive curtain wall failures on large buildings.

·    Terrain lower than 10 ft above sea level may be flooded as far inland as 6 miles.

·    Major beach erosion.

 

Category 5 - Catastrophic Damage

·  Shrubs and trees blown down; all signs down

·  Severe and extensive window and door damage to buildings (glass broken).

·  Complete roof failure on many residences and industrial buildings.

·  Some buildings completely destroyed.

·  Small buildings turned over or blown away.

·  Mobile homes completely destroyed.

·  Very severe damage from flooding to buildings less than 15 feet above sea level and within 500 yards of the shoreline.

·  Flooding of low-lying areas could reach 10 miles inland.