CK12 Earth Science

Table 16.4: Saffir - Simpson Hurricane Scale

Category Kph Mph Damage

1 (weak) 119-153 74-95 Above normal; no

real damage to

structures

2 (moderate) 154-177 96-110 Some roofing, door,

and window dam-

age, considerable

damage to vegeta-

tion, mobile homes,

and piers

3 (strong) 178-209 111-130 Somebuildingsdam-

aged; mobile homes

destroyed

4 (very strong) 210-251 131-156 Complete roof fail-

ure on small resi-

dences; major ero-

sion of beach ar-

eas; major damage

to lower floors of

structuresnearshore

5 (devastating) >251 >156 Complete roof

failure on many

residences and in-

dustrial buildings;

some complete

building failures

Hurricanes move with the prevailing winds. In the Northern Hemisphere, they originate in
the trade winds and move to the west. When they reach the latitude of the westerlies, they
switch direction and travel toward the north or northeast. Hurricanes typically travel from
5 to 40 kph (3 to 25 mph) and can cover 800 km (500 miles) in one day. Their speed and
direction depend on the conditions that surround them. This uncertainty makes it hard for
meteorologists to accurately predict where a hurricane will go and how strong it will be when
it reaches land.

Damage from hurricanes tends to come from the high winds and rainfall, which can cause
flooding. Near the coast, flooding is also caused bystorm surge(Figure16.33). Storm
surge occurs as the storm’s low pressure center comes onto land, causing the sea level to rise
unusually high. A storm surge is often made worse by the hurricane’s high winds blowing
seawater across the ocean onto the shoreline. Storm surge may rise as high as 7.0 to 7.5 m