Hurricane Weather Center


	Search for		More

Welcome

• Make TBO your Home Page
• Advertise with us
• Web site feedback

Rating Storm Strengths

By The Tampa Tribune

Storm strengths:
As a storm approaches, forecasters will issue alerts depending on where the storm is headed and its strength. Here are terms you need to know:

Tropical depression: A storm with a counterclockwise wind rotation around an area of low pressure. A depression's highest winds can be 38 mph. This is the first stage of a storm that could grow into a hurricane. They are given numbers by the National Hurricane Center in Miami.

Tropical storm: A storm with winds of 39-73 mph. Once a depression becomes a tropical storm, the Hurricane Center gives it a name.

Tropical storm watch: Issued by the Hurricane Center, this means an area may be threatened by a tropical storm � winds up to 73 mph � within 36 hours. This could be a broad stretch of coastline.

Tropical storm warning: An area is expected to be affected by tropical storm conditions � winds from 39-73 mph � within 24 hours. The area under a warning will be smaller than under a watch.

Hurricane: A storm with winds more than 74 mph. They are classified in categories of 1-5 according to wind speeds with 1 a minimal hurricane.

Hurricane watch: Issued for an area that may be threatened by hurricane conditions � winds more than 74 mph � within 36 hours.

Hurricane warning: Issued for an area expected to be under hurricane conditions within 24 hours.

Measuring hurricanes
You'll frequently hear of hurricanes described in categories, such as a Category 1 storm.

Forecasters use the Saffir-Simpson Scale as a convenient way for emergency officials and the public to tell what kind of damage to expect from a storm � from the wind and storm surge.

Under the Saffir-Simpson Scale, hurricanes are ranked in categories from 1 to 5, with 1 a minimal hurricane and 5 a catastrophic storm. The scale uses wind speed to make the rankings.

Emergency officials use the categories to determine what areas to evacuate according to the storm's strength. Though not as common, Category 3 and stronger storms do far more damage than weaker storms and are considered major storms.

Here is the Saffir-Simpson Scale:

	Damage	Winds	Storm Surge
5	Catastrophic	156 mph	18 ft. +
4	Extreme	131-155 mph	13-18 ft.
3	Extensive	111-130 mph	9-12 ft.
2	Moderate	96-110 mph	6-8 ft.
1	Minimal	74-95 mph	4-5 ft.

Note: Only three Category 5 storms have hit the United States since modern record-keeping began: the 1935 Labor Day hurricane that hit the Florida Keys, killing 408 people; Hurricane Camille, which devastated the Mississippi coast in 1969, killing 256 people and causing $1.4 billion in damage and Hurricane Andrew. Andrew was the most destructive United States hurricane of record after it blasted its way across south Florida in 1992, caused 23 deaths and resulted in $26.5 billion in damage.

Measuring tornadoes
Tornadoes are ranked in the Fujita Tornado Scale from F-0 to F-5 according to wind speed. Hurricanes also spin off small tornadoes, often miles from the eye and highest winds. Though they may not reach the power of the higher levels on the Fujita Scale, these tornadoes can cause considerable damage. They are also difficult to forecast, and warning times may be short.

Here is the Fujita Scale:

Number	Winds (mph)	Damage
F-0	Up to 72	Light
4F-1	73-112	Moderate
F-2	113-157	Considerable
F-3	158-206	Severe
F-4	207-260	Devastating
F-5	261 and above	Incredible

Return to Top