officially become a hurricane? Tropical storms and hurricanes have precise scientific definitions and criteria, usually measured by wind speed.

A tropical depression has sustained winds of 33 knots (38 mph) or less, while tropical storms have sustained winds of 33 to 64 knots (73 mph). A storm becomes a hurricane once its winds reach 64 knots or 73 mph.

The strength of a hurricane is ranked from 1 to 5 according to what is known as the Saffir-Simpson scale of strength. Here is a short explanation of the different categories of a hurricane: Category 1 -- The hurricane has winds of 74 mph to 95 mph and is accompanied by a 4-foot to 5-foot storm surge. It tends to cause minimal damage; Category 2 -- The hurricane has winds from 96 mph to 110 mph with a storm surge of 6 feet to 8 feet. Damage tends to be moderate; Category 3 -- The hurricane has winds from 111 mph to 130 mph and is accompanied by a storm surge of 9 feet to 12 feet. Damage is usually extensive; Category 4 -- Winds can reach anywhere from 131 mph to 155 mph with a storm surge of 13 feet to 18 feet. Category 4 hurricanes cause extreme damage. Last summer's Hurricane Georges that crippled the Caribbean was a category 4 hurricane; and Category 5 -- Any hurricane with winds greater than 155 mph. It is has a storm surge that is higher than 18 feet.

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