How fast does it have to be spinning to quality as a Hurricane?

Answer 1

Hurricanes begin as tropical disturbances in warm ocean waters with surface temperatures of at least 80 degrees Fahrenheit. These low pressure systems are fed by energy from the warm seas. If a storm achieves wind speeds of 38 miles an hour, it becomes known as a tropical depression. A tropical depression becomes a tropical storm, and is given a name, when its sustained wind speeds top 39 miles an hour. When a storm's sustained wind speeds reach 74 miles an hour it becomes a hurricane and earns a category rating of 1 to 5 on the Saffir-Simpson scale.

The Saffir-Simpson scale was developed in 1971 and until 2008 and Hurricane Ike, used to be a measure of both wind speed and storm surge. Hurricane Ike measured at a category 2 on the Saffir-Simpson scale, but it's storm surge at landfall was at a level to match a category 4 storm. It was felt that many may have underestimated the need to evacuate based on the storms category 2 rating so for the 2009 hurricane season the scale was revamped to measure only wind speed. The storm surge will now be estimated by location.

The Saffir-Simpson Wind Scale:

Category One Hurricane (Sustained winds 74-95 mph)

Category Two Hurricane (Sustained winds 96-110 mph)

Category Three Hurricane (Sustained winds 111-130 mph)

Category Four Hurricane (Sustained winds 131-155 mph)

Category Five Hurricane (Sustained winds greater than 155 mph)