The formation of a hurricane depends on at least three conditions: a pre-existing disturbance with thunderstorms, warm ocean temperatures up to 80¼F and to a depth of about 150 feet, as well as light upper level winds that change very little in direction and speed throughout the depth of the atmosphere.
Hurricanes are low pressure weather systems generally forming in tropical latitudes and strengthening into tropical cyclones with wind speeds of 74 miles per hour and higher. Even with today’s sophisticated computer-forecasting models, a hurricane’s path, strength and potential for damage cannot be exactly predicted. This is why preparing your family and possessions for the worst possible situation is a smart move.
As hurricanes approach land, a hurricane watch or warning is issued for coastal and inland residents in the storm’s path. A HURRICANE WATCH indicates hurricane conditions are possible within 24-36 hours. A HURRICANE WARNING indicates hurricane conditions are expected within 24 hours.
The strength of hurricanes, based on wind speed, is indicated by category number. The higher the number, the more dangerous the storm:
The Saffir-Simpson Hurricane Wind Scale
The Saffir-Simpson Hurricane Wind Scale is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall. This hurricane season marks the first time this new version of the hurricane intensity rating scale will be utilized. This new scale keeps the same wind speed ranges as the original Saffir-Simpson Scale for each of the five hurricane categories, but no longer ties specific storm surge and flooding effects to each category. The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 categorization based on the hurricane’s intensity at the indicated time. The scale provides examples of the type of damage and impacts in the United States associated with winds of the indicated intensity.
| Cat. | Wind Speed | Damage | Category at U.S. Landfall |
| 1 | 74-95 mph | Minimal. No real damage to structures. Damage to shrubbery and trees, unanchored mobile homes, signs; possible power outages; windows of high-rise buildings can be blown out; people, pets and livestock could be injured by flying debris | Irene (1999) Lilli (2002) Gaston (2004) Humberto (2007) Hanna (2008) |
| 2 | 96-110 mph | Moderate. Major damage to mobile homes. Smaller trees toppled. Some roof coverings damaged; near total power outage; windows of high-rise buildings can be blown out; people, pets and livestock to be injured by flying debris | Bonnie (1998) Floyd (1999) Isabel (2003) Frances (2004) |
| 3 | 111-130 mph | Extensive. Mobile homes destroyed. Large trees toppled. Structural damage to roofs, small homes and utility buildings. High risk of injury or death to people, pets and livestock due to flying and falling debris | Ivan (2004) Jeanne (2004) Katrina (2005) Wilma (2005) Rita (2005) |
| 4 | 131-155 mph | Extreme. Roof systems on small buildings completely fail. Extensive damage to roofs, windows, and doors. Some exterior walls fail. High risk of injury or death to people, pets and livestock due to flying and falling debris | Hugo (1989) Charley (2004) Dennis (2005) Gustav (2008) Ike (2008) |
| 5 | >155 mph | Catastrophic. Complete buildings fail. Widespread, severe damage to roofs, windows and doors. Extensive glass failures. High risk of injury or death to people, pets and livestock due to flying and falling debris | Labor Day (1935) Camille (1969) Andrew (1992) |
Tropical Storm: 39-73 mph
*Source: http://www.nhc.noaa.gov/sshws_table.shtml?large
