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 48 hours. A HURRICANE WARNING indicates hurricane conditions are expected within 36 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 | Very dangerous winds will produce some damage: Well-constructed frame homes could have damage to roof, shingles, vinyl siding and gutters. Large branches of trees will snap and shallowly rooted trees may be toppled. Extensive damage to power lines and poles likely will result in power outages that could last a few to several days. | Irene (1999) Lilli (2002) Gaston (2004) Humberto (2007) Hanna (2008) Hermine (2016) Nate (2017) Florence (2018) Barry (2019) Hannah (2020) Isaias (2020) Nicholas (2021) |
| 2 | 96-110 mph | Extremely dangerous winds will cause extensive damage: Well-constructed frame homes could sustain major roof and siding damage. Many shallowly rooted trees will be snapped or uprooted and block numerous roads. Near-total power loss is expected with outages that could last from several days to weeks. | Bonnie (1998) Floyd (1999) Isabel (2003) Frances (2004) Arthur (2014) Matthew (2016) Dorian (2019) Sally (2020) Delta (2020) |
| 3 (major) | 111-129 mph | Devastating damage will occur: Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes. | Ivan (2004) Jeanne (2004) Katrina (2005) Wilma (2005) Rita (2005) Matthew (2016) Zeta (2020) Idalia (2023) |
| 4 (major) | 130-156 mph | Catastrophic damage will occur: Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and power poles downed. Fallen trees and power poles will isolate residential areas. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or months. | Hugo (1989) Charley (2004) Dennis (2005) Gustav (2008) Ike (2008) Harvey (2017) Irma (2017) Maria (2017) Laura (2020) Ida (2021) Ian (2022) |
| 5 (major) | >156 mph | Catastrophic damage will occur: A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months. | Labor Day (1935) Camille (1969) Andrew (1992) Michael (2018) |
Tropical Storm: 39-73 mph
*Source: http://www.nhc.noaa.gov/sshws_table.shtml?large
2012 Revision to the Saffir-Simpson Hurricane Wind Scale