US Hurricane Intensity Categories

hurricane

Saffir-Simpson Hurricane Wind Scale Predicts Hurricane Wind Damage

The United States, like most other countries affected by tropical cyclones, also called hurricanes, has developed a scale to measure the storms’ intensity. The National Hurricane Center calls their scale the Saffir-Simpson Scale. It divides all hurricanes in the Atlantic Ocean and Northeast Pacific Ocean into five categories, determined by their sustained wind speeds.

History of the Saffir-Simpson (Hurricane) Wind Scale

This system was originally developed by Herbert Saffir, a civil engineer, and Dr. Robert Simpson, the director of the National Hurricane Center (NHC) in 1971. Their intention was to express the expected structural damage that could be caused by a hurricane with a given maximum wind speed. Mr. Saffir and Dr. Simpson believed that this intensity scale would be a beneficial guide to civil engineers when establishing building codes in hurricane-prone areas.

In 1973, the Saffir-Simpson Hurricane Scale was released to the general public. At this time, the scale incorporated wind speeds, central pressure and storm surge as part of the categories. The central core pressure was used during the 1970s and 1980s as a proxy for wind speeds, because reconnaissance aircraft flights measuring wind speeds and other factors were not commonly available until the 1990s.

Storm surge was also a common indicator on the original hurricane scale, which is not present on the experimental hurricane scale that the NHC is developing (under development in 2009). The removal of storm surge is in an effort to reduce confusion regarding the potential damage of a hurricane, since storm surge height is affected by a variety of factors, including hurricane size, hurricane speed and angle to the coast, depth of near-shore waters, and shape of the shore line.

Hurricane Categories

Tropical Storm

  • Wind Speeds: 39-73 mph (33-63 kt or 63-118 km/hr)

Category 1 Hurricane (Damaging winds are expected)

  • Wind Speeds: 74-95 mph (64-82 kt or 119-153 km/hr)
  • Structure Damage: No substantial damage to building, though unanchored mobile homes (mostly of pre-1994 construction) may sustain damage. Poorly constructed signs may sustain some damage and loose outdoor items will become projectiles. Poorly anchored roofing may be sheared off.
  • Tree Damage: Large branches of healthy trees my snap, while some trees will be uprooted
  • Power Outage: Power outages possible due to downed power lines and poles.
  • Examples: Hurricane Cindy (2005), Hurricane Gaston (2004), Hurricane Irene (1999), Hurricane Allison (1995)

Category 2 Hurricane (Very strong winds will produce widespread damage)

  • Wind Speeds: 96-110 mph (83-95 kt or 154-177 km/hr)
  • Structure Damage: Metal roofing materials, doors and windows are likely to be damaged. Considerable damaged to mobile homes (mostly of pre-1994 construction) and poorly constructed signs. Glass windows in high rise buildings may become airborne, along with outdoor items.
  • Tree Damage: Manly large branches will break and many trees are likely to be uprooted or snapped.
  • Power Outage: Extensive damaged to power lines and poles, most likely causing widespread power outages that could last several days.
  • Examples: Hurricane Erin (1995), Hurricane Isabel (2003), Hurricane Bonnie (1998), Hurricane Gloria (1985)

Category 3 Hurricane (Major Hurricane: Dangerous winds will cause extensive damage)

  • Wind Speeds: 111-130 mph (96-113 kt or 178-209 km/hr)
  • Structure Damage: Structural damage to house and buildings may occur, resulting in a small amount of wall failure. Most mobile homes (mostly of pre-1994 construction) will be destroyed, along with poorly constructed signs. Windows in high-rise buildings are likely to become airborne.
  • Tree Damage: Many trees will be uprooted and snapped, blocking many roadways.
  • Power Outage: Near total power loss expected, with it taking possibly several days to weeks to be fully restored.
  • Examples: Hurricane Rita (2005), Hurricane Katrina (2005), Hurricane Jeanne (2004), Hurricane Keith (2000), Hurricane Fran (1996)

Category 4 Hurricane (Major Hurricane: Extremely dangerous winds causing devastating damage are expected)

  • Wind Speeds: 131-155 mph (144-135 kt or 210-249 km/hr)
  • Structure Damage: Some complete roof structures failures and some wall failures expected while all signs are blown down, along with complete destruction of mobile homes (mostly of pre-1994 construction). Extensive damage to doors and windows of both high rise buildings and homes, which may become airborne.
  • Tree Damage: Fallen trees may cut off access to residential areas for weeks.
  • Power Outage: Electricity will be unavailable for weeks.
  • Examples: Hurricane Charley (2004), Hurricane Hugo (1989). Hurricane Donna (1960)

Category 5 Hurricane (Major Hurricane: Catastrophic damage is expected)

  • Wind Speeds: 156 mph and greater (135+ kt or 249 km/hr)
  • Structure Damage: Many industrial buildings and homes will suffer complete roof failures, with small buildings possible being completely destroyed. All signs are blown down and there is complete destruction of mobile homes (built in any year). Extensive window and door damage will occur and nearly all windows in high-rise building will be airborne.
  • Tree Damage: Nearly all trees will be snapped or uprooted. Residential areas will be totally isolated.
  • Power Outage: Power polls downed and power outages will last for weeks or possibly months.
  • Examples: Hurricane Camille (1969), Hurricane Andrew (1992)

Hurricane Preparation

The best preparation for anyone living in a hurricane prone area is to prepare an emergency kit and have the supplies at home prior to hurricane season to secure it. Residents should always listen to the updated watches and warnings issued by the U.S. National Weather Service’s National Hurricane Center, and if an evacuation is issued for the area, leave. Property is replaceable, but lives are not.

The Saffir-Simpson Scale is a guide for the potential storm damage resulting from a hurricane. It’s important to remember that the scale does not estimate the damage resulting from other hurricane-related weather such as tornadoes, flooding resulting from rainfall, and storm surge. The damages from the listed will apply to the coast with peak wind speeds and other areas will receive less damage. However, if a storm moves very slowly over an area even a Category 1 hurricane can cause total destruction of property. In Florida, South Carolina or North Carolina, a residence constructed according to the latest building codes has a chance of reduced structural damage.