What is the Saffir-Simpson Hurricane Scale?
In 1992 we moved to Homestead, Florida on a clear and beautiful Thursday after a headache of a closing. The house needed a lot of work but we were game to take it on. That Saturday in the middle of piling boxes and furniture into different rooms, we got a phone call: “There’s a tropical storm on the other side of the Bahamas. Just wanted you to know.” Good thing we got that call because we had not watched the news or weather in 3 days. Sunday night, technically Monday morning, Hurricane Andrew came ashore and swept through southern Dade county. It had intensified from a tropical storm to a category five hurricane in just over twelve hours and the destruction it left behind proved how incredibly strong a category five hurricane can be.
The Saffir-Simpson Hurricane Scale was developed in 1971 by engineer Herbert Saffir and metereologist Bob Simpson. It was introduced to the public in 1973 and gained widespread acceptance starting in 1974. Today it is the classification system used to categorize Western Hemisphere tropical cyclones that exceed the strength of tropical depressions and tropical storms.
Saffir initially developed the scale in 1969 while working for the United Nations. He was commissioned to study low-income housing and realized there was no way to measure hurricanes. Using the Richter Scale as a model he developed a similar 1-5 scale as a way to describe the likely effects of a hurricane’s winds on structures such as buildings. Saffir gave his scale to the National Hurricane Center where Simpson added the effects of storm surge and flooding.
The scale has some flaws though and the National Hurricane Center has now introduced the Saffir-Simpson Hurricane Wind Scale which categorizes hurricanes based on wind effects alone. The NHC has done this because several hurricanes have caused far greater or lesser damage than their category indicated they would. For example, Hurricane Katrina was a category three when it made landfall but because of New Orleans’ low-lying location and dense population, Katrina caused much more damage than expected. The main problem with the Saffir-Simpson scale has been that it does not take location into consideration so the scale does not predict that a category two hurricane that strikes a major city will cause far more damage than a category five hurricane that strikes a rural area. The Saffir-Simpson Hurricane Scale and Hurricane Wind Scale are divided into five categories.
A Category One hurricane has sustained winds of 74 to 95 miles per hour. A Category One storm usually does not cause significant structural damage. However, it can topple unanchored mobile homes or destroy older ones. Roof shingles can blow off and people or animals that are outside can be injured or killed by flying debris. Flooding can also cause damage, especially when the storm moves very slowly.
A Category Two hurricane has sustained winds of 96 to 110 miles per hour. A Category Two storm can lift a house and damage poorly built doors and windows. Landscaping, signs and piers can also be damaged. Mobile homes, whether anchored or not, can be severely damage and older ones often receive significant structural damage.
A Category Three hurricane has sustained winds of 111 to 130 miles per hour. A Category Three or higher storm is classified as a major hurricane. In this middle range of classification, a storm can cause structural damage to small buildings. Mobile homes are destroyed. Gable roofs are torn off, and flooding in coastal areas can cause significant damage, especially to smaller buildings. Recent Category Three hurricanes were Jeanne in 2004 and Bertha in 2008.
A Category Four hurricane has sustained winds of 131 to 155 miles per hour. A storm in this category can cause complete structural failure of roofs, flooding far inland, complete destruction of mobile homes and significant beach erosion. Notable Category Four hurricanes were the 1900 Galveston Hurricane, Iris in 2001 and Charley in 2004.
A Category Five hurricane has sustained winds over 155 miles per hour. Category Five storms cause complete destruction of mobile homes and many wood frame structures as well as complete roof failure on many buildings. Vegetation is destroyed and trees are completely uprooted. Windows and doors fail, one of the reasons for roof failures and why hurricane resistant windows are mandatory in most coastal areas. Flooding causes major damage in coastal areas. Waterfront homes are flattened. Category Five storms rarely make landfall at that intensity. Some of the ones that have are the Labor Day Hurricane of 1935, the 1959 Mexico Hurricane, Camille in 1969, Gilbert in 1988, Andrew in 1992, and Dean and Felix in 2007.
Following the extraordinary 2005 hurricane season, some newspaper columnists and scientists suggested adding a Category Six which would include storms with wind speeds greater than 174 or 180 miles per hour. The idea was not widely accepted for several reasons, one being that storms of that intensity are extremely rare. Robert Simpson was one of the detractors of the suggestion, saying that if the wind speed is over 155 miles per hour the damage to a building will be “"serious no matter how well it's engineered".
The Saffir-Simpson Hurricane Scale has drawn criticism for its simplicity and because it does not take into consideration many factors that affect how damaging a hurricane can be. Some scientists have proposed using other classification scales such as Hurricane Intensity Index, which is based on the pressure caused by a hurricane’s winds, and the Hurricane Hazard Index, which is based on surface wind speeds and the radius of maximum winds within a storm. Like the idea of adding a sixth category, the use of other scales has not gained wide popularity and none are currently in use by officials. Until such time as another classification system is either introduced or used, the Saffir-Simpson Hurricane Scale and Hurricane Wind Scales will be the official way of classifying Atlantic hurricanes.
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