The Saffir-Simpson scale was developed in 1971 by Herbert Saffir, a civil engineer, and meteorologist Bob Simpson, former director of the U.S. National Hurricane Center. It was introduced in 1973, and has since become the best known guide for describing individual hurricanes to the general public.
Saffir, was studying low cost housing in hurricane prone areas, when he realized that there was no easy way to describe hurricane strength and the subsequent dangers. Based on the Richter scale that describes the magnitude of earthquakes, he created a scale for hurricanes, one a 1-5 scale. Initially, he based his scale on wind speed, and the damages that could be expected, due to his experience in housing and wind damage.
With Simpson’s background in meteorology, he was able to add effects of storm surge and flooding.
In 2009, the National Hurricane Center removed pressure and storm surge from the categories, making it chiefly a wind scale. By 2010, information that proved inaccurate in previous hurricanes such as Katrina, such as storm surge, and amount of rain were removed from the scale.
The Saffir-Simpson Hurricane Wind Scale concentrates on the wind speed of the various categories, but it also gives examples of the type of damage and impacts that may be expected from winds of different intensities. According to the scale, the intensity rises by about a factor of four for each category increase. Examples are cited from previous hurricanes.
Storm surge, and other factors that were a part of the scale in the early years, were found to be confusing and inaccurate. Generalizations were not effective, in view of the fact that the storm’s impact would be different in areas where topography, population and other factors differed.
A Category One Hurricane has sustained winds at between 74-95 mph. These produce damage much like any high intensity thunderstorm. Mobile homes may be destroyed, and people and animals can be injured from flying debris. Trees may be uprooted, and roofs, chimneys and other structural features destroyed.
Category Two Hurricanes have sustained winds between 96-110 mph. These will cause considerable damage to structures, even those that are made of masonry materials. There will be downed trees, and power outages.
A Category Three Hurricane has winds of 111-130 mph, causing extreme damage to homes and businesses. There is a higher risk of injury or death to people and animals. It is expected that power poles and trees will be downed, and that there may be electrical outages that will last for seven or more days.
Category Four Hurricanes have wind speeds of 131-155 mph, and are catastrophic. It is common that there will be extensive damage to high rise buildings, as well as homes, businesses, and ships. Power may be out for extended periods and there will be problems with obtaining fresh water. Areas hit by a Category Four will be devastated for weeks or months, making them virtually uninhabitable.
The most feared, of course, is the Category Five. These are rare, but when they do occur they bring with them winds greater than 155 mph. These produce the same results as the Category Four, only greater, and are capable of destroying cities and towns. Clean up and recovery from a Category Five Hurricane takes months or even years.
Thanks to this scale, the average person can determine the intensity of the oncoming hurricane, and decide what their course of action will be.
http://www.nhc.noaa.gov/sshws.shtml
