The 'Saffir-Simpson Hurricane Scale' is a scale classifying most
Western Hemisphere tropical cyclones that exceed the intensities of "
tropical depressions" and "
tropical storms", and thereby become hurricanes. The categories into which the scale divides hurricanes are distinguished by the intensities of their respective sustained
winds. The classifications are intended primarily for use in measuring the potential damage and
flooding a hurricane will cause upon landfall. The Saffir-Simpson Hurricane Scale is used 'only' to describe hurricanes forming in the
Atlantic Ocean and northern
Pacific Ocean east of the
International Date Line. Other areas label their tropical cyclones as "cyclones" and "typhoons", and use their own
classification scales.
History
The scale was developed in 1969 by
civil engineer Herbert Saffir and
Bob Simpson, at that time the director of the
U.S. National Hurricane Center.
[1]
The initial scale was developed by Saffir while on commission from the
United Nations to study low-cost housing in hurricane-prone areas. While performing the study, Saffir realized there was no simple scale for describing the likely effects of a hurricane. Knowing the utility of the
Richter magnitude scale in describing earthquakes, he devised a 1–5 scale based on
wind speed that showed expected damage to structures. Saffir gave the scale to the
NHC, and Simpson added in the effects of
storm surge and flooding. The scale does not take into account
rainfall or location, which means a Category 2 hurricane that hits a major city will likely do far more damage than a Category 5 hurricane that hits a rural area.
[2]
Categories
The
U.S. National Hurricane Center classifies hurricanes of Category 3 and above as ''major hurricanes''. The definition of sustained winds recommended by the
World Meteorological Organization (WMO) and used by most weather agencies is that of a 10-minute average at a height of 10 m (33 ft) . The U.S. weather service defines sustained winds based on 1-minute average speed, also measured 10 m (33 ft) above the surface..
[3][4] Central pressure values are approximate. Intensity of example hurricanes is from both the time of landfall and the maximum intensity.
[5]
The five categories are, in order of increasing intensity:
Category 1
Category 1 storms usually cause no real
damage to
building structures; however, these storms can still cause damage, primarily to unanchored
mobile homes,
shrubbery, and
trees. Also, they produce some
coastal
flooding, as well as minor
pier damage.
[5]
Storms of this intensity include
Bess, in 1974;
Jerry, in 1989;
Ismael, in 1995;
Danny, in 1997, and
Gaston in 2004.
Category 2
Storms of this intensity damage some
roofing material, and also produce damage to
doors and
windows. Considerable damage is caused to
vegetation, mobile homes, poorly constructed signs, and piers. Also, small craft in unprotected anchorages may break their
moorings.
Hurricanes that peaked at Category 2 intensity, and made landfall while still in that category include
Carol of 1954;
Diana in 1990;
Erin during the
1995 Atlantic hurricane season;
Marty in 2003; and
Juan, which struck
Canada in 2003.
Category 3
Tropical cyclones of this intensity and higher receive the name of
major hurricanes when located in the Atlantic or Eastern Pacific
basins. These storms can cause some structural damage to small
residences and utility buildings, with a minor amount of
curtainwall failures. Buildings that lack a solid foundation, such as mobile homes, are usually destroyed. Flooding near the coast destroys smaller structures, while larger structures are hit by
floating
debris. Additionally,
terrain may be flooded well inland.
A few examples of storms of this intensity include
Alma of 1966,
Alicia of 1983,
Roxanne of 1995,
Fran of 1996, and
Isidore of 2002.
Category 4
Category 4 hurricanes tend to produce more extensive curtainwall failures, with some complete roof
structural failure on small residences. They also cause major erosion of beach areas. Terrain may be flooded well inland as well.
Hurricanes of this intensity are extremely dangerous to populated areas. The
Galveston Hurricane of 1900, the deadliest natural disaster to hit the
United States, would be classified as Category 4 if it were to occur today. Other examples of storms at this intensity are
Hazel (1954),
Iniki (1992),
Iris (2001) and
Charley (2004).
Category 5
Category 5 is the highest category a tropical cyclone can obtain in the Saffir-Simpson scale. These storms cause complete roof failure on many residences and industrial buildings, and some complete building failures with small utility buildings blown over or away. The storm's flooding causes major damage to the lower floors of all structures near the
shoreline. Massive
evacuation of residential areas may be required if the hurricane threatens populated areas.
Storms of this intensity can be extremely damaging. Several historical examples include the
Labor Day Hurricane of 1935, the
1959 Mexico Hurricane,
Hurricane Camille in 1969,
Gilbert in 1988,
Andrew in 1992,
Wilma in 2005,
Dean, and
Felix in 2007
Category 6
There is no such category on this scale, and any mention of a Category 6 tropical cyclone is fictitious or incorrect.
According to
Robert Simpson, there is no reason for a Category 6 on the Saffir-Simpson Scale because it is designed to measure the potential damage of a hurricane to man-made structures.
[7] If the speed of the hurricane is above 250 km/h (156 mph), then the damage to a building will be "serious no matter how well it's engineered". However, the result of new technologies in construction leads some to suggest that an increase in the number of categories is necessary. This suggestion was emphasized after the devastating effects of the
2005 Atlantic hurricane season. During that year
Hurricane Emily,
Hurricane Katrina,
Hurricane Rita, and
Hurricane Wilma all became Category 5 hurricanes. A few newspaper columnists and scientists have brought up the suggestion of introducing Category 6 since then.
[8][9]
See also
★
Beaufort scale - For winds less intense than hurricane strength.
★
Fujita scale - For tornado intensity with damage correlated to wind speeds. The system was also intended for applicability in hurricanes and indeed is utilized by engineers in hurricane damage assessment.
★
Severe weather terminology
★
List of notable tropical cyclones
★
List of Category 5 Atlantic hurricanes
★
List of Category 5 Pacific hurricanes
References
1. Hurricane scale invented to communicate storm danger
2. Wilma's Rage Suggests New Hurricane Categories Needed: History of the Scale
3. Tropical cyclone definitions Tropical Cyclone Weather Services Program
4. Hurricane Glossary of Terms Federal Emergency Management Agency Accessed through the Wayback Machine.
5. Saffir-Simpson Hurricane Scale Information National Hurricane Center
6. Saffir-Simpson Hurricane Scale Information National Hurricane Center
7. The Saffir/Simpson Hurricane Scale: An Interview with Dr. Robert Simpson Debi Iacovelli
8. Wilma's Rage Suggests New Hurricane Categories Needed
9. Category 6 Hurricanes? They've Happened: Global Warming Winds Up Hurricane Scientists as NOAA Issues Its Atlantic Hurricane Predictions for Summer 2006
External links
★
Descriptions of the likely damage and flooding caused by each category of hurricane - The National Hurricane Center
★
An Interview with Dr. Robert Simpson - The Mariners Weather Log, April 1999
★
Q&A with Herbert Saffir - The South Florida Sun-Sentinel, June 2001
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