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The scale separates hurricanes into five different categories based on wind. The U.S. National Hurricane Center classifies hurricanes of Category 3 and above as major hurricanes, and the [[Joint Typhoon Warning Center (JTWS)]] classifies typhoons of 150 mph or greater (strong Category 4 and Category 5) as super typhoons (although all tropical cyclones can be very dangerous). Most weather agencies use the definition for sustained winds recommended by the World Meteorological Organization (WMO), which specifies measuring winds at a height of 33 ft (10.1 m) for 10 minutes, and then taking the average. By contrast, the U.S. National Weather Service, Central Pacific Hurricane Center and the Joint Typhoon Warning Center define sustained winds as average winds over a period of one minute, measured at the same 33 ft (10.1 m) height,[10][11] and that is the definition used for this scale.
 
The scale separates hurricanes into five different categories based on wind. The U.S. National Hurricane Center classifies hurricanes of Category 3 and above as major hurricanes, and the [[Joint Typhoon Warning Center (JTWS)]] classifies typhoons of 150 mph or greater (strong Category 4 and Category 5) as super typhoons (although all tropical cyclones can be very dangerous). Most weather agencies use the definition for sustained winds recommended by the World Meteorological Organization (WMO), which specifies measuring winds at a height of 33 ft (10.1 m) for 10 minutes, and then taking the average. By contrast, the U.S. National Weather Service, Central Pacific Hurricane Center and the Joint Typhoon Warning Center define sustained winds as average winds over a period of one minute, measured at the same 33 ft (10.1 m) height,[10][11] and that is the definition used for this scale.
  
The scale is roughly logarithmic in wind speed, and the top wind speed for Category “c” (c = 1 ... 4; there is no upper limit for category 5) can be expressed as 83×10<sup>({{frac|''c''|15}})</sup>&nbsp;miles per hour rounded to the nearest multiple of 5 – except that after the change mentioned above, Category 4 is now widened by 1 mph in each direction and that the calculated value for Category 2 (c = 2) is rounded down from 112.8 mph to 110 mph.
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The scale is roughly logarithmic in wind speed, and the top wind speed for Category “c” (c = 1 ... 4; there is no upper limit for category 5) can be expressed as 83×10<sup>(''c''/15)</sup> miles per hour rounded to the nearest multiple of 5 – except that after the change mentioned above, Category 4 is now widened by 1 mph in each direction and that the calculated value for Category 2 (c = 2) is rounded down from 112.8 mph to 110 mph.
  
 
[[File:Saffir Simpson scale 2.png|thumb|none|400px|Saffir-Simpson scale. Source: wikipedia]]
 
[[File:Saffir Simpson scale 2.png|thumb|none|400px|Saffir-Simpson scale. Source: wikipedia]]

Revision as of 16:54, 9 April 2019

Article Information
Category: Weather Weather
Content source: SKYbrary About SKYbrary
Content control: SKYbrary About SKYbrary
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Tag(s) Weather Risk Management

Description

The Saffir–Simpson hurricane wind scale (SSHWS), formerly the Saffir–Simpson hurricane scale (SSHS), classifies hurricanes – Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms – into five categories distinguished by the intensities of their sustained winds.

The scale was developed in 1971 by civil engineer Herbert Saffir and meteorologist Robert Simpson, who at the time was director of the U.S. National Hurricane Center (NHC).

Categories

The scale separates hurricanes into five different categories based on wind. The U.S. National Hurricane Center classifies hurricanes of Category 3 and above as major hurricanes, and the Joint Typhoon Warning Center (JTWS) classifies typhoons of 150 mph or greater (strong Category 4 and Category 5) as super typhoons (although all tropical cyclones can be very dangerous). Most weather agencies use the definition for sustained winds recommended by the World Meteorological Organization (WMO), which specifies measuring winds at a height of 33 ft (10.1 m) for 10 minutes, and then taking the average. By contrast, the U.S. National Weather Service, Central Pacific Hurricane Center and the Joint Typhoon Warning Center define sustained winds as average winds over a period of one minute, measured at the same 33 ft (10.1 m) height,[10][11] and that is the definition used for this scale.

The scale is roughly logarithmic in wind speed, and the top wind speed for Category “c” (c = 1 ... 4; there is no upper limit for category 5) can be expressed as 83×10(c/15) miles per hour rounded to the nearest multiple of 5 – except that after the change mentioned above, Category 4 is now widened by 1 mph in each direction and that the calculated value for Category 2 (c = 2) is rounded down from 112.8 mph to 110 mph.

Saffir-Simpson scale. Source: wikipedia

Category 1

Category 1 storms usually cause no significant structural damage to most well-constructed permanent structures; however, they can topple unanchored mobile homes, as well as uproot or snap weak trees. Poorly attached roof shingles or tiles can blow off. Coastal flooding and pier damage are often associated with Category 1 storms. Power outages are typically widespread to extensive, sometimes lasting several days. Even though it is the least intense type of hurricane, they can still produce widespread damage and can be life-threatening storms.

Hurricanes that peaked at Category 1 intensity, and made landfall at that intensity include: Flossy (1956), Gladys (1968), Agnes (1972), Juan (1985), Ismael (1995), Claudette (2003), Gaston (2004), Stan (2005), Humberto (2007), Isaac (2012), Manuel (2013), Earl (2016), Hermine (2016), Newton (2016), Franklin (2017), and Nate (2017).

Category 2[edit] Category 2 Sustained winds Most recent 43–49 m/s 83–95 kn 154–177 km/h 96–110 mph Arthur 2014-07-03 2130Z.png Arthur in 2014 approaching North Carolina. See also: List of Category 2 Pacific hurricanes Extremely dangerous winds will cause extensive damage

Storms of Category 2 intensity often damage roofing material (sometimes exposing the roof) and inflict damage upon poorly constructed doors and windows. Poorly constructed signs and piers can receive considerable damage and many trees are uprooted or snapped. Mobile homes, whether anchored or not, are typically damaged and sometimes destroyed, and many manufactured homes also suffer structural damage. Small craft in unprotected anchorages may break their moorings. Extensive to near-total power outages and scattered loss of potable water are likely, possibly lasting many days.[5]

Hurricanes that peaked at Category 2 intensity, and made landfall at that intensity include: Able (1952), Alice (1954), Fifi (1974), Diana (1990), Calvin (1993), Gert (1993), Rosa (1994), Erin (1995), Alma (1996), Juan (2003), Alex (2010), Richard (2010), Tomas (2010), Carlotta (2012), Ernesto (2012), and Arthur (2014).

Category 3[edit] Category 3 Sustained winds Most recent 50–58 m/s 96–112 kn 178–208 km/h 111–129 mph Otto 2016-11-24 1605Z.jpg Otto in 2016 at its Nicaragua landfall. See also: List of Category 3 Atlantic hurricanes and List of Category 3 Pacific hurricanes Devastating damage will occur

Tropical cyclones of Category 3 and higher are described as major hurricanes in the Atlantic or Eastern Pacific basins. These storms can cause some structural damage to small residences and utility buildings, particularly those of wood frame or manufactured materials with minor curtain wall failures. Buildings that lack a solid foundation, such as mobile homes, are usually destroyed, and gable-end roofs are peeled off. Manufactured homes usually sustain severe and irreparable damage. Flooding near the coast destroys smaller structures, while larger structures are struck by floating debris. A large number of trees are uprooted or snapped, isolating many areas. Additionally, terrain may be flooded well inland. Near-total to total power loss is likely for up to several weeks and water will likely also be lost or contaminated.[5]

Hurricanes that peaked at Category 3 intensity, and made landfall at that intensity include: Easy (1950), Carol (1954), Hilda (1955), Celia (1970), Ella (1970), Eloise (1975), Olivia (1975), Alicia (1983), Elena (1985), Roxanne (1995), Fran (1996), Isidore (2002), Jeanne (2004), Lane (2006), Karl (2010), and Otto (2016).

Category 4[edit] Category 4 Sustained winds Most recent 58–70 m/s 113–136 kn 209–251 km/h 130–156 mph Michael 2018-10-10 1840Z.jpg Michael in 2018 during its Florida landfall. See also: List of Category 4 Atlantic hurricanes and List of Category 4 Pacific hurricanes Catastrophic damage will occur

Category 4 hurricanes tend to produce more extensive curtainwall failures, with some complete structural failure on small residences. Heavy, irreparable damage and near complete destruction of gas station canopies and other wide span overhang type structures are common. Mobile and manufactured homes are often flattened. Most trees, except for the heartiest, are uprooted or snapped, isolating many areas. These storms cause extensive beach erosion, while terrain may be flooded far inland. Total and long-lived electrical and water losses are to be expected, possibly for many weeks.[5]

The 1900 Galveston hurricane, the deadliest natural disaster to hit the United States, peaked at an intensity that corresponds to a modern-day Category 4 storm. Other examples of storms that peaked at Category 4 intensity, and made landfall at that intensity include: Hazel (1954), Flora (1963), Cleo (1964), Betsy (1965), Frederic (1979), Joan (1988), Iniki (1992), Luis (1995), Iris (2001), Charley (2004), Dennis (2005), Gustav (2008), Ike (2008), Joaquin (2015), Harvey (2017), and Michael (2018).

Category 5[edit] Category 5 Sustained winds Most recent ≥ 70 m/s ≥ 137 kn ≥ 252 km/h ≥ 157 mph Maria 2017-09-19 0000Z.jpgMaria in 2017 making landfall in Dominica. See also: List of Category 5 Atlantic hurricanes and List of Category 5 Pacific hurricanes Catastrophic damage will occur

Category 5 is the highest category of 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. Collapse of many wide-span roofs and walls, especially those with no interior supports, is common. Very heavy and irreparable damage to many wood frame structures and total destruction to mobile/manufactured homes is prevalent. Only a few types of structures are capable of surviving intact, and only if located at least 3 to 5 miles (5 to 8 km) inland. They include office, condominium and apartment buildings and hotels that are of solid concrete or steel frame construction, multi-story concrete parking garages, and residences that are made of either reinforced brick or concrete/cement block and have hipped roofs with slopes of no less than 35 degrees from horizontal and no overhangs of any kind, and if the windows are either made of hurricane-resistant safety glass or covered with shutters. Unless all of these requirements are met, the absolute destruction of a structure is certain.[5]

The storm's flooding causes major damage to the lower floors of all structures near the shoreline, and many coastal structures can be completely flattened or washed away by the storm surge. Virtually all trees are uprooted or snapped and some may be debarked, isolating most affected communities. Massive evacuation of residential areas may be required if the hurricane threatens populated areas. Total and extremely long-lived power outages and water losses are to be expected, possibly for up to several months.[5]