Saffir–Simpson scale
Category | m/s
|
knots | mph | km/h
|
---|---|---|---|---|
5 | ≥ 70 | ≥ 137 | ≥ 157 | ≥ 252 |
4 | 58–70 | 113–136 | 130–156 | 209–251 |
3 | 50–58 | 96–112 | 111–129 | 178–208 |
2 | 43–49 | 83–95 | 96–110 | 154–177 |
1 | 33–42 | 64–82 | 74–95 | 119–153 |
TS | 18–32 | 34–63 | 39–73 | 63–118 |
TD | ≤ 17 | ≤ 33 | ≤ 38 | ≤ 62 |
The Saffir–Simpson hurricane wind scale (SSHWS) classifies
To be classified as a hurricane, a
The Saffir–Simpson hurricane wind scale is based on the highest wind speed averaged over a one-minute interval 10 m above the surface. Although the scale shows wind speeds in continuous speed ranges, the US National Hurricane Center and the Central Pacific Hurricane Center assign tropical cyclone intensities in 5-knot (kn) increments (e.g., 100, 105, 110, 115 kn, etc.) because of the inherent uncertainty in estimating the strength of tropical cyclones. Wind speeds in knots are then converted to other units and rounded to the nearest 5 mph or 5 km/h.[2]
The Saffir–Simpson hurricane wind scale is used officially only to describe hurricanes that form in the Atlantic Ocean and northern Pacific Ocean east of the International Date Line. Other areas use different scales to label these storms, which are called cyclones or typhoons, depending on the area. These areas (except the JTWC) use three-minute or ten-minute averaged winds to determine the maximum sustained wind speed, creating an important difference which frustrates direct comparison between maximum wind speeds of storms measured using the Saffir–Simpson hurricane wind scale (usually 14% more intense) and those measured using a ten-minute interval (usually 12% less intense).[3]
There is some criticism of the SSHWS for not accounting for rain, storm surge, and other important factors, but SSHWS defenders say that part of the goal of SSHWS is to be straightforward and simple to understand. There have also been proposals for the addition of higher categories to the scale (which would then set a maximum cutoff for Category 5), but none have been adopted as of March 2024[update].
History
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).[4] The scale was introduced to the general public in 1973,[5] and saw widespread use after Neil Frank replaced Simpson at the helm of the NHC in 1974.[6]
The scale was created by Herbert Saffir, a
In 2009, the NHC eliminated pressure and storm surge ranges from the categories, transforming it into a pure wind scale, called the Saffir–Simpson Hurricane Wind Scale (Experimental) [SSHWS].[8] The updated scale became operational on May 15, 2010.[9] The scale excludes flood ranges, storm surge estimations, rainfall, and location, which means a Category 2 hurricane that hits a major city will likely do far more cumulative damage than a Category 5 hurricane that hits a rural area.[10] The agency cited examples of hurricanes as reasons for removing "scientifically inaccurate" information, including Hurricane Katrina (2005) and Hurricane Ike (2008), which both had stronger than estimated storm surges, and Hurricane Charley (2004), which had weaker than estimated storm surge.[11] Since being removed from the Saffir–Simpson hurricane wind scale, storm surge prediction and modeling is handled by computer numerical models such as ADCIRC and SLOSH.
In 2012, the NHC expanded the windspeed range for Category 4 by 1 mph in both directions, to 130–156 mph, with corresponding changes in the other units (113–136 kn, 209–251 km/h), instead of 131–155 mph (114–135 kn, 210–249 km/h). The NHC and the Central Pacific Hurricane Center assign tropical cyclone intensities in 5 knot increments, and then convert to mph and km/h with a similar rounding for other reports. So an intensity of 115 kn is rated Category 4, but the conversion to miles per hour (132.3 mph) would round down to 130 mph, making it appear to be a Category 3 storm. Likewise, an intensity of 135 kn (~155 mph, and thus Category 4) is 250.02 km/h, which, according to the definition used before the change would be Category 5. To resolve these issues, the NHC had been obliged to incorrectly report storms with wind speeds of 115 kn as 135 mph, and 135 kn as 245 km/h. The change in definition allows storms of 115 kn to be correctly rounded down to 130 mph, and storms of 135 kn to be correctly reported as 250 km/h, and still qualify as Category 4. Since the NHC had previously rounded incorrectly to keep storms in Category 4 in each unit of measure, the change does not affect the classification of storms from previous years.[8] The new scale became operational on May 15, 2012.[12]
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 classifies typhoons of 150 mph (240 km/h) or greater (strong Category 4 and Category 5) as super typhoons. 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,[13][14] and that is the definition used for this scale.
The scale is roughly logarithmic in wind speed.
The five categories are described in the following subsections, in order of increasing intensity.[15] Intensity of example hurricanes is from both the time of landfall and the maximum intensity.
Category 1
Category 1 | |
---|---|
Sustained winds | Most recent landfall |
33–42 m/s 64–82 kn 119–153 km/h 74–95 mph |
Nicole in 2022 nearing landfall in Florida |
Very dangerous winds will produce some damage
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.[8]
Hurricanes that peaked at Category 1 intensity and made landfall at that intensity include:
(2022).Category 2
Category 2 | |
---|---|
Sustained winds | Most recent landfall |
43–49 m/s 83–95 kn 154–177 km/h 96–110 mph |
Puerto Angel, Mexico
|
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
Hurricanes that peaked at Category 2 intensity and made landfall at that intensity include: Alice (1954), Ella (1958), Ginny (1963), Fifi (1974), Diana (1990), Gert (1993), Rosa (1994), Erin (1995), Alma (1996), Marty (2003), Juan (2003), Alex (2010), Richard (2010), Tomas (2010), Carlotta (2012), Arthur (2014), Sally (2020), Olaf (2021), Rick (2021) and Agatha (2022).
Category 3
Category 3 | |
---|---|
Sustained winds | Most recent landfall |
50–58 m/s 96–112 kn 178–208 km/h 111–129 mph |
Grace in 2021 just prior to its Veracruz landfall
|
Devastating damage will occur
Tropical cyclones of Category 3 and higher are described as major hurricanes in the Atlantic, Eastern Pacific, and Central 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.[8]
Hurricanes that peaked at Category 3 intensity and made landfall at that intensity include: Easy (1950), Carol (1954), Hilda (1955), Audrey (1957), Olivia (1967), Ella (1970), Caroline (1975), Eloise (1975), Olivia (1975), Alicia (1983), Elena (1985), Roxanne (1995), Fran (1996), Isidore (2002), Jeanne (2004), Lane (2006), Karl (2010), Otto (2016), Zeta (2020), and Grace (2021).
Category 4
Category 4 | |
---|---|
Sustained winds | Most recent landfall |
58–70 m/s 113–136 kn 209–251 km/h 130–156 mph |
Lidia in 2023 just prior to its Jalisco landfall |
Catastrophic damage will occur
Category 4 hurricanes tend to produce more extensive curtainwall failures, with some complete
The
Category 5
Category 5 | |
---|---|
Sustained winds | Most recent landfall |
≥ 70 m/s ≥ 137 kn ≥ 252 km/h ≥ 157 mph |
Otis in 2023 nearing its landfall in Acapulco, Mexico |
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. The 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 most of these requirements are met, the catastrophic destruction of a structure may occur.[8]
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.[8]
Historical examples of storms that made landfall at Category 5 status include: "Cuba" (1924), "Okeechobee" (1928), "Bahamas" (1932), "Cuba–Brownsville" (1933), "Labor Day" (1935), Janet (1955), Inez (1966), Camille (1969), Edith (1971), Anita (1977), David (1979), Gilbert (1988), Andrew (1992), Dean (2007), Felix (2007), Irma (2017),[16] Maria (2017),[17] Michael (2018),[18] Dorian (2019), and Otis (2023) (the only Pacific hurricane to make landfall at Category 5 intensity).
Criticism
Some scientists, including
Proposed extensions
After the series of powerful storm systems of the
According to Robert Simpson, co-creator of the scale, there are no reasons for a Category 6 on the Saffir–Simpson scale because it is designed to measure the potential damage of a hurricane to human-made structures. Simpson explained that "... when you get up into winds in excess of 155 mph (249 km/h) you have enough damage if that extreme wind sustains itself for as much as six seconds on a building it's going to cause rupturing damages that are serious no matter how well it's engineered."[6] Nonetheless, the counties of Broward and Miami-Dade in Florida have building codes which require that critical infrastructure buildings be able to withstand Category 5 winds.[28]
See also
- Beaufort scale – Relates wind speed to observable conditions at sea and on land
- Enhanced Fujita scale – For tornado intensity with damage correlated to wind speeds. The system was also intended for applicability in hurricanes, and is utilized by engineers in hurricane damage assessment.
- Rohn emergency scale for measuring the magnitude (intensity) of any emergency
- Hurricane engineering
- Hypercane
- Outline of tropical cyclones
References
- ^ "Saffir-Simpson Hurricane Wind Scale". National Hurricane Center. 2018. Retrieved November 14, 2020.
- ^ "Minor Modification to Saffir-Simpson Hurricane Wind Scale For the 2012 Hurricane Season" (PDF). National Hurricane Center. 2012. Retrieved November 14, 2020.
- ^ United States Navy: "Section 2. Intensity Observations and Forecast Errors". Archived from the original on September 16, 2007. Retrieved July 4, 2008.
For US Navy interests, the factor 0.88 is used in going from a 1-minute system to a 10-minute system such that TEN-MINUTE MEAN = 0.88 * ONE-MINUTE MEAN or ONE-MINUTE MEAN = 1.14 * TEN-MINUTE MEAN.
Retrieved on 2018-10-07. - ^ Williams, Jack (May 17, 2005). "Hurricane scale invented to communicate storm danger". USA Today. Retrieved February 25, 2007.
- ^ Staff writer (May 9, 1973). "'73, Hurricanes to be Graded". Associated Press. Archived from the original on May 19, 2016. Retrieved December 8, 2007.
- ^ Sun-Sentinel. Fort Lauderdale, FL. Archived from the originalon October 23, 2009. Retrieved September 10, 2006.
- ^ Press Writer (August 23, 2001). "Hurricanes shaped life of scale inventor". Archived from the original on April 17, 2016. Retrieved March 20, 2016.
- ^ a b c d e f g h The Saffir–Simpson Hurricane Wind Scale National Hurricane Center. Accessed 2009-05-15.
- ^ National Hurricane Operations Plan Archived July 8, 2011, at the Wayback Machine, NOAA. Accessed July 3, 2010.
- ^ LiveScience. Retrieved October 20, 2005.
- ^ "Experimental Saffir–Simpson Hurricane Wind Scale" (PDF). National Hurricane Center. 2009. Archived from the original (PDF) on August 6, 2009. Retrieved August 17, 2009.
- ^ Public Information Statement, NOAA. Accessed March 9, 2012.
- ^ Tropical Cyclone Weather Services Program (June 1, 2006). "Tropical cyclone definitions" (PDF). National Weather Service. Retrieved November 30, 2006.
- ^ Federal Emergency Management Agency (2004). "Hurricane Glossary of Terms". Archived from the original on December 14, 2005. Retrieved March 24, 2006. Accessed through the Wayback Machine.
- ^ "Name That Hurricane: Famous Examples of the 5 Hurricane Categories". Live Science. Retrieved September 11, 2017.
- ^ "Famous Hurricanes of the 20th and 21st Century in the United States" (PDF). www.weather.gov/crh/.
- ^ Blake, Eric (September 20, 2017). Hurricane Maria Tropical Cyclone Update (Report). Miami, Florida: National Hurricane Center. Retrieved September 20, 2017.
- ^ John L. Beven II; Robbie Berg; Andrew Hagen (April 19, 2019). Tropical Cyclone Report: Hurricane Michael (PDF) (Technical report). National Hurricane Center. Retrieved April 19, 2019.
- .
- .
- ^ Benfield Hazard Research Centre (2006). "Atmospheric Hazards". Hazard & Risk Science Review 2006. University College London. Archived from the original on 7 August 2008. Retrieved 8 December 2007.
- ^ Bill Blakemore (May 21, 2006). "Category 6 Hurricanes? They've Happened: Global Warming Winds Up Hurricane Scientists as NOAA Issues Its Atlantic Hurricane Predictions for Summer 2006". ABC News. Retrieved September 10, 2006.
- ^ "Climate scientists mull Category 6 storm classification, report says". ABC News. February 22, 2018.
- ^ "Hurricane Irma: Will Irma become world's first CATEGORY 6 hurricane with 200mph winds?". Daily Express. September 5, 2017.
- ^ Debi Iacovelli and Tim Vasquez (1998). "Supertyphoon Tip: Shattering all records" (PDF). Monthly Weather Log. National Oceanic and Atmospheric Administration. Retrieved September 19, 2010.
- ^ "Category 6? Scientists warn hurricanes could keep getting stronger". Tampa Bay Times. November 30, 2018. Retrieved November 30, 2018.
- . Retrieved February 5, 2024.
- ^ Jennifer Kay (September 2017). "Irma could test strength of Florida's strict building codes". The Washington Post. Washington, DC. Archived from the original on September 17, 2017. Retrieved September 16, 2017.
External links
- "Saffir–Simpson Hurricane Wind Scale". U.S. National Hurricane Center.
- "An Interview with Dr. Robert Simpson". The Mariners Weather Log. April 1999. Archived from the original on October 23, 2009. Retrieved October 1, 2005.
- "Q&A with Herbert Saffir". The South Florida Sun-Sentinel. June 2001. Archived from the original on February 28, 2010. Retrieved October 1, 2005.