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Hurricane intensity scale

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.

Saffir–Simpson calibration
Category Wind speeds
(for one-infinitesimal maximum sustained winds)
thousand/s knots (kn) mph km/h
5 ≥ 70 grand/s ≥ 137 kn ≥ 157 mph ≥ 252 km/h
4   58–70 one thousand/southward   113–136 kn   130–156 mph   209–251 km/h
Three   50–58 yard/s   96–112 kn   111–129 mph   178–208 km/h
Two   43–49 m/southward   83–95 kn   96–110 mph   154–177 km/h
Ane   33–42 yard/s   64–82 kn   74–95 mph   119–153 km/h
Related classifications
(for i-minute maximum sustained winds)
Tropical storm   18–32 g/s   34–63 kn   39–73 mph   63–118 km/h
Tropical depression   ≤ 17 chiliad/s   ≤ 33 kn   ≤ 38 mph   ≤ 62 km/h

To exist classified as a hurricane, a tropical cyclone must have one-minute-average maximum sustained winds at 10 m above the surface of at least 74 mph (Category ane).[i] The highest classification in the scale, Category 5, consists of storms with sustained winds of at to the lowest degree 157 mph. Come across the table to the right for all 5 categories with wind speeds in various units. The classifications can provide some indication of the potential damage and flooding a hurricane will crusade upon landfall.

The Saffir–Simpson hurricane wind scale is based on the highest wind speed averaged over a 1-minute interval 10 m above the surface. Although the scale shows wind speeds in continuous speed ranges, the National Hurricane Center and the Cardinal 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. Air current speeds in knots are then converted to other units and rounded to the nearest 5 mph or 5 km/h.[two]

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 utilize unlike scales to characterization these storms, which are called cyclones or typhoons, depending on the surface area. These areas (except the JTWC) use three-minute or ten-minute averaged winds to make up one's mind 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 air current scale (normally 14% more than intense) and those measured using a ten-minute interval (commonly 12% less intense).[3]

There is some criticism of the SSHWS for not accounting for rain, tempest surge, and other of import factors, but SSHWS defenders say that office of the goal of SSHWS is to be straightforward and simple to understand.

History [edit]

The scale was developed in 1971 by civil engineer Herbert Saffir and meteorologist Robert Simpson, who at the fourth dimension was manager of the U.South. National Hurricane Center (NHC).[4] The scale was introduced to the full general public in 1973,[5] and saw widespread use subsequently Neil Frank replaced Simpson at the helm of the NHC in 1974.[6]

The initial scale was developed past Herbert Saffir, a structural engineer, who in 1969 went on committee for the United nations to report low-cost housing in hurricane-prone areas.[7] While conducting the report, Saffir realized there was no simple scale for describing the likely furnishings of a hurricane. Mirroring the utility of the Richter magnitude scale for describing earthquakes, he devised a ane–5 scale based on wind speed that showed expected harm to structures. Saffir gave the calibration to the NHC, and Simpson added the furnishings of storm surge and flooding.

In 2009, the NHC made moves to eliminate pressure and tempest surge ranges from the categories, transforming it into a pure air current calibration, called the Saffir–Simpson Hurricane Wind Scale (Experimental) [SSHWS].[8] The new scale became operational on May fifteen, 2010.[9] The scale excludes flood ranges, storm surge estimations, rainfall, and location, which means a Category 2 hurricane that hits a major urban center volition likely do far more than cumulative impairment than a Category 5 hurricane that hits a rural surface area.[10] The agency cited various hurricanes as reasons for removing the "scientifically inaccurate" data, 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 tempest surge.[11] Since being removed from the Saffir–Simpson hurricane current of air scale, storm surge predicting and modeling is now handled with the employ of figurer numerical models such as ADCIRC and SLOSH.

In 2012, the NHC expanded the windspeed range for Category iv by ane 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 Centre assign tropical cyclone intensities in 5 knot increments, and 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. Also, 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 problems, the NHC had been obliged to incorrectly written report storms with wind speeds of 115 kn every bit 135 mph, and 135 kn as 245 km/h. The alter 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 authorize as Category iv. Since the NHC had previously rounded incorrectly to go along storms in Category 4 in each unit of measurement of measure, the modify does non affect the nomenclature of storms from previous years.[viii] The new scale became operational on May 15, 2012.[12]

Categories [edit]

The scale separates hurricanes into five unlike categories based on wind. The U.South. National Hurricane Center classifies hurricanes of Category 3 and above as major hurricanes, and the Joint Typhoon Warning Centre classifies typhoons of 150 mph or greater (strong Category 4 and Category 5) as super typhoons (although all tropical cyclones can exist very unsafe). Most weather agencies use the definition for sustained winds recommended by the World Meteorological Organisation (WMO), which specifies measuring winds at a peak of 33 ft (10.one 1000) for 10 minutes, and then taking the average. By contrast, the U.S. National Conditions Service, Central Pacific Hurricane Center and the Joint Typhoon Alert Center define sustained winds as average winds over a menstruum of one infinitesimal, measured at the aforementioned 33 ft (10.1 yard) height,[xiii] [14] and that is the definition used for this scale.

The scale is roughly logarithmic in air current speed.

The v categories are described in the following subsections, in guild of increasing intensity.[xv] Intensity of example hurricanes is from both the fourth dimension of landfall and the maximum intensity.

Category one [edit]

Category 1
Sustained winds Most contempo landfall
33–42 m/s
64–82 kn
119–153 km/h
74–95 mph 		Pamela 2021-10-13 0905Z.jpgPamela in 2021 nearing landfall in Mexico

Very dangerous winds volition produce some damage

Category i storms usually cause no significant structural damage to most well-constructed permanent structures; nevertheless, they can topple unanchored mobile homes, likewise equally uproot or snap weak copse. Poorly attached roof shingles or tiles can blow off. Coastal flooding and pier impairment are oftentimes associated with Category 1 storms. Power outages are typically widespread to all-encompassing, sometimes lasting several days. Fifty-fifty though it is the least intense type of hurricane, they can yet produce widespread impairment and tin be life-threatening storms.[viii]

Hurricanes that peaked at Category 1 intensity and fabricated landfall at that intensity include: Agnes (1972), Juan (1985), Ismael (1995), Danny (1997), Stan (2005), Humberto (2007), Isaac (2012), Manuel (2013), Earl (2016), Hermine (2016), Nate (2017), Barry (2019), Lorena (2019), Hanna (2020), Isaias (2020), Nana (2020), Gamma (2020), and Pamela (2021).

Category 2 [edit]

Category 2
Sustained winds Most recent landfall
43–49 thou/s
83–95 kn
154–177 km/h
96–110 mph 		Rick 2021-10-24 2015Z.jpg
Rick in 2021 nearly landfall in Lázaro Cárdenas, United mexican states

Extremely dangerous winds will cause extensive damage

Storms of Category 2 intensity ofttimes harm roofing cloth (sometimes exposing the roof) and inflict damage upon poorly synthetic doors and windows. Poorly constructed signs and piers can receive considerable damage and many copse are uprooted or snapped. Mobile homes, whether anchored or not, are typically damaged and sometimes destroyed, and many manufactured homes besides suffer structural impairment. Pocket-size arts and crafts in unprotected anchorages may break their moorings. Extensive to near-total power outages and scattered loss of potable water are likely, perhaps lasting many days.[8]

Hurricanes that peaked at Category 2 intensity and made landfall at that intensity include: Alice (1954), Ella (1958), Fifi (1974), Diana (1990), Gert (1993), Rosa (1994), Erin (1995), Alma (1996), Juan (2003), Alex (2010), Richard (2010), Tomas (2010), Carlotta (2012), Ernesto (2012), Arthur (2014), Emerge (2020), Olaf (2021), and Rick (2021).

Category three [edit]

Category iii
Sustained winds Well-nigh recent landfall
50–58 1000/s
96–112 kn
178–208 km/h
111–129 mph 		Grace 2021-08-21 0610Z.jpg
Grace in 2021 only prior to its Veracruz landfall

Devastating damage volition occur

Tropical cyclones of Category 3 and college are described every bit major hurricanes in the Atlantic or Eastern Pacific basins. These storms tin 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 every bit mobile homes, are usually destroyed, and gable-end roofs are peeled off. Manufactured homes usually sustain severe and irreparable impairment. 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. Almost-total to total ability loss is likely for up to several weeks and water will likely also be lost or contaminated.[viii]

Hurricanes that peaked at Category 3 intensity and made landfall at that intensity include: Easy (1950), Carol (1954), Hilda (1955), Audrey (1957), Celia (1970), 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 iv [edit]

Category 4
Sustained winds Most recent landfall
58–70 m/s
113–136 kn
209–251 km/h
130–156 mph 		Ida 2021-08-29 1400Z.png

Ida in 2021 nearing landfall in Louisiana

Catastrophic impairment will occur

Category 4 hurricanes tend to produce more extensive curtainwall failures, with some complete structural failure on small-scale residences. Heavy, irreparable impairment and nigh-complete destruction of gas station canopies and other wide bridge overhang blazon structures are common. Mobile and manufactured homes are oftentimes flattened. Nigh copse, except for the hardiest, are uprooted or snapped, isolating many areas. These storms cause extensive beach erosion, while terrain may exist flooded far inland. Total and long-lived electric and water losses are to be expected, possibly for many weeks.[8]

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: Flora (1963), Betsy (1965), Carmen (1974), Frederic (1979), Joan (1988), Iniki (1992), Luis (1995), Iris (2001), Charley (2004), Dennis (2005), Gustav (2008), Ike (2008), Joaquin (2015), Harvey (2017), Laura (2020), Eta (2020), Iota (2020) and Ida (2021).

Category 5 [edit]

Category 5
Sustained winds Nigh contempo landfall
≥ 70 chiliad/s
≥ 137 kn
≥ 252 km/h
≥ 157 mph 		Dorian 2019-09-01 1601Z.png Dorian in 2019 nearing its Bahamas landfall

Catastrophic damage will occur

Category five is the highest category of the Saffir–Simpson scale. These storms cause complete roof failure on many residences and industrial buildings, and some complete edifice failures with small utility buildings blown over or away. The plummet of many broad-span roofs and walls, peculiarly those with no interior supports, is common. Very heavy and irreparable damage to many forest-frame structures and full destruction to mobile/manufactured homes is prevalent. Only a few types of structures are capable of surviving intact, and simply if located at to the lowest degree three to 5 miles (five 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 almost of these requirements are met, the catastrophic destruction of a structure may occur.[viii]

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

Historical examples of storms that fabricated landfall at Category five status include: "Cuba" (1924), "Okeechobee" (1928), "Bahamas" (1932), "Cuba–Brownsville" (1933), "Labor Day" (1935), Janet (1955), Camille (1969), Edith (1971), Anita (1977), David (1979), Gilbert (1988), Andrew (1992), Dean (2007), Felix (2007), Irma (2017),[xvi] Maria (2017),[17] Michael (2018),[18] and Dorian (2019). No Category five hurricane is known to have made landfall at that force in the eastern Pacific bowl.[19]

Criticism [edit]

Some scientists, including Kerry Emanuel and Lakshmi Kantha, take criticized the scale as beingness simplistic, indicating that the calibration takes into business relationship neither the concrete size of a storm nor the amount of atmospheric precipitation it produces.[ten] Additionally, they and others betoken out that the Saffir–Simpson calibration, unlike the Richter scale used to measure earthquakes, is not continuous, and is quantized into a small number of categories. Proposed replacement classifications include the Hurricane Intensity Alphabetize, which is based on the dynamic pressure caused by a storm'due south winds, and the Hurricane Adventure Index, which is based on surface current of air speeds, the radius of maximum winds of the tempest, and its translational velocity.[20] [21] Both of these scales are continuous, akin to the Richter scale;[22] however, neither of these scales accept been used by officials.[ commendation needed ]

Proposed extensions [edit]

After the series of powerful storm systems of the 2005 Atlantic hurricane season, every bit well as after Hurricane Patricia, a few newspaper columnists and scientists brought upwardly the suggestion of introducing Category half dozen, and they have suggested pegging Category 6 to storms with winds greater than 174 or 180 mph (78 or 80 1000/south; 151 or 156 kn; 280 or 290 km/h).[x] [23] Fresh calls were fabricated for consideration of the upshot later on Hurricane Irma in 2017,[24] which was the subject field of a number of seemingly credible false news reports as a "Category half-dozen" storm,[25] partly in consequence of then many local politicians using the term. Only a few storms of this intensity have been recorded. Of the 37 hurricanes currently considered to accept attained Category 5 condition in the Atlantic, 18 had wind speeds at 175 mph (78 grand/s; 152 kn; 282 km/h) or greater and only eight had wind speeds at 180 mph (80 yard/s; 160 kn; 290 km/h) or greater (the 1935 Labor Day hurricane, Allen, Gilbert, Mitch, Rita, Wilma, Irma, and Dorian). Of the 18 hurricanes currently considered to have attained Category v status in the eastern Pacific, simply five had wind speeds at 175 mph (78 m/s; 152 kn; 282 km/h) or greater (Patsy, John, Linda, Rick, and Patricia), and only iii had wind speeds at 180 mph (lxxx m/s; 160 kn; 290 km/h) or greater (Linda, Rick, and Patricia). About storms which would be eligible for this category were typhoons in the western Pacific, almost notably typhoons Tip, Halong, and Surigae in 1979, 2019, and 2021, respectively, each with sustained winds of 190 mph (305 km/h),[26] and typhoons Haiyan, Meranti, and Goni in 2013, 2016 and 2020, respectively, each with sustained winds of 195 mph (315 km/h). Occasionally, suggestions of using even higher wind speeds as the cutoff have been made. In a newspaper commodity published in November 2018, NOAA research scientist Jim Kossin said that the potential for more intense hurricanes was increasing equally the climate warmed, and suggested that Category six would begin at 195 mph (87 m/s; 169 kn; 314 km/h), with a further hypothetical Category 7 beginning at 230 mph (100 thousand/s; 200 kn; 370 km/h).[27]

Co-ordinate to Robert Simpson, at that place are no reasons for a Category vi on the Saffir–Simpson Scale because it is designed to measure the potential damage of a hurricane to homo-made structures. Simpson stated 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 every bit much as six seconds on a building it'south going to cause rupturing damages that are serious no affair how well information technology's engineered."[6] Yet, the counties of Broward and Miami-Dade in Florida have building codes that require that disquisitional infrastructure buildings be able to withstand Category 5 winds.[28]

See also [edit]

  • Beaufort scale – Relates air current speed to observable conditions at sea and on country
  • Enhanced Fujita scale – For tornado intensity with impairment correlated to air current speeds. The arrangement was also intended for applicability in hurricanes, and is utilized by engineers in hurricane damage assessment.
  • Hurricane engineering
  • Hypercane
  • List of tropical cyclones
  • Rohn Emergency Scale for measuring the magnitude (intensity) of any emergency

References [edit]

  1. ^ "Saffir-Simpson Hurricane Wind Scale". National Hurricane Center. 2018. Retrieved November xiv, 2020.
  2. ^ "Small-scale Modification to Saffir-Simpson Hurricane Current of air Scale For the 2012 Hurricane Flavour" (PDF). National Hurricane Middle. 2012. Retrieved November 14, 2020.
  3. ^ United States Navy: "Section 2. INTENSITY OBSERVATION AND FORECAST ERRORS". Archived from the original on September 16, 2007. Retrieved July 4, 2008. For US Navy interests, the gene 0.88 is used in going from a 1-minute system to a 10-minute organization such that TEN-Minute Mean = 0.88 * ONE-MINUTE Hateful or ONE-MINUTE MEAN = ane.fourteen * X-Minute MEAN. {{cite web}}: CS1 maint: bot: original URL status unknown (link) Retrieved on 2018-ten-07.
  4. ^ Williams, Jack (May 17, 2005). "Hurricane calibration invented to communicate tempest danger". USA Today . Retrieved February 25, 2007.
  5. ^ Staff writer (May 9, 1973). "'73, Hurricanes to be Graded". Associated Press. Archived from the original on May xix, 2016. Retrieved December 8, 2007.
  6. ^ a b Debi Iacovelli (July 2001). "The Saffir/Simpson Hurricane Calibration: An Interview with Dr. Robert Simpson". Sun-Sentinel. Fort Lauderdale, FL. Archived from the original on October 23, 2009. Retrieved September 10, 2006.
  7. ^ Press Writer (August 23, 2001). "Hurricanes shaped life of scale inventor". Archived from the original on Apr 17, 2016. Retrieved March 20, 2016.
  8. ^ a b c d eastward f thou h The Saffir–Simpson Hurricane Wind Scale National Hurricane Center. Accessed 2009-05-15.
  9. ^ National Hurricane Operations Plan Archived July 8, 2011, at the Wayback Automobile, NOAA. Accessed July 3, 2010.
  10. ^ a b c Ker Than (Oct 20, 2005). "Wilma's Rage Suggests New Hurricane Categories Needed". LiveScience . Retrieved October 20, 2005.
  11. ^ "Experimental Saffir–Simpson Hurricane Wind Scale" (PDF). National Hurricane Center. 2009. Archived from the original (PDF) on August 6, 2009. Retrieved August 17, 2009.
  12. ^ Public Information Statement, NOAA. Accessed March 9, 2012.
  13. ^ Tropical Whirlwind Weather Services Program (June 1, 2006). "Tropical whirlwind definitions" (PDF). National Weather Service. Retrieved November 30, 2006.
  14. ^ Federal Emergency Direction Bureau (2004). "Hurricane Glossary of Terms". Archived from the original on December 14, 2005. Retrieved March 24, 2006. Accessed through the Wayback Car.
  15. ^ "Proper name That Hurricane: Famous Examples of the five Hurricane Categories". Live Scientific discipline . Retrieved September eleven, 2017.
  16. ^ "Famous Hurricanes of the 20th and 21st Century in the Usa" (PDF). www.conditions.gov/crh/.
  17. ^ Blake, Eric (September xx, 2017). Hurricane Maria Tropical Whirlwind Update (Report). Miami, Florida: National Hurricane Center. Retrieved September 20, 2017.
  18. ^ John 50. Beven Two; Robbie Berg; Andrew Hagen (April 19, 2019). Tropical Cyclone Report: Hurricane Michael (PDF) (Technical report). National Hurricane Center. Retrieved April xix, 2019.
  19. ^ National Hurricane Center; Hurricane Research Division (May 26, 2020). "Pacific hurricane best rail (HURDAT)" (Database). 2. United States National Oceanic and Atmospheric Administration. Archived from the original on March nineteen, 2021. Retrieved March 24, 2021.
  20. ^ Kantha, L. (January 2006). "Time to Supplant the Saffir–Simpson Hurricane Scale?". Eos. 87 (1): 3, six. Bibcode:2006EOSTr..87....3K. doi:10.1029/2006eo010003.
  21. ^ Kantha, Lakshmi (February 2008). "Tropical Cyclone Destructive Potential by Integrated Kinetic Free energy". Bulletin of the American Meteorological Society. 89 (two): 219–221. Bibcode:2008BAMS...89..219K. CiteSeerX10.1.i.693.5083. doi:10.1175/BAMS-89-2-219.
  22. ^ Benfield Hazard Enquiry Centre (2006). "Atmospheric Hazards". Risk & Chance Science Review 2006. Academy College London. Archived from the original on 7 August 2008. Retrieved eight December 2007.
  23. ^ Bill Blakemore (May 21, 2006). "Category 6 Hurricanes? They've Happened: Global Warming Winds Upwardly Hurricane Scientists as NOAA Issues Its Atlantic Hurricane Predictions for Summer 2006". ABC News . Retrieved September 10, 2006.
  24. ^ "Climate scientists mull Category 6 storm classification, report says". ABC News. February 22, 2018.
  25. ^ "Hurricane Irma: Volition Irma go world'due south first CATEGORY 6 hurricane with 200mph winds?". Daily Express. September five, 2017.
  26. ^ Debi Iacovelli and Tim Vasquez (1998). "Supertyphoon Tip: Shattering all records" (PDF). Monthly Atmospheric condition Log. National Oceanic and Atmospheric Administration. Retrieved September 19, 2010.
  27. ^ "Category 6? Scientists warn hurricanes could keep getting stronger". Tampa Bay Times. November xxx, 2018. Retrieved November 30, 2018.
  28. ^ Jennifer Kay (September 2017). "Irma could test forcefulness of Florida'southward strict edifice codes". The Washington Post. Washington, DC. Archived from the original on September 17, 2017. Retrieved September 16, 2017.

External links [edit]

  • "Saffir–Simpson Hurricane Air current Scale". U.S. National Hurricane Center.
  • "An Interview with Dr. Robert Simpson". The Mariners Weather Log. Apr 1999. Archived from the original on October 23, 2009. Retrieved October i, 2005.
  • "Q&A with Herbert Saffir". The South Florida Sun-Sentinel. June 2001. Archived from the original on February 28, 2010. Retrieved Oct 1, 2005.

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Source: https://en.wikipedia.org/wiki/Saffir%E2%80%93Simpson_scale

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