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74-650: The U.S. Army Corps of Engineers began developing the model with the Weather Bureau in 1959. The standard was developed before the Saffir-Simpson hurricane scale came into use, and the features of the Standard Project fit poorly with the scale. The wind speed for the project hurricane was just 100 miles per hour, which falls into Category 2; other features more closely resemble a much more severe Category 4. The United States Army Corps of Engineers generally calls it

148-480: A Category 4 hurricane that struck Galveston, Texas , drove a devastating surge ashore; between 6,000 and 12,000 people died, making it the deadliest natural disaster ever to strike the United States. The highest storm tide noted in historical accounts was produced by the 1899 Cyclone Mahina , estimated at almost 44 feet (13.41 m) at Bathurst Bay , Australia , but research published in 2000 concluded that

222-476: 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. 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. Since being removed from

296-409: A hurricane, a tropical cyclone must have one-minute-average maximum sustained winds at 10 m (33 ft) above the surface of at least 74 mph (64 kn, 119 km/h; Category 1). The highest classification in the scale, Category 5 , consists of storms with sustained winds of at least 157 mph (137 kn, 252 km/h). The classifications can provide some indication of

370-519: A map of MOMs or Maximum of Maximums. For hurricane evacuation studies, a family of storms with representative tracks for the region, and varying intensity, eye diameter, and speed are modeled to produce worst-case water heights for any tropical cyclone occurrence. The results of these studies are typically generated from several thousand SLOSH runs. These studies have been completed by the United States Army Corps of Engineers , under contract to

444-439: A number of days as water was continually built-up inside the estuary from the onshore winds and freshwater rains flowing into the bay. In many locations, water levels were shy of records by only 0.1 feet (3 cm). Surge can be measured directly at coastal tidal stations as the difference between the forecast tide and the observed rise of water. Another method of measuring surge is by the deployment of pressure transducers along

518-449: A phenomenon referred to as wind setup , which is the tendency for water levels to increase at the downwind shore and to decrease at the upwind shore. Intuitively, this is caused by the storm blowing the water toward one side of the basin in the direction of its winds. Strong surface winds cause surface currents at a 45° angle to the wind direction, by an effect known as the Ekman spiral . Because

592-541: A representative storm, actually excluded the fiercest storms from the database. "Storms like Hurricane Camille in 1969 were taken out of the data set as lying too far out of the norm; the Berkeley researchers noted that 'excluding outlier data is not appropriate in the context of dealing with extreme hazards.' Also, the calculations of the cost-benefit ratio did not take into account the costs of failure, both economic and social, far greater in an urban area like New Orleans than

666-582: A rural one." Saffir-Simpson hurricane scale The Saffir–Simpson hurricane wind scale ( SSHWS ) classifies hurricanes —which in the Western Hemisphere are tropical cyclones that exceed the intensities of tropical depressions and tropical storms —into five categories distinguished by the intensities of their sustained winds . This measuring system was formerly known as the Saffir–Simpson hurricane scale , or SSHS . To be classified as

740-474: A station provides a translation from the geodetic vertical datum to mean sea level (MSL) at that location, then subtracting the tidal prediction yields a surge height above the normal water height. The U.S. National Hurricane Center forecasts storm surge using the SLOSH model, which is an abbreviation for Sea, Lake and Overland Surges from Hurricanes. The model is accurate to within 20 percent. SLOSH inputs include

814-505: A storm surge. This was the case on the western Florida coast in 2017, just before Hurricane Irma made landfall, uncovering land usually underwater. This phenomenon is known as a reverse storm surge , or a negative storm surge . The deadliest storm surge on record was the 1970 Bhola cyclone , which killed up to 500,000 people in the area of the Bay of Bengal . The low-lying coast of the Bay of Bengal

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888-418: A storm's wind-powered currents. Powerful wind whips up large, strong waves in the direction of its movement. Although these surface waves are responsible for very little water transport in open water, they may be responsible for significant transport near the shore. When waves are breaking on a line more or less parallel to the beach, they carry considerable water shoreward. As they break, the water moving toward

962-528: 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

1036-430: Is another important element in storm surge extent. Areas, where the land lies less than a few meters above sea level, are at particular risk from storm surge inundation. The size of the storm also affects the surge height; this is due to the storm's area not being proportional to its perimeter. If a storm doubles in diameter, its perimeter also doubles, but its area quadruples. As there is proportionally less perimeter for

1110-416: Is defined as the rise of water beyond what would be expected by the normal movement caused by tides, storm surge is measured using tidal predictions, with the assumption that the tide prediction is well-known and only slowly varying in the region subject to the surge. Since tides are a localized phenomenon, storm surge can only be measured in relationship to a nearby tidal station. Tidal benchmark information at

1184-421: Is measured as the rise in water level above the normal tidal level, and does not include waves. The main meteorological factor contributing to a storm surge is high-speed wind pushing water towards the coast over a long fetch . Other factors affecting storm surge severity include the shallowness and orientation of the water body in the storm path, the timing of tides , and the atmospheric pressure drop due to

1258-666: Is particularly high, there are specific storm surge warnings. These have been implemented, for instance, in the Netherlands , Spain , the United States, and the United Kingdom . Similarly educating coastal communities and developing local evacuation plans can reduce the relative impact on people. A prophylactic method introduced after the North Sea flood of 1953 is the construction of dams and storm-surge barriers ( flood barriers ). They are open and allow free passage, but close when

1332-564: Is particularly vulnerable to surges caused by tropical cyclones. The deadliest storm surge in the twenty-first century was caused by Cyclone Nargis , which killed more than 138,000 people in Myanmar in May 2008. The next deadliest in this century was caused by Typhoon Haiyan (Yolanda), which killed more than 6,000 people in the central Philippines in 2013. and resulted in economic losses estimated at $ 14 billion (USD). The 1900 Galveston hurricane ,

1406-516: 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

1480-681: Is relatively steep and deep; storm surge is not as great but the waves are larger compared to the west coast of Florida. Conversely, on the Gulf side of Florida, the edge of the Floridian Plateau can lie more than 160 kilometres (99 mi) offshore. Florida Bay , lying between the Florida Keys and the mainland, is very shallow with depths between 0.3 m (0.98 ft) and 2 m (6.6 ft). These shallow areas are subject to higher storm surges with smaller waves. Other shallow areas include much of

1554-455: 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 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 October 2024 . In 1971,

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1628-498: 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

1702-728: 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: Juan (1985), Ismael (1995), Danny (1997), Stan (2005), Humberto (2007), Isaac (2012), Manuel (2013), Earl (2016), Newton (2016), Nate (2017), Barry (2019), Lorena (2019), Hanna (2020), Isaias (2020), Gamma (2020), Nicholas (2021), Pamela (2021), Julia (2022), Lisa (2022), Nicole (2022), Debby (2024), and Oscar (2024). Extremely dangerous winds will cause extensive damage Storms of Category 2 intensity often damage roofing material, sometimes exposing

1776-431: The 2005 Atlantic hurricane season , as well as after Hurricane Patricia , a few newspaper columnists and scientists brought up the suggestion of introducing Category 6. They have suggested pegging Category 6 to storms with winds greater than 174 or 180 mph (78 or 80 m/s; 151 or 156 kn; 280 or 290 km/h). Fresh calls were made for consideration of the issue after Hurricane Irma in 2017, which

1850-524: 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)

1924-579: The Coriolis effect , which bends currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. When this bend brings the currents into more perpendicular contact with the shore, it can amplify the surge, and when it bends the current away from the shore it has the effect of lessening the surge. The effect of waves, while directly powered by the wind, is distinct from

1998-719: The Federal Emergency Management Agency (FEMA) , for several states and are available on their Hurricane Evacuation Studies (HES) website. They include coastal county maps, shaded to identify the minimum category of hurricane that will result in flooding, in each area of the county. Storm surge is responsible for significant property damage and loss of life as part of cyclones. Storm surge both destroys built infrastructure, like roads and undermines foundations and building structures. Unexpected flooding in estuaries and coastal areas can catch populations unprepared, causing loss of life. The deadliest storm surge on record

2072-445: The Gulf of Mexico coast, and the Bay of Bengal . The difference is due to how much flow area the storm surge can dissipate to. In deeper water, there is more area and a surge can be dispersed down and away from the hurricane. On a shallow, gently sloping shelf, the surge has less room to disperse and is driven ashore by the wind forces of the hurricane. The topography of the land surface

2146-644: The Richter scale as models, he proposed a simplified 1–5 grading scale as a guide for areas that do not have hurricane building codes. The grades were based on two main factors: objective wind gust speeds sustaining for 2–3 seconds at an elevation of 9.2 meters, and subjective levels of structural damage. Saffir gave the proposed scale to the NHC for their use, where Simpson changed the terminology from "grade" to "category", organized them by sustained wind speeds of 1 minute duration, and added storm surge height ranges, adding barometric pressure ranges later on. In 1975,

2220-450: The 21 hurricanes currently considered to have attained Category 5 status in the eastern Pacific, only 5 had wind speeds at 175 mph (78 m/s; 152 kn; 282 km/h) or greater ( Patsy , John , Linda , Rick , and Patricia ). Only 3 had wind speeds at 180 mph (80.5 m/s; 156 kn; 290 km/h) or greater (Linda, Rick, and Patricia). Most storms which would be eligible for this category were typhoons in

2294-526: The Atlantic Coast. Coasts with sea ice may experience an "ice tsunami" causing significant damage inland. Extratropical storm surges may be possible further south for the Gulf coast mostly during the wintertime, when extratropical cyclones affect the coast, such as in the 1993 Storm of the Century . November 9–13, 2009, marked a significant extratropical storm surge event on the United States east coast when

Standard Project Hurricane - Misplaced Pages Continue

2368-501: 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

2442-452: The Ekman spiral effects spread vertically through the water, the effect is proportional to depth. The surge will be driven into bays in the same way as the astronomical tide. The pressure effects of a tropical cyclone will cause the water level in the open ocean to rise in regions of low atmospheric pressure and fall in regions of high atmospheric pressure. The rising water level will counteract

2516-607: The Hurricane Intensity Index, which is based on the dynamic pressure caused by a storm's winds, and the Hurricane Hazard Index, which is based on surface wind speeds, the radius of maximum winds of the storm, and its translational velocity. Both of these scales are continuous, akin to the Richter scale. However, neither of these scales has been used by officials. After the series of powerful storm systems of

2590-662: 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. The new scale became operational on May 15, 2012. 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 . 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

2664-544: The Saffir-Simpson Scale was first published publicly. 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]. The updated scale became operational on May 15, 2010. The scale excludes flood ranges, storm surge estimations, rainfall, and location, which means

2738-432: 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 extended the wind speed 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

2812-429: 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." Nonetheless,

2886-458: 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). There

2960-404: The central pressure of a tropical cyclone, storm size, the cyclone's forward motion, its track, and maximum sustained winds. Local topography, bay and river orientation, depth of the sea bottom, astronomical tides, as well as other physical features, are taken into account in a predefined grid referred to as a SLOSH basin. Overlapping SLOSH basins are defined for the southern and eastern coastline of

3034-1175: 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. Terrain may be flooded well inland. Near-total to total power loss is likely for up to several weeks. Home water access will likely be lost or contaminated. 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), Grace (2021), John (2024), and Rafael (2024). 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

Standard Project Hurricane - Misplaced Pages Continue

3108-434: The coastline just ahead of an approaching tropical cyclone. This was first tested for Hurricane Rita in 2005. These types of sensors can be placed in locations that will be submerged and can accurately measure the height of water above them. After surge from a cyclone has receded, teams of surveyors map high-water marks (HWM) on land, in a rigorous and detailed process that includes photographs and written descriptions of

3182-628: The continental U.S. Some storm simulations use more than one SLOSH basin; for instance, Hurricane Katrina SLOSH model runs used both the Lake Pontchartrain / New Orleans basin, and the Mississippi Sound basin, for the northern Gulf of Mexico landfall. The final output from the model run will display the maximum envelope of water, or MEOW, that occurred at each location. To allow for track or forecast uncertainties, usually several model runs with varying input parameters are generated to create

3256-453: 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. Storm surge A storm surge , storm flood , tidal surge , or storm tide is a coastal flood or tsunami -like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones . It

3330-513: The cutoff have been made. In a newspaper article published in November 2018, NOAA research scientist Jim Kossin said that the potential for more intense hurricanes was increasing as the climate warmed , and suggested that Category 6 would begin at 195 mph (85 m/s; 170 kn; 315 km/h), with a further hypothetical Category 7 beginning at 230 mph (105 m/s; 200 kn; 370 km/h). In 2024 another proposal to add "Category 6"

3404-568: 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

3478-518: The equivalent of a fast-moving Category 3. The standard project hurricane became "enshrined within the corps," according to an investigation of the levee failures in New Orleans following Hurricane Katrina , who noted that "the corps saw little need to go back and reanalyze "the true risks of catastrophic flooding" in New Orleans. Even when the National Oceanic and Atmospheric Administration ,

3552-471: The evaluation, HWMs are divided into four categories based on the confidence in the mark; in the U.S., only HWMs evaluated as "excellent" are used by the National Hurricane Center in the post-storm analysis of the surge. Two different measures are used for storm tide and storm surge measurements. Storm tide is measured using a geodetic vertical datum ( NGVD 29 or NAVD 88 ). Since storm surge

3626-934: The hardiest, are uprooted or snapped, isolating many areas. These storms cause extensive beach erosion . Terrain may be flooded far inland. Total and long-lived electrical and water losses are to be expected, possibly for many weeks. 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), Gracie (1959), Donna (1960), Carla (1961), Flora (1963), Betsy (1965), Celia (1970), Carmen (1974), Madeline (1976), Frederic (1979), Joan (1988), Iniki (1992), Charley (2004), Dennis (2005), Ike (2008), Harvey (2017), Laura (2020), Eta (2020), Iota (2020), Ida (2021), Lidia (2023), and Helene (2024). Catastrophic damage will occur Category 5

3700-763: 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. 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), Maria (2017), Michael (2018), Dorian (2019), and Otis (2023) (the only Pacific hurricane to make landfall at Category 5 intensity). Some scientists, including Kerry Emanuel and Lakshmi Kantha, have criticized

3774-612: 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. 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

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3848-940: The land is under threat of a storm surge. Major storm surge barriers are the Oosterscheldekering and Maeslantkering in the Netherlands, which are part of the Delta Works project; the Thames Barrier protecting London ; and the Saint Petersburg Dam in Russia . Another modern development (in use in the Netherlands) is the creation of housing communities at the edges of wetlands with floating structures, restrained in position by vertical pylons. Such wetlands can then be used to accommodate runoff and surges without causing damage to

3922-438: The low atmospheric pressure such that the total pressure at some plane beneath the water surface remains constant. This effect is estimated at a 10 mm (0.39 in) increase in sea level for every millibar (hPa) drop in atmospheric pressure. For example, a major storm with a 100 millibar pressure drop would be expected to have a 1.0 m (3.3 ft) water level rise from the pressure effect. The Earth's rotation causes

3996-410: The majority of this likely was wave run-up because of the steep coastal topography. However, much of this storm surge was likely due to Mahina's extreme intensity, as computer modeling required an intensity of 880 millibars (26 inHg) (the same intensity as the lowest recorded pressure from the storm) to produce the recorded storm surge. In the United States, one of the greatest recorded storm surges

4070-415: The marks. HWMs denote the location and elevation of floodwaters from a storm event. When HWMs are analyzed, if the various components of the water height can be broken out so that the portion attributable to surge can be identified, then that mark can be classified as storm surge. Otherwise, it is classified as storm tide. HWMs on land are referenced to a vertical datum (a reference coordinate system). During

4144-542: The potential damage and flooding a hurricane will cause upon landfall . 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

4218-469: The remnants of Hurricane Ida developed into a nor'easter off the southeast U.S. coast. During the event, winds from the east were present along the northern periphery of the low-pressure center for a number of days, forcing water into locations such as Chesapeake Bay . Water levels rose significantly and remained as high as 8 feet (2.4 m) above normal in numerous locations throughout the Chesapeake for

4292-1065: 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 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. 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), Agatha (2022), and Francine (2024). Devastating damage will occur Tropical cyclones of Category 3 and higher are described as major hurricanes in

4366-813: The same 33 ft (10.1 m) height, and that is the definition used for this scale. The five categories are described in the following subsections, in order of increasing intensity. Example hurricanes for each category are limited to those which made landfall at their maximum achieved category on the scale. Very dangerous winds will produce some damage Category 1 storms usually cause no significant structural damage to most well-constructed permanent structures. 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

4440-402: The scale as being too simplistic, namely that the scale takes into account neither the physical size of a storm nor the amount of precipitation it produces. They and others point out that the Saffir–Simpson scale, unlike the moment magnitude scale used to measure earthquakes , is not continuous, and is quantized into a small number of categories. Proposed replacement classifications include

4514-403: The scale was developed by civil engineer Herbert Saffir and meteorologist Robert Simpson , who at the time was director of the U.S. National Hurricane Center (NHC). In 1973, the scale was introduced to the general public, and saw widespread use after Neil Frank replaced Simpson at the helm of the NHC in 1974. The scale was created by Herbert Saffir, a structural engineer , who in 1969

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4588-471: The shore has considerable momentum and may run up a sloping beach to an elevation above the mean water line, which may exceed twice the wave height before breaking. The rainfall effect is experienced predominantly in estuaries . Hurricanes may dump as much as 12 in (300 mm) of rainfall in 24 hours over large areas and higher rainfall densities in localized areas. As a result, surface runoff can quickly flood streams and rivers. This can increase

4662-452: The shoreline, tends to produce a lower surge but higher and more powerful waves. A wide shelf, with shallower water, tends to produce a higher storm surge with relatively smaller waves. For example, in Palm Beach on the southeast coast of Florida , the water depth reaches 91 metres (299 ft) 3 km (1.9 mi) offshore, and 180 m (590 ft) 7 km (4.3 mi) out. This

4736-561: The storm. As extreme weather becomes more intense and the sea level rises due to climate change , storm surges are expected to cause more risk to coastal populations. Communities and governments can adapt by building hard infrastructure, like surge barriers , soft infrastructure, like coastal dunes or mangroves , improving coastal construction practices and building social strategies such as early warning, education and evacuation plans. At least five processes can be involved in altering tide levels during storms. Wind stresses cause

4810-523: The structures while also protecting conventional structures at somewhat higher low-lying elevations, provided that dikes prevent major surge intrusion. Other soft adaptation methods can include changing structures so that they are elevated to avoid flooding directly, or increasing natural protections like mangroves or dunes . For mainland areas, storm surge is more of a threat when the storm strikes land from seaward, rather than approaching from landward. Water can also be sucked away from shore prior to

4884-456: The successor agency to the Weather Bureau , recommended increasing the strength of the model, the corps did not change its construction plans." Dr. David Daniel, the chairman of a panel reviewing the corps' investigation, said in an interview, "It was not a terribly sophisticated or detailed analysis by today's standards." The creators of the standard project hurricane, in an attempt to find

4958-495: The surge to dissipate to, the surge height ends up being higher. Similar to tropical cyclones, extratropical cyclones cause an offshore rise of water. However, unlike most tropical cyclone storm surges, extratropical cyclones can cause higher water levels across a large area for longer periods of time, depending on the system. In North America, extratropical storm surges may occur on the Pacific and Alaska coasts, and north of 31°N on

5032-412: The water level near the head of tidal estuaries as storm-driven waters surging in from the ocean meet rainfall flowing downstream into the estuary. In addition to the above processes, storm surge and wave heights on shore are also affected by the flow of water over the underlying topography, i.e. the shape and depth of the ocean floor and coastal area. A narrow shelf , with deep water relatively close to

5106-409: The western Pacific, most notably typhoons Tip , Halong , Mawar , and Bolaven in 1979, 2019, 2023 and 2023 respectively, each with sustained winds of 190 mph (305 km/h), and typhoons Haiyan , Meranti , Goni , and Surigae in 2013, 2016, 2020 and 2021 respectively, each with sustained winds of 195 mph (315 km/h). Occasionally, suggestions of using even higher wind speeds as

5180-546: 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. The storm's flooding causes major damage to the lower floors of all structures near the shoreline. 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

5254-524: Was commissioned by the United Nations to study low-cost housing in hurricane-prone areas. In 1971, while conducting the study, Saffir realized there was no simple scale for describing the likely effects of a hurricane. By using subjective damage-based scales for earthquake intensity like the Modified Mercalli intensity scale or MSK-64 intensity scale and the objective numerical gradation method of

5328-412: Was made, with a minimum wind speed of 192 mph (309 km/h), with risk factors such as the effects of climate change and warming ocean temperatures part of that research. In the NHC area of responsibility, only Patricia had winds greater than 190 mph (85 m/s; 165 kn; 305 km/h). According to Robert Simpson, co-creator of the scale, there are no reasons for a Category 6 on

5402-401: Was the 1970 Bhola cyclone . Additionally, storm surge can cause or transform human-utilized land through other processes, hurting soil fertility , increasing saltwater intrusion , hurting wildlife habitat, and spreading chemical or other contaminants from human storage. Although meteorological surveys alert about hurricanes or severe storms, in the areas where the risk of coastal flooding

5476-627: Was the subject of a number of seemingly credible false news reports as a "Category 6" storm, partly in consequence of so many local politicians using the term. Only a few storms of this intensity have been recorded. Of the 42 hurricanes currently considered to have attained Category 5 status in the Atlantic, 19 had wind speeds at 175 mph (78 m/s; 152 kn; 282 km/h) or greater. Only 9 had wind speeds at 180 mph (80.5 m/s; 156 kn; 290 km/h) or greater (the 1935 Labor Day hurricane , Allen , Gilbert , Mitch , Rita , Wilma , Irma , Dorian , and Milton ). Of

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