Maximum sustained wind

The maximum sustained wind associated with a tropical cyclone is a common indicator of the intensity of the storm. Within a mature tropical cyclone, it is found within the eyewall at a distance defined as the radius of maximum wind, or RMW. Unlike gusts, the value of these winds are determined via their sampling and averaging the sampled results over a period of time. Wind measuring has been standardized globally to reflect the winds at 10 metres (33 ft) above the Earth's surface, and the maximum sustained wind represents the highest average wind over either a one-minute (US) or ten-minute time span (see the definition, below), anywhere within the tropical cyclone. Surface winds are highly variable due to friction between the atmosphere and the Earth's surface, as well as near hills and mountains over land.

Over the ocean, satellite imagery determines the value of the maximum sustained winds within a tropical cyclone. Land, ship, aircraft reconnaissance observations, and radar imagery can also estimate this quantity, when available. This value helps determine damage expected from a tropical cyclone, through use of such scales as the Saffir–Simpson scale.

Saffir–Simpson scale
Category Wind speeds
(for 1-minute maximum sustained winds)
m/s knots (kn) mph km/h
Five ≥ 70 m/s   ≥ 137 kn   ≥ 157 mph   ≥ 252 km/h  
Four   58–70 m/s     113–136 kn     130–156 mph     209–251 km/h  
Three   50–58 m/s     96–112 kn     111–129 mph     178–208 km/h  
Two   43–49 m/s     83–95 kn     96–110 mph     154–177 km/h  
One   33–42 m/s     64–82 kn     74–95 mph     119–153 km/h  
Related classifications
(for 1-minute maximum sustained winds)
Tropical storm   18–32 m/s     34–63 kn     39–73 mph     63–118 km/h  
Tropical depression   ≤ 17 m/s     ≤ 33 kn     ≤ 38 mph     ≤ 62 km/h  


The maximum sustained wind normally occurs at a distance from the center known as the radius of maximum wind, within a mature tropical cyclone's eyewall, before winds decrease at farther distances away from a tropical cyclone's center.[1] Most weather agencies use the definition for sustained winds recommended by the World Meteorological Organization (WMO), which specifies measuring winds at a height of 10 metres (33 ft) for 10 minutes, and then taking the average. However, the United States National Weather Service defines sustained winds within tropical cyclones by averaging winds over a period of one minute, measured at the same 10 metres (33 ft) height.[2] This is an important distinctions, as the value of the highest one-minute sustained wind is about 14% greater than a ten-minute sustained wind over the same period.[3]

Determination of value

In most tropical cyclone basins, use of the satellite-based Dvorak technique is the primary method used to determine a tropical cyclone's maximum sustained winds.[4] The extent of spiral banding and difference in temperature between the eye and eyewall is used within the technique to assign a maximum sustained wind and pressure.[5] Central pressure values for their centers of low pressure are approximate. The intensity of example hurricanes is derived from both the time of landfall and the maximum intensity.[6] The tracking of individual clouds on minutely satellite imagery could be used in the future in estimating surface winds speeds for tropical cyclones.[7]

Ship and land observations are also used, when available. In the Atlantic as well as the Central and Eastern Pacific basins, reconnaissance aircraft are still utilized to fly through tropical cyclones to determine flight level winds, which can then be adjusted to provide a fairly reliable estimate of maximum sustained winds. A reduction of 10 percent of the winds sampled at flight level is used to estimate the maximum sustained winds near the surface, which has been determined during the past decade through the use of GPS dropwindsondes.[8] Doppler weather radar can be used in the same manner to determine surface winds with tropical cyclones near land.[9]

Satellite Images of Selected Tropical Cyclones and Associated T-Number from Dvorak technique
Wilma-17-1315z-T30-discussion1500z Dennis-06-1445z-T40-discussion1500z Jeanne-22-1945z-T50-discussion2100z Emily-14-1915z-T60-discussion15-0300z
Tropical Storm Wilma at T3.0 Tropical Storm Dennis at T4.0 Hurricane Jeanne at T5.0 Hurricane Emily at T6.0


Friction between the atmosphere and the Earth's surface causes a 20% reduction in the wind at the surface of the Earth.[10] Surface roughness also leads to significant variation of wind speeds. Over land, winds maximize at hill or mountain crests, while sheltering leads to lower wind speeds in valleys and lee slopes.[11] Compared to over water, maximum sustained winds over land average 8% lower.[12] More specifically, over a city or rough terrain, the wind gradient effect could cause a reduction of 40% to 50% of the geostrophic wind speed aloft; while over open water or ice, the reduction is between 10% and 30%.[8][13][14]

Relationship to tropical cyclone strength scales

In most basins, maximum sustained winds are used to define their category. In the Atlantic and northeast Pacific oceans, the Saffir–Simpson scale is used. This scale can be used to determine possible storm surge and damage impact on land.[15] In most basins, the category of the tropical cyclone (for example, tropical depression, tropical storm, hurricane/typhoon, super typhoon, depression, deep depression, intense tropical cyclone) is determined from the cyclone's maximum sustained wind. Only in Australia is this quantity not used to define the tropical cyclone's category; in their basin, wind gusts are used.[16]

See also


  1. ^ Brian W. Blanchard and S. A. Hsu. ON THE RADIAL VARIATION OF THE TANGENTIAL WIND SPEED OUTSIDE THE RADIUS OF MAXIMUM WIND DURING HURRICANE WILMA (2005). Archived 2012-09-05 at the Wayback Machine Retrieved on 2008-07-04.
  2. ^ Tropical Cyclone Weather Services Program (June 1, 2006). "Tropical cyclone definitions" (PDF). National Weather Service. Retrieved 2006-11-30.
  3. ^ United States Navy: SECTION 2. INTENSITY OBSERVATION AND FORECAST ERRORS at the Wayback Machine (archived 2007-09-16) Retrieved on 2018-10-07.
  4. ^ "Objective Dvorak Technique". University of Wisconsin–Madison. Retrieved 2006-05-29.
  5. ^ Chris Landsea (June 8, 2010). Subject: H1) What is the Dvorak technique and how is it used? Atlantic Oceanographic and Meteorological Laboratory. Retrieved on 2011-01-14.
  6. ^ National Hurricane Center (June 22, 2006). "Saffir-Simpson Hurricane Scale Information". National Oceanic and Atmospheric Administration. Retrieved 2007-02-25.
  7. ^ A. F. Hasler, K. Palaniappan, C. Kambhammetu, P. Black, E. Uhlhorn, and D. Chesters. High-Resolution Wind Fields within the Inner Core and Eye of a Mature Tropical Cyclone from GOES 1-min Images. Retrieved on 2008-07-04.
  8. ^ a b Franklin, James L., Michael L. Black, and Krystal Valde. GPS dropwindsonde wind profiles in hurricanes and their operational implications. Retrieved on 2008-07-04.
  9. ^ J. TUTTLE and R. GALL. A single-radar technique for estimating the winds in tropical cyclones. Retrieved on 2008-06-12.
  10. ^ Jeff Haby. The Importance of Friction. Retrieved on 2008-07-04.
  11. ^ Mapping of Topographic Effects on Maximum Sustained Surface Wind Speeds in Landfalling Hurricanes. Retrieved on 2008-07-04.
  12. ^ Peter Black. Subject: Re: Offshore vs nearshore sonde composite. Retrieved on 2008-07-04.
  13. ^ Harrison, Roy (1999). Understanding Our Environment. Cambridge: Royal Society of Chemistry. p. 11. ISBN 0-85404-584-8.
  14. ^ Thompson, Russell (1998). Atmospheric Processes and Systems. New York: Routledge. pp. 102–103. ISBN 0-415-17145-8.
  15. ^ Williams, Jack (May 17, 2005). "Hurricane scale invented to communicate storm danger". USA Today. Retrieved 2007-02-25.
  16. ^ Bureau of Meteorology. Bureau of Meteorology: Tropical Cyclone Information Resources. Retrieved on 2008-01-17.
1903 Jamaica hurricane

The 1903 Jamaica hurricane devastated Martinique, Jamaica, and the Cayman Islands in August 1903. The second tropical cyclone of the season, the storm was first observed well east of the Windward Islands on August 6. The system moved generally west-northwestward and strengthened into a hurricane on August 7. It struck Martinique early on August 9, shortly before reaching the Caribbean Sea. Later that day, the storm became a major hurricane. Early on August 11, it made landfall near Morant Point, Jamaica, with winds of 120 mph (195 km/h), with would be the hurricane's maximum sustained wind speed. Early on the following day, the storm brushed Grand Cayman at the same intensity. The system weakened before landfall near Playa del Carmen, Quintana Roo, early on August 13, with winds of 100 mph (155 km/h). The system emerging into the Gulf of Mexico early on August 14 after weakening while crossing the Yucatán Peninsula, but failed to re-strengthen. Around 00:00 UTC on August 16, the cyclone made landfall north of Tampico, Tamaulipas, with winds of 80 mph (130 km/h). The hurricane soon weakened to a tropical storm and dissipated over San Luis Potosí late on August 16.

In Martinique, hundreds of homes were deroofed in Fort-de-France, while about 5,000 people were left homeless in the villages of Fond, Fourniols, La Haye, Recluce, and Tivoli, all of which were established after the eruption of Mount Pelée in 1902. The hurricane also left extensive damage to crops and eight fatalities. In Jamaica, several communities were completely or nearly destroyed, including Manchioneal, Port Antonio, and Port Maria. Thousands of homes also suffered damage in the capital city of Kingston. Banana crops were devastated so severely that many growers were forced into bankruptcy. Numerous ships were wrecked, particularly on the north coast of the island. There were at least 65 deaths and about $10 million (1903 USD) in damage. In the Cayman Islands, more than 200 houses and seven of eight churches on Grand Cayman were destroyed or heavily damaged. Of the 23 ships in the harbor, only the Governor Blake survived. Most of the crews on board those ships were reported killed, but loss of life onshore was minimal. The storm also caused heavy damage on the Yucatán Peninsula. Many ships were wrecked and communications were cut off in several places. In the Tampico area, there was considerable damage to the port and many ships were sunk or driven ashore. Much of the land between Tampico and Cárdenas in San Luis Potosí was submerged due to flooding. In all, the storm is believed to have killed at least 149 people.

1949 Florida hurricane

The 1949 Florida hurricane was the second recorded storm and the strongest and most intense tropical cyclone of the 1949 Atlantic hurricane season. It was the most intense tropical cyclone to affect the United States during the season, with a minimum central pressure of 954 mbar (28.18 inHg) at landfall. The cyclone originated from an easterly wave near the Leeward Islands, and it rapidly intensified to a hurricane near the Bahamas. It strengthened to a major hurricane northwest of Nassau, Bahamas, and it struck West Palm Beach, Florida as a Category 4 hurricane with maximum sustained winds near 130 mph (210 km/h) and peak gusts near 160 mph (260 km/h) above the surface. It turned north over the Florida peninsula, and it transitioned to an extratropical low pressure area over New England. The tropical cyclone inflicted $52,000,000 (1949 USD) in damage, most of which was incurred in the state of Florida. It was the costliest storm of the season.

2019 North Indian Ocean cyclone season

The 2019 North Indian Ocean cyclone season is an ongoing event in the annual cycle of tropical cyclone formation. The North Indian Ocean cyclone season has no official bounds, but cyclones tend to form between April and December, with the two peaks in May and November. These dates conventionally delimit the period of each year when most tropical cyclones form in the northern Indian Ocean. The season's first named storm, Pabuk, entered the basin on January 4, becoming the earliest-forming cyclonic storm of the North Indian Ocean on record. The second cyclone of the season, Fani, was the strongest tropical cyclone in the Bay of Bengal by 3-minute maximum sustained wind speed and minimum barometric pressure since the 1999 Odisha cyclone (while being equal in maximum 3-minute sustained wind speed to Phailin of the 2013 season).

The scope of this article is limited to the Indian Ocean in the Northern Hemisphere, east of the Horn of Africa and west of the Malay Peninsula. There are two main seas in the North Indian Ocean — the Arabian Sea to the west of the Indian subcontinent, abbreviated ARB by the India Meteorological Department (IMD); and the Bay of Bengal to the east, abbreviated BOB by the IMD.

The official Regional Specialized Meteorological Centre in this basin is the India Meteorological Department (IMD), while the Joint Typhoon Warning Center (JTWC) and the National Meteorological Center of CMA (NMC) unofficially release full advisories. On average, three to four cyclonic storms form in this basin every season.

Chicago Mercantile Exchange Hurricane Index

The Chicago Mercantile Exchange Hurricane Index (CMEHI) is an index which describes the potential for damage from an Atlantic hurricane in the United States. The CMEHI is used as the basis for trading hurricane futures and options on the Chicago Mercantile Exchange (CME).

Cyclone Alan

Tropical Cyclone Alan was considered to be one of the worst natural disasters experienced in French Polynesia. The system, first noted as a tropical disturbance on April 17, 1998 east of the Northern Cook Islands, initially moved erratically prior to its designation as Alan upon developing into a tropical cyclone on April 21. The following day, Alan reached its estimated peak intensity with 10-minute maximum sustained wind speeds of 75 km/h (45 mph), posing several forecasting challenges due to difficulties in establishing its location and intensity. On April 23, Alan appeared to become sheared with the low-level circulation center displaced about 20 km (10 mi) from the nearest atmospheric convection. However, over the next day, after the mid-level trough of low pressure shearing the system moved faster than expected, Alan became better organized. While situated about 555 km (345 mi) west-northwest of the French Polynesian island of Tahiti, the system drifted south-southeastward. Early on April 25, Alan passed near to or over the French Polynesian Society Islands of Maupiti, Bora-Bora, and Raiatea. However, strong wind shear pulled the system apart, with visible imagery confirming the system's degeneration into a depression with a fully exposed low-level circulation. The system affected French Polynesia with high winds and torrential rain, causing several landslides on the Society Islands. The landslides resulted in the collapse of two bridges, and also overturned trees, in turn obstructing roads. Overall, ten people died as a result of the system, while thirty others were injured, with a majority of the casualties a result of landslides. On the islands of Raiatea, Taha'a and Huahine, several churches, schools and clinics were damaged, while water and electricity supplies were cut off. On the islands, around 750 houses were destroyed, with 430 and 150 wrecked on Huahine and Ra'iātea, respectively.

Cyclone Fantala

Very Intense Tropical Cyclone Fantala was the strongest tropical cyclone of the South-West Indian Ocean in terms of sustained winds. Part of the 2015–16 cyclone season, Fantala formed on 11 April to the south of Diego Garcia, an island in the central Indian Ocean. With a ridge to the south, the storm moved westward for several days while gaining strength, aided by warm waters and decreasing wind shear. Late on 17 April, the Météo-France office on Réunion (MFR) estimated peak 10-minute winds of 250 km/h (155 mph), making Fantala the strongest tropical cyclone of the basin in terms of 10-minute sustained winds. The Joint Typhoon Warning Center (JTWC) estimated peak 1-minute winds of 285 km/h (180 mph), equivalent to Category 5 intensity on the Saffir-Simpson scale, and the strongest on record in the South-West Indian Ocean, in terms of maximum sustained wind speed. Early on 18 April, Fantala reached its peak intensity, with a minimum central pressure of 910 millibars (27 inHg).

While near peak intensity, Fantala passed near the Farquhar Group of the Seychelles, damaging most of the buildings in the small archipelago. Later on 18 April, Fantala had weakened to an intense tropical cyclone and slowed its forward motion, eventually reversing its direction of movement. After fluctuating in strength, the disorganized system reversed direction again, making its closest approach to Madagascar. Fantala degenerated into a remnant low on 24 April, and the remnants continued toward Tanzania. There, heavy rainfall resulted in flooding that washed away roads and houses, killing 13 people. Rains extended further into Kenya, with similar effects.

Hurricane Danielle (1998)

Hurricane Danielle resulted in minor damage throughout its duration as a tropical cyclone in late August and early September 1998. The fourth named storm and second hurricane of the annual hurricane season, Danielle originated from a tropical wave that emerged off the western coast of Africa on August 21. Tracking generally west-northwestward, the disturbance was initially disorganized; under favorable atmospheric conditions, shower and thunderstorm activity began to consolidate around a low-pressure center. Following a series of satellite intensity estimates, the system was upgraded to Tropical Depression Four during the pre-dawn hours of August 24, and further to Tropical Storm Danielle that afternoon. Moving around the southern periphery of the Azores High located in the northeastern Atlantic, quick intensification to hurricane status occurred early on August 25. By 0600 UTC the following day, Danielle reached an initial peak intensity of 105 mph (165 km/h), a Category 2 hurricane. Increased wind shear from a nearby trough encroached on further development later that day, and subsequently led to slight weakening. By 1200 UTC on August 27, despite continued unfavorable conditions, Danielle reached a second peak intensity equal to the first. Weakening once ensued late on August 27 in addition to the days following, and Danielle was a low-end Category 1 hurricane by August 31 as its forward speed slowed.

As the cyclone reached the western periphery of the ridge that steered it across the Atlantic for much of its existence, it began yet another period of intensification, and once again attained a peak intensity as a Category 2 hurricane. Passing northwest of Bermuda, Danielle weakened to Category 1 hurricane strength, but for a final time intensified into a 105 mph (165 km/h) tropical cyclone thereafter. As the cyclone passed over increasingly cool sea surface temperatures and became intertwined in a baroclinic zone, it began to undergo an extratropical transition. At 0000 UTC on September 4, Danielle was no longer considered a tropical cyclone, despite retaining hurricane-force winds. Several days later, the remnants of Danielle merged with a larger extratropical low and became indistinguishable. As a tropical cyclone, it produced heavy rainfall in Puerto Rico and the Lesser Antilles, leading to flooding. Tropical storm-force winds were observed in Bermuda even though the cyclone passed well northwest of the island. During Danielle's transition to an extratropical cyclone, it produced light rain and led to minor beach erosion in Newfoundland. The larger extratropical low that merged with the system resulted in large waves off the coast of the United Kingdom, leading to major beach erosion and coastal flooding. Overall, no fatalities were reported with the system and it caused an estimated $50,000 (1998 USD) in damage.

Hurricane Frances

Hurricane Frances was the second most intense tropical cyclone in the Atlantic during 2004 that proved to be very destructive in Florida. The sixth named storm, the fourth hurricane, and the third major hurricane of the 2004 Atlantic hurricane season. The system crossed the open Atlantic in mid and late August, moving to the north of the Lesser Antilles while strengthening. Its outer bands struck Puerto Rico and the British Virgin Islands while passing north of the Caribbean Sea. The storm's maximum sustained wind peaked at 145 mph (233 km/h), achieving Category 4 on the Saffir-Simpson Hurricane Scale. As the system's forward motion slowed, the eye passed over San Salvador Island and very close to Cat Island in the Bahamas. Frances was the first hurricane to impact the entire Bahamian archipelago since 1928, and almost completely destroyed the agricultural economy there.

Frances then passed over the central sections of Florida, in the United States, three weeks after Hurricane Charley, causing significant damage to the state's citrus crop, closing major airports and schools, and forcing the cancellation of a collegiate football game. The storm then moved briefly offshore from Florida, into the northeast Gulf of Mexico, and made a second U.S. landfall, at the Florida Panhandle, before accelerating northeast through the eastern United States near the Appalachians and into Atlantic Canada while weakening. A significant tornado outbreak accompanied the storm across the eastern United States, nearly equaling the outbreak from Hurricane Beulah. Very heavy rains fell in association with this slow-moving and relatively large hurricane, which caused floods in Florida and North Carolina. Some 49 people died from the cyclone. Damages totaled US$10.1 billion (2004 dollars).

List of Category 5 Pacific hurricanes

Category 5 hurricanes are tropical cyclones that reach Category 5 intensity on the Saffir–Simpson Hurricane Scale. They are by definition the strongest hurricanes that can form on planet Earth. They are rare in the eastern Pacific Ocean and generally form only once every several years. In general, Category 5s form in clusters in single years. Landfalls by such storms are rare due to the generally westerly path of tropical cyclones in the northern hemisphere.

The term "hurricane" is used for tropical cyclones in the Pacific Ocean, north of the equator and east of the international date line. A Category 5 Pacific hurricane is therefore a tropical cyclone in the north Pacific Ocean that reached Category 5 intensity east of the international dateline. Identical phenomena in the north Pacific Ocean west of the dateline are called "typhoons" or "super typhoons". Category 5 super typhoons generally happen several times per season, so cyclones of that intensity are not exceptional for that region. This difference in terminology therefore excludes storms such as Super Typhoon Paka and Super Typhoon Oliwa of 1997, and Typhoon Genevieve of 2014, which formed east of the dateline but did not reach Category 5 intensity until after crossing the dateline.

Radius of outermost closed isobar

The radius of outermost closed isobar (ROCI) is one of the quantities used to determine the size of a tropical cyclone. It is determined by measuring the radii from the center of the storm to its outermost closed isobar in four quadrants, which is then averaged to come up with a scalar value. It generally delimits the outermost extent of a tropical cyclone's wind circulation.Use of this measure has objectively determined that tropical cyclones in the northwest Pacific Ocean are the largest on earth on average, with North Atlantic tropical cyclones roughly half their size. Active databases of ROCI are maintained by the National Hurricane Center for systems tracked in the eastern north Pacific and north Atlantic basins.


A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as banded structure. Rainbands within tropical cyclones are curved in orientation. Tropical cyclone rainbands contain showers and thunderstorms that, together with the eyewall and the eye, constitute a hurricane or tropical storm. The extent of rainbands around a tropical cyclone can help determine the cyclone's intensity.

Rainbands spawned near and ahead of cold fronts can be squall lines which are able to produce tornadoes. Rainbands associated with cold fronts can be warped by mountain barriers perpendicular to the front's orientation due to the formation of a low-level barrier jet. Bands of thunderstorms can form with sea breeze and land breeze boundaries, if enough moisture is present. If sea breeze rainbands become active enough just ahead of a cold front, they can mask the location of the cold front itself. Banding within the comma head precipitation pattern of an extratropical cyclone can yield significant amounts of rain or snow. Behind extratropical cyclones, rainbands can form downwind of relative warm bodies of water such as the Great Lakes. If the atmosphere is cold enough, these rainbands can yield heavy snow.

Timeline of the 1972 Atlantic hurricane season

The 1972 Atlantic hurricane season is one of five Atlantic hurricane seasons not to have any major hurricanes, the others being 1968, 1986, 1994, and 2013. Although Subtropical Storm Alpha formed on May 23, the season officially began on June 1 and ended on November 30, dates that conventionally delimit the period of each year when most tropical cyclones develop in the Atlantic basin. The season's final storm, Subtropical Storm Delta, dissipated on November 7.

The season produced nineteen tropical or subtropical cyclones, of which seven intensified into tropical or subtropical storms; three became hurricanes, but none further intensified into major hurricanes, the first such occurrence since the 1968 season. Despite the inactivity, the 1972 season resulted in one of the worst natural disasters in American history, Hurricane Agnes. Agnes was a weak but large storm that initially made landfall on the Florida Panhandle before moving up the eastern United States. The hurricane killed 122 people and caused $2.1 billion (1972 USD) in damage, mostly due to flooding in Pennsylvania and New York.This timeline includes information that was not operationally released, meaning that data from post-storm reviews by the National Hurricane Center, such as a storm that was not operationally warned upon, has been included. This timeline documents tropical cyclone formations, strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season.

Timeline of the 1998 Atlantic hurricane season

The 1998 Atlantic hurricane season was an above-average Atlantic hurricane season in which fourteen named storms, ten hurricanes, and three major hurricanes formed. Although Tropical Storm Alex formed on July 27, the season officially began on June 1 and ended on November 30, dates that conventionally delimit the period of each year when most tropical cyclones develop in the Atlantic basin. The final storm, Hurricane Nicole, lasted until December 1, one day after the official end of the season.

The season produced fourteen tropical depressions, all of which intensified into tropical storms, ten became hurricanes, and three became major hurricanes. The two most significant storms of the season, in terms of loss of life and damage, were hurricanes Georges and Mitch. The former traveled across much of the Greater and Lesser Antilles and made landfall in Mississippi as a Category 2 hurricane. Resulting in extensive damage and a large number of fatalities. Hurricane Mitch's slow movement over Central America caused catastrophic flooding, making it the second deadliest Atlantic tropical cyclone on record.This timeline includes information that was not operationally released, meaning that data from post-storm reviews by the National Hurricane Center, such as a storm that was not operationally warned upon, has been included. This timeline documents tropical cyclone formations, strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season.

Tropical Depression One (1979)

Tropical Depression One brought severe flooding to Jamaica in June 1979. The second tropical cyclone of the Atlantic hurricane season, the depression developed from a tropical wave to the south of Grand Cayman on June 11. Tracking generally northward, the depression passed west of Jamaica. On June 12, the depression peaked with maximum sustained winds of 35 mph (55 km/h), never having reached tropical storm status. The following day, it made landfall in Cuba, where minimal impact was recorded. Early on June 14, the depression emerged into the western Atlantic Ocean and then moved parallel to the east coast of Florida for a few days. The depression made another landfall in South Carolina on June 16 and dissipated shortly thereafter.

The slow movement of the depression to the west of Jamaica resulted in torrential rainfall, peaking at 32 in (810 mm) in Friendship, a city in Westmoreland Parish. Throughout western Jamaica, about 1,000 homes were destroyed or severely damaged, while up to 40,000 people were left homeless. The city of New Market was submerged for at least six months. Crops, electricity, telephones, buildings, and railways also suffered damage during the disaster. There were 40 deaths and approximately $27 million (1979 USD) in damage. The depression also brought heavy precipitation to Cuba and the Bahamas, while farther north, light rainfall and rough seas plagued the East Coast of the United States. One individual in South Carolina went missing and was later presumed to have died after their boat was torn loose from its mooring.


A typhoon is a mature tropical cyclone that develops between 180° and 100°E in the Northern Hemisphere. This region is referred to as the Northwestern Pacific Basin, and is the most active tropical cyclone basin on Earth, accounting for almost one-third of the world's annual tropical cyclones. For organizational purposes, the northern Pacific Ocean is divided into three regions: the eastern (North America to 140°W), central (140°W to 180°), and western (180° to 100°E). The Regional Specialized Meteorological Center (RSMC) for tropical cyclone forecasts is in Japan, with other tropical cyclone warning centers for the northwest Pacific in Hawaii (the Joint Typhoon Warning Center), the Philippines and Hong Kong. While the RSMC names each system, the main name list itself is coordinated among 18 countries that have territories threatened by typhoons each year A hurricane is a storm that occurs in the Atlantic Ocean or the northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a tropical cyclone occurs in the South Pacific or the Indian Ocean.Within the northwestern Pacific, there are no official typhoon seasons as tropical cyclones form throughout the year. Like any tropical cyclone, there are a few main requirements for typhoon formation and development: (1) sufficiently warm sea surface temperatures, (2) atmospheric instability, (3) high humidity in the lower to middle levels of the troposphere, (4) enough Coriolis effect to develop a low pressure center, (5) a pre-existing low level focus or disturbance, and (6) a low vertical wind shear. While the majority of storms form between June and November, a few storms do occur between December and May (although tropical cyclone formation is at a minimum during that time). On average, the northwestern Pacific features the most numerous and intense tropical cyclones globally. Like other basins, they are steered by the subtropical ridge towards the west or northwest, with some systems recurving near and east of Japan. The Philippines receive the brunt of the landfalls, with China and Japan being impacted slightly less. Some of the deadliest typhoons in history have struck China. Southern China has the longest record of typhoon impacts for the region, with a thousand-year sample via documents within their archives. Taiwan has received the wettest known typhoon on record for the northwest Pacific tropical cyclone basins.

Typhoon Betty (1987)

Typhoon Betty, known in the Philippines as Typhoon Herming, was a powerful and destructive tropical cyclone that struck the Philippines in August 1987. The seventh typhoon and second super typhoon of the active typhoon season, it formed from the monsoon trough that spawned a tropical cyclone on August 8 while around positioned well to the east of the Philippines. It drifted northwestward, becoming a tropical storm on August 9 and a typhoon on August 10. Betty turned westward, where it rapidly intensified before attaining peak intensity on August 11. The next day, Typhoon Betty made landfall in the central Philippines. Betty weakened rapidly over the country, but restrengthened somewhat over the South China Sea. Land interaction weakened Betty slightly before it hit central Vietnam on August 16. The next day, Betty dissipated.

Across the Philippines, Typhoon Betty brought widespread flooding, which resulted in severe destruction. Damage added up to $100 million (1987 USD). In the Maguindanao and Albay provinces alone, 10,000 people were evacuated and 1,000 were homeless. However, the capital city of Manila avoided any serious damage. Nationwide, around 200,000 people were reportedly homeless, 18,000 of winch were from Marinduque and another 11,400 resided on Mindoro Island. In the former, 4,000 dwellings sustained damage, and all of the banana crop there was lost. In all, 25,518 homes received damage. Roughly 400,000 people were directly affected by the storm. Overall, 85 people were killed and 324 others were wounded. After striking the Philippines, six people were killed by Betty in Vietnam. Approximately 10,000 structures were damaged and 103 people were injured. Elsewhere, in northern Thailand, one person was killed and three others were hurt by the typhoon. Several villages were flooded, and numerous streets were damaged.

Typhoon Dinah (1987)

Typhoon Dinah, known as Typhoon Luding in the Philippines, was the fourth typhoon to form during August 1987. An area of low pressure developed near Guam on August 19, and two days later, the low reached tropical storm intensity as it moved generally west. Intensification was initially gradual, with Dinah becoming a typhoon early on August 24 before it subsequently intensified at a faster pace. Dinah reached its highest strength on August 26 before turning northward on August 28 and into a less favorable conditions aloft, which prompted weakening. Dinah entered the Sea of Japan after passing near Okinawa on August 29, where Dinah leveled off in intensity. The system then began to recurve towards southwestern Japan, and after tracking through the area, Dinah transitioned into an extratropical cyclone on August 31, although the remnants could be traced for four more days as it approached the International Date Line.

Across Okinawa, one person was killed, six more were injured, eight homes were destroyed or seriously damaged, and 13 boats sunk or were damaged. Damage exceeded $1.3 million (1987 USD). On the island of Kyushu, 250 homes were flooded and about 450,000 homeowners lost power. Throughout Japan, eight people perished, damage totaled $604 million and 89 were wounded. The typhoon destroyed nearly 40,000 dwellings and an additional 600 were flooded. In South Korea, 4,372 structures were destroyed, leaving more than 11,000 people homeless. Nationwide, the typhoon was responsible for flooding 80,000 ha (197,685 acres) of crops. Property damage was estimated at $39.1 million.

Typhoon Rose (1971)

Typhoon Rose, known in the Philippines as Typhoon Uring, was the most violent and intense tropical cyclone to strike Hong Kong since Typhoon Wanda in 1962. The 21st named storm of the 1971 Pacific typhoon season, Rose developed from an area of disturbed weather while west of Guam on August 9. Moving west-northwestward, the storm briefly became a typhoon on the following day. After weakening to a tropical storm on August 11, Rose re-intensified into a typhoon several hours later. The system then curved westward and reached a primary peak intensity with winds of 205 km/h (125 mph) on August 13. Later that day, the typhoon made landfall near Palanan, Isabela in the Philippines. Rose weakened significantly while crossing the island of Luzon and was a minimal typhoon upon reaching the South China Sea on August 14.

The storm intensified significantly and re-curved northwestward in response to a weakening high-pressure area. Early on August 16, Rose attained its maximum sustained wind speed of 220 km/h (140 mph) – equivalent to a Category 4 hurricane on the National Hurricane Center's Saffir–Simpson hurricane wind scale. Later that day, a ship observed the typhoon's minimum barometric pressure of 950 mbar (28 inHg). Thereafter, the storm weakened slightly before making landfall at Lantau Island, Hong Kong, with winds of 165 km/h (105 mph) late on August 16. Rose rapidly weakened to a tropical storm early the following day and dissipated several hours later.

Mostly minor wind impact was recorded in the Philippines, limited to downed communication lines and damaged houses. Offshore Hong Kong, storm surge and heavy waves sank or severely damaged at least 300 boats, causing 110 deaths and 283 injuries. Inland, heavy rainfall flooded low-lying areas and resulted in numerous landslides. A fire ignited at a large power sub-station in Kwun Tong and was difficult to extinguish due to strong winds. The fire caused blackouts in Kowloon Peninsula and New Territories, trapping thousands of people in elevators. A total of 5,644 people were left homeless, while 653 huts were destroyed. Approximately 30,000 telephones became out of service. Twenty other fatalities occurred in Hong Kong.


The WxChallenge is a weather forecasting competition among colleges in North America. The competition is run by the University of Oklahoma. In its first official semester, fall 2006, there were 1,262 participants from 53 institutions. A similar competition, the National Collegiate Weather Forecasting Contest, recently ended, partially due to this competition.

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