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Outline of tropical cyclones  Tropical cyclonesportal |
The following is a glossary of tropical cyclone terms.
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| Outline of tropical cyclones Tropical cyclonesportal |
The following is a glossary of tropical cyclone terms.
One of the quantities used to determine the size of a tropical cyclone. The ROCI 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. [14]
| Category | 1-minute maximum sustained winds | |||
|---|---|---|---|---|
| m/s | knots (kn) | mph | km/h | |
| 5 | ≥ 70 m/s | ≥ 137 kn | ≥ 157 mph | ≥ 252 km/h |
| 4 | 58–70 m/s | 113–136 kn | 130–156 mph | 209–251 km/h |
| 3 | 50–58 m/s | 96–112 kn | 111–129 mph | 178–208 km/h |
| 2 | 43–49 m/s | 83–95 kn | 96–110 mph | 154–177 km/h |
| 1 | 33–42 m/s | 64–82 kn | 74–95 mph | 119–153 km/h |
| TS | 18–32 m/s | 34–63 kn | 39–73 mph | 63–118 km/h |
| TD | ≤ 17 m/s | ≤ 33 kn | ≤ 38 mph | ≤ 62 km/h |
The danger of life-threatening inundation from rising water moving inland from the shoreline somewhere within the specified area, generally within 36 hours, in association with an ongoing or potential tropical cyclones, a subtropical cyclone or a post-tropical cyclone. The warning may be issued earlier when other conditions, such as the onset of tropical-storm-force winds are expected to limit the time available to take protective actions for surge (e.g., evacuations). The warning may also be issued for locations not expected to receive life-threatening inundation but which could potentially be isolated by inundation in adjacent areas. [1]
The possibility of life-threatening inundation from rising water moving inland from the shoreline somewhere within the specified area, generally within 48 hours, in association with an ongoing or potential tropical cyclones, a subtropical cyclone or a post-tropical cyclone. The watch may be issued earlier when other conditions, such as the onset of tropical-storm-force winds are expected to limit the time available to take protective actions for surge (e.g., evacuations). The warning may also be issued for locations not expected to receive life-threatening inundation but which could potentially be isolated by inundation in adjacent areas. [1]
A subtropical cyclone is a weather system that has some characteristics of both tropical and an extratropical cyclone.
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.
Tropical cyclones and subtropical cyclones are named by various warning centers to simplify communication between forecasters and the general public regarding forecasts, watches and warnings. The names are intended to reduce confusion in the event of concurrent storms in the same basin. Once storms develop sustained wind speeds of more than 33 knots, names are generally assigned to them from predetermined lists, depending on the basin in which they originate. Some tropical depressions are named in the Western Pacific; while tropical cyclones must contain a significant amount of gale-force winds before they are named in the Southern Hemisphere.
Tropical cyclone warnings and watches are alerts issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of tropical storm or hurricane intensity. They are notices to the local population and civil authorities to make appropriate preparation for the cyclone, including evacuation of vulnerable areas where necessary. It is important that interests throughout the area of an alert make preparations to protect life and property, and do not disregard it on the strength of the detailed forecast track.
An annular tropical cyclone is a tropical cyclone that features a normal to large, symmetric eye surrounded by a thick and uniform ring of intense convection, often having a relative lack of discrete rainbands, and bearing a symmetric appearance in general. As a result, the appearance of an annular tropical cyclone can be referred to as akin to a tire or doughnut. Annular characteristics can be attained as tropical cyclones intensify; however, outside the processes that drive the transition from asymmetric systems to annular systems and the abnormal resistance to negative environmental factors found in storms with annular features, annular tropical cyclones behave similarly to asymmetric storms. Most research related to annular tropical cyclones is limited to satellite imagery and aircraft reconnaissance as the conditions thought to give rise to annular characteristics normally occur over open water, well removed from landmasses where surface observations are possible.
The 2004 Pacific typhoon season was an extremely active season that featured the second-highest ACE ever recorded in a single season, second only to 1997, which featured 29 named storms, nineteen typhoons, and six super typhoons. It was an event in the annual cycle of tropical cyclone formation, in which tropical cyclones form in the western Pacific Ocean. The season ran throughout 2004, though most tropical cyclones typically develop between May and October. The season's first named storm and also the first typhoon, Sudal, developed on April 4, later was reached typhoon status two days later, and became the first super typhoon of the year three days later. The season's last named storm, Noru, dissipated on December 21.
A Pacific hurricane is a mature tropical cyclone that develops within the northeastern and central Pacific Ocean to the east of 180°W, north of the equator. For tropical cyclone warning purposes, the northern Pacific is divided into three regions: the eastern, central, and western, while the southern Pacific is divided into 2 sections, the Australian region and the southern Pacific basin between 160°E and 120°W. Identical phenomena in the western north Pacific are called typhoons. This separation between the two basins has a practical convenience, however, as tropical cyclones rarely form in the central north Pacific due to high vertical wind shear, and few cross the dateline.
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, central, and western. 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 Philippines, and Hong Kong. Although the RSMC names each system, the main name list itself is coordinated among 18 countries that have territories threatened by typhoons each year.
Tropical cyclones are ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basins they are located in. Only a few scales of classifications are used officially by the meteorological agencies monitoring the tropical cyclones, but other scales also exist, such as accumulated cyclone energy, the Power Dissipation Index, the Integrated Kinetic Energy Index, and the Hurricane Severity Index.
Hurricane Ioke, also referred to as Typhoon Ioke, had the highest accumulated cyclone energy (ACE) of any tropical cyclone on record. The first and only storm to form in the Central Pacific in the 2006 Pacific hurricane season, Ioke was a record breaking, long-lived and extremely powerful storm that traversed the Pacific for 17 days, reaching the equivalent of Category 5 status on the Saffir–Simpson hurricane scale on three different occasions. It was the most intense hurricane ever recorded in the Central Pacific, as well as the fifth-most intense Pacific hurricane on record, tied with 1973's Hurricane Ava. Ioke was the ninth named storm, fifth hurricane, and third major hurricane of the active 2006 Pacific hurricane season.
The 2006 Central Pacific cyclone, also known as Invest 91C or Storm 91C, was an unusual weather system that formed in 2006. Forming on October 30 from a mid-latitude cyclone in the north Pacific mid-latitudes, it moved over waters warmer than normal. The system acquired some features more typical of subtropical and even tropical cyclones. However, as it neared the western coastline of North America, the system fell apart, dissipating soon after landfall, on November 4. Moisture from the storm's remnants caused substantial rainfall in British Columbia and the Pacific Northwest. The exact status and nature of this weather event is unknown, with meteorologists and weather agencies having differing opinions.
The 1998–99 South-West Indian Ocean cyclone season was a quiet season that had the fourth-lowest number of days with tropical storm or tropical cyclone activity. Most of the storms formed either in the Mozambique Channel or in the far eastern portion of the basin, with five storms crossing from the adjacent Australian basin east of 90° E. As a result, few storms impacted Madagascar, and none made landfall on the African continent. Throughout most of the season, there was below-normal sea surface temperatures in the Indian Ocean east of Madagascar. In February, typically the peak in activity, Réunion island recorded its highest average monthly pressure since 1953. Due to generally unfavorable conditions, there were only six tropical storms tracked by the Météo-France office (MFR) on Réunion. There were only two tropical cyclones – a storm with winds of at least 120 km/h (75 mph).
Severe Tropical Cyclone Gwenda is tied with Cyclone Inigo as the most intense Australian tropical cyclone on record, with a barometric pressure of 900 hPa (mbar) and was the most intense storm worldwide in 1999. Forming out of a tropical disturbance over the Arafura Sea on 2 April 1999, the precursor to Gwenda tracked slowly westward and gradually became more organised. On 4 April, the system developed into a Category 1 cyclone and was named Gwenda. It began to undergo explosive intensification the following day, and in a 30-hour span ending early on 7 April, the storm's maximum 10-minute sustained wind speed increased from 75 km/h (45 mph) to 225 km/h (140 mph) and its barometric pressure decreased to 900 hPa (mbar). The Joint Typhoon Warning Center reported that the storm had peaked as a high-end Category 4 equivalent on the Saffir–Simpson hurricane scale.
Throughout 2006, 133 tropical cyclones formed in seven bodies of water known as tropical cyclone basins. Of these, 80 have been named, including two tropical cyclones in the South Atlantic Ocean, and a tropical cyclone in the Mediterranean Sea, by various weather agencies when they attained maximum sustained winds of 65 km/h (40 mph). The strongest storms of the year were Typhoon Yagi in the Western Pacific, and Cyclone Glenda of the Australian region. The deadliest and costliest storms of the year were a series of five typhoons that struck the Philippines and China; Chanchu, Bilis, Saomai, Xangsane, and Durian, with most of the damage being caused by Durian of November. So far, 27 Category 3 tropical cyclones formed, including five Category 5 tropical cyclones in the year.
Typhoon Haiyan's meteorological history began with its origins as a tropical disturbance east-southeast of Pohnpei and lasted until its degeneration as a tropical cyclone over southern China. The thirteenth typhoon of the 2013 Pacific typhoon season, Haiyan originated from an area of low pressure several hundred kilometers east-southeast of Pohnpei in the Federated States of Micronesia on November 2. Tracking generally westward, environmental conditions favored tropical cyclogenesis and the system developed into a tropical depression the following day. After becoming a tropical storm and attaining the name Haiyan at 0000 UTC on November 4, the system began a period of rapid intensification that brought it to typhoon intensity by 1800 UTC on November 5. By November 6, the Joint Typhoon Warning Center (JTWC) assessed the system as a Category 5-equivalent super typhoon on the Saffir–Simpson hurricane wind scale; the storm passed over the island of Kayangel in Palau shortly after attaining this strength.
Severe Tropical Storm Zelda was the last tropical cyclone of the 1991 Pacific typhoon season; it struck the Marshall Islands on November 28. The area of low pressure that eventually became Zelda formed near the International Date Line, and strengthened into a tropical depression on November 27. The Joint Typhoon Warning Center (JTWC) reported that the depression had reached tropical storm intensity near the Marshall Islands on November 28, thus naming it Zelda. On November 29, the storm quickly strengthened to 65 knots according to the JTWC, equivalent to a Category 1 typhoon on the Saffir–Simpson hurricane wind scale. It reached a peak of 80 kn according to the JTWC, and 60 kn according to the Japanese Meteorological Agency (JMA), with a barometric pressure of 975 hectopascals (28.8 inHg). Zelda weakened into a tropical storm on December 2, and then a tropical depression two days later. The JTWC discontinued warnings late on December 4, while the JMA declared the storm to be extratropical the next day and continued to track until it crossed the International Date Line again on December 7.
Hurricane Genevieve, also referred to as Typhoon Genevieve, was the first tropical cyclone to track across all three northern Pacific basins since Hurricane Dora in 1999. Genevieve developed from a tropical wave into the eighth tropical storm of the 2014 Pacific hurricane season well east-southeast of Hawaii on July 25. However, increased vertical wind shear caused it to weaken into a tropical depression by the following day and degenerate into a remnant low on July 28. Late on July 29, the system regenerated into a tropical depression, but it weakened into a remnant low again on July 31, owing to vertical wind shear and dry air.
Hurricane Patricia was the most intense tropical cyclone ever recorded in the Western Hemisphere and the second-most intense worldwide in terms of barometric pressure. It also featured the highest one-minute maximum sustained winds ever recorded in a tropical cyclone. Originating from a sprawling disturbance near the Gulf of Tehuantepec in mid-October 2015, Patricia was first classified a tropical depression on October 20. Initial development was slow, with only modest strengthening within the first day of its classification. The system later became a tropical storm and was named Patricia, the twenty-fourth named storm of the annual hurricane season. Exceptionally favorable environmental conditions fueled explosive intensification on October 22. A well-defined eye developed within an intense central dense overcast and Patricia grew from a tropical storm to a Category 5 hurricane in just 24 hours—a near-record pace. The magnitude of intensification was poorly forecast and both forecast models and meteorologists suffered from record-high prediction errors.
Typhoon Songda was the sixth most intense tropical cyclone of the Northwest Pacific Ocean in 2016. Also known as the Ides of October storm, it struck the Pacific Northwest region of the United States and Canada as a powerful extratropical cyclone. Songda was the twentieth named storm and the ninth typhoon of the annual typhoon season. The system developed into a tropical storm south of Minamitorishima on October 8 and strengthened into a typhoon on October 10. Songda reached its peak intensity southeast of Japan late on October 11 at an unusually high latitude, before it became extratropical on October 13.
Hurricane Hector was a powerful and long-lasting tropical cyclone that traversed the Pacific Ocean during late July and August 2018. Hector was the eighth named storm, fourth hurricane, and third major hurricane of the 2018 Pacific hurricane season. It originated from a disturbance that was located north of South America on July 22. The disturbance tracked westward and entered the eastern Pacific around July 25. It gradually organized over the next several days, becoming a tropical depression at 12:00 UTC on July 31. The system was upgraded into a tropical storm about 12 hours later and received the name Hector. Throughout most of its existence, the cyclone traveled due west or slightly north of west. A favorable environment allowed the fledgling tropical storm to rapidly intensify to its initial peak as a Category 2 hurricane by 18:00 UTC on August 2. Wind shear caused Hector to weaken for a brief period before the storm began to strengthen again. Hector reached Category 3 status by 00:00 UTC on August 4 and went through an eyewall replacement cycle soon after, which caused the intensification to halt. After the replacement cycle, the cyclone continued to organize, developing a well-defined eye surrounded by cold cloud tops.
This article incorporates public domain material from Glossary of NHC Terms. NOAA.
