A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands in tropical cyclones can be either stratiform or convective and are curved in shape. They consist of showers and thunderstorms, and along with the eyewall and the eye, they make up a tropical cyclone. The extent of rainbands around a tropical cyclone can help determine the cyclone's intensity.
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 eye is a region of mostly calm weather at the center of a tropical cyclone. The eye of a storm is a roughly circular area, typically 30–65 kilometers in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the most severe weather and highest winds of the cyclone occur. The cyclone's lowest barometric pressure occurs in the eye and can be as much as 15 percent lower than the pressure outside the storm.
Vernon Francis Dvorak was an American meteorologist. He studied meteorology at the University of California, Los Angeles and wrote his Master thesis An investigation of the inversion-cloud regime over the subtropical waters west of California in 1966. In 1973 he developed the Dvorak technique to analyze tropical cyclones from satellite imagery. He worked with the National Environmental Satellite, Data, and Information Service. He lived in Ojai, California, until his death on September 19, 2022.
The central dense overcast, or CDO, of a tropical cyclone or strong subtropical cyclone is the large central area of thunderstorms surrounding its circulation center, caused by the formation of its eyewall. It can be round, angular, oval, or irregular in shape. This feature shows up in tropical cyclones of tropical storm or hurricane strength. How far the center is embedded within the CDO, and the temperature difference between the cloud tops within the CDO and the cyclone's eye, can help determine a tropical cyclone's intensity with the Dvorak technique. Locating the center within the CDO can be a problem with strong tropical storms and minimal hurricanes as its location can be obscured by the CDO's high cloud canopy. This center location problem can be resolved through the use of microwave satellite imagery.
A tropical cyclone is a rapidly rotating storm system with a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its location and strength, a tropical cyclone is called a hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, or simply cyclone. A hurricane is a strong tropical cyclone that occurs in the Atlantic Ocean or northeastern Pacific Ocean. A typhoon occurs in the northwestern Pacific Ocean. In the Indian Ocean and South Pacific, comparable storms are referred to as "tropical cyclones". In modern times, on average around 80 to 90 named tropical cyclones form each year around the world, over half of which develop hurricane-force winds of 65 kn or more.
Hurricane Dora was one of few tropical cyclones to track across all three north Pacific basins and the first since Hurricane John in 1994. The fourth named storm, third hurricane, and second major hurricane of the 1999 Pacific hurricane season, Dora developed on August 6 from a tropical wave to the south of Mexico. Forming as a tropical depression, the system gradually strengthened and was upgraded to Tropical Storm Dora later that day. Thereafter Dora began heading in a steadily westward direction, before becoming a hurricane on August 8. Amid warm sea surface temperatures and low wind shear, the storm continued to intensify, eventually peaking as a 140 mph (220 km/h) Category 4 hurricane on August 12.
Hurricane Adolph was the first and one of only two East Pacific hurricanes in May to reach Category 4 strength on the Saffir-Simpson Hurricane Scale since record keeping began in the East Pacific, with the other being Amanda of 2014. Adolph was the first depression of the season, forming on May 25; it became a hurricane two days later. After rapidly intensifying, Adolph became the most powerful storm in terms of maximum sustained winds this season, along with Hurricane Juliette. The storm briefly threatened land before dissipating on June 1, after moving over colder waters.
The 1968 Pacific hurricane season ties the record for having the most active August in terms of tropical storms. It officially started on May 15, 1968, in the eastern Pacific and June 1 in the central Pacific and lasted until November 30, 1968. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean.
Hurricane Guillermo was the ninth-most intense Pacific hurricane on record, attaining peak winds of 160 mph (260 km/h) and a barometric pressure of 919 hPa (27.14 inHg). Forming out of a tropical wave on July 30, 1997, roughly 345 mi (555 km) south of Salina Cruz, Mexico, Guillermo tracked in a steady west-northwestward direction while intensifying. The system reached hurricane status by August 1 before undergoing rapid intensification the following day. At the end of this phase, the storm attained its peak intensity as a powerful Category 5 hurricane. The storm began to weaken during the afternoon of August 5 and was downgraded to a tropical storm on August 8. Once entering the Central Pacific Hurricane Center's area of responsibility, Guillermo briefly weakened to a tropical depression before re-attaining tropical storm status. On August 15, the storm reached an unusually high latitude of 41.8°N before transitioning into an extratropical cyclone. The remnants persisted for more than a week as they tracked towards the northeast and later south and east before being absorbed by a larger extratropical system off the coast of California on August 24.
The radius of maximum wind (RMW) is the distance between the center of a cyclone and its band of strongest winds. It is a parameter in atmospheric dynamics and tropical cyclone forecasting. The highest rainfall rates occur near the RMW of tropical cyclones. The extent of a cyclone's storm surge and its maximum potential intensity can be determined using the RMW. As maximum sustained winds increase, the RMW decreases. Recently, RMW has been used in descriptions of tornadoes. When designing buildings to prevent against failure from atmospheric pressure change, RMW can be used in the calculations.
In the south-west Indian Ocean, tropical cyclones form south of the equator and west of 90° E to the coast of Africa.
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 mean sea level, and the maximum sustained wind represents the highest average wind over either a one-minute (US) or ten-minute time span, 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.
Hurricane Elida was the first of three tropical cyclones of the 2002 Pacific hurricane season to reach Category 5 strength on the Saffir-Simpson Hurricane Scale. Elida was one of only sixteen known Category 5 hurricanes in the eastern north Pacific tropical cyclone basin, east of the International Date Line and north of the Equator. Although heavy waves affected the Mexican coastline due to Elida, no damages or casualties were reported in relation to the hurricane.
Hurricane Hernan was the fourth and final tropical cyclone to strike Mexico at hurricane intensity during the 1996 Pacific hurricane season. The thirteenth tropical cyclone, eighth named storm, and fifth hurricane of the season, Hernan developed as a tropical depression from a tropical wave to the south of Mexico on September 30. The depression quickly strengthened, and became Tropical Storm Hernan later that day. Hernan curved north-northwestward the following day, before eventually turning north-northeastward. Still offshore of the Mexican coast on October 2, Hernan intensified into a hurricane. Six hours later, Hernan attained its peak as an 85 mph (140 km/h) Category 1 hurricane on the Saffir-Simpson Hurricane Wind Scale (SSHWS). After weakening somewhat, on 1000 UTC October 3, Hurricane Hernan made landfall near Barra de Navidad, Jalisco, with winds of 75 mph (120 km/h). Only two hours after landfall, Hernan weakened to a tropical storm. By October 4, Tropical Storm Hernan had weakened into a tropical depression, and dissipated over Nayarit on the following day.
Severe Tropical Cyclone Monica was the most intense tropical cyclone, in terms of maximum sustained winds, on record to impact Australia. The 17th and final storm of the 2005–06 Australian region cyclone season, Monica originated from an area of low pressure off the coast of Papua New Guinea on 16 April 2006. The storm quickly developed into a Category 1 cyclone the next day, at which time it was given the name Monica. Travelling towards the west, the storm intensified into a severe tropical cyclone before making landfall in Far North Queensland, near Lockhart River, on 19 April 2006. After moving over land, convection associated with the storm quickly became disorganised.
Typhoon Alex, known in the Philippines as Typhoon Etang, affected the Taiwan, China, and South Korea during July 1987. Typhoon Alex developed from the monsoon trough that spawned a tropical disturbance late on July 21 southwest of Guam which organized into a tropical depression shortly thereafter. The system steadily became better organized, and the next day, a tropical depression had developed. Satellite intensity estimates gradually increased, and on July 23, the depression intensified into Tropical Storm Alex. After initially tracking west-northwest, Tropical Storm Alex started tracking northwest. An eye developed on July 24, and on the next day, Alex was classified as a typhoon, when Alex attained its peak intensity of 120 km/h (75 mph) and a minimum barometric pressure of 970 mbar (29 inHg). Alex weakened while tracking more northward, though interaction with Taiwan resulted in a more westward track starting on July 27. The storm struck near Shanghai as a tropical storm, and weakened over land, although it remained identifiable through August 2.
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.
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.
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.
