Rapid intensification is a meteorological situation where a tropical cyclone intensifies dramatically in a short period of time. The United States National Hurricane Center defines rapid intensification as an increase in the maximum sustained winds of a tropical cyclone of at least 30 knots (35 mph; 55 km/h) in a 24-hour period.
In order for rapid intensification to occur, several conditions must be in place. Water temperatures must be extremely warm (near or above 30 °C, 86 °F), and water of this temperature must be sufficiently deep such that waves do not churn deeper cooler waters up to the surface. Wind shear must be low; when wind shear is high, the convection and circulation in the cyclone will be disrupted. Dry air can also limit the strengthening of tropical cyclones.
Usually, an anticyclone in the upper layers of the troposphere above the storm must be present as well—for extremely low surface pressures to develop, air must be rising very rapidly in the eyewall of the storm, and an upper-level anticyclone helps channel this air away from the cyclone efficiently. [ further explanation needed ] Hot towers have been implicated in tropical cyclone rapid intensification, though they have diagnostically seen varied impacts across basins.
The United States National Hurricane Center previously defined rapid deepening of a tropical cyclone, when the minimum central pressure decreased by 42 millibars (1.240 inHg) over a 24-hour period. However it is now defined as an increase in the maximum sustained winds of a tropical cyclone of at least 30 knots (35 mph; 55 km/h) in a 24-hour period. Recent research suggests though that MSLP is a better predictor of damage from hurricanes making landfall in the continental United States.
In meteorology, a cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure. Cyclones are characterized by inward spiraling winds that rotate about a zone of low pressure. The largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as tropical cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes, and dust devils lie within smaller mesoscale. Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the tropical upper tropospheric trough during the summer months in the Northern Hemisphere. Cyclones have also been seen on extraterrestrial planets, such as Mars, Jupiter, and Neptune. Cyclogenesis is the process of cyclone formation and intensification. Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones. These zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, extratropical cyclones occlude as cold air masses undercut the warmer air and become cold core systems. A cyclone's track is guided over the course of its 2 to 6 day life cycle by the steering flow of the subtropical jet stream.
A subtropical cyclone is a weather system that has some characteristics of a tropical and an extratropical cyclone.
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.
Hurricane Linda was the second-strongest eastern Pacific hurricane on record. Forming from a tropical wave on September 9, 1997, Linda steadily intensified and reached hurricane status within 36 hours of developing. The storm rapidly intensified, reaching sustained winds of 185 mph (295 km/h) and an estimated central pressure of 902 millibars (26.6 inHg); both were records for the eastern Pacific until Hurricane Patricia surpassed them in 2015. The hurricane was briefly forecast to move toward southern California, but instead, it turned out to sea and lost its status as a tropical cyclone on September 17, before dissipating on September 21. Linda was the fifteenth tropical cyclone, thirteenth named storm, seventh hurricane, and fifth major hurricane of the 1997 Pacific hurricane season.
The eye is a region of mostly calm weather at the center of strong tropical cyclones. 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 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.
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of producing anything from cloudiness and mild showers to heavy gales, thunderstorms, blizzards, and tornadoes. These types of cyclones are defined as large scale (synoptic) low pressure weather systems that occur in the middle latitudes of the Earth. In contrast with tropical cyclones, extratropical cyclones produce rapid changes in temperature and dew point along broad lines, called weather fronts, about the center of the cyclone.
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain or squalls. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, and simply cyclone. A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean; in the south Pacific or Indian Ocean, comparable storms are referred to simply as "tropical cyclones" or "severe cyclonic storms".
Hurricane Gladys was the farthest tropical cyclone from the United States to be observed by radar in the Atlantic basin since Hurricane Carla in 1961. The seventh named storm and fifth hurricane of the 1975 Atlantic hurricane season, Gladys developed from a tropical wave while several hundred miles southwest of Cape Verde on September 22. Initially, the tropical depression failed to strengthened significantly, but due to warm sea surface temperatures and low wind shear, it became Tropical Storm Gladys by September 24. Despite entering a more unfavorable environment several hundred miles east of the northern Leeward Islands, Gladys became a Category 1 hurricane on the Saffir–Simpson hurricane wind scaleon September 28. Shortly thereafter, the storm reentered an area favorable for strengthening. Eventually, a well-defined eye became visible on satellite imagery.
Tropical cyclone forecasting is the science of forecasting where a tropical cyclone's center, and its effects, are expected to be at some point in the future. There are several elements to tropical cyclone forecasting: track forecasting, intensity forecasting, rainfall forecasting, storm surge, tornado, and seasonal forecasting. While skill is increasing in regard to track forecasting, intensity forecasting skill remains nearly unchanged over the past several years. Seasonal forecasting began in the 1980s in the Atlantic basin and has spread into other basins in the years since.
Hurricane Emilia was, at the time, the strongest tropical cyclone on record in the Central Pacific Ocean, and the second of such to be classified as a Category 5 hurricane – the highest rating on the Saffir–Simpson hurricane wind scale. However, hurricanes Gilma later that year, Ioke in 2006, and hurricanes Lane and Walaka in 2018 later reached lower barometric pressures in the Central Pacific. The fifth named storm and the first of three Category 5 hurricanes of the 1994 hurricane season, Emilia developed from an area of low pressure southeast of Hawaii on July 16. Tracking westward, the initial tropical depression intensified into a tropical storm several hours after tropical cyclogenesis. Subsequently, Emilia entered the Central Pacific Ocean and moved into the area of responsibility of the Central Pacific Hurricane Center (CPHC).
The following is a glossary of tropical cyclone terms.
Hurricane Dora was the strongest tropical cyclone in the northeastern Pacific in 2011. Dora developed from a tropical wave south of Honduras on July 18. Moving northwestward in favorable conditions, the system quickly intensified to tropical storm status and attained hurricane intensity the next day. Rapid intensification ensued shortly thereafter, bringing the storm to its peak intensity on July 21 as a Category 4 hurricane, with a minimum barometric pressure of 929 mbar and maximum sustained winds of 155 mph (250 km/h). However, the storm's path into an area with cool sea surface temperatures and wind shear caused Dora to quickly deteriorate and weaken. By July 24, Dora had degenerated into a remnant low-pressure area west of the Baja California Peninsula. Dora brought stormy conditions to the southwestern Mexico coast and the Baja California Peninsula throughout its existence. Remaining off the coast from its formation to dissipation, Dora's effects on land were slight. However, the outer rainbands of the hurricane caused flooding and mudslides in southern Mexico and Guatemala, while rough surf toppled a lighthouse and damaged 60 restaurants along the coast. The hurricane's remnants contributed to heightened shower and thunderstorm activity across New Mexico and Arizona in late July.
A post-tropical cyclone is a former tropical cyclone.
The 2019 Atlantic hurricane season was the fourth consecutive year of above-average and damaging seasons dating back to 2016. It is tied with 1969 as the fourth-most active Atlantic hurricane season on record in terms of named storms, with 18 named storms and 20 tropical cyclones in total, although many were weak and short-lived, especially towards the end of the season. The season officially began on June 1 and ended on November 30. These dates historically describe the period each year when most tropical cyclones form in the Atlantic basin and are adopted by convention. However, tropical cyclogenesis is possible at any time of the year, as demonstrated by the formation of Subtropical Storm Andrea on May 20, marking the record fifth year in a row where a tropical or subtropical cyclone developed before the official start of the season, breaking the previous record of four consecutive years set in 1951–1954. For a second year in a row, no tropical cyclones formed during the month of June.
Hurricane Mitch's meteorological history began with its origins over Africa as a tropical wave and lasted until its dissipation as an extratropical cyclone north of the United Kingdom. Tropical Depression Thirteen formed on October 22, 1998, over the southwestern Caribbean Sea from a tropical wave that exited Africa on October 10. It executed a small loop, and while doing so intensified into Tropical Storm Mitch. A weakness in a ridge allowed the storm to track slowly to the north. After becoming disorganized due to wind shear from a nearby upper-level low, Mitch quickly intensified in response to improving conditions which included warm waters and good outflow. It became a hurricane on October 24 and developed an eye. After turning to the west, Mitch rapidly intensified, first into a major hurricane on October 25 and then into a Category 5 on the Saffir-Simpson Hurricane Scale the next day.
Hurricane Genevieve, also referred to as Typhoon Genevieve, was the fourth-most intense tropical cyclone of the North Pacific Ocean in 2014. A long-lasting system, Genevieve was the first one 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.
Severe Tropical Cyclone Ernie was one of the quickest strengthening tropical cyclones on record. Ernie was the first Category 5 severe tropical cyclone in the Australian region since Cyclone Marcia in 2015, and also the strongest tropical cyclone in the Australian region since Cyclone Ita in 2014. Ernie developed from a tropical low into a cyclone south of Indonesia in the northeast Indian Ocean on 6 April 2017, and proceeded to intensify extremely rapidly to a Category 5 severe tropical cyclone. A few days later, on 10 April, the system was downgraded below cyclone intensity following a period of rapid weakening, located southwest of its original position. Ernie had no known impacts on any land areas.
The 2018 Pacific hurricane season produced the highest accumulated cyclone energy value on record in the basin. With 23 named storms, it was the fourth-most active season on record, tied with 1982. The season also featured seven landfalls, six of which occurred in Mexico. The season officially began on May 15 in the eastern Pacific, and on June 1 in the central Pacific; they both ended on November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Pacific basin. However, tropical cyclone formation is possible at any time of the year, as illustrated when the first tropical depression formed on May 10, five days prior to the official start of the season.
The meteorological history of Hurricane Florence spanned 22 days from its inception on August 28, 2018, to its dissipation on September 18. Originating from a tropical wave over West Africa, Florence quickly organized upon its emergence over the Atlantic Ocean. Favorable atmospheric conditions enabled it to develop into a tropical depression on August 31 just south of the Cape Verde islands. Intensifying to a tropical storm the following day, Florence embarked on a west-northwest to northwest trajectory over open ocean. Initially being inhibited by increased wind shear and dry air, the small cyclone took advantage of a small area of low shear and warm waters. After achieving hurricane strength early on September 4, Florence underwent an unexpected period of rapid deepening through September 5, culminating with it becoming a Category 4 hurricane on the Saffir-Simpson scale. Thereafter, conditions again became unfavorable and the hurricane quickly diminished to a tropical storm on September 7.
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