In meteorology, a cyclone is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above. 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 the smaller mesoscale.
A subtropical cyclone is a weather system that has some characteristics of both tropical and extratropical cyclones.
The 1967 Atlantic hurricane season was an active Atlantic hurricane season overall, producing 13 nameable storms, of which 6 strengthened into hurricanes. The season officially began on June 1, 1967, and lasted until November 30, 1967. These dates, adopted by convention, historically describe the period in each year when most tropical cyclogenesis occurs in the Atlantic Ocean. The season's first system, Tropical Depression One, formed on June 10, and the last, Tropical Storm Heidi, lost tropical characteristics on November 2.
The 1991 Atlantic hurricane season was the first season since 1984 in which no hurricanes developed from tropical waves, which are the source for most North Atlantic tropical cyclones. The hurricane season officially began on June 1, and ended on November 30. It was the least active in four years due to higher than usual wind shear across the Atlantic Ocean. The first storm, Ana, developed on July 2 off the southeast United States and dissipated without causing significant effects. Two other tropical storms in the season – Danny and Erika – did not significantly affect land. Danny dissipated east of the Lesser Antilles, and Erika passed through the Azores before becoming extratropical. In addition, there were four non-developing tropical depressions. The second depression of the season struck Mexico with significant accompanying rains.
The 2006 Atlantic hurricane season was the least active in the basin since 1997, with nine named storms as well as an additional unnamed tropical storm identified by the National Hurricane Center. 2006 was the first season since 2001 in which no hurricanes made landfall in the United States, and was the first since 1994 in which no tropical cyclones formed during October. Following the intense activity of 2003, 2004, and 2005, forecasters predicted that the 2006 season would be only slightly less active. Instead, it turned out to be a below average season, as activity was slowed by a rapidly forming moderate El Niño event, the presence of the Saharan Air Layer over the tropical Atlantic, and the steady presence of a robust secondary high-pressure area to the Azores High centered on Bermuda. There were no tropical cyclones after October 2.
Hurricane Vince was an unusual tropical cyclone that developed in the northeastern Atlantic basin. Forming in October during the 2005 Atlantic hurricane season, it strengthened over waters thought to be too cold for tropical development. Vince was the twentieth named storm and twelfth hurricane of the extremely active season.
Tropical Storm Ana was the first named storm of the 2003 Atlantic hurricane season. A pre-season storm, it developed initially as a subtropical cyclone from a non-tropical low on April 20 to the west of Bermuda. It tracked east-southeastward and organized, and on April 21 it transitioned into a tropical cyclone with peak winds of 60 mph (97 km/h). Tropical Storm Ana turned east-northeastward, steadily weakening due to wind shear and an approaching cold front, and on April 24 it became an extratropical cyclone. The storm brushed Bermuda with light rain, and its remnants produced precipitation in the Azores and the United Kingdom. Swells generated by the storm capsized a boat along the Florida coastline, causing two fatalities.
Subtropical Storm Nicole was the first subtropical storm to receive a name using the standard hurricane name list that did not become a tropical cyclone. The fifteenth tropical or subtropical cyclone and fourteenth named storm of the 2004 Atlantic hurricane season, Nicole developed on October 10 near Bermuda from a broad surface low that developed as a result of the interaction between an upper level trough and a decaying cold front. The storm turned to the northeast, passing close to Bermuda as it intensified to reach peak winds of 50 mph (80 km/h) on October 11. Deep convection developed near the center of the system as it attempted to become a fully tropical cyclone. However, it failed to do so and was absorbed by an extratropical cyclone late on October 11.
Hurricane Gordon was the first tropical cyclone since 1992 to affect the Azores while retaining tropical characteristics. The eighth tropical storm, third hurricane, and first major hurricane of the 2006 Atlantic hurricane season, Gordon formed on September 10 in the tropical Atlantic Ocean. It gradually matured into a hurricane as it tracked northward, reaching its peak intensity with winds of 195 km/h (121 mph) early on September 14 while located about 925 km (575 mi) southeast of Bermuda. After becoming nearly stationary, Gordon weakened to minimal hurricane status, although it re-intensified after accelerating to the east. It weakened again after moving over cooler waters, and passed through the Azores on September 20. Shortly thereafter, it became an extratropical cyclone and subsequently affected Spain, Ireland, and the United Kingdom.
Hurricane Florence attained Category 1 intensity on three separate occasions in mid-September 2000. The tenth tropical cyclone, sixth named storm, and third hurricane of the 2000 Atlantic hurricane season, Florence developed on September 10 from a cold front to the southwest of Bermuda. Initially a subtropical cyclone, it quickly organized, attaining hurricane status twice in a two-day period before weakening while remaining nearly stationary. Florence accelerated northeastward, reaching peak winds as a hurricane after passing near Bermuda. On September 17, the storm was absorbed by a larger extratropical cyclone. Hurricane Florence threatened Bermuda during its third time at hurricane intensity, bringing tropical storm force winds to the island but causing no reported damage. However, three deaths in North Carolina were blamed on rip currents triggered by the hurricane on September 12.
Tropical Storm Laura was a large but short-lived tropical cyclone that developed over the north-central Atlantic Ocean in late September during the 2008 Atlantic hurricane season. Laura's remnants later impacted the Netherlands, Germany, and Norway. The 12th named storm of the season, Laura formed out of a large extratropical area of low pressure located about 1,015 miles (1,633 km) west of the Azores on September 29. Laura slowly developed tropical characteristics throughout the day as it moved over warmer waters. On the afternoon of September 30, Laura had acquired enough tropical characteristics to be designated a tropical storm. Shortly after being declared tropical, Laura began to undergo an extratropical transition, which did not fully take place until the morning of October 1. Laura degenerated into a post-tropical cyclone later that morning, and the final advisory by the National Hurricane Center was issued. The remnants of Laura contributed to heavy rainfall and power outages in the British Isles, the Netherlands, and Norway on October 5 to 8.
Tropical Storm Grace holds the record for being the farthest northeast forming tropical cyclone in the Atlantic basin. The seventh named storm of the slightly below average 2009 Atlantic hurricane season, Grace formed from an extratropical cyclone over the Azores on 4 October. It strengthened to attain peak sustained winds of 65 mph (100 km/h) and developed an eye-like feature, although cold sea surface temperatures inhibited the development of thunderstorm activity near the center. The storm lost its tropical characteristics on 6 October, and the storm's remnants merged with a separate system near the British Isles on 7 October.
Hurricane Epsilon was the twenty-seventh named tropical or subtropical storm and the final of 15 hurricanes in the record-breaking 2005 Atlantic hurricane season. Originating from a cold front beneath an upper-level low, Epsilon formed on November 29 about 915 mi (1470 km) east of Bermuda, becoming the second tropical storm to do so in that area of the Atlantic within the span of a week. Initially, the National Hurricane Center (NHC) forecast the storm to transition into an extratropical cyclone within five days, due to conditions unfavorable for significant intensification. Epsilon continually defied forecasts, at first due to an unexpected loop to the southwest, and later due to retaining its strength despite cold waters and strong wind shear.
The following is a glossary of tropical cyclone terms.
Hurricane Alex was the first Atlantic hurricane to occur in January since Hurricane Alice of 1954–55. Alex originated as a non-tropical low near the Bahamas on January 7, 2016. Initially traveling northeast, the system passed by Bermuda on January 8 before turning southeast and deepening. It briefly acquired hurricane-force winds by January 10, then weakened slightly before curving towards the east and later northeast. Acquiring more tropical weather characteristics over time, the system transitioned into a subtropical cyclone well south of the Azores on January 12, becoming the first North Atlantic tropical or subtropical cyclone in January since Tropical Storm Zeta of 2005–2006. Alex continued to develop tropical features while turning north-northeast, and transitioned into a fully tropical cyclone on January 14. The cyclone peaked in strength as a Category 1 hurricane on the Saffir–Simpson scale (SSHWS), with maximum sustained winds of 85 mph and a central pressure of 981 mbar. Alex weakened to a high-end tropical storm before making landfall on Terceira Island on January 15. By that time, the storm was losing its tropical characteristics; it fully transitioned back into a non-tropical cyclone several hours after moving away from the Azores. Alex ultimately merged with another cyclone over the Labrador Sea on January 17.
Hurricane Ophelia was regarded as the worst storm to affect Ireland in 50 years, and was also the easternmost Atlantic major hurricane on record. The tenth and final consecutive hurricane and the sixth major hurricane of the very active 2017 Atlantic hurricane season, Ophelia had non-tropical origins from a decaying cold front on 6 October. Located within a favorable environment, the storm steadily strengthened over the next two days, drifting north and then southeastwards before becoming a hurricane on 11 October. After becoming a Category 2 hurricane and fluctuating in intensity for a day, Ophelia intensified into a major hurricane on 14 October south of the Azores, brushing the archipelago with high winds and heavy rainfall. Shortly after achieving peak intensity, Ophelia began weakening as it accelerated over progressively colder waters to its northeast towards Ireland and Great Britain. Completing an extratropical transition early on 16 October, Ophelia became the second storm of the 2017–18 European windstorm season. Early on 17 October, the cyclone crossed the North Sea and struck western Norway, with wind gusts up to 70 kilometres per hour (43 mph) in Rogaland county, before weakening during the evening of 17 October. The system then moved across Scandinavia, before dissipating over Norway on the next day.
The 2021 Atlantic hurricane season was the third-most active Atlantic hurricane season on record in terms of number of tropical cyclones, although many of them were weak and short-lived. With 21 named storms forming, it became the second season in a row and third overall in which the designated 21-name list of storm names was exhausted. Seven of those storms strengthened into a hurricane, four of which reached major hurricane intensity, which is slightly above-average. The season officially began on June 1 and ended on November 30. These dates historically describe the period in each year when most Atlantic tropical cyclones form. However, subtropical or tropical cyclogenesis is possible at any time of the year, as demonstrated by the development of Tropical Storm Ana on May 22, making this the seventh consecutive year in which a storm developed outside of the official season.
Tropical Storm Melissa was a nor'easter and a short-lived tropical cyclone that affected portions of the East Coast of the United States and Atlantic Canada in October 2019. The fourteenth depression and thirteenth named storm of the 2019 Atlantic hurricane season, Melissa originated from a cold front that developed over the southwestern Atlantic on October 6. The system developed tropical storm-force winds on October 8, before becoming a nor'easter on the next day. The system then began to organize, and was designated as Subtropical Storm Melissa on October 11. Melissa was then upgraded into a tropical storm, the following day. However, the storm soon began to disorganize and transition into an extratropical low by October 14, before dissipating later that same day.
Hurricane Pablo was a late-season tropical cyclone that became the farthest east-forming hurricane in the North Atlantic tropical cyclone basin on record, beating the previous record set by Hurricane Vince in 2005. The seventeenth tropical/subtropical cyclone, sixteenth named storm and sixth hurricane of the 2019 Atlantic hurricane season, Pablo originated from a baroclinic cyclone a few hundred miles west of the Azores Islands. The precursor cyclone formed on October 22, traveling eastward towards the island chain. The system initially had multiple centers of circulation, but they consolidated into one small low-pressure system embedded within the larger extratropical storm. On October 25, the embedded cyclone developed into a subtropical cyclone, receiving the name Pablo. The cyclone continued eastwards, transitioning into a fully-tropical storm later that day. Pablo quickly intensified between October 26 and 27, forming an eye and spiral rainbands. At 12:00 Coordinated Universal Time (UTC) on October 27, Pablo intensified into a Category 1 hurricane. The storm continued to strengthen, reaching its peak intensity of 80 mph (130 km/h) and a minimum central pressure of 977 mbar (28.9 inHg) at 18:00 UTC on the same day. The storm quickly weakened the next day, becoming extratropical again, and dissipated on October 29.
