A high-pressure area, high, or anticyclone, is an area near the surface of a planet where the atmospheric pressure is greater than the pressure in the surrounding regions. Highs are middle-scale meteorological features that result from interplays between the relatively larger-scale dynamics of an entire planet's atmospheric circulation.
The trade winds or easterlies are permanent east-to-west prevailing winds that flow in the Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere, strengthening during the winter and when the Arctic oscillation is in its warm phase. Trade winds have been used by captains of sailing ships to cross the world's oceans for centuries. They enabled European colonization of the Americas, and trade routes to become established across the Atlantic Ocean and the Pacific Ocean.
The 2003 Atlantic hurricane season was a very active season with tropical cyclogenesis occurring before and after the official bounds of the season—the first such occurrence since the 1970 season. The season produced 21 tropical cyclones, of which 16 developed into named storms; seven of those attained hurricane status, of which three reached major hurricane status. The strongest hurricane of the season was Hurricane Isabel, which reached Category 5 status on the Saffir–Simpson hurricane scale northeast of the Lesser Antilles; Isabel later struck North Carolina as a Category 2 hurricane, causing $3.6 billion in damage and a total of 51 deaths across the Mid-Atlantic region of the United States.
The 1997 Atlantic hurricane season was a below-average hurricane season. It officially began on June 1, and lasted until November 30 of that year. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The 1997 season was fairly inactive, with only seven named storms forming, with an additional tropical depression and an unnumbered subtropical storm. It was the first time since the 1961 season that there were no active tropical cyclones in the Atlantic basin during the entire month of August–historically one of the more active months of the season—a phenomenon that would not occur again until 2022. A strong El Niño is credited with reducing activity in the Atlantic, while increasing the number of storms in the eastern and western Pacific basins to 19 and 26 storms, respectively. As is common in El Niño years, tropical cyclogenesis was suppressed in the tropical latitudes, with only two becoming tropical storms south of 25°N.
The 1963 Atlantic hurricane season was a slightly below average season in terms of tropical cyclone formation, with a total of ten nameable storms. Even so, it was also a notoriously deadly and destructive season. The season officially began on June 15, 1963, and lasted until November 15, 1963. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The first system, an unnamed tropical storm, developed over the Bahamas on June 1.
The 1992 Atlantic hurricane season was a significantly below average season for overall tropical or subtropical cyclones as only ten formed. Six of them became named tropical storms, and four of those became hurricanes; one hurricane became a major hurricane. The season was also near-average in terms of accumulated cyclone energy. The season officially started on June 1 and officially ended on November 30. However, tropical cyclogenesis is possible at any time of the year, as demonstrated by formation in April of an unnamed subtropical storm in the central Atlantic.
The 1973 Atlantic hurricane season was a below average tropical cyclone season overall. Of the 24 tropical or subtropical cyclones which developed, only 8 became named storms, and of those, only 4 became hurricanes, with 1 reaching major hurricane status on the newly implemented Saffir–Simpson hurricane wind scale.
The 1975 Atlantic hurricane season was a near average hurricane season with nine named storms forming, of which six became hurricanes. Three of those six became major hurricanes, which are Category 3 or higher systems on the Saffir–Simpson scale. The season officially began on June 1 and lasted until November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic Ocean.
The 1976 Atlantic hurricane season was a fairly average Atlantic hurricane season in which 21 tropical or subtropical cyclones formed. 10 of them became nameable storms. Six of those reached hurricane strength, with two of the six becoming major hurricanes, which are Category 3 or higher on the Saffir–Simpson scale. The season officially began on June 1 and lasted until November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. However, the first system, a subtropical storm, developed in the Gulf of Mexico on May 21, several days before the official start of the season. The system spawned nine tornadoes in Florida, resulting in about $628,000 (1976 USD) in damage, though impact was minor otherwise.
The 1977 Atlantic hurricane season was a very inactive Atlantic hurricane season, with only six named storms. The season officially began on Wednesday, June 1, 1977 and lasted until Wednesday, November 30, 1977. These dates conventionally delimit the period of each year when most tropical cyclogenesis occurs in the Atlantic basin. The first tropical cyclone of the season developed over the western Caribbean Sea on June 13, 12 days after the start of the season. Three more organized during July and early August. Then, on August 29, the first named storm, Hurricane Anita formed and rapidly intensified to a Category 5 hurricane on September 1, before weakening slightly and striking Mexico as a high-end Category 4 hurricane on the Saffir–Simpson hurricane wind scale, bringing strong winds and heavy rainfall, causing 11 fatalities and leaving at least 25,000 people homeless.
The 1978 Atlantic hurricane season was a slightly above average hurricane season in terms of number of named storms. Eleven tropical cyclones were named in all, and five of these became hurricanes; two of the five became a major hurricane. This was also the last Atlantic hurricane season to use an all-female naming list. The season officially began on June 1, 1978, and ended on November 30, 1978. These dates, adopted by convention, denote the period in each year when most tropical cyclogenesis occurs in the Atlantic basin. However, the formation of subtropical or tropical cyclones is possible at any time of the year, as shown by the formation of an unnamed subtropical storm on January 18.
The 1981 Atlantic hurricane season featured direct or indirect impacts from nearly all of its 12 tropical or subtropical storms. Overall, the season was fairly active, with 22 tropical depressions, 12 of which became a namable storm, while 7 of those reached hurricane status and 3 intensified into major hurricanes. The season officially began on June 1, 1981, and lasted until November 30, 1981. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. However, tropical cyclogenesis can occur before these dates, as demonstrated with the development of two tropical depressions in April and Tropical Storm Arlene in May. At least one tropical cyclone formed in each month between April and November, with the final system, Subtropical Storm Three, becoming extratropical on November 17, 1981.
The 1982 Atlantic hurricane season was an extremely inactive Atlantic hurricane season with five named tropical storms and one subtropical storm. Two storms became hurricanes, one of which reached major hurricane status. The season officially began on June 1, 1982, and lasted until November 30, 1982. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. Activity started early with Hurricane Alberto forming on the first day of the season. Alberto threatened the Southwestern Florida coast as a tropical storm, meadering offshore in the southeastern Gulf of Mexico and causing 23 fatalities in Cuba. The next system, a subtropical storm, formed later in June and affected the same area as Alberto, causing $10 million in damage.
The 1984 Atlantic hurricane season was the most active since 1971, though the season was below average in hurricanes and major hurricanes. It officially began on June 1, 1984, and lasted until November 30, 1984. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The 1984 season was an active one in terms of named storms, but most of them were weak and stayed at sea. Most of the cyclones tracked through the northwest subtropical Atlantic west of the 50th meridian to near the Eastern coast of the United States between mid-August and early October. The most damaging storm was Hurricane Klaus, which caused $152 million (1984 dollars) in damage in Puerto Rico. Hurricane Diana was the first hurricane to strike a nuclear power plant without incident; it was also the first major hurricane to strike the U.S. East Coast in nearly 20 years. Also of note was Hurricane Lili, which lasted well after the official end of the season. It was downgraded from a named storm on December 24. Damage overall from the tropical cyclones in 1984 totaled $228.7 million. Unusually, no hurricanes developed from tropical waves in 1984, which usually are the source of the strongest storms in an Atlantic hurricane season.
The 1990 Atlantic hurricane season was the most active Atlantic hurricane season since 1969, with a total of 14 named storms. The season also featured eight hurricanes, one of which intensified into a major hurricane. It officially began on June 1, 1990, and lasted until November 30, 1990. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. However, tropical cyclogenesis can occur prior to the start of the season, as demonstrated with Tropical Depression One, which formed in the Caribbean Sea on May 24.
A tropical wave, in and around the Atlantic Ocean, is a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which moves from east to west across the tropics, causing areas of cloudiness and thunderstorms. Tropical waves form in the easterly flow along the equatorial side of the subtropical ridge or belt of high air pressure which lies north and south of the Intertropical Convergence Zone (ITCZ). Tropical waves are generally carried westward by the prevailing easterly winds along the tropics and subtropics near the equator. They can lead to the formation of tropical cyclones in the north Atlantic and northeastern Pacific basins. A tropical wave study is aided by Hovmöller diagrams, a graph of meteorological data.
The 2005 Atlantic hurricane season was the most active on record in terms of number of tropical cyclones, until surpassed by the 2020 season. It featured 28 tropical or subtropical storms. The United States National Hurricane Center named 27 storms, exhausting the annual pre-designated list, requiring the use of six Greek letter names, and adding an additional unnamed storm during a post-season re-analysis. A record 15 storms attained hurricane status, with maximum sustained winds of at least 74 miles per hour (119 km/h). Of those, a record seven became major hurricanes, rated Category 3 or higher on the Saffir–Simpson scale. Four storms of this season became Category 5 hurricanes, the highest ranking.
Hurricane Arlene was a long-lived tropical cyclone that moved eastward in an erratic fashion in the northern Atlantic Ocean in mid-August 1987. The first named storm of the 1987 Atlantic hurricane season, Arlene formed out of an area of low pressure associated with a decaying frontal system along the North Carolina coastline, Arlene tracked in a general eastward direction across the Atlantic Ocean, taking an erratic track with several curves. On August 13, the storm brushed Bermuda as a weak tropical storm before continuing out to sea. On August 20, the storm briefly stalled before becoming a hurricane two days later. Early on August 24, the storm transitioned into an extratropical cyclone over the far north Atlantic before curving southeast and dissipating near the Iberian Peninsula on August 26.
A cold-core low, also known as an upper level low or cold-core cyclone, is a cyclone aloft which has an associated cold pool of air residing at high altitude within the Earth's troposphere, without a frontal structure. It is a low pressure system that strengthens with height in accordance with the thermal wind relationship. If a weak surface circulation forms in response to such a feature at subtropical latitudes of the eastern north Pacific or north Indian oceans, it is called a subtropical cyclone. Cloud cover and rainfall mainly occurs with these systems during the day.
Centers of action are extensive and almost stationary low or high pressure areas which control the movement of atmospheric disturbances over a large area. This does not mean that the position of the center is constant over a specific area but that the monthly atmospheric pressure corresponds to a high or a low pressure.
