Atlantic tropical storm and hurricane frequency, by month Hurricane tracks from 1980 through 2014. Green tracks did not make landfall in US; yellow tracks made landfall but were not major hurricanes at the time; red tracks made landfall and were major hurricanes.
The Atlantic hurricane season is the period in a year, from June1 through November30, when tropical or subtropical cyclones are most likely to form in the North Atlantic Ocean. These dates, adopted by convention, encompass the period in each year when most tropical cyclogenesis occurs in the basin. Even so, subtropical or tropical cyclogenesis is possible at any time of the year, and often does occur.[2]
Worldwide, a season's climatological peak activity takes place in late summer, when the difference between air temperature and sea surface temperatures is the greatest. Peak activity in an Atlantic hurricane season happens from late August through September, with a midpoint on September 10.[3][4]
Atlantic tropical and subtropical cyclones that reach tropical storm intensity are named from a pre-determined list. On average, 10.1 named storms occur each season, with an average of 5.9 becoming hurricanes and 2.5 becoming major hurricanes, Category 3 or higher on the Saffir–Simpson scale. The most active season on record was 2020, during which 30named tropical cyclones formed. Despite this, the 2005 season had more hurricanes, developing a record of 15 such storms. The least active season was 1914, with only one known tropical cyclone developing during that year.[5]
The timing of the hurricane season was an important factor for maritime trade and naval activities.
The understanding that Atlantic hurricanes are most commonplace during a certain period of the year has been long recognized. Historical delineations of the Atlantic hurricane season varied but generally covered some part of the estival (Summer) and autumnal months.[6] Some early descriptions of the season's bounds theorized that the timing of the full moon or the moon's phases as a whole could be used to more precisely delineate the hurricane season.[7][6] In the second volume of Voyages and Descriptions (published in 1700), English explorer and naturalist William Dampier observed that hurricanes in the Caribbean Sea were expected in July, August, and September.[8] Mariners in the 18th century generally regarded the period from July to the end of October as the "hurricane season" based on the frequency of storms striking the Caribbean islands and the trajectories of ships traversing the Atlantic.[9][7]
The hurricane season was also an important influence on European naval operations within the West Indies, forcing the movement of materiel to be expedited before its onset or delayed until its end.[10][11][12] English admiral Edward Vernon described the "hurricane months" of August and September within the West Indies as a particularly vulnerable time for maritime logistics; Vernon argued that the most optimal time for a fleet to be dispatched from Great Britain to attack Spanish assets in the Americas was August or September, in part because such ships would more likely avoid hurricanes by the time they reached the West Indies.[13] American geographer Jedidiah Morse defined the hurricane season as the months of August, September, and October in his treatise The American Universal Geography.[14] American meteorologist William Charles Redfield defined the hurricane season as lasting from July15 to October15, citing the timeframe during which some insurance underwriters raised premiums in response to the increased likelihood of hurricanes.[6][15] Based on a catalog of 355storms between 1493–1855 in the North Atlantic compiled by M. André Poëy, W. H. Rosser described the months of July, August, September, and October as comprising the "true hurricane season of the West Indies" in his 1876book The Law of Storms Considered Practically.[16]
Still, the hurricane season will not allow itself to be 'cribbed, cabined and confined' within the limits of three short months, and skips along whenever its blithe fancy takes it, having a way of turning up at the most unexpected seasons...
In the early 1900s, the hurricane season served as the time in which U.S. Weather Bureau observations in the Caribbean were taken more frequently.
The concept of the hurricane season took on a more practical significance in forecasting operations as the United States Weather Bureau began to extend its weather prediction efforts and data collection into the tropics. In 1882, the bureau briefly considered an effort to adopt special hurricane signals between July and October20 to emphasize the danger of such storms during that period, but dropped the effort due to a lack of funding.[17] When the U.S. Weather Bureau built a network of weather observatories in the Caribbean in 1898, these sites telegraphed weather observations at 8a.m. daily to the bureau's regional headquarters in Havana, Cuba, during the hurricane season; this season was defined as lasting from the beginning of June through October.[18][19][20] By 1907, these stations in the West Indies operated within a hurricane season defined as beginning on June15 and ending on November15.[21] The starting date of these regular reports was moved back to June1 by 1915.[22] In 1917, an increase in funding for the U.S. Weather Bureau's observing networks in the Caribbean region led to these stations reporting twice daily during a hurricane season expanded to cover the June1 to November30 period.[23][24] This delineation was maintained when the bureau (in cooperation with United Fruit Company) began to broadcast special weather bulletins for Caribbean shipping during the hurricane season in 1922, providing information on active hurricanes and warnings twice daily.[25]
The basic concept of an official hurricane season began during 1935,[26] when dedicated wire circuits known as hurricane circuits began to be set up along the Gulf and Atlantic coasts,[27] a process completed by 1955.[28] It was originally the time frame when the tropics were monitored routinely for tropical cyclone activity, and was originally defined as from June 15 through October 31.[29] Over the years, the beginning date was shifted back to June 1, while the end date was shifted to November 15,[27] before settling at November 30 by 1965.[30][31] This was when hurricane reconnaissance planes were sent out to fly across the Atlantic and Gulf of Mexico on a routine basis to look for potential tropical cyclones, in the years before the continuous weather satellite era.[29] Since regular satellite surveillance began, hurricane hunter aircraft fly only into storm areas which are first spotted by satellite imagery.[32] The six-month official hurricane season established in 1965 by the National Hurricane Center (NHC) remains the current delineation of the Atlantic hurricane season.[33] These bounds contain over 97percent of Atlantic tropical cyclone activity. While this definition was chosen in part to make it easier for the public to remember the timing of hurricanes, storms have often formed outside the official seasonal bounds.[34][35] Following several consecutive years of Atlantic tropical cyclones developing before the official June1 start date, the World Meteorological Organization recommended in 2021 that the NHC assess moving the start date to May15.[36] In response, the NHC formed a team to develop quantiative criteria to evaluate extending the seasonal bounds.[37][38] The agency's routine tropical weather outlooks, historically issued during the hurricane season beginning on June1, were instead started on May15 beginning in 2021.[39]
During the hurricane season, the National Hurricane Center routinely issues their Tropical Weather Outlook product, which identifies areas of concern within the tropics which could develop into tropical cyclones. If systems occur outside the defined hurricane season, special Tropical Weather Outlooks will be issued.[40] Routine coordination occurs at 1700 UTC each day between the Weather Prediction Center and National Hurricane Center to identify systems for the pressure maps three to seven days into the future within the tropics, and points for existing tropical cyclones six to seven days into the future.[41] Possible tropical cyclones are depicted with a closed isobar, while systems with less certainty to develop are depicted as "spot lows" with no isobar surrounding them.
The North Atlantic hurricane database, or HURDAT, is the database for all tropical storms and hurricanes for the Atlantic Ocean, Gulf of Mexico and Caribbean Sea, including those that have made landfall in the United States. The original database of six-hourly positions and intensities were put together in the 1960s in support of the Apollo space program to help provide statistical track forecast guidance. In the intervening years, this database— which is now freely and easily accessible on the Internet from the National Hurricane Center's (NHC) webpage— has been utilized for a wide variety of uses: climatic change studies, seasonal forecasting, risk assessment for county emergency managers, analysis of potential losses for insurance and business interests, intensity forecasting techniques and verification of official and various model predictions of track and intensity.
HURDAT was not designed with all of these uses in mind when it was first put together and not all of them may be appropriate given its original motivation. HURDAT contains numerous systematic as well as some random errors in the database. Additionally, analysis techniques have changed over the years at NHC as their understanding of tropical cyclones has developed, leading to biases in the historical database. Another difficulty in applying the hurricane database to studies concerned with landfalling events is the lack of exact location, time and intensity at hurricane landfall.
HURDAT is regularly updated annually to reflect the previous season's activity. The older portion of the database has been regularly revised since 2001. The first time in 2001 led to the addition of tropical cyclone tracks for the years 1851 to 1885. The second time was in October 2002 when Hurricane Andrew (August 1992) was upgraded to a Category 5. Recent efforts into uncovering undocumented historical hurricanes in the late 19th and 20th centuries by various researchers have greatly increased our knowledge of these past events. Tropical storms from 1851 to 1970 have already been reanalyzed with most recently, re-analysis of tropical storms from 1961 to 1965 being completed and integrated into HURDAT database in November 2019, and re-analysis of tropical storms from 1966 to 1970 being completed and integrated into HURDAT database in January 2022.[42] Possible changes for the years 1971 onward are not yet incorporated into the HURDAT database. Due to these issues, a re-analysis of the Atlantic hurricane database is being attempted that will be completed in three years.
In addition to the groundbreaking work by Partagas Cigars, additional analyses, digitization and quality control of the data was carried out by researchers at the NOAA Hurricane Research Division funded by the NOAA Office of Global Programs.[43]
The National Hurricane Center's Best Track Change Committee has approved changes for a few recent cyclones, such as Hurricane Andrew. Official changes to the Atlantic hurricane database are approved by the National Hurricane Center Best Track Change Committee.
Tied for fifth most active season on record (with 1887, 2010, 2011 and 2012). First season of an ongoing period of increased activity in the Atlantic (+AMO).
Second-costliest hurricane season on record. Holds the records for most hurricanes, major hurricanes, and Category 5 hurricanes. Most retired names. The first year to use the Greek alphabet, later also used in 2020. The first season on record with a Category 5 hurricane in July. Includes 1 subtropical storm and 1 subtropical depression.
Featured one unnamed subtropical storm in December. First season since 1986 and 1994 with no major hurricanes. First season in the satellite era where no hurricanes reached Category 2 strength.
First season of a 7-year period of early season activity in the Atlantic. Erika was the second Atlantic tropical storm to have its name retired, following Allison in 2001.
Record fifth consecutive season for a storm to develop before the official start. Includes two subtropical storms. Record fourth consecutive season with a Category 5 hurricane.
Most active season in terms of tropical depressions and named storms. Holds record for the earliest formation date for the third, sixth, and every storm after. Second and final season after 2005 to use the Greek alphabet. Tied with 2005 for a record 7 tropical cyclones that became major hurricanes. Second most hurricanes in a season with fourteen. Record-breaking fifth consecutive above-normal season. Record sixth straight season with at least one pre-season storm. First recorded season with two major hurricanes in November.
Record seventh consecutive season for a storm to develop before the official start (Ana). Third most active season on record. Record for the earliest formation date for the fifth storm (Elsa). Record-breaking sixth consecutive above-normal season.
First season since 1997 in which no tropical cyclones formed in August. First season not to have above-average activity since 2015. First season since 1988 and 1996 with more than one Atlantic–Pacific crossover hurricane (Bonnie and Julia). Featured the formation of two hurricanes in November. Hurricane Ian was the hurricane with the strongest winds of 2022.[48] First Category 5 hurricane since 2019.
Featured one unnamed subtropical storm in January. First season since 1968 in which two named storms were simultaneously active in June (Bret and Cindy) Fourth most active season on record (tied with 1933).
A 2011 study analyzing one of the main sources of hurricanes - the African easterly wave (AEW) - found that the change in AEWs is closely linked to increased activity of intense hurricanes in the North Atlantic. The synoptic concurrence of AEWs in driving the dynamics of the Sahel greening also appears to increase tropical cyclogenesis over the North Atlantic.[49]
Tropical cyclone count adjusted for lack of observation prior to 1965.
The 20-year average of the number of annual Category 4 and 5 hurricanes in the Atlantic region has approximately doubled since the year 2000.[50]
The number of $1 billion Atlantic hurricanes almost doubled from the 1980s to the 2010s, and inflation-adjusted costs have increased more than elevenfold.[51] The increases have been attributed to climate change and to greater numbers of people moving to coastal areas.[51]
A subtropical cyclone is a weather system that has some characteristics of both tropical and extratropical cyclones.
The National Hurricane Center (NHC) is the division of the United States' NOAA/National Weather Service responsible for tracking and predicting tropical weather systems between the Prime Meridian and the 140th meridian west poleward to the 30th parallel north in the northeast Pacific Ocean and the 31st parallel north in the northern Atlantic Ocean. The agency, which is co-located with the Miami branch of the National Weather Service, is situated on the campus of Florida International University in University Park, Miami, Florida.
The 1914 Atlantic hurricane season was the least active Atlantic hurricane season on record, with only one known tropical storm. Although hurricane season typically encompasses a much larger time-span, actual activity was confined to the middle of September. The only tropical cyclone of the year developed in the region of The Bahamas on September 15 and drifted northwestward, moving inland over Florida and Georgia. Thorough warnings before the storm prevented any major damage. The 1914 season is one of only two that did not produce any hurricanes. Due to the lack of modern technology such as satellite imagery, information is often sparse, and an additional tropical depression may have existed in late October.
A Pacific hurricane is a 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.
An Atlantic hurricane is a type of tropical cyclone that forms in the Atlantic Ocean primarily between June and November. The terms "hurricane", "typhoon", and "cyclone" can be used interchangeably to describe this weather phenomenon. These storms are rotating, organized systems of clouds and thunderstorms that originate over tropical or subtropical waters and have closed low-level circulation, not to be confused with tornadoes. They form over low pressure systems. In the North Atlantic, central North Pacific, and eastern North Pacific, the term "hurricane" is mainly used, whereas "typhoon" is more commonly used for storms originating in the western North Pacific. The term "cyclone" is used in the South Pacific and Indian Ocean.
The Atlantic hurricane reanalysis project of the National Oceanic and Atmospheric Administration seeks to correct and add new information about past North Atlantic hurricanes. It was started around 2000 to update HURDAT, the official hurricane database for the Atlantic Basin, which has become outdated since its creation due to various systematic errors introduced into the database over time. This effort has involved reanalyses of ship observations from the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) as well as reanalyses done by other researchers over the years. It has been ongoing as of 2024.
Traditionally, areas of tropical cyclone formation are divided into seven basins. These include the north Atlantic Ocean, the eastern and western parts of the northern Pacific Ocean, the southwestern Pacific, the southwestern and southeastern Indian Oceans, and the northern Indian Ocean. The western Pacific is the most active and the north Indian the least active. An average of 86 tropical cyclones of tropical storm intensity form annually worldwide, with 47 reaching hurricane/typhoon strength, and 20 becoming intense tropical cyclones, super typhoons, or major hurricanes.
The Hurricane Databases (HURDAT), managed by the National Hurricane Center (NHC), are two separate databases that contain details on tropical cyclones, that have occurred within the Atlantic Ocean and Eastern Pacific Ocean since 1851 and 1949 respectively.
The history of Atlantic tropical cyclone warnings details the progress of tropical cyclone warnings in the North Atlantic Ocean. The first service was set up in the 1870s from Cuba with the work of Father Benito Viñes. After his death, hurricane warning services were assumed by the US Army Signal Corps and United States Weather Bureau over the next few decades, first based in Jamaica and Cuba before shifting to Washington, D.C. The central office in Washington, which would evolve into the National Meteorological Center and the Weather Prediction Center, assumed the responsibilities by the early 20th century. This responsibility passed to regional hurricane offices in 1935, and the concept of the Atlantic hurricane season was established to keep a vigilant lookout for tropical cyclones during certain times of the year. Hurricane advisories issued every 12 hours by the regional hurricane offices began at this time.
A post-tropical cyclone is a former tropical cyclone that no longer possesses enough tropical qualities to be considered a tropical cyclone. The word may refer to a former tropical cyclone undergoing extratropical transition or a tropical cyclone degenerating into a remnant low. A tropical cyclone degenerating into a trough or wave, or having its low level circulation dissipate overland, lacks a cyclonic circulation and is referred as remnants instead of a post-tropical cyclone. However, post-tropical cyclones or remnants can continue producing high winds and heavy rains.
1 2 3 "Observations on Hurricanes". The Seaman's Practical Guide, for Barbadoes and the Leeward Islands; with Observations on the Islands From Blanco to the Rocas, on the Coast of La Guayra. London: Smith, Elder & Co. 1832. p.15.
↑ Dampier, William (1700). "Chapter VI: Of Storms". Voyages and Descriptions. Vol.2 (2nded.). London. p.68.
↑ Long, Edward (1784). "General Description of Jamaica". The History of Jamaica, or, General Survey of the Antient and Modern State. Vol.1. London: T. Lowndes. p.364.
↑ Beatson, Robert (1790). Naval and Military Memoirs of Great Britain, From the Year 1727, to the Present Time. Vol.3. London: J. Strachan. p.171.
↑ "The political History of Europe, for the Year 1782, Chapter IX". The Gentleman's and London Magazine, for January 1785. John Exshaw. January 1785. p.650.
↑ Campbell, John (1785). Lives of the British Admirals: Containing a New and Accurate Naval History, From the Earliest Periods. Vol.4. London. p.212.
↑ Vernon, Edward (1740). Britain's Mistakes in the Commencement and Conduct of the Present War. London: T. Cooper. p.18.
↑ Morse, Jedidiah (1819). "West-Indies". The American Universal Geography. Vol.1 (7thed.). Charlestown, Boston, Massachusetts: S. Etheridge. p.706.
↑ "Theory of Storms". The North American Review (Literature Review). 58 (123): 339. April 1844. JSTOR25099713.
↑ Rosser, W. H. (1876). "Hurricane Seasons and Storm Paths". The Law of Storms Considered Practically. London: Charles Wilson. p.90.
↑ "Hurricane Signals". Report of the Commissioner of Navigation (Report). Washington, D. C.: Government Printing Office. 1885. p.166.
↑ Pietruska, Jamie L. (2016). "Hurricanes, Crops, and Capital: The Meteorological Infrastructure of American Empire in the West Indies". The Journal of the Gilded Age and Progressive Era. 15 (4). Cambridge University Press: 418–445. doi:10.1017/S1537781416000256. S2CID164639962.
↑ Hayes, M. W. (1902). "Value of the Climate and Crop and Storm Warning Services of the Weather Bureau to the Industries of Cuba and Other Islands of the West Indies". In Alexander, William H. (ed.). Hurricanes: Especially Those of Porto Rico and St. Kitts. p.58 – via Google Books.
↑ Moore, Willis L. (1908). "List of Observing Stations and Changes Therin During 1906". Report of the Chief of the Weather Bureau 1906–1907. Washington, D. C.: United States Weather Bureau. p.7 – via Google Books.
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