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Atlantic hurricane season

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The Atlantic hurricane season is a specific period each year when tropical or subtropical cyclones are most likely to form. This period occurs in the North Atlantic Ocean and is defined by convention to cover the months of highest tropical cyclogenesis. Cyclogenesis is the process where a storm system begins to develop. While these storms are most common during the official season, they can actually form at any time of the year. The current official season runs from June 1 to November 30. This six-month window contains over 97 percent of all Atlantic tropical cyclone activity.

1851-2017 Atlantic hurricanes and tropical storms by month
1851-2017 Atlantic hurricanes and tropical storms by month

Storm activity follows a predictable cycle driven by temperature differences. Climatological peak activity usually occurs in the late summer months. This happens because the difference between air temperature and sea surface temperatures is at its greatest. The peak of the season typically spans from late August through September. Scientists identify September 10 as the midpoint of this peak period. When these storms reach tropical storm intensity, they are given names from a predetermined list. On average, a season produces 14 named storms. Out of these, about 7 become hurricanes and 3 become major hurricanes. Major hurricanes are defined as Category 3 or higher on the Saffir-Simpson scale.

Historical views on when the season begins have changed many times. In 1700, the naturalist William Dampier noted that Caribbean hurricanes were expected in July, August, and September. During the 18th century, mariners often used a period from July to the end of October. This was based on how often storms hit Caribbean islands and the paths of ships. In his writings, geographer Jedidiah Morse defined the season as August through October. Meteorologist William Charles Redfield suggested a timeframe from July 15 to October 15. He noted that insurance underwriters often raised premiums during this specific window. Later, in 1876, W. H. Rosser described July through October as the "true hurricane season of the West Indies."

As weather science grew, the U.S. Weather Bureau began to formalize the season for safety. In 1898, the bureau established a network of weather observatories in the Caribbean. These sites telegraphed daily weather observations at 8 a.m. to Havana, Cuba. At that time, the season was defined as June through October. By 1917, increased funding allowed these stations to report weather twice a day. The season was expanded to cover June 1 through November 30 in that same year. In 1935, the concept of an official season became more practical with the creation of hurricane circuits. These were dedicated wire circuits set up along the Gulf and Atlantic coasts to monitor activity.

John Thomas Serres - The wreck of the H.M.S. Deal Castle off Puerto Rico, in the hurricane of 1780 with the crew escaping on a raft
John Thomas Serres - The wreck of the H.M.S. Deal Castle off Puerto Rico, in the hurricane of 1780 with the crew escaping on a raft

Modern tracking relies on advanced technology and official agencies. The National Hurricane Center (NHC) maintains the current six-month schedule established in 1965. Before continuous satellite surveillance, hurricane reconnaissance planes flew routine missions to find storms. Today, hurricane hunter aircraft fly into specific storm areas identified by satellite imagery. The NHC also issues a Tropical Weather Outlook to identify areas of concern. In 2021, the World Meteorological Organization recommended that the NHC assess moving the start date to May 15. This was suggested because storms have frequently formed before the June 1 start date. Currently, the NHC has begun issuing routine weather outlooks starting on May 15.

1915 Galveston hurricane partial weather map Aug 13 1915 8 AM CT
1915 Galveston hurricane partial weather map Aug 13 1915 8 AM CT

Scientists use a massive database called HURDAT to study these events. HURDAT is the North Atlantic hurricane database for the Atlantic, Gulf of Mexico, and Caribbean. It was originally created in the 1960s to support the Apollo space program. Researchers use this data for climate change studies and risk assessments. The database is updated annually to reflect the most recent season. Since 2001, experts have been working on a re-analysis project to fix older data. This project has added tracks for years between 1851 and 1885. In 2002, researchers even upgraded Hurricane Andrew to a Category 5 in the records.

Adjusted Tropical Storm Count
Adjusted Tropical Storm Count

Extreme weather records show how much these seasons can vary. The 2020 season was the most active on record with 30 named tropical cyclones. However, the 2005 season holds the record for the most hurricanes, with 15. In contrast, 1914 was the least active season, with only one known tropical cyclone. Understanding these patterns is vital for maritime and naval logistics. Historically, Admiral Edward Vernon noted that August and September were vulnerable months for ships. He argued that fleets should depart Great Britain in late summer to avoid storms. Today, this knowledge helps businesses and emergency managers prepare for the unpredictable nature of the Atlantic.

1851-2017 Atlantic hurricanes and tropical storms by month
1851-2017 Atlantic hurricanes and tropical storms by month
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1851-2017 Atlantic hurricanes and...
File:John Thomas Serres - The wreck of the H.M.S. Deal Castle off Puerto Rico, in the hurricane of 1780 with the crew escaping on a raft.jpg
John Thomas Serres - The wreck of the...
File:1915 Galveston hurricane partial weather map Aug 13 1915 8 AM CT.png
1915 Galveston hurricane partial weather...
File:Adjusted Tropical Storm Count.png
Adjusted Tropical Storm Count.png
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