Hurricane Alley

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Atlantic hurricane tracks since 1851. Atlantic hurricane tracks.jpg
Atlantic hurricane tracks since 1851.

Hurricane Alley is an area of warm water in the Atlantic Ocean stretching from the west coast of northern Africa to the east coast of Central America and Gulf Coast of the Southern United States. Many hurricanes form within this area. The sea surface temperature of the Atlantic in Hurricane Alley has grown slightly warmer over the past decades [1] . A particularly warm summer in 2005 led climate scientists to begin studying whether this trend would lead to an increase in hurricane activity. [2] See Effects of Climate Change below.

Atlantic Ocean Ocean between Europe, Africa and the Americas

The Atlantic Ocean is the second largest of the world's oceans, with an area of about 106,460,000 square kilometers. It covers approximately 20 percent of the Earth's surface and about 29 percent of its water surface area. It separates the "Old World" from the "New World".

Central America central geographic region of the Americas

Central America is located on the southern tip of North America, or is sometimes defined as a subcontinent of the Americas, bordered by Mexico to the north, Colombia to the southeast, the Caribbean Sea to the east, and the Pacific Ocean to the west and south. Central America consists of seven countries: Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama. The combined population of Central America has been estimated to be 41,739,000 and 42,688,190.

Gulf Coast of the United States Coastline in the United States

The Gulf Coast of the United States is the coastline along the Southern United States where they meet the Gulf of Mexico. The coastal states that have a shoreline on the Gulf of Mexico are Texas, Louisiana, Mississippi, Alabama, and Florida, and these are known as the Gulf States.


How hurricanes form

The warm waters of Hurricane Alley are depicted in orange Hurricane Alley.jpg
The warm waters of Hurricane Alley are depicted in orange

Hurricanes form over tropical waters in areas of high humidity, light winds, and warm sea surface temperatures. These areas which were described above are usually between the latitudes of 8° and 20° north. [3] The perfect temperature for a hurricane is approximately 26 °C. This temperature has been set as a standard. If the water is colder the hurricane will most likely weaken, but if the waters are warmer rapid growth can occur. [4]

The area between 10° and 20°N create the most hurricanes in a given season because of the warmer temperatures. Hurricanes do not form outside this range because the Coriolis effect is not strong enough to create the tight circulation needed and above this range the temperatures are too cool. [5] The waters are only at the necessary temperatures from July until Mid-October. In the Atlantic this is the height of the season.

Atlantic hurricane season tropical cyclone season

The Atlantic hurricane season is the period in a year when hurricanes usually form in the Atlantic Ocean. Tropical cyclones in the North Atlantic are called hurricanes, tropical storms, or tropical depressions. In addition, there have been several storms over the years that have not been fully tropical and are categorized as subtropical depressions and subtropical storms. Even though subtropical storms and subtropical depressions are not technically as strong as tropical cyclones, the damages can still be devastating.

Since hurricanes rely on sea surface temperature, sometimes an active season in the beginning becomes quiet later. This is because the hurricanes are so strong that they churn the waters and bring colder waters up from the deep. This creates an area of the sea the size of the hurricane, which has cooler waters, which can be 5-10 °C lower than before the hurricane. When a new hurricane moves over the cooler waters they have no fuel to continue to thrive, so they weaken or even die out. [6]

Sea surface temperature Water temperature close to the oceans surface

Sea surface temperature (SST) is the water temperature close to the ocean's surface. The exact meaning of surface varies according to the measurement method used, but it is between 1 millimetre (0.04 in) and 20 metres (70 ft) below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a short distance of the shore. Localized areas of heavy snow can form in bands downwind of warm water bodies within an otherwise cold air mass. Warm sea surface temperatures are known to be a cause of tropical cyclogenesis over the Earth's oceans. Tropical cyclones can also cause a cool wake, due to turbulent mixing of the upper 30 metres (100 ft) of the ocean. SST changes diurnally, like the air above it, but to a lesser degree. There is less SST variation on breezy days than on calm days. In addition, ocean currents such as the Atlantic Multidecadal Oscillation (AMO), can effect SST's on multi-decadal time scales, a major impact results from the global thermohaline circulation, which affects average SST significantly throughout most of the world's oceans.

Effects of climate change

The relationship of "hurricane alley" to climate change is unclear. Recent scientific evidence suggests that hurricane intensity may be increasing due to warmer tropical sea surface temperature, but the connection to Atlantic hurricane frequency is less conclusive. [7] There is a debate as to whether climate change is causing more severe storms, but more research is needed into hurricane dynamics.

Climate change Change in the statistical distribution of weather patterns for an extended period

Climate change occurs when changes in Earth's climate system result in new weather patterns that last for at least a few decades, and maybe for millions of years. The climate system is comprised of five interacting parts, the atmosphere (air), hydrosphere (water), cryosphere, biosphere, and lithosphere. The climate system receives nearly all of its energy from the sun, with a relatively tiny amount from earth's interior. The climate system also gives off energy to outer space. The balance of incoming and outgoing energy, and the passage of the energy through the climate system, determines Earth's energy budget. When the incoming energy is greater than the outgoing energy, earth's energy budget is positive and the climate system is warming. If more energy goes out, the energy budget is negative and earth experiences cooling.

According to an Azores High hypothesis of geographer Kam-biu Liu, an anti-phase pattern is expected to exist between the Gulf of Mexico coast and the North American Atlantic coast. During the quiescent periods (3000–1400 BC, and 1000 AD to present), a more northeasterly position of the Azores High would result in more hurricanes being steered towards the Atlantic coast. During the hyperactive period (1400 BC to 1000 AD), more hurricanes were steered towards the Gulf coast as the Azores High was shifted to a more southwesterly position near the Caribbean. [8] [9] Such a displacement of the Azores High is consistent with paleoclimatic evidence that shows an abrupt onset of a drier climate in Haiti around 3200 years BP, [10] and a change towards more humid conditions in the Great Plains during the late-Holocene as more moisture was pumped up the Mississippi Valley through the Gulf coast. Preliminary data from the northern Atlantic coast seem to support the Azores High hypothesis. A 3,000-year proxy record from a coastal lake in Cape Cod suggests that hurricane activity has increased significantly during the past 500–1,000 years, just as the Gulf coast was amid a quiescent period of the last millennium.[ citation needed ]

Azores High

The Azores High also known as North Atlantic (Subtropical) High/Anticyclone or the Bermuda-Azores High, is a large subtropical semi-permanent centre of high atmospheric pressure typically found south of the Azores in the Atlantic Ocean, at the Horse latitudes. It forms one pole of the North Atlantic oscillation, the other being the Icelandic Low. The system influences the weather and climatic patterns of vast areas of North Africa and southern Europe, and to a lesser extent, eastern North America. The aridity of the Sahara Desert and the summer drought of the Mediterranean Basin is due to the large-scale subsidence and sinking motion of air in the system. In its summer position, the high is centered near Bermuda, and creates a southwest flow of warm tropical air toward the East Coast of the United States. In summer, the Azores-Bermuda High is strongest. The central pressure hovers around 1024 mbar (hPa).

Gulf of Mexico An Atlantic Ocean basin extending into southern North America

The Gulf of Mexico is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. The U.S. states of Texas, Louisiana, Mississippi, Alabama, and Florida border the Gulf on the north, which are often referred to as the "Third Coast", in comparison with the U.S. Atlantic and Pacific coasts.

Haiti country in the Caribbean

Haiti, officially the Republic of Haiti and formerly called Hayti, is a country located on the island of Hispaniola, east of Cuba in the Greater Antilles archipelago of the Caribbean Sea. It occupies the western three-eighths of the island, which it shares with the Dominican Republic. Haiti is 27,750 square kilometres (10,714 sq mi) in size and has an estimated 10.8 million people, making it the most populous country in the Caribbean Community (CARICOM) and the second-most populous country in the Caribbean as a whole.

Related Research Articles

The North Atlantic Oscillation (NAO) is a weather phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level (SLP) between the Icelandic Low and the Azores High. Through fluctuations in the strength of the Icelandic low and the Azores high, it controls the strength and direction of westerly winds and location of storm tracks across the North Atlantic. It is part of the Arctic oscillation, and varies over time with no particular periodicity.

Thermohaline circulation A part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes

Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, factors which together determine the density of sea water. Wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins. While the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth's oceans a global system. On their journey, the water masses transport both energy and mass of substances around the globe. As such, the state of the circulation has a large impact on the climate of the Earth.

1966 Atlantic hurricane season hurricane season in the Atlantic Ocean

The 1966 Atlantic hurricane season featured the tropical cyclone with the longest track in the Atlantic basin – Hurricane Faith. Also during the year, the Miami, Florida Weather Office was re-designated the National Hurricane Center. 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. It was a near average season in terms of tropical storms, with a total of 11 named storms. The first system, Hurricane Alma, developed over eastern Nicaragua on June 4. Alma brought severe flooding to Honduras and later to Cuba, after crossing the western Caribbean Sea. The storm also brought relatively minor impact to the Southeastern United States. Alma caused 91 deaths and about $210.1 million (1966 USD) in damage.

Cape Verde hurricane

A Cape Verde hurricane, or Cabo Verde hurricane is an Atlantic hurricane that originates at low-latitude in the deep tropics from a tropical wave that has passed over or near the Cape Verde islands after exiting the coast of West Africa. The average hurricane season has about two Cape Verde hurricanes, which are often the largest and most intense storms of the season due to having plenty of warm open ocean over which to develop before encountering land or other factors prompting weakening. A good portion of Cape Verde storms are large, and some, such as Hurricane Ivan and Hurricane Irma, have set various records. Most of the longest-lived tropical cyclones in the Atlantic basin are Cape Verde hurricanes. While many move harmlessly out to sea, some move across the Caribbean sea and into the Gulf of Mexico, becoming damaging storms for Caribbean nations, Central America, Mexico, Bermuda, the United States, and occasionally even Canada. Research projects since the 1970s have been launched to understand the formation of these storms.

2006 Atlantic hurricane season Summary of the relevant tropical storms

The 2006 Atlantic hurricane season was the least active since 1997 as well as 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 2005, forecasters predicted that the 2006 season would be only slightly less active. Instead 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.

Paleotempestology The study of past tropical cyclone activity using geological proxies and historical documents

Paleotempestology is the study of past tropical cyclone activity by means of geological proxies as well as historical documentary records. The term was coined by Kerry Emanuel.

Loop Current A warm ocean current that flows northward between Cuba and the Yucatán Peninsula into the Gulf of Mexico, loops east and south and exits to the east through the Florida Straits to join the Gulf Stream

A parent to the Florida Current, the Loop Current is a warm ocean current that flows northward between Cuba and the Yucatán Peninsula, moves north into the Gulf of Mexico, loops east and south before exiting to the east through the Florida Straits and joining the Gulf Stream. The Loop Current is an extension of the western boundary current of the North Atlantic subtropical gyre. Serving as the dominant circulation feature in the Eastern Gulf of Mexico, the Loop Currents transports between 23 and 27 sverdrups and reaches maximum flow speeds of from 1.5 to 1.8 meters/second.

Tropical cyclone Is a rotating storm system

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. 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".

Tropical cyclone observation

Tropical cyclone observation has been carried out over the past couple of centuries in various ways. The passage of typhoons, hurricanes, as well as other tropical cyclones have been detected by word of mouth from sailors recently coming to port or by radio transmissions from ships at sea, from sediment deposits in near shore estuaries, to the wiping out of cities near the coastline. Since World War II, advances in technology have included using planes to survey the ocean basins, satellites to monitor the world's oceans from outer space using a variety of methods, radars to monitor their progress near the coastline, and recently the introduction of unmanned aerial vehicles to penetrate storms. Recent studies have concentrated on studying hurricane impacts lying within rocks or near shore lake sediments, which are branches of a new field known as paleotempestology. This article details the various methods employed in the creation of the hurricane database, as well as reconstructions necessary for reanalysis of past storms used in projects such as the Atlantic hurricane reanalysis.

Tropical cyclone basins area of tropical cyclone formation

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.

Climate of the United States

The climate of the United States varies due to differences in latitude, and a range of geographic features, including mountains and deserts. Generally, on the mainland, the climate of the U.S. becomes warmer the further south one travels, and drier the further west, until one reaches the West Coast.

Climate of the Tampa Bay area

The Tampa Bay area has a humid subtropical climate. There are two basic seasons in the Tampa Bay area, a hot and wet season from May through October, and a mild and dry season from November through April.

Warm core ring A type of mesoscale eddy which breaks off from a warm ocean current. The ring is an independent circulatory system of warm water which can persist for several months

A warm core ring is a type of mesoscale eddy which breaks off from an ocean current, e.g. the Gulf Stream or the Kuroshio Current. The ring is an independent circulatory system of warm water which can persist for several months. The rest of this article will use the Gulf Stream by way of an example but these mesoscale eddies also form in most powerful ocean currents, such as the Kuroshio or Agulhas currents.

Tropical cyclones and climate change

Tropical cyclones and climate change concerns how tropical cyclones have changed, and are expected to further change, under global warming. The topic receives considerable attention from climate scientists who study the connections between storms and climate, and notably since 2005 makes news during active storm seasons.

1872 Atlantic hurricane season hurricane season in the Atlantic Ocean

The 1872 Atlantic hurricane season was quiet, lasting from mid-summer through mid-autumn. There were five tropical cyclones, of which four attained hurricane status. However, in the absence of modern satellite and other remote-sensing technologies, only storms that affected populated land areas or encountered ships at sea were recorded, so the actual total could be higher. An undercount bias of zero to six tropical cyclones per year between 1851 and 1885 and zero to four per year between 1886 and 1910 has been estimated. Of the known 1872 cyclones, significant changes were made to the tracks of Hurricane Two and Hurricane Four in 1995 by Jose Fernandez-Partagas and Henry Diaz, who also proposed smaller changes to the known track of Hurricane Three. Further analysis, in 2003, revised the track of Hurricane Five.

Meteorological history of Hurricane Sandy

Hurricane Sandy was the fourth-costliest Atlantic hurricane on record. It lasted for over a week in late October-early November 2012. Classified as the eighteenth named storm, tenth hurricane, and second major hurricane of the annual hurricane season, Sandy originated from a tropical wave on October 22. Performing a small loop over the central Caribbean Sea, the system intensified into a tropical storm a day later and became the final hurricane of the season before briefly coming ashore the coast of Jamaica on October 24. After emerging between Jamaica and Cuba, Sandy began a period of rapid intensification into a Category 3 hurricane on the Saffir–Simpson hurricane wind scale, with maximum sustained winds of 115 mph (185 km/h). It made landfall at this intensity near Santiago de Cuba on October 25.

Climate of Nova Scotia

Nova Scotia lies in the mid-temperate zone and, although the province is almost surrounded by water, the climate is closer to continental rather than maritime. The temperature extremes of the continental climate are moderated by the ocean.


  1. Goudzari, Sara (May 2, 2006). "Hurricane Alley Heats Up". LiveScience. Retrieved 9 September 2008.
  2. "Hurricane Alley Heats Up". National Aeronautics and Space Administration. August 9, 2005. Retrieved 9 September 2008.
  3. Steve Graham; Holli Riebeek (1 November 2006). "Hurricanes: The Greatest Storms on Earth". NASA . Retrieved 29 July 2013.
  4. "Seeing into the Heart of a Hurricane". Earth Observatory.
  5. "NWS JetStream - Tropical Cyclone Introduction". National Weather Service.
  6. "Seeing into the Heart of a Hurricane". Earth Observatory.
  7. "Hurricanes and Climate". Hurricanes: Science and Society. University of Rhode Island.
  8. Liu, Kam-biu (1999). Millennial-scale variability in catastrophic hurricane landfalls along the Gulf of Mexico coast. 23d Conf. on Hurricanes and Tropical Meteorology. Dallas, TX: Amer. Meteor. Soc. pp. 374–377.
  9. Liu, Kam-biu; Fearn, Miriam L. (2000). "Reconstruction of Prehistoric Landfall Frequencies of Catastrophic Hurricanes in Northwestern Florida from Lake Sediment Records". Quaternary Research. 54 (2): 238–245. Bibcode:2000QuRes..54..238L. doi:10.1006/qres.2000.2166.
  10. Higuera-Gundy, Antonia; et al. (1999). "A 10,300 14C yr Record of Climate and Vegetation Change from Haiti". Quaternary Research. 52 (2): 159–170. Bibcode:1999QuRes..52..159H. doi:10.1006/qres.1999.2062.

Further reading

See also