Hurricane Danny was the first

major hurricane Major (commandant in certain jurisdictions) is a military rank of commissioned officer status, with corresponding ranks existing in many military forces throughout the world. When used unhyphenated and in conjunction with no other indicators ...

to develop between the

Lesser Antilles The Lesser Antilles ( es, link=no, Antillas Menores; french: link=no, Petites Antilles; pap, Antias Menor; nl, Kleine Antillen) are a group of islands in the Caribbean Sea. Most of them are part of a long, partially volcanic island arc bet ...

and

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since

Hurricane Julia The name Julia has been used for three tropical cyclones in the Atlantic Ocean and one subtropical medicane. In the Atlantic: * Hurricane Julia (2010) – Category 4 hurricane, churned across the open ocean without threatening land * Tropical ...

in 2010. The fourth tropical cyclone, and first hurricane of the

2015 Atlantic hurricane season The 2015 Atlantic hurricane season was the last of three consecutive below average Atlantic hurricane seasons. It produced twelve tropical cyclones, eleven named storms, four hurricanes, and two major hurricanes. The Accumulated Cyclone Energy ...

, Danny originated from a well-defined tropical wave that emerged over the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

on August 14. Traveling west, the system gradually coalesced into a

tropical depression 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 and squalls. Depend ...

by August 18. After becoming a tropical storm later that day, dry air slowed further development. On August 20–21, dry air became removed from the system, and Danny

rapidly intensified In meteorology, rapid intensification is a situation where a tropical cyclone intensifies dramatically in a short period of time. The United States National Hurricane Center defines rapid intensification as an increase in the maximum sustained wi ...

into a Category 3 hurricane on the Saffir–Simpson hurricane wind scale. Its peak was short-lived as

wind shear Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizont ...

soon increased and prompted significant weakening. Degrading to a tropical storm by August 23, Danny approached the

. It degenerated into a tropical wave as it traversed the archipelago on August 24 and was last noted over Hispaniola the following day. The hurricane prompted the issuance of several

tropical storm warning Tropical cyclone warnings and watches are alerts issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of tropical storm or hurricane intensity. They are notices to the local popul ...

s for the Lesser Antilles. Leeward Islands Air Transport cancelled 40 flights and sandbags were distributed in the

United States Virgin Islands The United States Virgin Islands,. Also called the ''American Virgin Islands'' and the ''U.S. Virgin Islands''. officially the Virgin Islands of the United States, are a group of Caribbean islands and an unincorporated and organized territory ...

. Danny ultimately only brought light rain to the region, with its effects considered beneficial due to a severe drought.

Meteorological history

On August 14, 2015, a well-defined tropical wave, accompanied by significant surface

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

falls, traversed

and emerged over the Atlantic Ocean that evening. A broad surface low developed along the wave on August 15. Embedded within

monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal osci ...

flow, various environmental factors enabled gradual

development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking, development phase, including finance and budgeting *Development (music), the process thematic material is reshaped * Photograph ...

of the disturbance, including low

, above-average

sea surface temperature Sea surface temperature (SST), or ocean surface temperature, is the ocean temperature close to the surface. The exact meaning of ''surface'' varies according to the measurement method used, but it is between and below the sea surface. Air mas ...

s, moderate moisture content, and favorable diffluence. A subtropical ridge to the north steered the system generally west-northwest throughout its entire existence. On August 17, the surface low became increasingly defined and

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the conve ...

more persistent. It subsequently acquired enough organization to be classified a tropical depression at 06:00 UTC on August 18. At this time, it was situated about 825 mi (1,325 km) west-southwest of Praia, Cape Verde. The depression traversed a region generally favoring further development; however, occasional intrusions of dry air from the Saharan Air Layer initially inhibited rapid growth. The system reached tropical storm-status by 12:00 UTC on August 18—based on satellite intensity estimates using the

Dvorak Technique The Dvorak technique (developed between 1969 and 1984 by Vernon Dvorak) is a widely used system to estimate tropical cyclone intensity (which includes tropical depression, tropical storm, and hurricane/typhoon/intense tropical cyclone intensitie ...

—and it was assigned the name ''Danny'' accordingly. Banding features developed around the circulation early on August 19. A temporary intrusion of dry air caused convection to collapse later that day, but cloud cover redeveloped within hours. Improving upper-level outflow supported the formation of a

central dense overcast The central dense overcast, or CDO, of a tropical cyclone or strong subtropical cyclone is the large central area of thunderstorms surrounding its circulation center, caused by the formation of its eyewall. It can be round, angular, oval, or irr ...

and a wide- eye soon developed. Danny reached hurricane-strength by 12:00 UTC on August 20, by which time it was located 1,095 mi (1,760 km) east of the

Windward Islands french: Îles du Vent , image_name = , image_caption = ''Political'' Windward Islands. Clockwise: Dominica, Martinique, Saint Lucia, Saint Vincent and the Grenadines, and Grenada. , image_alt = , locator_map = , location = Caribbean Sea No ...

. A trough over the mid-Atlantic weakened the subtropical ridge and caused the hurricane to move at a relatively slow pace of . ISS-44 Hurricane Danny

An unusually small hurricane, with

gale A gale is a strong wind; the word is typically used as a descriptor in nautical contexts. The U.S. National Weather Service defines a gale as sustained surface winds moving at a speed of between 34 and 47 knots (, or ). Danny was prone to significant fluctuations in intensity, making forecasts particularly difficult. Indeed, the storm soon underwent an unpredicted period of

rapid intensification In meteorology, rapid intensification is a situation where a tropical cyclone intensifies dramatically in a short period of time. The United States National Hurricane Center defines rapid intensification as an increase in the maximum sustained wi ...

aided by nearly non-existent upper-level wind shear. Low-level moisture wrapped around the circulation during this phase, mitigating the influence of the Saharan air layer. Danny achieved its peak intensity around 12:00 UTC on August 21 as a Category 3 hurricane on the Saffir–Simpson hurricane wind scale;

maximum sustained wind The maximum sustained wind associated with a tropical cyclone is a common indicator of the intensity of the storm. Within a mature tropical cyclone, it is found within the eyewall at a distance defined as the radius of maximum wind, or RMW. Unl ...

s were estimated at 125 mph (205 km/h) alongside a

barometric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, 7 ...

of 960

mbar The bar is a metric unit of pressure, but not part of the International System of Units (SI). It is defined as exactly equal to 100,000 Pa (100 kPa), or slightly less than the current average atmospheric pressure on Earth at sea lev ...

(hPa; ). Shortly thereafter, increasing shear and dry air initiated a rapid weakening phase. The storm's eye became obscured by clouds and disappeared from satellite image late on August 21. Throughout August 22, Danny's structure deteriorated with its surface and mid-level circulations becoming tilted with height due to the shear. The surface low soon became exposed with convection displaced to the northeast, and Danny weakened to a tropical storm by 00:00 UTC on August 23. The storm briefly leveled off in intensity somewhat later that day, with its circulation back under convection; intense

lightning Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an avera ...

was observed near the cyclone's center. Late on August 23, Danny's structure began degrading once more with its circulation becoming significantly displaced from the remaining ragged convection. Early on August 24, hurricane hunters struggled to find a circulation center as Danny neared the

, and the system weakened to a tropical depression by 12:00 UTC as it passed between Guadeloupe and Dominica. Hours later it degenerated into a tropical wave, marking its dissipation as a tropical cyclone. The remnants of Danny continued to the west-northwest for another day and were last noted over Hispaniola.

Preparations and impact

On August 22, governments across the

issued tropical storm watches. The islands of Antigua,

Anguilla Anguilla ( ) is a British Overseas Territory in the Caribbean. It is one of the most northerly of the Leeward Islands in the Lesser Antilles, lying east of Puerto Rico and the Virgin Islands and directly north of Saint Martin. The terr ...

Barbuda Barbuda (), is an island located in the eastern Caribbean forming part of the sovereign state of Antigua and Barbuda. It is located north of the island of Antigua and is part of the Leeward Islands of the West Indies. The island is a popula ...

, Montserrat,

Nevis Nevis is a small island in the Caribbean Sea that forms part of the inner arc of the Leeward Islands chain of the West Indies. Nevis and the neighbouring island of Saint Kitts constitute one country: the Federation of Saint Kitts and ...

Saba Saba may refer to: Places * Saba (island), an island of the Netherlands located in the Caribbean Sea * Şaba (Romanian for Shabo), a town of the Odesa Oblast, Ukraine * Sabá, a municipality in the department of Colón, Honduras * Saba (river), ...

, St. Eustatius, and St. Kitts were placed under a

the following day. These advisories were discontinued following Danny's degradation to a tropical depression on August 24. Leeward Islands Air Transport cancelled 40 flights across the eastern Caribbean due to the hurricane and cruise ships altered their courses. Although members of the Haiti Office of Civil Protection issued an official statement to residents saying Danny was not a threat to the country, they convened to discuss potential preparations and the status of emergency supplies. Officials in the

distributed sandbags and opened shelters. Météo-France issued an "orange" alert for Guadeloupe

Saint Barthélemy Saint Barthélemy (french: Saint-Barthélemy, ), officially the Collectivité territoriale de Saint-Barthélemy, is an overseas collectivity of France in the Caribbean. It is often abbreviated to St. Barth in French, and St. Barts in English ...

, and Saint Martin, advising residents about heavy rain and strong winds. Officials in Guadeloupe shut down several roads a precautionary measure. The expected rainfall was welcomed across the entire affected region, which was suffering from a severe drought. About of rain fell in Dominica, leading to minor rockslides, and was observed in Antigua. Some disruption to electrical and water supplies occurred on Guadeloupe. Rainfall was less than expected across Puerto Rico, with most areas receiving less than ; a peak value of was observed in Naguabo. The Carraízo Dam, then at a critically low , received . Though relatively light, the accumulations increased the water level by . Similarly, water levels at the Fajardo Dam rose by . Just a few days after Danny,

Tropical Storm Erika Tropical Storm Erika was one of the deadliest and most destructive natural disasters in Dominica since Hurricane David in 1979. The fifth named storm of the 2015 Atlantic hurricane season, Erika developed from a westward-moving tropical wa ...

brought devastating floods to Dominica, killing 30 people and wrecking tremendous damage. Other Caribbean islands received additional rainfall from the storm.

Notes

References

External links

The National Hurricane Center's advisory archive
of Hurricane Danny * for Hurricane Danny {{DEFAULTSORT:Danny (2015) 2015 Atlantic hurricane season Cape Verde hurricanes Category 3 Atlantic hurricanes Hurricanes in Antigua and Barbuda Hurricanes in the British Virgin Islands Hurricanes in Dominica Hurricanes in Guadeloupe Hurricanes in the United States Virgin Islands 2015 in Antigua and Barbuda 2015 in the British Virgin Islands 2015 in Dominica 2015 in Guadeloupe 2015 in the United States Virgin Islands 2015 in Saba (island) 2015 in Sint Eustatius August 2015 events August 2015 events in the United States Tropical cyclones in 2015

Meteorological history

Preparations and impact

See also

Notes

References

External links