In the south-west
Indian Ocean
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...
,
tropical cyclone
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 ...
s form south of the
equator
The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...
and west of
90° E to the coast of
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
.
Warnings and nomenclature
In 1946, Réunion's first airstrip opened, then called Gillot, and now called
Roland Garros Airport. In 1950, the first meteorological station on the island opened at the airport, operated by
Météo-France
Météo-France is the French national meteorological service.
Organisation
The organisation was established by decree in June 1993 and is a department of the Ministry of Transportation. It is headquartered in Paris but many domestic operatio ...
(MFR). The agency began publishing annual reviews in the
1962–63 season. Each year, the
Météo-France
Météo-France is the French national meteorological service.
Organisation
The organisation was established by decree in June 1993 and is a department of the Ministry of Transportation. It is headquartered in Paris but many domestic operatio ...
office (MFR) based on
Réunion
Réunion (; french: La Réunion, ; previously ''Île Bourbon''; rcf, label= Reunionese Creole, La Rényon) is an island in the Indian Ocean that is an overseas department and region of France. It is located approximately east of the island ...
island issues warnings on tropical cyclones within the basin, which is defined as the waters of the
Indian Ocean
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...
from the coast of Africa to 90°
E, south of the
equator
The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...
. The agency issues the warnings as part of its role as a
Regional Specialized Meteorological Center, designated as such in 1993 by the
World Meteorological Organization
The World Meteorological Organization (WMO) is a specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology and geophysics.
The WMO originated from the Internati ...
. Intensities are estimated through 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 ...
, which utilizes images from satellites by the American
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...
.
The
Joint Typhoon Warning Center
The Joint typhoon Warning Center (JTWC) is a joint United States Navy – United States Air Force command in Pearl Harbor, Hawaii. The JTWC is responsible for the issuing of tropical cyclone warnings in the North-West Pacific Ocean, South P ...
– a joint
United States Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
–
United States Air Force
The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...
task force – also issues tropical cyclone warnings for the region.
Wind estimates from Météo-France and most other basins throughout the world are
sustained over 10 minutes, while estimates from the United States-based Joint Typhoon Warning Center are sustained over 1 minute. 1-minute winds are about 1.12 times the amount of 10-minute winds.
If a tropical storm in the basin strengthens to attain 10 minute sustained winds of at least 118 km/h (74 mph), the MFR classifies it as a
tropical cyclone
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 ...
, equivalent to a
hurricane
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 ...
or
typhoon
A typhoon is a mature tropical cyclone that develops between 180° and 100°E in the Northern Hemisphere. This region is referred to as the Northwestern Pacific Basin, and is the most active tropical cyclone basin on Earth, accounting for a ...
(a use of "tropical cyclone" which is more restrictive than the usual definition).
History of the basin
The first storm in the MFR database of the basin originated on January 11, 1848. In January 1960, the first
named storm
Tropical cyclones and subtropical cyclones are named by various warning centers to simplify communication between forecasters and the general public regarding forecasts, watches and warnings. The names are intended to reduce confusion in the ...
was Alix, and each subsequent year had a list of storm names. Beginning in 1967, satellites helped locate cyclones in the basin, and in the following year, the MFR began estimating storm intensities from the satellite images. By 1977, the agency was 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 ...
on an unofficial basis, but officially adopted it in 1981. Originally, the basin only extended to 80° E, and while it was extended eastward to the current 90° E, a lack of satellite imagery initially made data uncertain east of 80° E. The World Meteorological Organization designated the MFR as a Regional Tropical Cyclones Advisory Centre in 1988, and upgraded it to a
Regional Specialized Meteorological Center in 1993. In May 1998, two Europe-based
Meteosat
The Meteosat series of satellites are geostationary meteorological satellites operated by EUMETSAT under the Meteosat Transition Programme (MTP) and the Meteosat Second Generation (MSG) program.
The MTP program was established to ensure the ope ...
satellites began providing complete coverage of the basin. On July 1, 2002, the MFR shifted the cyclone year to begin on this date and end on June 30 of the following year; previously, the cyclone year began on August 1 and ended on the subsequent July 31. In 2003, the MFR extended their area of warning responsibility to 40°
S, having previously been limited at 30° S.
During 2011, MFR started a reanalysis project of all tropical systems between 1978 and 1998, with methods such as a Dvorak technique reanalysis and use of microwave imagery.
Preliminary results from this reanalysis project include correcting an increasing trend in the number of very intense tropical cyclones in the basin since 1978.
This also revealed a seemingly systematic underestimation of tropical cyclone intensities in the past.
Statistics
From the
1980–81 to the
2010–11
1 (one, unit, unity) is a number representing a single or the only entity. 1 is also a numerical digit and represents a single unit of counting or measurement. For example, a line segment of ''unit length'' is a line segment of length 1. I ...
season, there was an average of 9.3 tropical storms each year in the basin. A tropical storm has 10 minute winds of at least 65 km/h (40 mph). There are an average of five storms that become tropical cyclones, which have 10 minute winds of at least 120 km/h (75 mph). As of 2002, there was an average of 54 days when tropical systems were active in the basin, of which 20 had
tropical cyclones active, or a system with winds of over 120 km/h (75 mph). The median start date for the season was November 17, and the median end date was April 20.
Climatology
Generally, the
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 oscil ...
does not cross into the
Mozambique Channel
The Mozambique Channel (french: Canal du Mozambique, mg, Lakandranon'i Mozambika, pt, Canal de Moçambique) is an arm of the Indian Ocean located between the Southeast African countries of Madagascar and Mozambique. The channel is about long ...
until December; as a result, storms rarely form there before that time.
From 1948 to 2010, 94 tropical systems developed in the small body of water, of which about half made
landfall. Occasionally, small storms form in the Mozambique Channel that resemble
Mediterranean tropical cyclone
Mediterranean tropical-like cyclones, often referred to as medicanes (a portmanteau of Mediterranean hurricanes) but sometimes also as Mediterranean cyclones or as Mediterranean hurricanes, are meteorological phenomena occasionally observed over ...
s or storms in the northeastern
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 ...
; these systems are well-organized but have weaker
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 convec ...
than typical tropical cyclones, and originate over cooler than normal
water temperatures of less than . A survey in 2004 conducted by weather expert Gary Padgett found meteorologists split whether these storms should be classified as tropical or
subtropical
The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...
.
In an average year, ten tropical depressions or storms strike Madagascar, and most generally do not cause much damage.
Occasionally, storms or their remnants enter the interior of southeastern Africa, bringing heavy rainfall to
Zimbabwe
Zimbabwe (), officially the Republic of Zimbabwe, is a landlocked country located in Southeast Africa, between the Zambezi and Limpopo Rivers, bordered by South Africa to the south, Botswana to the south-west, Zambia to the north, and Mozam ...
.
Seasons
Before 1900
1900–1950
1950–1959
1959
1960s
1970s
1980s
1990s
2000s
2010s
2020s
See also
*
Tropical cyclone
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 ...
*
Atlantic hurricane season
The Atlantic hurricane season is the period in a year from June through November when tropical cyclones form in the Atlantic Ocean, referred to in North American countries as hurricanes, tropical storms, or tropical depressions. In addition ...
*
Pacific hurricane season
A Pacific hurricane is a mature 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 regio ...
*
Pacific typhoon season
The following is a list of Pacific typhoon seasons. The seasons are limited to the north of the equator between the 100th meridian east and the 180th meridian (aka Prime Antimeridian).
Seasons Pre-1940
1940s
1950s
1960s
1970s
1980s
...
*
North Indian Ocean tropical cyclone
In the Indian Ocean north of the equator, tropical cyclones can form throughout the year on either side of India, although most frequently between April and June, and between October and December.
Sub-basins
The North Indian Ocean is the lea ...
*
Australian region tropical cyclone
*
South Pacific tropical cyclone
*
South Atlantic tropical cyclone
South Atlantic tropical cyclones are unusual weather events that occur in the Southern Hemisphere. Strong wind shear, which disrupts the formation of cyclones, as well as a lack of weather disturbances favorable for development in the South Atl ...
*
Mediterranean tropical-like cyclone
Mediterranean tropical-like cyclones, often referred to as medicanes (a portmanteau of Mediterranean hurricanes) but sometimes also as Mediterranean cyclones or as Mediterranean hurricanes, are meteorological phenomena occasionally observed over ...
Notes
References
{{DEFAULTSORT:List Of Southwest Indian Ocean Cyclone Seasons
Indian Ocean Southwest
Southwest Indian cyclone seasons