Intense Tropical Cyclone Enawo was the strongest

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. Depen ...

of the 2016–17 South-West Indian Ocean cyclone season. Enawo was the strongest tropical cyclone to strike

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

since Gafilo in 2004, killing 78 people and causing $400 million in damages. Forming as a moderate tropical storm on 3 March, Enawo initially drifted and intensified slowly. It strengthened into a tropical cyclone on 5 March and further an intense tropical cyclone on 6 March. Enawo made

landfall Landfall is the event of a storm moving over land after being over water. More broadly, and in relation to human travel, it refers to 'the first land that is reached or seen at the end of a journey across the sea or through the air, or the fact ...

over

Sava Region Sava is a region in northern Madagascar. Its capital is Sambava. Until 2009 Sava belonged to Antsiranana Province. The region is situated at the northern part of the east coast of Madagascar. It is bordered by the region Diana to the north, Sofi ...

on 7 March just after reaching peak intensity, and it emerged back into 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 t ...

as a post-tropical depression late on 9 March, before dissipating two days later. The most severe impacts were seen in the districts of

Antalaha Antalaha is an urban municipality in northern Madagascar. It belongs to the district of Antalaha, which is a part of Sava Region. The population of Antalaha was 67.888 in 2018. Antalaha has a maritime harbour. A local airport serves Antalaha. ...

and

Maroantsetra Maroantsetra , formerly Louisbourg, is a market town and domestic seaport in Analanjirofo Region, Madagascar, at the northern end of the Bay of Antongil. In 2005 it had a population of 42,529 people. History Maurice Benyovszky arrived in Maroant ...

Meteorological history

monsoon trough The monsoon trough is a portion of the Intertropical Convergence Zone in the Western Pacific,Bin WangThe Asian Monsoon.Retrieved 2008-05-03. as depicted by a line on a weather map showing the locations of minimum sea level pressure, and as such, ...

started to persist west of

Diego Garcia Diego Garcia is an island of the British Indian Ocean Territory, a disputed overseas territory of the United Kingdom. It is a militarised atoll just south of the equator in the central Indian Ocean, and the largest of the 60 small islands of ...

in late February 2017 as the

Madden–Julian oscillation The Madden–Julian oscillation (MJO) is the largest element of the intraseasonal (30- to 90-day) variability in the tropical atmosphere. It was discovered in 1971 by Roland Madden and Paul Julian of the American National Center for Atmospheric ...

(MJO) over the

grew more noticeable. On 2 March, a zone of disturbed weather formed within the area, although it was initially difficult to define a clear centre; later, 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 ...

(JTWC) issued a

Tropical Cyclone Formation Alert A Tropical Cyclone Formation Alert (TCFA) is a bulletin released by the U.S. Navy-operated Joint Typhoon Warning Center in Honolulu, Hawaii or the Fleet Weather Center in Norfolk, Virginia, warning of the possibility of a tropical cyclone formin ...

for the improving low-level structure and favourable environmental conditions. Only six hours after the system about north of

Mauritius Mauritius ( ; french: Maurice, link=no ; mfe, label= Mauritian Creole, Moris ), officially the Republic of Mauritius, is an island nation in the Indian Ocean about off the southeast coast of the African continent, east of Madagascar. It ...

intensifying to a tropical disturbance, Météo-France upgraded it to a moderate tropical storm at 06:00 UTC on 3 March with the name ''Enawo'' from the Mauritius Meteorological Services, because of the recent ASCAT-B data suggesting

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 ).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 ...

, the centre was located in the eastern part of deep

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 ...

. Enawo developed into a severe tropical storm at around 18:00 UTC on 4 March, displaying an impressive embedded centre pattern associated with extremely cold cloud tops. The JTWC indicated a system equivalent to Category 1 on the

Saffir–Simpson scale The Saffir–Simpson hurricane wind scale (SSHWS) classifies hurricanes—which in the Western Hemisphere are tropical cyclones that exceed the intensities of tropical depressions and tropical storms—into five categories distinguished b ...

at the same time. Météo-France upgraded Enawo to a tropical cyclone at 06:00 UTC on 5 March, after it resumed a west to west-southwest track steered by the mid-troposphere ridge south of

. Enawo formed a ragged eye soon afterward, thanks to favourable conditions of excellent outflow, weaker vertical wind shear, and warm

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; however, the strengthening phase was halted for a half of day owing to a possible

eyewall replacement cycle In meteorology, eyewall replacement cycles, also called concentric eyewall cycles, naturally occur in intense tropical cyclones, generally with winds greater than , or major hurricanes ( Category 3 or above). When tropical cyclones reach this int ...

. Enawo started to intensify again and developed a well-defined eye indicated by both of satellite and microwave imageries, prompting Météo-France upgrading the system to an intense tropical cyclone at 12:00 UTC based on the structural improvements. The JTWC reported that Enawo had become a Category 4-equivalent cyclone at 18:00 UTC, with one-minute maximum sustained winds at . Early on 7 March, cloud tops cooled again around the eye, despite the fluctuating eye definition. Enawo reached its peak intensity at 06:00 UTC on 7 March, with ten-minute maximum sustained winds at and the central pressure at 932 hPa (27.32 inHg). Soon after that, Enawo made landfall over the area between

and

Sambava Sambava is a city and commune (commune urbaine; mg, kaominina) at the east coast of northern Madagascar. It is the capital of Sambava District and Sava Region. The population of the commune was 84,039 in as of the 2018 commune census. Infrast ...

, Madagascar at around 09:30 UTC (12:30 EAT), becoming the strongest landfall to the country since Gafilo in 2004. The cyclone started to rapidly weaken due to land interaction with a cloud-filled eye and the warming cloud tops; the JTWC also issued a final warning later for the inland movement. After classified as an overland depression early on 8 March and moving further inland, it started to accelerated southwards the next day along the weakening mid-troposphere ridge on Madagascar, with deep convection rather far away from the ill-defined centre. Meanwhile, gale-force winds still maintained over the eastern coast throughout the inland period. Enawo emerged into the Indian Ocean late on 9 March and was considered as a post-tropical depression by Météo-France because of the asymmetric and shallow core. However, the JTWC started to issue a tropical cyclone warning on Enawo again due to a warm anomaly at 10 km altitude. Despite a final warning from the JTWC again for winds below gale-force a half of day later, Météo-France indicated that Ex-Enawo strengthened again during its

extratropical transition Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of ...

, according to data from ships. The system became fully extratropical soon afterward, before dissipating late on 11 March.

Preparations and impact

Madagascar

When Enawo attained intense tropical cyclone status, MFR warned of a significant storm surge of up to , declaring the storm to have become "very dangerous". Accordingly, Meteo Madagascar issued a red alert for several regions expected to be impacted by the storm. The National Bureau of Risk and Disaster Management advised the evacuation of low-lying areas and the acquisition of supplies in advance of the storm. The Piroi regional center of the

International Red Cross The International Committee of the Red Cross (ICRC; french: Comité international de la Croix-Rouge) is a humanitarian organization which is based in Geneva, Switzerland, and it is also a three-time Nobel Prize Laureate. State parties (signato ...

made preparations. Enawo made landfall halfway between the towns of

and

as an Intense Tropical Cyclone at approximately 09:30 UTC (12:30 a.m.

local time Local time is the time observed in a specific locality. There is no canonical definition. Originally it was mean solar time, but since the introduction of time zones it is generally the time as determined by the time zone in effect, with daylight s ...

) on 7 March. In the district of

, landslides and strong winds caused widespread infrastructural damage, which also rendered 500 people homeless. There, a landslide killed one adult and two children, in addition to injuring six others. The city of

was particularly hard hit, where the port became inaccessible and half the population was rendered homeless. Rice fields in

and

districts were submerged after heavy rain and suffered severe losses. The Lohoko River burst its banks near Farahalana, inundating part of the town. As of 17 March, 78 deaths have been reported across the country, with 18 other people reported missing. Total damages were estimated to be US$400 million, including $US207 million to the agricultural sector alone.

Réunion

Although the cyclone was not expected to bring direct impacts to Réunion, a storm surge warning was in effect for the northern part of the island due to swells of from the cyclone.

References

External links