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The 1989–90 South-West Indian Ocean cyclone season was an average cyclone season, with nine named storms and five tropical cyclones – a storm attaining maximum sustained winds of at least . The season officially ran from November 1, 1989, to April 30, 1990. Storms were officially tracked by the Météo-France office (MFR) on Réunion while the Joint Typhoon Warning Center (JTWC) in an unofficial basis. The first storm, Cyclone Alibera, was the second longest-lasting tropical cyclone on record in the basin, with a duration of 22 days. Alibera meandered and changed directions several times before striking southeastern Madagascar on January 1, 1989, where it was considered the worst storm since 1925. The cyclone killed 46 people and left widespread damage. Only the final storm of the year – Severe Tropical Storm Ikonjo – also had significant impact on land, when it left $1.5 million in damage (1990 USD) in the Seychelles. Of the remaining storms, several passed near the Mascarene Islands but did not cause much impact. In early February, Severe Tropical Storm Cezera and Tropical Cyclone Dety were active at the same time and interacted with each other through the process of the Fujiwhara effect. Cyclone Gregoara was the strongest of the season, which originated as Cyclone Walter from the adjacent Australian basin. Gregoara attained peak winds of over the open waters of the Indian Ocean in March, although the JTWC considered Alibera to be stronger. In April, Moderate Tropical Storm Hanta approached the northwest coast of Madagascar, but dissipated over the Mozambique Channel. ==Season summary== ImageSize = width:1000 height:200 PlotArea = top:10 bottom:80 right:20 left:20 Legend = columns:3 left:30 top:58 columnwidth:270 AlignBars = early DateFormat = dd/mm/yyyy Period = from:01/12/1989 till:01/06/1990 TimeAxis = orientation:horizontal ScaleMinor = grid:black unit:month increment:1 start:01/12/1989 Colors = id:canvas value:gray(0.88) id:GP value:red id:TD value:rgb(0.38,0.73,1) legend:Tropical_Depression id:TS value:rgb(0,0.98,0.96) legend:Moderate_Tropical_Storm id:ST value:rgb(0.80,1,1) legend:Severe_Tropical_Storm id:TC value:rgb(1,1,0.80) legend:Tropical_Cyclone id:IT value:rgb(1,0.76,0.25) legend:Intense_Tropical_Cyclone id:VI value:rgb(1,0.38,0.38) legend:Very_Intense_Tropical_Cyclone Backgroundcolors = canvas:canvas BarData = barset:Hurricane bar:Month PlotData= barset:Hurricane width:11 align:left fontsize:S shift:(4,-4) anchor:till from:14/12/1989 till:07/01/1990 color:TC text:"Alibera (TC)" from:29/12/1989 till:09/01/1990 color:TC text:"Baomavo (TC)" from:31/01/1990 till:11/02/1990 color:ST text:"Cezera (STS)" from:02/02/1990 till:11/02/1990 color:TC text:"Dety (TC)" from:01/03/1990 till:08/03/1990 color:TC text:"Edisoana (TC)" from:07/03/1990 till:16/03/1990 color:TS text:"Felana (MTS)" barset:break from:13/03/1990 till:27/03/1990 color:IT text:"Walter-Gregoara (ITC)" from:11/04/1990 till:14/04/1990 color:TS text:"Hanta (MTS)" from:11/05/1990 till:21/05/1990 color:ST text:"Ikonjo (STS)" bar:Month width:5 align:center fontsize:S shift:(0,-20) anchor:middle color:canvas from:01/12/1989 till:01/01/1990 text:December from:01/01/1990 till:01/02/1990 text:January from:01/02/1990 till:01/03/1990 text:February from:01/03/1990 till:01/04/1990 text:March from:01/04/1990 till:01/05/1990 text:April from:01/05/1990 till:01/06/1990 text:May TextData = pos:(569,23) text:"(For further details, please see" pos:(713,23) text:"scales)" During the season, the Météo-France office (MFR) on Réunion island issued warnings in tropical cyclones within the basin. Using satellite imagery from National Oceanic and Atmospheric Administration, the agency estimated intensity through the Dvorak technique, and warned on tropical cyclones in the region from the coast of Africa to 90° E, south of the equator. At the time, the World Meteorological Organization recognized the MFR as a Regional Tropical Cyclone Advisory Centre, and would later label the agency as a Regional Specialized Meteorological Center in 1993. The Joint Typhoon Warning Center (JTWC), which is a joint United States Navy – United States Air Force task force, also issued tropical cyclone warnings for the southwestern Indian Ocean. The season's nine named storms and five tropical cyclones – a storm attaining maximum sustained winds of at least – is the same as the long term average for the basin. Operationally, the MFR considered the tropical cyclone year to begin on August 1 and continue to July 31 of the following year.〔 However, the JTWC began the year on July 1 and it lasted through June 30 of the following year.〔 The latter agency tracked two short-lived tropical cyclones in July 1989, labeling them Tropical Cyclone 01S and 02S, but they are not considered part of MFR's season.〔 After these early storms, another tropical depression formed east of Diego Garcia on September 21, classified as Tropical Cyclone 03S. Forming from the near-equatorial trough, the system moved generally to the southwest, dissipating on September 27 as it approached Mauritius.〔 In the next month, Tropical Cyclone 04S formed closer to Diego Garcia on October 11. The JTWC classified it as a tropical depression on October 13 but dropped advisories the next day. The system initially drifted to the south but later turned to the northwest, dissipating on October 17.〔 The final of a series of early tropical systems was a tropical depression that formed east of Diego Garcia on October 28. It moved southeastward, classified by the JTWC as Tropical Cyclone 05S on October 31. The agency briefly estimated peak winds of , making it a tropical storm, before the storm looped back to the west and dissipated on November 2.〔 Later, the precursor to Australian Tropical Cyclone Bessi was tracked in the eastern portion of the south-west Indian Ocean basin in the middle of April. The Australian Bureau of Meteorology (BOM) classified the system as a minimal tropical storm while still west of 90° E, although the MFR did not classify the system before it entered the Australian basin on April 15. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「1989–90 South-West Indian Ocean cyclone season」の詳細全文を読む スポンサード リンク
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