1997-98 South-West Indian Ocean cyclone season
Encyclopedia
The 1997–98 South-West Indian Ocean cyclone season was an event in the annual cycle of tropical cyclone
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...

 formation. It ran from November 15, 1997 to April 30, 1998, except for Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...

 and the Seychelles
Seychelles
Seychelles , officially the Republic of Seychelles , is an island country spanning an archipelago of 115 islands in the Indian Ocean, some east of mainland Africa, northeast of the island of Madagascar....

, where it ran until May 15. These dates conventionally delimit the period of each year when most tropical cyclones form in the basin, which is west of 90°E
90th meridian east
The meridian 90° east of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Asia, the Indian Ocean, the Southern Ocean, and Antarctica to the South Pole.The Ninety East Ridge is named after the meridian....

 and south of the Equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

. Tropical cyclones in this basin are monitored by the Regional Specialised Meteorological Centre in Réunion
Réunion
Réunion is a French island with a population of about 800,000 located in the Indian Ocean, east of Madagascar, about south west of Mauritius, the nearest island.Administratively, Réunion is one of the overseas departments of France...

.

Tropical Depression A1

The first advisory by the Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...

 was released on January 18, while the cyclone was inland over Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...

. Some ships reported gale-force winds from the center and was forecast to intensify. By 1200 UTC January 18, winds had decreased to 35 mph (55 km/h) and became a tropical low. The next day, the low moved southward and started to strengthen again to a 40 mph (60 km/h) minimal tropical storm. The low turned eastsouthward and scraped the Mozambique coastline and re-entered the channel. Even though the low was over open waters, the system did not strengthen and the JTWC discontinued warnings on January 23. Torrential rains poured in Mozambique and Malawi, which destroyed crops and flooded villages. This system was classified as Tropical Cyclone 13S by the JTWC.

Tropical Cyclone Anacelle

Anacelle began its life when the Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...

 issued its first advisory on a cyclone 275 nautical miles (509.3 km) northeast of St. Brandon Island. The storm intensified as it moved westward and turned south on February 9. At February 10, passed very close to St. Brandon Island with maximum sustained winds of 105 mph (165 km/h). Cotinuing southward, Anacelle boosted itself up to 135 mph (205 km/h), its peak intensity, on February 11. Anacelle passed over Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...

 and turned southwestward. Anacelle dropped below hurricane-force winds on February 13 and became extatropical twenty-four hours later. No damage from Anacelle is available.

Tropical Storm 21S

A tropical disturbance drifted near the coast of Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...

 to the southern tip of Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

 in early February. Early on February 9, scatterometer data indicated that a 40 mi/h area of winds within the center. The Joint Typhoon Warning Center issued its first warnings on that days as Tropical Cyclone 21S. The system was located 225 nautical miles (416.7 km) south of Tulear. Tropical Cyclone 21S had formed in a high wind shear environment and was unable to strengthen further. The weak cyclone moved off to the south-southeast and weakened into a tropical depression the next day.

Moderate Tropical Storm Beltane

The activity in the Mozambique Channel continued with a tropical disturbance forming on February 16. Convection began to organize very quickly, turning the disturbance into a tropical cyclone named Beltrane. By 600 UTC, Beltrane moved 150 nautical miles (277.8 km) northwest of Tulear, Madagascar, with winds of 40 mi/h. Beltrane peaked at 45 mi/h winds on February 16 at 1800 UTC off the southern tip of Madagascar. By the morning of February 18, all convection in Beltrane was sheared apart. The last Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...

 advisory was released that evening, in the Mozambique Channel, 100 nautical miles (185.2 km) from its point of origin.

Tropical Storm Victor-Cindy

Victor was briefly renamed by Mauritius as tropical cyclone Cindy as it passed into the South-West Indian Ocean. The system lasted almost 50 days since the initial low had developed.

Tropical Depression D1

The first advisory on Tropical Cyclone 24S was issued on February 16 by the Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...

, about 500 nautical miles (926 km) east of La Reunion
La Reunion
La Reunion may refer to:* La Reunion , a communal settlement near present-day Dallas, Texas*La Réunion, Lot-et-Garonne, a town in the Lot-et-Garonne department of France*Réunion, an island in the Indian Ocean east of Madagascar...

. At that time, Tropical Cyclone 24S had winds of 40 mi/h. Tropical Cyclone 24S moved to the southeast on February 17, but moved eastward the next day. Wind shear and low temperatures made it impossible for 18th. The final warning on Tropical Cyclone 24S was released on February 19 after being forecast to merge with cold front in the forecast period.

Moderate Tropical Storm Donaline

The Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...

 on Guam
Guam
Guam is an organized, unincorporated territory of the United States located in the western Pacific Ocean. It is one of five U.S. territories with an established civilian government. Guam is listed as one of 16 Non-Self-Governing Territories by the Special Committee on Decolonization of the United...

 issued their first bulletins on a developing depression in the west-central South Indian Ocean on March 6. The depression became a storm on March 7 with winds of 45 mi/h. Donaline began by drifting generally to the east, but by March 8, Donaline had started moving south. At this time, the storm had reached its peak intensity of 65 mph (100 km/h). Afterwards, Donaline began to weaken and accelerate to the south-southeast. Donaline's low-level circulation had becoming completely exposed to shear on March 9 and the final warning was released on March 10, when it was downgraded to a depression.

Severe Tropical Storm Elsie

The Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...

 issued their first bulletin on a rapidly developing tropical system on March 12. Elsie moved in a south-southwesterly direction for the next five days and reached its peak of 105 mph (165 km/h) on March 13. The cyclone at this point was only 1000 nautical miles (1,852 km) east of Rodrigues Island. Elsie had weakened as fast as it had intensified and by March 14, the storm was encountering wind shear. The south-southwestern motion stopped on March 17 and the final warning was issue twelve hours later. The final warning indicated that Elsie was finish its extratropical transition within 24 hours.

Tropical Depression Fiona

The Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...

 issued their first bulletin on Tropical Cyclone 28S on March 17. The initial warning indicated winds of 45 mph (70 km/h) and conditions were right for more strengthening. A passing shortwave inhibited future development and decreased the winds to 40 mi/h. During this time Fiona had drifted westward to an area about 215 nautical miles (398.2 km) northeast of Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...

. The weak Fiona moved to the southeast and curved back to the west later. After the trough lifted, Fiona gained some intensity but wind shear prohibited further development. The storm passed within 75 nautical miles (138.9 km) east of Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...

 at around 1500 UTC on March 19. Continuing south, Fiona weakened and the final advisory was issued on March 20. Winds of 44 mi/h were reported in the eastern section of Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...

, but no rainfall or pressure measurements were recorded.

Moderate Tropical Storm Gemma

The Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...

 issued their first bulletin about a developing tropical depression on April 7. The depression had maximum sustained winds of 35 mi/h. However, at the same time as Tropical Depression 32S foming, the JTWC issued a bulletin on the newly formed Tropical Depression 33S, which was located to the east-southeast. By 1200 UTC on March 7, the two systems had merged, resulting in a broad and weak wind field. Following the 32S-33S merger, the depression strengthened and was given the name Gemma on April 9. Gemma reached 65 mi/h winds and halted its westward motion, turning it into a south-southeasterly motion. On April 11, Gemma reached its peak intensity of 80 mph (130 km/h). Afterwards, Gemma began to weaken due to wind shear separating the system.

Microwave imagery on April 12 indicated that low-level features were still intact, despite the wind shear. By April 13, the weakening Gemma was down to 50 mi/h winds and the next day, Gemma was falling apart. The Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...

 issued their final bulletin about Gemma on April 15, just 230 nautical miles (426 km) east of its point of origin.

Tropical Depression 33S

The Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...

 issued their first bulletin on the newly formed Tropical Depression 33S on April 7 at 0000 UTC. The depression was only 300 nautical miles (555.6 km) southeast of Tropical Depression 32S (which later became Tropical Cyclone Gemma). Tropical Depression 33S moved northeastward while Tropical Depression 32S moved eastward. By 1200 UTC April 7, the center of TD-33S had pulled in closer to TD-32S. The depressions merged together the same day, ending the life of Tropical Depression 33S. Maximum sustained winds from Tropical Depression 33S were 35 mi/h.

Tropical Storm 34S

The Joint Typhoon Warning Center began tracking the newly-formed Tropical Cyclone 34S on April 19 near Diego Garcia
Diego Garcia
Diego Garcia is a tropical, footprint-shaped coral atoll located south of the equator in the central Indian Ocean at 7 degrees, 26 minutes south latitude. It is part of the British Indian Ocean Territory [BIOT] and is positioned at 72°23' east longitude....

. The cyclone was expected to reach hurricane-status, but it did not reach above gale intensity due to wind shear. Maximum sustained winds of 45 mi/h were recorded on April 19 and April 20. A scatterometer pass on the next day found that the system was weakening and lessening in its circulation. The Joint Typhoon Warning Center quit tracking the storm on April 22, as the cyclone weakened into a depression.

Tropical Depression H4

The South Indian Ocean basin, the tropical cyclone season is considered to end on July 31 while the Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...

 (JTWC) considers it to begin on July 1. Therefore, RSMC La Reunion regarded this system as the last of the 1997-98
1997-98 South-West Indian Ocean cyclone season
The 1997–98 South-West Indian Ocean cyclone season was an event in the annual cycle of tropical cyclone formation. It ran from November 15, 1997 to April 30, 1998, except for Mauritius and the Seychelles, where it ran until May 15. These dates conventionally delimit the period of each year when...

 season, while the JTWC regarded it as the first of the 1998-99 season, and classified it as Tropical Cyclone 01S.

La Reunion issued the first advisory for this disturbance on July 20 while it was centered about 800 nautical miles (1,481.6 km) east of Diego Garcia
Diego Garcia
Diego Garcia is a tropical, footprint-shaped coral atoll located south of the equator in the central Indian Ocean at 7 degrees, 26 minutes south latitude. It is part of the British Indian Ocean Territory [BIOT] and is positioned at 72°23' east longitude....

. For the next couple of days the system moved slowly toward the west-southwest. On July 22, it was upgraded to a tropical depression by La Reunion. Tropical Depression H4 was already weakening on the 23rd when the JTWC issued its first advisory, placing the center about 300 nmi (555.6 km) southeast of Diego Garcia. The system experienced considerable vertical wind shear throughout its life, but by July 23, the hostile conditions had abated somewhat. Given its proximity to Diego Garcia, the JTWC decided to initiate advisories on the system. In post-operational analysis, the JTWC upgraded the system to a tropical cyclone on the 22nd.

Storm names

A tropical disturbance is named when it reaches moderate tropical storm strength. If a tropical disturbance reaches moderate tropical storm status west of 55°E
55th meridian east
The meridian 55° east of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Europe, Asia, the Indian Ocean, the Southern Ocean, and Antarctica to the South Pole....

, then the Sub-regional Tropical Cyclone Advisory Centre in Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

 assigns the appropriate name to the storm. If a tropical disturbance reaches moderate tropical storm status between 55°E
55th meridian east
The meridian 55° east of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Europe, Asia, the Indian Ocean, the Southern Ocean, and Antarctica to the South Pole....

 and 90°E
90th meridian east
The meridian 90° east of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Asia, the Indian Ocean, the Southern Ocean, and Antarctica to the South Pole.The Ninety East Ridge is named after the meridian....

, then the Sub-regional Tropical Cyclone Advisory Centre in Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...

 assigns the appropriate name to the storm. A new annual list is used every year so no names are retired.
  • Anacelle
  • Beltane
  • Cindy
  • Donaline
  • Elsie
  • Fiona
  • Gemma

See also

  • List of Southern Hemisphere tropical cyclone seasons
  • Atlantic hurricane seasons: 1997
    1997 Atlantic hurricane season
    The 1997 Atlantic hurricane season is the most recent Atlantic hurricane season to feature no tropical cyclones in August. The season officially began on June 1, 1997, and lasted until November 30, 1997...

    , 1998
    1998 Atlantic hurricane season
    The 1998 Atlantic hurricane season officially began on June 1, 1998, and lasted until November 30, 1998. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin; however, the season extended through December 1 as Hurricane Nicole remained...

  • Pacific hurricane seasons: 1997
    1997 Pacific hurricane season
    The 1997 Pacific hurricane season was a very active hurricane season. With hundreds of deaths and billions of dollars in damage, this season was the costliest and one of the deadliest Pacific hurricane seasons. This was due to a strong El Niño...

    , 1998
    1998 Pacific hurricane season
    The 1998 Pacific hurricane season was a moderately active Pacific hurricane season with seven tropical cyclones directly affecting land. The season officially started on May 15 in the eastern Pacific, and on June 1 in the central Pacific, and ended on November 30; these dates conventionally delimit...

  • Pacific typhoon seasons: 1997
    1997 Pacific typhoon season
    The 1997 Pacific typhoon season has no official bounds; it ran year-round in 1997, but most tropical cyclones tend to form in the northwestern Pacific Ocean between May and November. These dates conventionally delimit the period of each year when most tropical cyclones form in the northwestern...

    , 1998
    1998 Pacific typhoon season
    The 1998 Pacific typhoon season has no official bounds, but most tropical cyclones tend to form in the northwestern Pacific Ocean between May and November...

  • North Indian Ocean cyclone seasons: 1997
    1997 North Indian Ocean cyclone season
    The 1997 North Indian Ocean cyclone season had no bounds, but cyclones tend to form between April and December, with peaks in May and November. These dates conventionally delimit the period of each year when most tropical cyclones form in the northern Indian Ocean.-Season summary:Five tropical...

    , 1998
    1998 North Indian Ocean cyclone season
    The 1998 North Indian Ocean cyclone season was an active season in annual cycle of tropical cyclone formation. The season has no official bounds but cyclones tend to form between April and December. These dates conventionally delimit the period of each year when most tropical cyclones form in the...


External links

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