2007–08 South-West Indian Ocean cyclone season

The 2007–08 South-West Indian Ocean cyclone season was the third most active tropical cyclone season, along with the 1985–86 season and behind the 1993–94 season and the 2018–19 season, with twelve named tropical cyclones developing in the region. It began on November 15, 2007, and ended on April 30, 2008, with the exception for Mauritius and the Seychelles, which ended 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 and south of the Equator. Tropical cyclones in this basin are monitored by the Regional Specialised Meteorological Centre in Réunion.

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Seasonal summary

Systems Tropical Cyclone 01U

On July 26, a tropical disturbance developed within a near-equatorial trough. The next day, convection began to develop around the low while located about east of Diego Garcia. Moderate wind shear temporarily caused the convection to become displaced from the center on July 27. However, later that day, the Joint Typhoon Warning Center (JTWC) assessed the chances of the low developing into a tropical cyclone as "fair". By July 29 the low was designated as Tropical Disturbance 01 while located near the edge of Météo-France's area of responsibility. With developing banding features, increasing convection and very warm sea-surface temperatures (exceeding ), the JTWC issued a Tropical Cyclone Formation Alert (TCFA) for the low as they assessed the chances of development of a tropical cyclone within 48 hours as "good".

In the post-storm report issued by the Australian Bureau of Meteorology, the system was estimated to have become a Category 1 cyclone, with winds peaking at , shortly before leaving Météo-France's area of responsibility early on July 29. After leaving Météo-France's area of responsibility, the JTWC designated the storm as Tropical Cyclone 01S. In Météo-France's post-storm analysis, the disturbance was declassified as a tropical cyclone and the numbering, 01, was removed for unknown reasons.

Tropical Disturbance 01

The first officially recognized tropical disturbance developed early on October 10. The disturbance featured persistent convection around an elongated low level circulation located about west-northwest of Diego Garcia. With marginally favorable. conditions for further development, the JTWC assessed the chances of the low developing into a tropical cyclone as "poor". Further development took place later that day, with banding features developing and deepening convection as it traveled towards the south-southwest. In response to the increased development, the JTWC increased the chances of a tropical cyclone developing to "fair". On October 12, Météo-France designated the system as Tropical Disturbance 01–20072008. However, little or no further development was expected.

Late on October 12 through early on October 13, Dvorak Technique intensity estimates for the low from the JTWC reached T2.5—the equivalent of a minimal tropical storm—and there was a possibility that the system was briefly a tropical storm by one-minute standards. Despite favorable upper-level conditions and low wind shear, the disturbance was situated over cool sea-surface temperatures which provided little energy to fuel convective activity. With little thunderstorm and shower activity development, Météo-France issued their final advisory on the dissipating low the next day. Since the disturbance never impacted land, there were no reports of damage or injuries from it.

Severe Tropical Storm Lee–Ariel

On November 13, the Australian Bureau of Meteorology (BoM) began monitoring a tropical low situated about northwest of the Keeling Islands. The next day, the low was upgraded to a Category 1 cyclone and given the name Lee. Shortly after being named, the JTWC issued a TCFA as deep convection persisted around the center of circulation. The system was moving towards the southwest within an area of moderate wind shear. Several hours later, the JTWC designated Lee as Tropical Cyclone 03S. With continued development, Lee strengthened into a Category 2 cyclone, according to the BoM, with winds of 10-minute winds). At 1200 UTC, Lee crossed into Météo-France's area of responsibility at peak intensity. Upon entering their AoR, it was given a second name, Ariel, and designated as a severe tropical storm.

Roughly six hours later, the JTWC assessed Lee–Ariel to have reached its peak intensity with winds of 1-minute sustained), based on the development of an eye-like structure. The next day, foreword motion slowed significantly due to a subtropical ridge located to the north of the storm. This ridge also caused the storm to turn towards the west, keeping a slow pace. Strong wind shear began to impact the system later that day, causing it to weaken into a moderate tropical storm. Despite the strong shear, most forecast models showed the storm re-intensifying several days out in an area of lower shear. Most of the deep convection was torn away from the system, with little remaining around the center of circulation.

The storm weakened to a tropical depression around 0600 UTC on November 17 as convection continued to dissipate. Despite moving into an area favorable for intensification, Météo-France issued their final advisory on ex-Lee–Ariel on November 18 as it continued to weaken. The remnants of the system persisted for another ten days, completing an erratic counter-clockwise loop before taking a general westward direction.

Severe Tropical Storm Bongwe

An area of disturbed weather developed east of Diego Garcia on November 15. The system slowly organised as it moved southeastward and began interacting with Severe Tropical Storm Ariel, and the JTWC issued a TCFA on November 17. The JTWC upgraded the system to Tropical Cyclone 04S early the next day. Also on November 18, RSMC La Réunion classified the system as Tropical Disturbance 03. Later that day, RSMC La Réunion upgraded it to Tropical Depression 03. It was upgraded to Moderate Tropical Storm Bongwe on November 19 and a Severe Tropical Storm later that day. Increased wind shear early on November 20 slowed the intensification trend, and weakened it to a moderate tropical storm. However, it restrengthened to a severe tropical storm on November 22. The restrengthening trend was short-lived, however, as the storm weakened once again on November 23, down to a depression and then a disturbance, until it finally dissipated on November 24.

Moderate Tropical Storm Celina

An area of disturbed weather developed early on the December 12 north-northeast of Rodrigues. Later that day it was designated as Tropical Disturbance 04R. The JTWC then issued a TCFA on the developing system late on December 12. The JTWC issued its first warning on December 13, designating the storm as Tropical Cyclone 06S. Although the low level circulation center was exposed the system was upgraded to a tropical depression by Météo-France on December 14 due to a better low level circulation. Early on December 17 Mauritius Meteorological Service upgraded the system to a moderate tropical storm and named it "Celina" as it approaches Mauritius Island.

Weakening took place on December 18, and the JTWC issued its final advisory early that day. Météo-France maintained the system as a tropical depression. Météo-France issued its final advisory on December 21 as it began to dissipate just east of southeastern Madagascar.

On December 20, the remnant low of Celina passed about southwest of Reunion, producing heavy rains over the island. Some areas received of rain in the span of three hours, with the highest total amounting to in La Plaine des Chicots. These rains led to the death of one woman after she drowned in her car which was overcome by floodwaters in a ravine. Wind gusts were recorded up to .

Moderate Tropical Storm Dama

An area of disturbed weather begin developing east of 90°E near Cocos Island, eventually crossing into the southwestern Indian Ocean early on December 17. The JTWC issued a TCFA early December 18. RSMC Réunion designated the system a tropical disturbance early in the afternoon as the convection begin to deepen and isolate itself from the disturbance to its northwest. The Joint Typhoon Warning Center designated the tropical disturbance as Tropical Cyclone 07S. The weak vertical wind shear allowed the system to deepen into a tropical depression in the early evening of December 18. The system temporarily reached moderate tropical storm intensity on December 19 but persistent vertical wind shear caused it to rapidly weaken back into a tropical depression. However, the next day, decreasing wind shear allowed convection to form closer to the center for 05R to reclassify as a moderate tropical storm status and earned the name "Dama." The Joint Typhoon Warning Center and Météo-France issued its final advisory on December 21 as it transitioned to an extratropical system.

Moderate Tropical Storm Elnus

Early on December 30 an area of disturbed weather formed west of Madagascar and was designated as 06R. Later that day it was upgraded to Tropical Disturbance 06R, whilst the JTWC issued a TCFA on the developing system. On December 31, Météo-France upgraded the disturbance to tropical depression status. Soon after, the JTWC upgraded the system to Tropical Cyclone 09S. Early on January 1, the depression was upgraded to Moderate Tropical Storm Elnus, while located in the Mozambique Channel. On January 2, Météo-France downgraded the system to Tropical Depression ex-Elnus, and then to a tropical disturbance the next day. The JTWC issued its last advisory on January 4 as it transitioned to an extratropical system. Météo-France noted the storm was becoming extratropical on January 4, and on January 6 issued its final advisory on Extratropical Depression ex-Elnus as the system passed to the south of Madagascar.

On January 3, Elnus passed about east of Europa Island, producing winds up to along with a pressure of 997 hPa (mbar). The storm also enhanced rainfall, peaking around , over parts of Malawi, causing minor flooding. Heavy rains in Madagascar briefly displaced 90 families in Antananarivo.

Tropical Disturbance 07

On January 6, the JTWC began monitoring an exposed low-level circulation located about north of Réunion traveling towards the south. Although moderate wind shear hampered significant development, deep convection developed towards the north of the low. Early the next day, the low was designated as Tropical Disturbance 07-20072008 by Météo-France. Later that day, despite weakening wind shear and increasing convection, the disturbance degenerated into a zone of disturbed weather. Although convection began to decrease by January 8, due to increasing wind shear, Météo-France redesigned the system as a tropical disturbance. At this time, the disturbance was assessed to have reached its peak intensity with winds of with a minimum pressure of 1003 hPa (mbar). Later that day, the low rapidly weakened and dissipated while located northwest of Réunion. Due to the proximity to Réunion, the disturbance produced numerous showers and thunderstorms for a few days.

Tropical Cyclone Fame