2008–09 South-West Indian Ocean cyclone season

The 2008–09 South-West Indian Ocean cyclone season was a slightly above average event in tropical cyclone formation. It began on November 15, 2008, and officially ended on April 30, 2009, with the exception for Mauritius and the Seychelles, for which it ended on May 15, 2009. 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 were monitored by the Regional Specialised Meteorological Centre in Réunion.

As predicted by the sub regional office of Mauritius ten named storms formed in this basin. It officially began on November 15, but began 1 month earlier when Tropical Storm Asma formed on October 16. Most of the storms that formed this year were weak or stayed at sea. Only two storms reached hurricane strength this year, both of which were Category 3 or higher, and only 3 storms made landfall in the entire season. Overall, the impact of this season was relatively minor, but damaging for Madagascar, due to the heavy rains from Eric, Fanele, Izilda and Jade.

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Seasonal summary

Systems Zone of Disturbed Weather 01

On October 6, the Joint Typhoon Warning Center (JTWC) began monitoring an area of persistent convection about 575 km (355 mi) southeast of Diego Garcia. Although the center of circulation (CoC) was elongated, the system was located within an area of low wind shear and development of the low was possible. At 12:00 UTC later that day, the Regional Specialized Meteorological Centre (RSMC), Météo-France (MFR), began issuing advisories on "Zone of Disturbed Weather 01". Despite a banding feature developed around the CoC, significant development was not anticipated. The low gradually weakened throughout October 7, and dissipated the next day.

Moderate Tropical Storm Asma

On October 16, MFR designated an area of low pressure north-west of Diego Garcia as Tropical Disturbance 02. Later that evening the JTWC issued a Tropical Cyclone Formation Alert on the system. At 2100 UTC on October 16, the JTWC issued their first advisory and designated it as Tropical Cyclone 01S. Early the next day the disturbance intensified into a tropical depression, but on October 18 MFR downgraded the system to a tropical disturbance, noting that the near gale-force winds that were near the center are now several hundred kilometers away from the center. The next day MFR re-upgraded the system to a tropical depression due to a slight decrease in vertical wind shear that had inhibited the disturbance and a slight re-location of the center. Later that day MFR upgraded the depression to a Moderate Tropical storm, so the Sub-Regional Tropical Cyclone Advisory Centre in Mauritius assigned the name Asma to the tropical storm. Early on October 20, Asma reached its peak intensity with winds of with a minimum pressure of 985 hPa (mbar). The storm featured good outflow and was situated over warm waters; however, moderate wind shear was forecast to prevent the cyclone from intensifying any further. Shortly after reaching peak intensity, the combination of cooler waters and higher wind shear caused the storm to weaken slightly. Continued weakening took place throughout the day as deep convection associated with Asma dissipated and the strongest winds were displaced from the center. By the morning of October 21, Asma was downgraded to a tropical depression as the low became further disorganized. Later that day, the depression degenerated to a tropical disturbance as only an exposed low remained. The final advisory was issued at 0600 UTC on October 22 as no redevelopment took place. However, only 12 hours after the final advisory was issued, the disturbance began to regenerate and MFR began issuing advisories on the regenerated system. The redevelopment was short lived and Asma dissipated less than 24 hours later.

Officials in Madagascar issued storm warnings as Tropical Storm Asma was forecast to make landfall in the northern portion of the island on October 23. Despite warnings, residents did not take precautions before the storm. Following the regeneration of Asma, the storm produced heavy rains over northern Madagascar which caused flooding in eight rural communities. One person was killed in Doany common rural district of Andapa. A total of 448 hectares of farmland were also inundated by floodwaters. Six oxen and 24 pigs were also killed and three bridges were damaged. Following the damages caused by the storm, officials provided first aid kits, nine tons of rice, 100 cartons of soap, 60 cartons of clothing, 120 mosquito nets, 20 bags of pulses and 30 tents to the affected population. The heavy rains were accompanied by winds gusting up to . After brushing Madagascar, Asma brought unseasonable heavy rains to parts of Mozambique and Tanzania.

Moderate Tropical Storm Bernard

On November 15, a low-pressure area was located about 795 km (495 mi) east-southeast of Diego Garcia, accompanied by persistent convection. It was centered east of a ridge and was within an area of moderate vertical wind shear. Over the next several days, the system moved slowly eastward with little development. On November 19, convection developed around the circulation after being nearly stationary for a few days. At 0600 UTC, MFR designated the system as Tropical Disturbance 03, about 695 km (430 mi) east-southeast of Diego Garcia. As rainbands and outflow developed, the JTWC issued a Tropical Cyclone Formation Alert. Later that day, MFR upgraded the disturbance to a tropical depression. About three hours later, the JTWC began issuing advisories on Tropical Cyclone 03S, although wind shear was forecast to prevent significant intensification. Located to the northeast of a low to mid-level trough and to the southwest of a near-equatorial ridge, the system began to accelerate to the east. At 0600 UTC on November 20, the JTWC assessed the system to have reached its peak intensity with winds of 75 km/h (45 mph 1-minute winds). Shortly after, MFR upgraded the depression to Moderate Tropical Storm Bernard, with peak winds of .

Just six hours after being named, Bernard was downgraded to a tropical depression as all associated deep convection dissipated. The sudden decrease was caused by the storm's unusually fast movement of towards the east-southeast over cooler waters. At the same time MFR downgraded Bernard to a depression, the JTWC issued their final advisory on Tropical Cyclone 03S as it had weakened below tropical storm status. Early the next morning, MFR downgraded the system to a tropical disturbance and issued their final advisory on the dissipating cyclone. The remnants of Bernard entered the Australia region, where it was briefly designated as Tropical Low 01U before dissipating.

Severe Tropical Storm Cinda

On the evening of December 16, the JTWC issued a Tropical Cyclone Formation alert on a rapidly organizing disturbance located west of Diego Garcia. The low level centre continued to improve with convection wrapping into the centre and the JTWC upgraded the disturbance into a tropical storm, at the same time MFR designated the system a tropical depression. Under low shear and favourable upper-level outflow, 04S was upgraded to Moderate Tropical Storm Cinda by MFR early on December 18. Soon after, Cinda was upgraded to a severe tropical storm as it moved south-southwestwards away from Diego Garcia. Later that same day, Cinda was downgraded to a moderate tropical storm. The wind shear kept the eye north of the convection. On the morning of December 21, Cinda degenerated into a remnant low about 250 miles off the coast of Madagascar amongst heavy wind shear.

Severe Tropical Storm Dongo

The origins of Dongo can be traced back to an area of low pressure that formed far from land late on January 7. At 06:00 UTC, MFR designated it as a Zone of Disturbed Weather 1,530 km (950 mi) northeast of Mauritius. However, strong wind shear was expected to inhibit short-term development. A few hours later, MFR further upgraded the low to a tropical disturbance. At 1500 UTC, the JTWC issued a Tropical Cyclone Formation Alert. Situated along the edge of a low-mid level ridge, the disturbance tracked towards the southwest. Despite a brief decease in convection, at 0600 UTC on January 9, MFR upgraded the disturbance to a tropical depression. Shortly after, the depression was upgraded to Moderate Tropical Storm Dongo. At the time of the upgrade, Dongo began to turn more towards the south as further development of the storm was anticipated. Roughly three hours later, the JTWC began issuing advisories on Tropical Cyclone 06S . After weakening slightly early on January 10, Dongo began to turn towards the southeast. Subsequently, convection rapidly decreased, leaving the center partially exposed even though conditions were favorable for intensification. Six hours later, however, Dongo intensified into a severe tropical storm while reaching its peak intensity with winds of 95 km/h (60 mph 10-minute winds) with a minimum pressure of 984 hPa (mbar) according to MFR. Furthermore, Dongo peak with winds of 100 km/h (65 mph 1-minute winds) according to the JTWC about 1,240 km (770 mi) east-southeast of Mauritius.

Tracking towards the south-southeast, Dongo approached cooler waters and began to transition into an extratropical cyclone. Wind shear was also increasing over the storm in response to an approaching upper-level trough. Despite moving over cooler waters, the storm remained a severe tropical storm until being declared extratropical at 0600 UTC on January 12. Several hours later, the JTWC issued their final advisory on the system Early on January 13, MFR followed suit, though it was later believed to have completed such transition earlier.

Moderate Tropical Storm Eric

On January 17, the MFR identified a Zone of Disturbed Weather northeast of La Réunion. The following day the disturbance organized quite significantly west-northwest of Madagascar and MFR classified it as a tropical disturbance. The disturbance intensified into a moderate tropical storm on the 19th. Eric crossed the coastline around Toamasina, which reported a surface low pressure of 992 hPa, mid morning on that day and skirted along the eastern Madagascar coast for much of the day before tracking southeast away from the coast on January 20. On January 20, the JTWC issued its final advisory on Eric, as it had been torn apart by the shear from the strong Fanele. MFR downgraded Eric to a tropical depression on January 21, noting it could re-deepen as it transitioned into an extratropical cyclone.

Eric killed two people, injured 24, left 992 homeless, and affected an additional 7,606 in eastern Madagascar. A total of 32 classrooms were destroyed by the storm, mainly UNICEF tents and 42 other classrooms were damaged.

Intense Tropical Cyclone Fanele