Timeline of the 2009–10 South-West Indian Ocean cyclone season

This timeline documents all of the events of the 2009–10 South-West Indian Ocean cyclone season which is the period that tropical cyclones formed in the Indian Ocean. Within the Indian Ocean most tropical cyclones form within the cyclone season which began on November 1 and will end on April 30. The scope of this article is limited to tropical cyclones that form in the Indian Ocean 30°E and 90°E to the south of the equator. When a zone of disturbed weather form or moves into the South-West Indian Ocean it is assigned a number and monitored by Météo-France who run the Regional Specialized Meteorological Center (RSMC) on Réunion Island. Should a tropical disturbance intensify and become a moderate tropical storm the two sub-regional tropical cyclone Advisory Centres in Mauritius and Madagascar in conjunction with RSMC La Réunion. The United States Joint Typhoon Warning Center (JTWC) also issue warnings on tropical cyclones in this region assigning a number with an "S" suffix. When monitoring a tropical cyclone the Joint Typhoon Warning Center will assess the cyclones intensity on the Saffir–Simpson hurricane scale whilst RSMC La Réunion, Mauritius and Madagascar use the Southwest Indian Ocean Tropical Cyclone Intensity Scale to assess a tropical cyclones intensity.

Timeline

July July 1 0000 UTC, (0400 RET) — The 2009–10 South-West Indian Ocean tropical cyclone year starts.

August

August 18 0000 UTC, (0400 RET) — RSMC La Réunion reports that Tropical Disturbance One has formed about 1200 km, (750 mi), to the east of Diego Garcia. 1200 UTC, (1600 RET) — RSMC La Réunion issues its final advisory on Tropical Disturbance One as it weakens into a zone of disturbed weather.

September September 20 0600 UTC, (1000 RET) — RSMC La Réunion reports that Zone of Disturbed Weather Two has formed about 2500 km, (1550 mi), to the Southeast of Jakarta, Indonesia. 1200 UTC, (1600 RET) — RSMC La Réunion issues its final advisory on Zone of Disturbed Weather Two.

October No tropical cyclones formed in the South-West Indian Ocean, during October 2009.

November November 7 1200 UTC, (1600 RET) — RSMC La Réunion reports that Tropical Disturbance Three has formed about 800 km, (500 mi), to the southeast of Male in the Maldives.

November 10 0600 UTC, (1000 RET) — RSMC La Réunion issues its final advisory on Tropical Disturbance Three.

November 13 0600 UTC, (1030 RET) — RSMC La Réunion reports that Zone of Disturbed Weather Four has formed about 2210 km, (1375 mi) to the north-east of Saint-Denis on La Réunion Island. 1800 UTC, (2230 RET) — RSMC La Réunion reports that Zone of Disturbed Weather Four has intensified into a tropical disturbance.

November 14 0000 UTC, (0430 RET) — RSMC La Réunion reports that Tropical Disturbance four has intensified into a tropical depression. 0600 UTC, (1030 RET) — The JTWC designates Tropical Depression Four as Tropical Storm 01S. 1200 UTC, (1630 RET) — RSMC La Réunion reports that Tropical Depression Four (01S) has intensified into a moderate tropical storm. 1800 UTC, (2230 RET) — The sub-regional tropical cyclone advisory center in Mauritius names Moderate Tropical Storm Four (01S) as Anja. 1800 UTC, (2230 RET) — RSMC La Réunion reports that Moderate Tropical Storm Anja (01S) has intensified into a severe tropical storm.

November 15 0000 UTC, (0430 RET) — The 2009–10 South-West Indian Ocean tropical cyclone season officially begins. 0000 UTC, (0430 RET) — The JTWC reports that Tropical Storm Anja (01S) has intensified into a category two tropical cyclone. 0600 UTC, (1030 RET) — RSMC La Réunion reports that Severe Tropical Storm Anja (01S) has rapidly intensified into a tropical cyclone. 0600 UTC, (1030 RET) — The JTWC reports that Tropical Cyclone Anja (01S) has intensified into a category three tropical cyclone. 1200 UTC, (1630 RET) — RSMC La Réunion reports that Tropical Cyclone Anja has reached its 10-minute peak sustained wind speeds of . 1200 UTC, (1630 RET) — The JTWC reports that Tropical Cyclone Anja (01S) has reached its 1-minute peak sustained wind speeds of .

November 17 0600 UTC, (1030 RET) — The JTWC reports that Tropical Cyclone Anja has weakened into a category two tropical cyclone. 1200 UTC, (1630 RET) — The JTWC reports that Tropical Cyclone Anja has weakened into a category one tropical cyclone. 1800 UTC, (2230 RET) — RSMC La Réunion reports that Tropical Cyclone Anja (01S) has weakened into a severe tropical storm.

November 18 0000 UTC, (0430 RET) — The JTWC reports that Tropical Cyclone Anja has weakened into a Tropical Storm. 0600 UTC, (1030 RET) — RSMC La Réunion reports that Severe Tropical Storm Anja (01S) has weakened into a tropical depression. 0600 UTC, (1030 RET) — The JTWC reports that Tropical Storm Anja has become extra-tropical and issues its final advisory. 1200 UTC, (1630 RET) — RSMC La Réunion reports that Tropical Depression Anja has weakened into a tropical disturbance.

November 20 0000 UTC, (0430 RET) — RSMC La Réunion issues its final advisory on Tropical Disturbance Anja. 0600 UTC, (1030 RET) — RSMC La Réunion reports that Zone of Disturbed Weather Five has formed about 1525 km, (950 mi), to the north-east of Saint-Denis on La Réunion Island.

November 22 0000 UTC, (0430 RET) — RSMC La Réunion reports that Zone of Disturbed Weather Five has intensified into a tropical disturbance. 1800 UTC, (2230 RET) — RSMC La Réunion reports that Tropical Disturbance Five has intensified, into a tropical depression.

November 23 0000 UTC, (0400 RET) — RSMC La Réunion reports that Tropical Depression Five has intensified into a moderate tropical storm. 0600 UTC, (1000 RET) — The sub-regional tropical cyclone advisory center in Madagascar names Moderate Tropical Storm Five as Bongani. 0600 UTC, (1000 RET) — RSMC La Réunion reports that Moderate Tropical Storm Bongani has reached its peak 10-minute sustained wind speeds of . 0600 UTC, (1000 RET) — The JTWC designates Moderate Tropical Storm Bongani as Tropical Storm 02S, has reached its peak one-minute sustained wind speeds of .

November 24 0000 UTC, (0400 RET) — RSMC La Réunion reports that Moderate Tropical Storm Bongani (02S) has weakened into a tropical depression. 0600 UTC, (1000 RET) — RSMC La Réunion reports that Tropical Depression Bongani (02S) has weakened into a tropical disturbance.

November 25 0600 UTC, (1000 RET) — RSMC La Réunion reports that Tropical Disturbance Bongani (02S) has weakened into a depression se comblant. 1200 UTC, (1600 RET) — The JTWC reports that Tropical Storm Bongani (02S) has weakened into a tropical depression.

November 26 1200 UTC, (1600 RET) — RSMC La Réunion issues the final advisory on Depression Se Comblant Bongani.

December December 3 0600 UTC, (1000 RET) — RSMC La Réunion reports that Zone of Disturbed Weather 06, has formed within the Australian region.

December 4 2100 UTC — Zone of disturbed weather 06 moves into the South-West Indian Ocean.

December 6 0000 UTC — RSMC La Réunion reports that Zone of Disturbed Weather 06 has intensified into a tropical disturbance.

December 7 0000 UTC — The JTWC designates Tropical Disturbance 06 as Tropical Storm 03S. 0600 UTC — RSMC La Réunion reports that Tropical Disturbance 06 (03S) has intensified into a tropical depression. 1200 UTC — RSMC La Réunion reports that Tropical Depression 06 (03S) has intensified into a moderate tropical storm. 1200 UTC — The sub-regional tropical cyclone advisory centre in Mauritius names Moderate Tropical Storm 06 (03S) as Cleo.

December 8 0000 UTC — RSMC La Réunion reports that Moderate Tropical Storm Cleo (03S) has intensified into a severe tropical storm. 0000 UTC — The JTWC reports that Tropical Storm Cleo (03S) has intensified into a category one tropical cyclone. 0600 UTC — RSMC La Réunion reports that Severe Tropical Storm has rapidly intensified into an intense tropical cyclone. 0600 UTC — The JTWC reports that Tropical Cyclone Cleo (03S) has intensified into a category three tropical cyclone. 1200 UTC — RSMC La Réunion reports that Intense Tropical Cyclone Cleo (03S) has reached its 10-minute sustained peak wind speeds of 195 km/h, (120 mph). 1200 UTC — The JTWC reports that Tropical Cyclone Cleo (03S) has intensified into a category four tropical cyclone. 1200 UTC — The JTWC reports that Tropical Cyclone Cleo (03S) has reached its 1-minute sustained peak wind speeds of 210 km/h, (130 mph).

December 9 0000 UTC — RSMC La Réunion reports that Intense Tropical Cyclone Cleo (03S) has weakened into a tropical cyclone. 0000 UTC — The JTWC reports that Tropical Cyclone Cleo (03S) has weakened into a category three tropical cyclone. 1200 UTC — RSMC La Réunion reports that Tropical Cyclone Cleo (03S) has weakened into a severe tropical storm. 1200 UTC — The JTWC reports that Tropical Cyclone Cleo (03S) has weakened into a category two tropical cyclone.

December 10 0000 UTC — The JTWC reports that Tropical Cyclone Cleo (03S) has weakened into a category one tropical cyclone. 0600 UTC — The JTWC reports that Tropical Cyclone Cleo (03S) has weakened into a tropical storm. 1800 UTC — RSMC La Réunion reports that Tropical Cyclone Cleo (03S) has weakened into a tropical storm.

December 11 0600 UTC — RSMC La Réunion reports that Tropical Cyclone Cleo (03S) has weakened into a tropical disturbance. 1200 UTC — The JTWC reports that Tropical Storm Cleo (03S) has weakened into a tropical depression.

December 12 0000 UTC — RSMC La Réunion reports that Tropical Disturbance Cleo has intensified into a tropical depression. 0600 UTC — RSMC La Réunion reports that Tropical Depression Cleo has weakened into a tropical disturbance. 1200 UTC — RSMC La Réunion reports that Tropical Disturbance Cleo has weakened into a zone of disturbed weather. 1200 UTC — RSMC La Réunion reports that Zone of Disturbed Weather 07 has formed about 1660 km, (1000 mi), to the south-east of Colombo, Sri Lanka.

December 13 0600 UTC — RSMC La Réunion reports that Zone of Disturbed Weather Cleo has re-intensified into a tropical disturbance. 0600 UTC — RSMC La Réunion reports that Zone of Disturbed Weather 07 has intensified into a tropical disturbance. 0600 UTC — The JTWC designates Tropical Disturbance 07 as Tropical Storm 05S.

December 14 0000 UTC — RSMC La Réunion reports that Tropical Disturbance 07 has weakened into a zone of disturbed weather. 0000 UTC — The JTWC issues their final advisory on Tropical Depression Cleo. 0600 UTC — The JTWC reports that Tropical Storm 05S has weakened into a tropical depression. 1200 UTC — RSMC La Réunion reports that Tropical Disturbance Cleo has weakened into a zone of disturbed weather.

December 17 0600 UTC — RSMC La Réunion reports that Zone of Disturbed Weather 07 has intensified into a tropical disturbance.

December 20 0600 UTC — The JTWC reports that Tropical Depression 05S has intensified into a Tropical Storm.

December 21 0600 UTC — RSMC La Réunion reports that Tropical Disturbance 07 (05S) has intensified into a tropical depression. 1200 UTC — RSMC La Réunion reports that Tropical Depression 07 (05S) has intensified into a moderate tropical storm. 1200 UTC — The sub-regional tropical cyclone advisory centre in Mauritius names Moderate Tropical Storm 07 (05S) as David.

December 22 1800 UTC — RSMC La Réunion reports that Moderate Tropical Storm David (05S) has intensified into a severe tropical storm.

December 23 0000 UTC — RSMC La Réunion reports that Severe Tropical Storm David (05S) has reached its 10-minute sustained peak wind speeds of 100 km/h, (65 mph). 1800 UTC — RSMC La Réunion reports that Severe Tropical Storm David (05S) has weakened into a tropical storm.

December 24 0600 UTC — RSMC La Réunion reports that Moderate Tropical Storm David (05S) has intensified into a severe tropical storm.

December 25 0000 UTC — RSMC La Réunion reports that Severe Tropical Storm David (05S) has weakened into a tropical storm. 1200 UTC — RSMC La Réunion reports that Tropical Storm David (05S) has weakened into a tropical depression.