The 2009–10 Australian region cyclone season was a below average tropical cyclone season, with eight tropical cyclones forming compared to an average of 12. The season began on 1 November 2009 and ran through until it end on 30 April 2010. The Australian region is defined as being to south of the equator, between the 90th meridian east and 160th meridian east. Tropical cyclones in this area are monitored by five Tropical Cyclone Warning Centres (TCWC's): Jakarta, Port Moresby, Perth, Darwin, and Brisbane, each of which have the power to name a tropical cyclone. The TCWC's in Perth, Darwin, and Brisbane are run by the Australian Bureau of Meteorology, who designate significant tropical lows with a number and the U suffix. The Joint Typhoon Warning Center also issues unofficial warnings for the region, designating significant tropical cyclones with the "S" suffix when they form west of 135°E, and the "P" suffix when they form east of 135°E.
Timeline
December
10 December
0600 UTC — TCWC Darwin reports that Tropical Low 01U has formed northeast of Darwin.
13 December
0000 UTC — TCWC Darwin reports that Tropical Low 01U has become a Category One Tropical Cyclone and is named as Cyclone Laurence.
14 December
2100 UTC — TCWC Darwin upgrades Tropical Cyclone Laurence to a Category 2 cyclone.
15 December
0300 UTC — TCWC Darwin upgrades Tropical Cyclone Laurence to a Category 3 cyclone. 1800 UTC — TCWC Perth upgrades Laurence into a Category 4 cyclone.
16 December
0000 UTC — TCWC Perth upgrades Severe Tropical Cyclone Laurence to a Category 5. 0300 UTC — TCWC Perth downgrades Laurence to a Category 3 cyclone. 2100 UTC — TCWC Perth downgrades Laurence to a Category 2 cyclone.
17 December
2100 UTC — TCWC Perth downgrades Laurence to Category 1 strength.
18 December
1200 UTC — TCWC Perth downgrades Laurence to a Tropical Low.
19 December
0400 UTC — TCWC Perth re-upgrades Tropical Low Laurence to a Category 1 cyclone. 1600 UTC — TCWC Perth re-upgrades Tropical Cyclone Laurence to a Category 2 cyclone.
20 December
1500 UTC — TCWC Perth re-upgrades Laurence to a Category 3 cyclone. 2000 UTC — TCWC Perth re-upgrades Severe Tropical Cyclone Laurence to a Category 4 cyclone.
21 December
0300 UTC — TCWC Perth re-upgrades Laurence to a Category 5 cyclone. 1200 UTC — TCWC Perth downgrades Laurence to a Category 4 cyclone. 2000 UTC — TCWC Perth downgrades Laurence to a Category 3 cyclone.
22 December
0700 UTC — TCWC Perth downgrades Tropical Cyclone Laurence to a Category 2 cyclone. 1200 UTC — TCWC Perth downgrades Laurence to a Category 1 cyclone.
23 December
1200 UTC - TCWC Perth downgrades Laurence to a Tropical low. 1200 UTC - TCWC Perth issues its final warning to Ex-Tropical Cyclone Laurence.
27 December
0600 UTC – TCWC Darwin reports that Tropical Low 02U has formed in the southern Arafura Sea
January
1 January
0600 UTC – TCWC Perth reports that Tropical Low 03U has formed near 8S 96E
16 January
0700 UTC – TCWC Darwin reports that Tropical Low 05U has formed in the Gulf of Carpentaria
19 January
0600 UTC – TCWC Perth reports that Tropical Low 06U has formed south of Timor
20 January
1500 UTC – TCWC Perth upgrades Tropical Low 06U to a category one tropical cyclone and names it Magda. 1800 UTC – TCWC Brisbane upgrades Tropical Low 05U to a category one tropical cyclone and names it Neville. 2100 UTC – The Joint Typhoon Warning Center issues its first warning on Tropical Cyclone 08S (Magda).
21 January
0100 UTC – TCWC Perth upgrades Tropical Cyclone Magda to Category 2 strength. 0100 UTC – TCWC Brisbane downgrades Tropical Cyclone Neville to a Tropical Low.
22 January
2000 UTC – TCWC Perth downgrades Tropical Cyclone Magda, to a tropical low. 2300 UTC – TCWC Brisbane issues their final warning for Tropical Low Ex-Neville. 2300 UTC – TCWC Perth issues their final warning for Tropical Low Ex-Magda. 2300 UTC – TCWC Brisbane upgrades 07U to category 1 Tropical Cyclone Olga.
23 January
1200 UTC – TCWC Brisbane upgrades Tropical Cyclone Olga to Category 2 strength.
24 January
0000 UTC – TCWC Brisbane downgrades Tropical Cyclone Olga to a Category 1 cyclone. 2300 UTC – TCWC Brisbane downgrades Tropical Cyclone Olga to a Tropical low.
29 January
1200 UTC – TCWC Brisbane upgrades Tropical Low Ex-Olga back to a Category 1 cyclone.
30 January
0000 UTC – TCWC Brisbane downgrades Tropical Cyclone Olga to a Tropical low.