A tropical low formed in the Timor Sea northwest of Darwin on 15 December and moved to the southwest and then to the southeast on 17 December. The low moved into the Joseph Bonaparte Gulf on 18 December and intensified to cyclone intensity north of Wyndham. The slow moving system reached category two intensity before moving to the west southwest crossing the coast near Wyndham early on 20 December.
Billy passed over Oombulgurri community at category 2 strength causing tree damage and power outages before weakening over land. Heavy rainfall caused some flooding and road closures in the northeast Kimberley. Wyndham recorded 384 mm in the 48 hours to 9am on 21 December. Billy weakened below cyclone strength by the afternoon of 20 December and tracked overland to the west southwest.
Ex-TC Billy moved off shore to the south of Kuri Bay about 0900 WDT 22 December. The system continued in a southwest direction passing close to Cape Leveque in the early hours of 23 December before finally moving out over open water after 0900 WDT 23 December. Once over water Billy re-intensified rapidly and reached category 2 by the afternoon of 23 December.
Billy continued to intensify quickly and reached category four intensity late on 24 December about 280 km north of Port Hedland. Billy then moved to the west northwest away from the Pilbara coast, weakening from late on 25 December due to increasing wind shear. Billy eventually weakened below cyclone intensity late on 28 December about 750 km north of Exmouth. The remains of Ex-TC Billy continued to move west until it moved out of the Perth area of responsibility on 6 January.
For more information see the TC Billy Report (pdf)
Track and intensity
All times in WDT.