Western Australia Tropical Cyclone Season Summary 2008-09

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Season Overview

There were a total of five Tropical Cyclones (TCs) in the Perth TCWC area of responsibility from July 2008 to June 2009. Of these, Billy, Freddy and Dominic occurred in the Northwest region between 110-125°E. Billy was the only severe TC, reaching category 4 intensity off the west Kimberley coast . There were two TCs that crossed the Western Australian coastline: Dominic as a category 2 cyclone near Onslow on the Pilbara coast; and Billy as a category 2 cyclone near Wyndham in the northeast Kimberley coast. In both cases there was only minimal damage. A low was named Gabrielle operationally in early March. However, upon post-analysis it was deemed not to have reached tropical cyclone intensity.

The most significant impacts were associated with two tropical lows during February that caused heavy rain and flooding to the Pilbara. The first low crossed the coast near Onslow and caused flooding along the Ashburton, Fortescue and nearby rivers. There was considerable damage to infrastructure especially to the railways and roads. The following low crossed the coast near Port Hedland ten days later. Fortunately the heavy rain fell to the east of the area subject to flooding from the initial low.

In addition there were financial losses associated with the disruption to industry during Billy, Dominic and Freddy.

Anika and Gabrielle were Indian Ocean systems that moved between Christmas and Cocos Islands and there were no known impacts associated with them.

Tracks of tropical cyclones, 2008-09.

Season tracks 2008/09

Tropical Cyclone Anika, 17-22 November 2008

During 17 November a low formed during an active phase of the Madden-Julian Oscillation (MJO) along the monsoon trough in the central Indian Ocean. The low developed quickly and was upgraded to Tropical Cyclone (TC) Anika at 0000 UTC (0900 WDT) 19 November. Anika moved on a steady east southeast path, passing to the northeast of the Cocos Islands. The system reached category 2 intensity early on 20 November before rapidly weakening later that day. Anika was downgraded to a tropical low at 0000 UTC (0900 WDT) 21 November as it moved over cooler seas surface temperatures and was affected by increased wind shear caused by the approach of a mid-level trough.

Anika was the first tropical cyclone of the Australian 2008/09 tropical cyclone season.

For full details see full pdf report (614kB).

Severe Tropical Cyclone Billy, 20 December 2008 - 5 January 2009

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 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 0900 WDT 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 full details see pdf report (485kB).

Tropical Cyclone Dominic, 22 - 27 January 2009

A low moved off the Kimberley coast during 24 January. This system moved steadily west and intensified into Tropical Cyclone Dominic by 0900 WDT 26 January. Dominic turned southwest and reached category 2 intensity before crossing the west Pilbara coast near Onslow at 0600 WDT 27 January. Wind gusts to 133 km/h (72 knots) were recorded at Onslow Airport and there was some minor structural damage and power lines brought down. Dominic weakened quickly over land although the remains of the system caused heavy rainfall and flooding in many parts of southern Western Australia. The Gascoyne River inundated many parts of Carnarvon. A train was derailed east of Kalgoorlie on 30 January apparently because of flowing water. Flash flooding was also reported in the wheatbelt including York and Quairading.

For full details see pdf report (906kB).

Severe Tropical Cyclone Freddy, 3 - 13 February 2009

A low that developed over the Kimberley moved off the coast on 3 February and slowly developed as it tracked west over open waters. Despite ongoing strong wind shear, the low reached cyclone intensity late on 7 February. After peaking on 8 February, Freddy weakened to below cyclone intensity during 9 February as it moved over progressively cooler ocean waters. A weak low level centre remained clearly visible on satellite images and Quickscat passes showed 20 to 25 knot winds present. The system finally dissipated on 13 February.

There were no known direct impacts from Freddy, although there were disruptions to some offshore industry operations.

For full details see pdf report (617kB).

Tropical Low 1, 11 - 17 February 2009

A weak low moved off the northwest Kimberley coast on 11 February and struggled to develop under strong wind shear. Despite convection continuing in the region of mid-level vorticity the surface low remained weak throughout its lifetime. The low approached the far west Pilbara coast on 16 February and combined with a mid-latitude upper trough to cause heavy rainfall over the western Pilbara and significant flooding on the Robe and Fortescue Rivers.

For full details see pdf report (593kB).

Tropical Low 2, 23 February - 2 March 2008

A weak low was initially identified off the Top End on 23 February and struggled to develop under easterly shear. The low remained ill-defined as it moved west southwest north of the Kimberley and then southwest eventually crossing the coast near Port Hedland at 9 pm WDT Saturday 28 February. Heavy rain caused some flooding from the east Pilbara extending to the eastern Gascoyne and adjacent northern Goldfields and Interior. Roads were closed and some mining operations were disrupted.

For full details see pdf report (95kB).

Tropical Low Gabrielle, 27 February - 6 March 2009

An Indian Ocean low formed in the monsoon trough in late February and was named Gabrielle on 2 March approximately 370 km south southeast of Christmas Island at 1200 UTC (2100 WDT). However, upon reanalysis the system was deemed not to have reached cyclone intensity on account of gales not extending more than half way around the centre at any one time. Gales or near gales were apparent in some sectors from 28 February to 5 March and shipping warnings continued until early on 6 March. There was no known impact from this low.

For full details see pdf report (406kB).

Severe Tropical Cyclone Ilsa, 15 - 24 March 2009

Ilsa was a small intense cyclone that moved in a general west southwest direction over open waters north and northwest of Western Australia. Ilsa reached category four intensity on 19 March, eventually weakening near 90°E by 24 March. There was no known impact associated with Ilsa.

For full details see pdf report (719kB).