Tropical Cyclone Grant

Northern Territory Regional Office

Track of Tropical Cyclone Grant

A tropical low formed within an active monsoon trough over the Arafura Sea, north of the Top End in the Northern Territory, during the 21 December. For the next few days, the movement of the tropical low was erratic due to the competing influence of strengthening monsoonal northwesterly winds to the lows north and southeasterly winds to the lows south. During the 23 and 24 December, the tropical low began intensifying and at 3:30 am on Christmas Day the tropical low was named Tropical Cyclone Grant, about 60 km north of the Cobourg Peninsula.

During the 25 December, TC Grant moved slowly to the southeast and intensified to a category 2 tropical cyclone at 3:30 pm when located approximately 20 km to the north northeast of Croker Island on the Cobourg Peninsula. TC Grant then took a southward path, passing just to the east of Croker Island before before making landfall on the Cobourg Peninsula at about 9:00 pm as a category 2 tropical cyclone.

During the early morning of 26 December, TC Grant moved southwards over the far eastern Van Diemen Gulf, crossing the coast again as a category 2 tropical cyclone over the far southeastern Van Diemen Gulf. TC Grant weakened rapidly once over land and was downgraded to below tropical cyclone intensity at 12:30 pm on 26 December, approximately 30 km northwest of Jabiru.

TC Grant caused torrential rainfall over parts of the Cobourg Peninsula and the adjacent north coast of the Arnhem district. Many trees were brought down in the community of Minjilang on the Cobourg Peninsula and the surrounding outstations and power supply was interrupted. Coastal erosion and minor flooding of low lying coastal areas was reported between the Cobourg Peninsula and Nhulunbuy due to spring tides, larger than usual swell and strong onshore monsoonal winds. The Automatic Weather Station at McCluer Island, 40 km east of Croker Island, reported a maximum wind gust of 118 km/h at 6:00 pm on 25 December. This was the strongest wind gust measured by an instrument for this event.

After crossing the coast, ex-TC Grant continued moving south then southeast over the Top End during the 26 December. Overnight on the 26 December and during the early morning of the 27 December heavy rainfall occurred over the Edith, Cullen and Fergusson River Catchments, including 385 mm at Edith River Falls in the 24 hours to 9am on 27 December. A rapid river rise damaged a railway bridge and caused a train to derail while crossing over it. Significant damage was also made to the Stuart Highway rendering it impassable for two to three days.

Ex-TC Grant moved steadily to the east over the Top End of the Northern Territory during the 27 December and moved over the Gulf of Carpentaria during the evening of the 28 December. Tides were abnormally high in the Gulf of Carpentaria during this time. The low continued moving east, crossing over northern Cape York Peninsula in Queensland during the 30 December before moving into the Coral Sea later that day.

TC Grant was the first tropical cyclone for the 2011/2012 cyclone season to occur within the Northern Region (Darwin's Tropical Cyclone Warning Centre area of responsibility) and the third tropical cyclone to occur within the Australian Region.

Extreme values during cyclone event (estimated)
Note that these values may be changed on the receipt of later information
Maximum Category:2
Maximum sustained wind speed:100 km/h
Maximum wind gust:140 km/h
Lowest central pressure:978 hPa