Australia: Tropical Cyclone Ilsa tracking south-southwestward across the Indian Ocean as of early April 13 /update 4

Event

Tropical Cyclone Ilsa is tracking south-southwestward across the Indian Ocean early April 13. As of 11:00 AWST, the storm's center of circulation was approximately 295 km (183 miles) north of Port Hedland, Western Australia. Forecast models indicate that the storm will turn to track sou-southeastwards then southeastwards while strengthening into a Category 5 Severe Tropical Cyclone through the evening of April 13 before making landfall over the coast of northwestern Western Australia, east of Port Hedland late April 13. The storm will then weaken rapidly while tracking east-southeastward across central Western Australia before dissipating in southwestern Northern Territory early April 15. Some uncertainty remains in the track and intensity forecast; changes could occur in the coming days.

As of early April 13, the Australian Bureau of Meteorology (BOM) has issued a cyclone warnings for areas south of Broome to Whim Creek, including Port Hedland, and extending inland as far as Parnngurr, including Nullagine, Marble Bar, and Telfer. A cyclone watch is in place for inland areas from Parnngurr to Kiwirrkurra and southwest of Balgo. Emergency WA has issued a yellow cyclone alert for residents between Bidyadanga and Whim Creek, including Port Hedland, extending inland to include Marble Bar, Nullagine, and Telfer in the Kimberley and Pilbara and a blue cyclone alert for residents south of Broome to Bidyadanga, not including Bidyadanga, and inland areas to Parnngurr and Kiwirrkurra in the Kimberley and Pilbara.

The very destructive core of Ilsa, with extreme gusts of up to 275 kph (171 mph), is forecast to impact the coast between west of Bidyadanga and De Grey late April 13 before tracking inland early April 14; very destructive winds with gusts up to 170 kph (106 mph) are possible at Telfer. Destructive winds with gusts up to 155 kph (96 mph) are likely between Bidyadanga and Port Hedland the afternoon or evening of April 13, as far inland as Marble Bar late April 13, and to Telfer early April 14, while damaging winds with gusts of up to 90 kph (56 mph) are possible between the area south of Broome to around Port Hedland, the early afternoon of April 13. The damaging winds may extend further west to Whim Creek April 13 if Ilsa tracks further to the west. Damaging winds are forecast to extend inland to Parnngurr the afternoon of April 14, and possibly to Kiwirrkurra the evening of April 14.

Heavy rainfall and squally thunderstorms are likely over the western Kimberley and may extend to the eastern Pilbara April 13 and Northern Interior April 14. Between 20-40 cm (8-16 inches) of rainfall is forecast April 13-14 near where Ilsa crosses the coast. Abnormally high tides are possible about the coast between Broome and Port Hedland April 13. A flood watch is also in place for the west Kimberley and De Grey rivers as well as catchments in Salt Lake, Sandy Desert, Warburton, and Western Desert districts. Authorities have also issued flood warnings for the De Grey River Catchment and Sandy Desert.

Authorities have shipped in food and fuel to last Bidyadanga, Western Australia's largest remote Aboriginal community, seven days. Several residents requiring medical treatment have been evacuated to Broome. A large number of people in Broome remain homeless following the catastrophic flooding in January; a lack of shelter is likely to exacerbate Ilsa's impact. Pre-emptive evacuations are ongoing across multiple communities in the northwestern region of Western Australia, including Eighty Mile, Punmu, Telfar, and Wallal Downs. Holidaymakers and people traveling in caravans between Port Hedland and Broome have been evacuated. Authorities in Port Hedland have set up evacuation shelters in the town. Further voluntary evacuations are likely across other communities. No mandatory evacuation orders have been issued for entire districts, although authorities are facilitating pre-emptive evacuation operations. Authorities are clearing boats from all berths in the inner harbor of the Port Hedland Port, including iron ore carriers. Roadhouses along the Great Northern Highway are closed, including in Pardoo. The Great Northern Highway between Pippingarra Road and Broome Road as well as several other smaller roads, are closed. Authorities have warned that the North West Coastal Highway could be closed between Port Hedland and Broome due to flooding.

Sustained heavy rainfall could trigger flooding in low-lying areas and those with easily overwhelmed drainage systems. If weather conditions prove hazardous, localized evacuations, flash flooding, and landslides are possible.

The inclement weather could trigger localized business, transport, and utility disruptions and render some bridges or roadways impassable. Flight disruptions at regional airports and temporary closures of ports are also possible. Exposure to raw sewage and other hazardous materials mixed with floodwaters poses a severe health threat.

Advice

Activate contingency plans in areas where officials forecast tropical cyclone conditions. Heed any evacuation orders that may be issued. Use extreme caution in low-lying coastal areas and near streams, creeks, and other waterways due to the potential for severe flooding and storm surge. Stockpile water, batteries, and other essentials in advance. Charge battery-powered devices when electricity is available; restrict the use of cellular phones to emergencies only. Power down mobile devices when not in use. Keep important documents and necessary medications in waterproof containers. Observe strict food and water precautions, as municipalities could issue boil-water advisories following flooding events. Take precautions against insect- and waterborne diseases in the coming weeks.

Plan accordingly for protracted commercial, transport, and logistics disruptions in areas in the path of the storm, especially if vital infrastructure is damaged. Seek updated information on road conditions before driving or routing shipments through areas where flooding has occurred. Confirm flights before checking out of hotels or driving to the airport; clearing passenger backlogs may take several days in some locations.

Resources

Joint Typhoon Warning Center
Australian Bureau of Meteorology
Emergency WA