Southern Indian Ocean: Tropical Low Three weakens as it tracks in the southern Indian Ocean on Dec. 10; landfall possible in Western Australia on Dec. 11 /update 1

Event

Tropical Low Three has weakened as it tracking southeast in the southern Indian Ocean, Dec. 10. As of 0200 AWST, the storm's center of circulation was approximately 653 km (405 miles) southeast of Christmas Island, Australia. Forecast models indicate the storm will largely maintain its strength as a tropical low or may strengthen into a category-1 tropical cyclone equivalent storm as it tracks southeastward in the Indian Ocean over the coming days. The system would then be given the name Imogen. The system is forecast to make landfall in Western Australia on Dec. 11, possibly near Port Hedland. Some uncertainty remains in the track and intensity forecast, and significant changes could occur in the coming days. Australia's Bureau of Meteorology (BOM) has issued a severe weather warning for Pilbara District, Western Australia for damaging winds and heavy rainfall in advance of the system; depending on the track, the warning could be expanded to include other districts. Weather warnings could remain active even after the system's immediate threat has diminished, as some areas may still be highly susceptible to rain-induced hazards. The possibility of localized evacuations cannot be discounted if weather conditions prove particularly hazardous.

Hazardous Conditions
Tropical Low Three will bring heavy rainfall, strong winds, and rough seas to areas of Western Australia, beginning Dec. 10. Forecast models indicate 5-10 cm (2-4 inches) are possible in the hardest-hit areas of Western Australia near where the system makes landfall, including portions of Kimberley and Pilbara districts. Lower amounts are expected farther away from the center of circulation. Sustained heavy rainfall could trigger flooding in low-lying communities near streams, creeks, and rivers, as well as in urban areas with easily overwhelmed or a lack of stormwater drainage systems. Sites located downstream of large reservoirs could experience flash flooding after relatively short periods of intense rainfall, especially in areas of Western Australia currently experiencing heavy rainfall from the antecedent tropical low. Rain-induced landslides cannot be discounted in steeply sloped terrains. Flooding could isolate some communities for several days. Coastal flooding and abnormally high tides are possible along Australia's western coast.

In addition to the heavy rain, flooding, and storm surge, the system may produce damaging wind gusts as it approaches landfall. Gusts reaching 90 kph (60 mph) are possible, especially in areas near the center of circulation. Widespread and prolonged power outages due to uprooted trees and toppled utility lines are possible.

Transport
Inclement weather associated with the storm could trigger localized business, transport, and utility disruptions through at least Dec. 10. Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Areal flooding in urban locations could also result in severe traffic congestion, while strong winds will pose a hazard to high-profile vehicles. Heavy rain and low visibility may trigger flight disruptions at regional airports including, but not limited to, those serving Broome (BME). Disruptions caused by inclement weather and resultant hazards, such as flooding, could persist well after conditions have improved. If there is severe damage to infrastructure, repair, or reconstruction efforts may exacerbate residual disruptions.

Advice

Activate contingency plans in areas where officials forecast tropical storm conditions. Heed all evacuation orders. Use extreme caution in low-lying coastal areas and near streams, creeks, and other waterways due to the high 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 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. Keep any necessary medications in a waterproof container.

Plan accordingly for 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

Bureau of Meteorology