Australia: Tropical Cyclone Megan tracking southwestward over far northern Northern Territory afternoon of March 18 /update 4

Category 3 Severe Tropical Cyclone Megan is tracking southwestward over far northern Northern Territory the afternoon of March 18 following landfall over the Pellew Islands earlier in the day. As of 12:30 ACST, the storm's center of circulation was approximately 743 km (461 miles) east-southeast of Darwin.

Forecast models indicate that the system will weaken into a Category 2 tropical cyclone as it moves inland over northeastern Northern Territory late March 18. The storm is expected to weaken into a Category 1 tropical cyclone as it generally tracks west-southwestward over northeastern Northern Territory March 19 before weakening into a tropical disturbance as it tracks west-northwestward further inland over northern Northern Territory March 20. Some uncertainty remains in the track and intensity forecast; changes could occur in the coming days.

As of the afternoon of March 18, the Australian Bureau of Meteorology (BOM) has issued a cyclone warning from Port Roper, Northern Territory, to Mornington Island, Queensland, not including Mornington Island, extending inland to Borroloola, McArthur River Mine, and Robinson River, but not including Ngukurr.

The core of Megan, with winds of up to 200 kph (124 mph), is impacting the Sir Edward Pellew Group and will extend to adjacent coastal areas between Bing Bong and the Northern Territory-Queensland border through March 18. Destructive winds gusting up to 150 kph (93 mph) are forecast to extend to adjacent inland areas, including Borroloola, the afternoon and evening of March 18. Gales with damaging wind gusts of up to 120 kph (75 mph) are occurring along the coast between Nathan River and the Northern Territory-Queensland border and are forecast to extend to adjacent inland areas, including Borroloola, McArthur River Mine, and Robinson River March 18. The winds may extend further east to Mornington Island in Queensland, not including Mornington Island March 18 if Megan tracks further east. Gales have now eased over Groote Eylandt.

Heavy to intense rainfall is likely about the southwestern Gulf of Carpentaria coast March 18 and may even occur about parts of the Gulf Country in Queensland. The heavy to intense rainfall will extend to adjacent inland areas in the Carpentaria and northern Barkly forecast districts as the system crosses the coast and moves inland March 19. Coastal residents between Bing Bong and the Northern Territory-Queensland border are warned of a dangerous storm tide as Megan makes landfall. Tides will likely rise significantly above the normal high tide, with damaging waves and dangerous flooding. Abnormally high tides are likely over the remaining parts of the southern Gulf of Carpentaria over the coming days and will likely rise above the normal high tide at times.

The BOM has issued a severe weather warning for heavy, locally intense rainfall and damaging winds across parts of Carpentaria and Barkly districts in Northern Territory. The BOM is also maintaining flood watches across the affected area and surrounding river catchments. A moderate flood warning is in place for the Daly River.

Reports indicate that around 700 people are being evacuated from the town of Borroloola to McArthur River Mines and onwards to the Foskey Pavilion and Marrara Sporting Stadium in Darwin via air. An unconfirmed number of residents in Gunbalanya in western Arnhem Land were evacuated due to rising floodwaters March 15 as heavy rainfall hit parts of the Top End. Authorities have advised residents in the cyclone warning area who are not able to shelter safely to relocate if safe to do so. Those choosing to self-evacuate are being advised to register with their local police station prior to departure. Emergency services have urged residents remaining in the area to prepare their properties, secure loose items, ensure enough water is on hand, check on neighbors, prepare to take shelter, and listen to emergency service warnings.

Heavy rainfall and strong winds have been ongoing over Groote Eylandt in recent days as the system passed to the east of the island; authorities have reported widespread flooding, downed trees, and some damage to infrastructure. Some residents are without power and water supply and several roads are impassable due to floodwaters, leaving some communities isolated. The GEMCO manganese mine is closed due to flooding and damage to itself and its wharf.

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

The inclement weather could trigger localized business, transport, and utility disruptions, rendering some bridges or roadways impassable. Flight disruptions at regional airports and temporary closures of ports are also possible. Stagnant pools of water during and after flooding increase insect- and waterborne diseases, such as dengue fever, cholera, and malaria. Raw sewage and other hazardous materials mixed with floodwaters pose a serious health threat.