Indian Ocean: TD Chalane tracking over Madagascar Dec. 27 /update 4

Event

After making landfall in northern Madagascar, Tropical Depression Chalane continues tracking southwestward over the country; as of 0900 EAT Dec. 27, the center of circulation was approximately 89 km (55 miles) north of Antananarivo, Madagascar, with the system carrying maximum sustained winds of 25 knots (45 kph, 30 mph). The latest forecast guidance indicates the storm will maintain its strength as it moves across Madagascar. Afterward, the system is expected to turn back to the west in the Mozambique Channel early Dec. 28 and will increase in strength to a moderate tropical storm. A subsequent landfall is forecast in central Mozambique, possibly just south of Beira, Dec. 30. The system will then track inland over Zimbabwe, and then on to Botswana, where it will likely dissipate over north-central areas of the country Jan. 1, 2021. Significant uncertainty remains in the track and intensity forecast, and significant changes could occur in the coming days.

Government Advisories
Meteo Madagascar has issued red- and yellow-level warnings for eastern coastal areas of central Madagascar, and yellow-level warnings for western coastal areas. Authorities in Madagascar could expand or rescind those warnings depending on the track of Chalane. Additionally, authorities in Mozambique, Zimbabwe, Botswana, possibly South Africa, may issue weather warnings over the coming days.

Hazardous Conditions
Depending on the track of the storm, there is likely to be strong winds and heavy rainfall in northern and central Madagascar beginning Dec. 26, Mozambique, especially Nampula, Zambezia and Sofala provinces, beginning Dec. 29, and Zimbabwe, much of Botswana, and far northern South Africa beginning Dec. 30. Sustained heavy rainfall could trigger flooding in low-lying communities near streams, creeks, and rivers, as well as in urban areas with easily overwhelmed stormwater drainage systems. Sites located downstream of large reservoirs could experience flash flooding after relatively short periods of intense rainfall.

Transport
In addition to the immediate threat to personal safety, inclement weather associated with the storm could trigger localized business, transport, and utility disruptions. 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. High winds and rough seas could prompt temporary port closures. Heavy rain and low visibility may trigger flight disruptions at regional airports. Disruptions triggered 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

Joint Typhoon Warning Center