Indian Ocean: Severe Tropical Storm Chido tracking westward towards Agalega, Mauritius, early Dec. 11 /update 1

Severe Tropical Storm Chido is tracking westward across the Indian Ocean, towards Agalega, Mauritius, early Dec. 11. As of 01:00 EAT, the system was around 1,083 km (673 miles) north-northeast of Port Louis, Mauritius.

Forecast models indicate that the storm will strengthen into a tropical cyclone as it continues westward and makes a close approach to Agalega, Mauritius, late Dec. 11, passing just south of the islands before weakening slightly and making landfall over the northern Diana Region in Madagascar late Dec. 13. The system is likely to weaken into a severe tropical storm as it tracks southwestward across the Mozambique Channel before making a close approach to Mayotte late Dec. 14 and landfall over eastern Nampula Province in Mozambique late Dec. 15. Some uncertainty remains in the track and intensity forecast; changes could occur in the coming hours and days.

The Mauritius Meteorological Services (MMS) has issued a special weather bulletin warning that a heavy rain warning, a strong wind warning, and a heavy swell warning are in force in Agalega. The weather will be cloudy to overcast with scattered moderate to heavy showers with thunderstorms. During the thundery showers, the public is advised to stay indoors, to avoid the plains, and to avoid taking shelter under trees. Wind will strengthen from late Dec. 10; gusts of up to 100 kph (62 mph) are expected from Dec. 11. The sea will gradually become very rough late Dec. 10 with swells of around 4 meters (13 feet); the public is advised not to venture at sea and to avoid the beaches. As Chido approaches Agalega, storm surges with waves reaching 7 meters (23 feet) may affect the coast Dec. 11.

Meteo Madagascar has issued green (lowest level on a three-tier scale) strong swell warnings across northern and northeastern Madagascar. Seas will be strong to very strong, with waves of around 2.5-3.5 meters (8-11.5) between Angotsy and Toamasina and 3.5-4.5 meters (11.5-15 feet) between Sambava and Angotsy, reaching 5-8 meters (16.5-26 feet) near the northern tip Dec. 12-13.

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. 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.