Madagascar: Adverse weather forecast across much of the country through at least March 9 /update 1

Severe weather is forecast across much of Madagascar through at least March 9. A low-pressure system with the potential for cyclonic development is expected to move southward and southwestward over the Mozambique Channel over the coming days, passing close to the southwest coast of Madagascar. The system will bring heavy rainfall and thunderstorms to southern regions and scattered showers and storms across much of the rest of the country. Storms may be accompanied by strong wind gusts and lightning. Rough seas are also expected in coastal areas. Rainfall totals of 5-12 cm (2-4.7 inches) are expected in southern regions. Heavy downpours may trigger flooding in low-lying areas and landslides on unstable slopes.

As of March 6, the Madagascar General Directorate of Meteorology has issued the following warnings:

• Red heavy rain warnings (the middle level on a three-tier scale): Taolagnaro District in Anosy Region, Morombe and Toliara I and II districts in Atsimo-Andrefana Region, and Manja and Morondava districts in Menabe Region.

• Yellow heavy rain warnings: Across Androy, Fitovinany, Ihorombe, Matsiatra Ambony, and Vatovavy regions and Amboasari Atsimo and Betroky districts in Anosy Region, Ampanihy, Ankazoabo Atsimo, Benenitra, Beroroho, Betioky Atsimo, and Sakaraha districts in Atsimo-Andrefana Region, and Mahabo District in Menabe Region.

• Yellow heavy swell warnings: Across parts of the western coastline.

Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.

Sustained heavy rainfall could trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed stormwater drainage systems. Sites downstream from large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Landslides are possible in hilly or mountainous areas, especially where heavy rain has saturated the soil. Disruptions to electricity and telecommunications services are possible where significant flooding, strong winds, or landslides impact utility networks.

Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters.

Severe weather could also trigger flight delays and cancellations at airports in the affected regions. Flooding could block regional rail lines; freight and passenger train delays and cancellations are possible in areas with heavy rainfall and potential track inundation.

Localized business disruptions may occur in low-lying areas; some businesses might not operate at full capacity because of flood damage to facilities and some employees' inability to reach work sites.

Flooding could heighten the threat of disease outbreaks. Backflow from drains mixed with floodwaters can become trapped in open areas when inundations recede. These stagnant pools often become breeding grounds for mosquitoes and bacteria, increasing the incidence of insect- and water-borne diseases. Exposure to contaminated water from inundated industrial sites, sewer systems, and septic tanks also poses a significant health threat.