Madagascar: Adverse weather forecast to continue across eastern regions through at least June 3 /update 1

Severe weather is forecast to continue across parts of eastern Madagascar through at least June 3. Heavy rainfall is expected across the Ambatosa, Analjirofo, central and northern Antsinana, and southern Sava regions over the coming days and strong winds will likely generate rough seas in coastal areas. Daily rainfall totals of 4-9 cm (1.6-3.1 inches) are likely across the affected area May 31 and further intermittent moderate showers are expected in the region June 1-2. The heavy downpours may trigger flooding, rising river levels, and landslides in the region. As of May 31, the Madagascar General Directorate of Meteorology has issued red heavy rainfall warnings (the highest level on a three-tier scale) across the affected area, as well red rough sea warnings for coastal areas. 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. Authorities may temporarily suspend port operations if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. 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.