Bay of Bengal: Deep Depression Yaas forms May 24, landfall forecast in India's Odisha and West Bengal states, May 26

Event

Deep Depression Yaas has formed in the Bay of Bengal off the eastern coast of India, May 24. The system is currently tracking in a northwestward in the Bay of Bengal towards northeastern India. As of 11:30 IST, the storm's center of circulation was approximately 667 km (414 miles) south-southeast of Kolkata, India. The system is forecast to track slowly north-northwest and to intensify into a severe cyclonic storm by May 25. The storm is forecast to continue to intensify and track north-northwestwards before making landfall as a Very Severe Cyclonic Storm between far northeastern Odisha and far southern West Bengal states, May 26. Following landfall, the system will weaken into a Cyclonic Storm as it tracks northwestward over Odisha and West Bengal states and into Jharkhand state. Finally, the storm will weaken rapidly into a Depression as it moves into Bihar State and dissipates.

Government Advisories
As of May 24, the India Meteorological Department (IMD) has issued yellow- and orange-level warnings for heavy rainfall, strong winds, and thunderstorms across portions of eastern India including, Andhra Pradesh, Odisha, West Bengal, Jharkhand, and Bihar States. Authorities will likely issue new warnings or update existing advisories throughout the system's progression in the coming days. Weather warnings could remain active even after the system’s immediate threat has diminished, as some areas may still be highly susceptible to rain-induced hazards. The possibility of localized evacuations cannot be discounted if weather conditions prove particularly hazardous.

Hazardous Conditions
The storm is likely to bring heavy rainfall, strong winds, and rough seas to coastal areas of eastern India and far western Myanmar over the coming days. Nepal and Bangladesh would also likely experience heavy rainfall and strong winds beginning May 26. Sustained heavy rains could trigger further flooding in low-lying communities near streams, creeks, rivers, and urban areas with easily overwhelmed or a lack of stormwater drainage systems. Sites located downstream of large reservoirs could experience flash flooding after relatively short periods of intense rainfall. Rain-induced landslides are possible in steeply sloped terrains. Flooding could isolate some communities for several days. Prolonged swells and storm surge generated by the system will likely result in coastal flooding as the system approaches land. Persistent onshore flow could make it difficult for the surge to recede and for water levels to decrease in coastal river catchments.

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 could render some bridges 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. 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.

Health
Stagnant pools of water during and after flooding increase the incidence of insect- and waterborne diseases, such as dengue fever, cholera, and malaria. The threat of these disease outbreaks is usually elevated in low-income or underdeveloped areas of major urban centers due to incomplete or open sewer lines. The latent threat of waterborne contaminants from inundated industrial sites cannot be discounted; exposure to raw sewage and other hazardous materials mixed with floodwaters poses a serious health threat.

Advice

Activate contingency plans in areas where officials forecast adverse conditions. Heed any evacuation orders that may be issued. 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 protracted 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
India Meteorological Department
Department of Meteorology and Hydrology (Myanmar)
Bangladesh Meteorological Department
Department of Hydrology and Meteorology (Nepal)