A. Situation analysis
Description of the disaster
According to India Meteorological Department (IMD) on 19 May 2021 forecast report, a low-pressure area is very likely to form over north Andaman Sea and adjoining east central Bay of Bengal (BOB) by 21 May 2021. It is very likely to intensify gradually into a cyclonic storm during subsequent 72 hours.
Wind Forecast in global and national model:
The European Centre for Medium-Range Weather Forecasts (ECMWF) model identified the probability of forming the low pressure with subsequent cyclonic storm since 16 May 2021. The forecast track of ECMWF model predicts the formation of the low pressure, movement of the cyclonic storm and landfall of the cyclonic storm. It shows a likelihood of forming a cyclonic storm on 23 May 2021 and landfall in West Bengal with a wind speed of more than 150 kilometers per hour on 26 May 2021.
It is expected to make a landfall on Sundarbans of West Bengal part but may have an impact on the coastal district of Bangladesh especially the western to central coastal districts. The diameter of the cyclone may be up to 500 kilometers as of 20 May 2021 forecast.
The Global Forecast System (GFS) identified the low pressure which may form cyclonic storm subsequently since 17 May 2021. There is highly likelihood of forming a cyclonic storm on 23 May 2021 which may landfall on 26 May on the coast of India’s West Bengal State, next to Bangladesh’s Sundarbans. This model also shows that it may make an impact on the western coastal district of Bangladesh. The diameter of the cyclonic storm may be more than 450 kilometers.
Bangladesh Meteorological Department (BMD) also identified the probability of forming a low pressure since 18 May 2021. The low-pressure area is very likely to form over north Andaman Sea and joining east central Bay of Bengal. It is likely to intensify into cyclonic storm. The cyclonic storm is likely to move northwest wards and cross India’s Odisha and West Bengal States, and Bangladesh’s Khulna-Barguna-Patuakhali coastal districts by 26 May 2021.
According to Weather Research and Forecasting (WRF) forecast model and weather bulletin of BMD, the cyclone may make a landfall on the coast of West Bengal but there are possibilities to make landfall on central coast of Bangladesh.
BDRCS with technical support from Red Cross Red Crescent Climate Centre prepared a probable impact map for Bangladesh based on the wind speed and landfall location which is currently expected to be between Odisha and West Bengal in India. The impact map shows that all of Bangladesh’s coast and islands may observe 60-100 kilometers per hour of wind speed given the cyclone’s diameter of up to 500 kilometers. Based on historical data and the impact analysis done for BDRCS’ Cyclone Early Action Protocol, a wind speed of 80 to 100 kilometers per hour will lead to all Kucha and Jhupri houses to be destroyed. The impact map has been generated using the reduction factor model. Storm surge forecast also shows 4.2 meters at Pasur river at the time of landfall. As there is a new moon at the time of landfall the normal tide is also 1 meter higher than regular time.
From the preliminary analysis of the impact map more than 3 million people along the sea facing coastal districts are in danger of higher level of risk/impact. A wind speed of 80 to 100 kilometers per hour will lead to the destruction of more than five hundred thousand Jhupri and Kucha houses.
The trigger used in BDRCS’ Cyclone Early Action Protocol (EAP) states that an activation will take place when the forecasted windspeed is greater than 125 kilometers per hour which corresponds to a return period of one in five years. The EAP impact analysis considers the exposure and vulnerability of all houses in the affected Unions and all Unions with more than 25 per cent of all houses at risk of being destroyed will be considered for early action implementation. The National Society has yet to revalidate their cyclone EAP triggered in 2020. However, given the slightly lower windspeed of the currently forecasted cyclone, the impact will still be considerable and this imminent DREF will allow BDRCS to support the affected communities adequately.