Red Cross/ Red Crescent Climate Centre

2018 South Asia monsoon

There are various forecast products available that could help humanitarian decision-making in the camps in Cox’s Bazar, where levels of exposure and vulnerability to an otherwise routine seasonal hazard – the South Asian monsoon – are acute and getting more serious by the day.

The Climate Centre’s advice is that the single-most useful are the English-language short-term rainfall forecasts (‘meteograms’) issued by the Bangladesh Meteorological Department (BMD). Look for rainfall in mm vertically in green on the lowermost chart, with dates along the bottom divided into 6-hour phases at 00:00, 06:00, 12:00 and 18:00 GMT. The rainfall readings at these times indicate the total in the preceding six hours.

Also on the BMD site are summaries of the weather for the next 24 hours and any relevant warnings.

There are two peak cyclone seasons in Bangladesh: April to May and October to November, and the BMD produces a special weather bulletin if there is a cyclone in the Bay of Bengal, as does the India Meteorological Department.

The single-most authoritative monsoon outlook covering June to Deptember – for a ‘normal’ monsoon – was issued by the South Asian Climate Outlook Forum (SASCOF) meeting in Pune, India, disseminated by the World Meteorological Organization, and given wide publicity regionally.

Seasonal forecasts from any source, however, are not regarded as useful for humanitarians in this context due to the difficulty of forecasting the monsoon reliably; they only provide a predicted monthly total and give no indication of the short-term intensity of rainfall – both key issues this year in Cox’s Bazar.

It’s also important to note that – again, given the sheer number of people involved and the level of exposure and vulnerability – even a below-average monsoon will pose grave risks. (‘Normal’ in the context of Bangladesh is conventionally regarded as up to 600mm of rain in July at the monsoon’s peak; by comparison the UK – a country famous for its rainy weather – got 1,133mm in the whole of last year.)

On average the wettest monsoon months in Bangladesh, both in terms of total rainfall and number of rainy days, are June, July and August; May and September are also very wet. July tends to see the most intense rain.

It can also be dangerously hot in April and May in the run-up to the monsoon proper, with possible highs well above 30 degrees Celsius.

(The single-most authoritative risk-mapping exercise for Cox’s Bazar that we are aware of remains the report released in January by IOM-UNHCR, which attempted to cover flood, landslide and access risks. It may be that the terrain has been altered since then by emergency earthworks, and new arrivals will have been generating new areas of humanitarian risk that may not have been mapped previously.)

This page of our website will be updated periodically as new information becomes available.

For any further questions disaster managers are encouraged to contact ifrc@iri.columbia.edu.