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The monsoon is set to complete its withdrawal from Bangladesh today, said the Bangladesh Meteorological Department on Sunday, officially noting the end of the most important season which has been rather erratic this time.  

Monsoon, the four-month-long period of the year starting in June, is expected to bring farmers relief by giving ample rain to naturally irrigate crop fields and replenish the ground water supply.

But the outgoing monsoon rather unleashed a spell of drought, followed by frequent extreme events of rain and flash floods, leaving property and crops in parts of Bangladesh in ruins, affecting millions.

‘The effects of bad monsoon are evident and reflected in the high food prices,’ said Arif Hossain, in-charge of BMD’s agriculture weather forecast.

The roars of thunder that lately filled the mornings and afternoons were actually the announcement of the monsoon withdrawal, with the dry, cold western wind gaining ground, pushing the southerly wind away.

The onset of monsoon is the arrival of southerly wind, which picks up a lot of moisture as it travels over the Indian Ocean towards Bangladesh and India.

‘Despite the withdrawal of monsoon, a wet spell for several days is likely to set in around October 16,’ meteorologist Monowar Hossain said.

Last year, the monsoon withdrew on October 16. The year before the past year, the monsoon withdrew from Bangladesh on October 20.

This is the earliest withdrawal of monsoon since 2018, when the withdrawal was completed on October 5. The earliest withdrawal of monsoon was recorded on September 27 in 1984. In 2021 and 2020, monsoons marked the most delayed withdrawal – both on October 22.

The outgoing monsoon set in on June 3, the third earliest onset of the season considering data saved with the BMD since 1981, renewing hopes among Bangladesh’s farmers hit frequently with disasters.

But the first month of the season - June – turned out to be rain deficient with an overall 9 per cent less rainfall compared with the normal average rain for the month. Sylhet division, however, recorded 122 per cent more rainfall than normal, witnessing a spell of flash flood that affected 50 lakh people in northern and northeastern districts.

June saw only one low pressure, one of the main factors influencing monsoon rains, to form over the Bay of Bengal. Bangladesh’s highest rainfall of 257mm was recorded on June 8 in Sylhet. June was 1.7C warmer compared with the month’s average temperature. June saw a rather rare heat wave. Farmers in Rajshahi suffered from a spell of drought.

Monsoon got even drier in July with 17.6 per cent less rainfall than the average normal. Except for Sylhet, seven divisions received less rainfall than expected despite two low pressures formed. July was 1.9C warmer than the average temperature for the month. The highest rainfall of 309mm was recorded in Cox’s Bazar on July 11. Six Rohingyas were killed due to landslide because of heavy rain. 

Finally, rain started pouring down in August with 56.2 per cent excess rainfall. Three low pressures formed over the month causing rain in almost all over Bangladesh except Rangpur.

In the third week of August, an unprecedented flash flood swept Bangladesh’s eastern, north-eastern and southeastern districts, affecting six million people and killing at least 70. The month’s highest maximum rainfall of 276mm was recorded in Feni on August 1.

September witnessed 33 per cent more rain than normal with three low pressures formed in the month. Cox’s Bazar recorded the country’s highest rainfall of 378mm on September 12. Still, the month was 1.8C warmer than the normal average.

A fresh flash flood struck following another spell of extreme rainfall over vast swathes in Bangladesh and India on October 1. The flood swept through the division of Mymensingh, affecting half a million people.

‘The flash floods were extreme in the sense that they occurred in unusual places at unusual time with unusual destructive power,’ said meteorologist Arif.

There were pockets of disasters in which farmers were very badly affected, he said, adding that from standing crops to domesticated animals were washed away by the flash floods.

The August flood, estimated by the Center for Policy Dialogue, affected 11 districts, inflicting losses of Tk 14,421.46 crore. The agriculture and forestry sector suffered the worst with damage estimated at Tk 5169.71 crore—which is 35.85 per cent of the total damage.

The BMD warned that a low pressure area might form over the Bay of Bengal in a day or two.

‘There is no denying that the extreme events are signs of changing climate,’ said Muhammad Abul Kalam Mallik.

‘The extremes are likely to increase. We need to prepare,’ he said.