In the three and a half months since the third week of May, rough weather events — heavy rains, squalls and high tides — prompted the Bangladesh Meteorological Department (BMD) to issue a marine cautionary signal 13 times.
Back-to-back low pressures together with a strong monsoon triggered the rough weather, leading to frequent cautionary signal number three, with its direct and indirect consequences felt across Bangladesh.
Direct consequences included strong waves and tides lashing the coast, rivers swelling and crossing danger marks, and heavy rains disrupting life and business.
Well-off city dwellers mostly felt the impact indirectly, through higher prices of Hilsa and vegetables.
“Bad weather greatly reduced Hilsa production. The sea remained so rough that we could barely afford to go fishing,” said Al Amin, a fish trader from Mohipur in Patuakhali.
Three trawlers Al Amin recently sent to the Bay of Bengal returned in less than two days. Each trawler caught Hilsa worth Tk5 lakh on average, just a fifth of regular seasonal production.
“Sea fishing accounts for at least 70% of annual Hilsa production,” said Md Anisur Rahman, a Hilsa researcher and former director at the Bangladesh Fisheries Research Institute.
Fishing usually requires fishers to travel 12 hours into the sea. In a recent field visit, BMD officials found that fishing by ordinary trawlers starts about 50km off the coast.
The BMD’s forecast reaches up to 57km off the coast.
Two of the latest low pressure systems formed less than two days apart. The last one appeared on August 27 and dissolved on August 29.
August is usually peak Hilsa season, when schools of fish swim upstream into rivers and kitchen markets overflow with fresh catch. The season continues until the ban comes in October.
This August alone, particularly after the 13th, the BMD issued cautionary signals four times. In July it was four times, in June three times and in May twice.
The signals meant serious disruption in fishing, especially after the universal two-month ban from March to April.
A cautionary signal can last three to five days, warning of heavy rain, wind speeds up to 50kmph and tides leaping five meters — either separately or at once.
Such conditions prevailed for 39 to 65 days out of the last 100 due to interaction between wind and temperature in the Bay of Bengal, which is about 15 times the size of Bangladesh.
“Monsoon was rather strong this year and the overall weather condition was not comfortable for many people,” said Muhammad Abul Kalam Mallik, a senior meteorologist at the BMD.
Worse than before?
Bangladesh this year saw the earliest onset of monsoon in four and a half decades. Monsoon signifies a seasonal shift in wind flow, particularly from south to north.
Since 1981, the BMD’s Changing Climate of Bangladesh report (2024) shows monsoon reached Bangladesh’s coast in late May 11 times, eight of them since 2000. Monsoon officially begins in June.
The influence of global warming on monsoon patterns in South and Southeast Asia is still being studied. Some studies suggest fewer low pressure systems in the Bay of Bengal due to global warming.
The BMD’s climate report echoed a World Bank study that global warming is altering Bangladesh’s seasonal pattern.
Ten or more low pressure systems formed in a single monsoon only six times between 1981 and 2019. The highest was 13 systems in 1989.
The ongoing monsoon has already seen at least six low pressure systems, with a month still to go. September, the last monsoon month, historically sees more low pressures than the others.
In April this year, US-based MIT predicted that monsoon and cyclone seasons would begin to overlap due to climate change, unleashing once-in-a-century storm tides once every decade.
A low pressure system forms when more air rises, lowering surface pressure. Scientists say higher temperatures increase both the air’s upward movement and its capacity to hold water vapor.
Both monsoon and low pressure systems move toward land, bringing rain, wind and tides.
Inside the impact zone
Frequent low pressures, with potential to intensify into cyclones, could bear long-term consequences for Bangladesh, a low-lying delta ranked among the most climate vulnerable in the world.
Since the monsoon set in, low-pressure-triggered inclement weather has breached levees, washed away houses and crops and repeatedly disrupted electricity supply to millions.
Waterway communication was often suspended while villages, towns and cities were swamped, forcing hundreds to leave their homes to escape flash floods and landslides.
Well-off citizens largely kept their livelihoods intact, but many of the poor — nearly a third of 171 million people — were left crippled. Farmers, rickshaw-pullers, transport and construction workers cannot afford to stay indoors.
Almost record-breaking rains swept parts of Bangladesh in June. Teknaf, the country’s southernmost tip, recorded over 1,144mm of rainfall — slightly below its historic record of 1,290mm and more than four times the normal amount expected in June, according to the Flood Forecasting and Warning Centre (FFWC).
Khagrachhari’s Ramgarh and Feni’s Parshuram also recorded far higher than usual rainfall in June.
In July, Teknaf saw 1,384mm of rain, just below its record 1,432mm, and again more than four times the normal average.
Cox’s Bazar recorded 1,401mm of rain against a monthly average of 945mm, Noakhali saw 1,171mm against 739mm, and Parshuram 872mm against 562mm.
On July 7, the FFWC reported the Muhuri River rose 509cm in six hours until 3pm, while the Belonia River rose 532cm in eight hours until 5pm.
Newspapers reported that the heavy rainfall continued for at least two more days, submerging villages, towns and cities under knee-deep water and washing away houses, crops and fish enclosures. A flash flood struck Feni, Noakhali and Cumilla.
For many living along the coast, the July disaster came just weeks after the May 30 one.
Heavy rain, wind and tides left millions without electricity in 14 coastal districts.