Bangladesh is likely to see higher-than-normal rainfall this winter with two to four low-pressure systems forming over the Bay of Bengal, at least two of which will potentially intensify into depressions or cyclones, according to a seasonal forecast issued by the Bangladesh Meteorological Department (BMD). This forecast is applicable for November, December, and January. Winter is the key cropping season for vegetables, potatoes, onions, garlic, and other essential produce that meet annual demand in the country. Agriculture experts warn that excessive rainfall during this period could severely damage these crops.
Typically, BMD prepares rainfall forecasts using both deterministic analysis and long-term climate averages. In climatology, rainfall over a period of 30 years or more is treated as the benchmark for “normal.” Deterministic forecasts express deviations from this average. If the expected rainfall is 20 percent below normal, it is considered lower than normal. A deviation of 20 percent or more above the average is considered higher than normal, while anything within that range is treated as normal precipitation.
According to the three-month outlook, rainfall this November may exceed normal levels by up to 21 millimeters across several regions. In Chattogram Division, the normal average for November is 39 millimeters. However, this year’s outlook forecasts around 60 millimeters. In December, the country’s normal rainfall is 9.6 millimeters. But Sylhet may see up to 18 millimeters this time around. Dhaka and Chattogram could receive as much as 15 millimeters. In January, the national average is 9 millimeters, with Khulna forecasted to receive 13 millimeters this time. Meanwhile, most other divisions—except Rajshahi—may see around 10 millimeters.
The BMD warned that excessive rainfall may lead to waterlogging, delayed crop growth, lodging of transplanted Aman, and crop failure. The forecast also mentions the risk of damage to the seedbeds of various crops.
Speaking to Bonik Barta, BMD meteorologist Dr. Muhammad Abul Kalam Mallik said, “Long-range forecasts are prepared based on climate behaviour. A specialist panel analyzes historical rainfall, low-pressure formation, and weather patterns over the same period. Forecast accuracy is classified as fair, good, very good, excellent, and extraordinary. Globally, long-range or three-month forecasts typically fall under the ‘fair’ category. However, it is usually mentioned in seasonal forecasts because the weather is usually like this during these times. Daily or five-day-ahead forecasts are more accurate.”
Global warming is disrupting the timing of seasonal transitions. Stating that meteorologists, climatologists, and researchers are also facing challenges due to climate change, he added, “Weather systems generally form in two ways. One emerges and dissipates quickly, while another develops and ends gradually. Due to global warming, seasonal patterns have shifted worldwide. In Bangladesh, there have been changes in both the arrival and the end of the seasons. The duration of each season has also changed, affecting rainfall patterns, thunderstorms, and other weather characteristics”.
Heavy rainfall on the last day of October and the first week of November this year already affected several regions in the country. BMD data show that rainfall exceeded monthly averages in at least 15 locations. Panchagarh’s Tetulia recorded the highest at 170 millimeters, followed by 166 millimeters in Sirajganj’s Tarash, 164 millimeters in Tangail, 121 millimeters in Narayanganj, and 117 millimeters in Gopalganj. Dhaka recorded 63 millimeters.
Officials said heavy rainfall in the first week of November caused significant agricultural damage. Crops worth more than BDT 2 billion were affected across 29 districts, impacting 125,926 farmers.
According to a report by the Department of Agricultural Extension (DAE), rainfall in November has affected crops on 32,450 hectares of land. Of that, at least 6,235 hectares have been damaged. This has amounted to losses of BDT 2.11 billion. Aman paddy suffered the most damage, with 3,710 hectares affected. Additionally, seedbeds and planted seedlings of 400 hectares of onions, 591 hectares of vegetables, 656 hectares of mustard, 336 hectares of potatoes, and 322 hectares of garlic were also damaged.
Dr. Jahangir Alam, an agricultural economist, believes that above-normal rainfall in winter in accordance with BMD is likely to affect crop production. Speaking to Bonik Barta, he said, “Excessive rainfall will have an impact on the agricultural sector. Production may drop. But such rainfall usually does not last long, so the overall damage to the farmers will likely be limited.”
He emphasized the importance of early warnings for farmers. He added, “Such a natural disaster occurs almost every year. But Bangladeshi farmers are highly adaptive to this disruption. If they receive early alerts, they can avoid sowing during rainy spells or harvest mature crops a few days earlier to reduce losses. Timely information is crucial for this.”
Rainfall during winter is particularly harmful for Rabi crops, with potatoes, tomatoes, and other winter vegetables being the most vulnerable. Untimely rainfall damages seedbeds and increases fungal infections such as blast. Besides, semi-ripe Aman often bends or collapses in such conditions.
DAE Director (Field Services Wing) Obaidur Rahman Mondol told Bonik Barta, “We have a web portal. We provide regular updates on the weather there. We provide advisory information on what the weather might be like in the coming few days, and what farmers should do or avoid during this time. That is why farmers are aware of the possibility of sowing seeds or damage during this time.”