There is a flood risk in Sylhet and Chattogram similar to 2022 and 2023

On 15, 16, and 17 June of 2022, record-breaking rainfall occurred in the districts of the Sylhet division and over India's Meghalaya and Assam states — precisely when the monsoon trough was positioned over the central part of Bangladesh. Coincidentally, the monsoon trough is again currently located over central Bangladesh this week.

When the monsoon trough remains over central Bangladesh, moisture from the Bay of Bengal enters the country, much like water being sprayed from a fire service hose. In this analogy, Bangladesh acts as the moisture pipeline, and the Bay of Bengal is the water-carrying fire truck supplying an immense amount of water vapour.

This moisture ascends along the slopes of the Arakan Hills near the Bangladesh–Myanmar border and the Meghalaya Plateau, causing continuous cloud formation and sustained heavy rainfall, especially over the districts of Chattogram (including Chattogram, Rangamati, and Khagrachhari), Sylhet (all districts), and Netrokona in Mymensingh division. Simultaneously, heavy rain is occurring in parts of India's Assam state (Karimganj, Cachar, and Hailakandi) and eastern Tripura state.

In August 2023, when record rainfall occurred in southern Chattogram, Cox's Bazar, and Bandarban districts, a monsoonal low-pressure system had crossed over Bangladesh's landmass while the summer monsoon was active. This combination of processes led to flooding in August 2023, resulting in around 60 deaths and the washing away of the under-construction Chattogram-Cox's Bazar railway line.

There are two additional atmospheric indicators from June 2022 that are also present in late May 2025:

• The presence of a high-velocity jet stream in the upper atmosphere flowing from west to east.
• The active phase of the Madden-Julian Oscillation (MJO) over the Indian Ocean, a key driver of monsoonal activity.

Therefore, the heavy rainfall that began in Bangladesh on 27 May 2025 — driven by a deep depression over the Bay of Bengal combined with the summer monsoon — closely resembles the meteorological patterns of June 2022 and August 2023.

As a result, there is strong scientific reasoning to be concerned that various districts in the Sylhet and Chattogram divisions face significant risks of flash floods and riverine flooding. This risk is particularly high from June 1 to June 3 in Chattogram and the Chattogram Hill Tracts, and from June 1 to June 5 in four districts of the Sylhet division.

Mostofa Kamal, the Lead Meteorologist at www.abohawa.com, is a PhD Student at the School of Environment & Sustainability at the University of Saskatchewan, Canada. He is also the Chair of AMS Board on Student Professional Development Committee.

Disclaimer: The views and opinions expressed in this article are those of the author and do not necessarily reflect the opinions and views of The Business Standard.