Heavy Rain Risk From September 24–28 Puts Nepal’s Preparedness to Test

NEPAL — Nepal could face a renewed spell of heavy rainfall from September 24 to 28, or Asoj 8 to 12, as a low-pressure system developing over the Bay of Bengal moves west-northwestward and potentially interacts with other atmospheric systems affecting the country. Meteorologists say the situation warrants close monitoring, although the precise amount, location and intensity of rainfall remain uncertain.The possibility of prolonged rainfall has also renewed concern about Nepal’s preparedness for floods, landslides, inundation and other monsoon-related hazards, particularly after multiple weather-related disasters during the current monsoon season.
Forecast models signal potentially intense rainfall:

Tribhuvan University hydrologist and meteorologist Binod Pokharel has said his analysis of several forecasting models indicates a significant probability of rainfall across Nepal during the September 24–28 period.

According to Pokharel, some models have projected accumulated rainfall exceeding 400 millimetres in certain locations, while one model scenario showed a maximum of about 741 millimetres. These figures should not be interpreted as a forecast that the entire country will receive rainfall of that magnitude; the heaviest totals could be concentrated in particular areas.

The 400–741 mm projections are model-based assessments cited by Pokharel and are not, as of the latest available information, an official DHM forecast confirming that those rainfall totals will occur.

Sanjib Adhikari, a meteorologist at Nepal’s Meteorological Forecasting Division, told The Kathmandu Post that the system’s initial track suggested the possibility of very heavy rainfall particularly in Sudurpaschim and central Nepal. He also stressed the need to monitor updated weather information as the system develops.

Official impact still uncertain:

Nepal’s Department of Hydrology and Meteorology has been monitoring the developing low-pressure system. According to information provided by the department to OnlineKhabar, the system could increase rainfall over Nepal, but its exact risk level and impact could not yet be determined with certainty.

That distinction is important because weather-model projections several days ahead can change as the position, strength and movement of the atmospheric system become clearer.

The India Meteorological Department confirmed on September 20 that a low-pressure area had formed over the North Andaman Sea on September 19 and had moved over the east-central Bay of Bengal and adjoining North Andaman Sea by the following morning.

IMD forecast that the system was very likely to strengthen into a depression over the east-central Bay of Bengal on September 21 and a deep depression over the west-central Bay of Bengal on September 22 before approaching the north Andhra Pradesh-south Odisha coast around September 23.

Its September 20 bulletin also forecast heavy to extremely heavy rainfall in parts of eastern and central India as the system intensifies, including extremely heavy rainfall in parts of south Odisha and north coastal Andhra Pradesh on September 23 and 24.

Possible interaction with western weather system

Meteorologists monitoring Nepal say the eventual rainfall pattern will depend partly on how moisture associated with the Bay of Bengal system interacts with atmospheric conditions to Nepal’s west.

The Kathmandu Post reported that the interaction between the eastern system and a western weather system could intensify moisture transport towards Nepal. If the systems reinforce each other, rainfall could become stronger and more persistent in some areas.

The current forecast therefore represents a developing risk rather than confirmation that extreme rainfall will occur at any specific location.

Nepal already has national monsoon response framework

The question of preparedness comes as Nepal already has a formal national plan for managing monsoon-related disasters.

The National Disaster Risk Reduction and Management Authority approved the Monsoon Preparedness and Response National Action Plan 2083 earlier this year. The plan estimated that around 51,868 households, comprising approximately 226,661 people, could be affected by monsoon-related disasters nationwide during the season. That projection covers the broader monsoon period and is not an estimate for the September 24–28 weather event.

NDRRMA also activated a Monsoon Response Command Post. At its first meeting in June, the command post directed relevant agencies to implement the national preparedness and response plan effectively and provide regular progress reports to the authority.

District authorities in several parts of Nepal have also prepared or updated local monsoon preparedness and response plans for 2083, indicating that formal response structures exist at both national and district levels.

Preparedness cannot yet be judged from plans alone

The existence of preparedness plans and command structures does not by itself establish how effectively Nepal would cope with a specific extreme-rainfall event.

No authoritative information reviewed for this report provides sufficient evidence to conclude whether the country is fully prepared for rainfall at the upper end of the model projections.

Likewise, the model estimate of more than 400 mm—and the maximum scenario of around 741 mm—should not be treated as an official rainfall prediction for Nepal until the developing system moves closer and DHM issues more precise forecasts and warnings.

DHM classifies 50 to less than 100 mm of rainfall within 24 hours as heavy, 100 to less than 200 mm as very heavy and 200 mm or more as extremely heavy rainfall.

With the potential weather event still several days away, meteorologists have emphasized monitoring updated official forecasts rather than treating early model scenarios as fixed outcomes. DHM continues to publish weather and hydrological warnings through its official monitoring systems.