Yangyel Lhaden

Bhutan is likely to experience a warmer and dry winter, according to the National Centre for Hydrology and Meteorology (NCHM).

The agency’s Winter Monsoon Rainfall and Temperature Forecast (December 2024–January 2025) predicts near-normal precipitation, warmer-than-usual days, and typical winter nights.

The NCHM’s Climate Predictability tool forecasts precipitation is expected to be near historical averages which is termed normal, with maximum temperatures above normal, indicating warmer days, and minimum temperatures close to normal, suggesting typical winter nights.

The NCHM used data from 1996 to the previous year (2023) to calculate average temperature and rainfall, which is termed “normal”.

When the predicted temperature and rainfall for the year are within a 10 percent increase of the normal, it is termed “slightly above normal”,  and when they are within a 10 percent decrease of the normal, it is termed “slightly below normal”.

Bhutan’s seasonal weather forecast is created using data from global and regional prediction centres, as well as national climate records. The final forecast also considers the South Asian Climate Outlook Forum (SASCOF) consensus, weather models from the World Meteorological Organization (WMO), and other international sources.

The forecast takes into account global climate factors like El Niño and the Indian Ocean Dipole, which influence weather patterns such as the monsoon.

Out of the total nine indicators, four indicate below-normal precipitation—SASCOF, International Research Institute for Climate and Society (IRI), Copernicus Climate Change Service ( C3S), and Japan Meteorological Agency (JMA), while five indicate above-normal temperature—Global Precipitation Climatology Centre, IRI, C3S, SASCOF, JMA during December to February.

In winter, the weather in Bhutan is mainly influenced by winds coming from the west, called the westerlies. When the westerlies reach Bhutan, they can lead to lower temperatures across the country, especially in the higher altitudes, where snowfall is more frequent.

The westerlies tend to be dry, and when they interact with other weather systems like Western disturbances, they bring precipitation to certain regions, particularly in the mountainous areas and may experience relatively dry spells when the westerlies dominate.

Following NCHM’s weather forecast on January 6, predicting snowfall in high-altitude areas, mountain passes, and parts of western, central, and northern Bhutan due to a western disturbance, snowfall was recorded from the evening of January 7. Most of these regions, including Gasa, high-altitude areas, and Jabana in Paro, experienced snowfall.

An NCHM official said that it was difficult to forecast whether the country was going to receive below or above normal snowfall in winter because formation of snow depended on several factors such as presence of moisture, sub-zero temperature, and wind conditions, among others.

It has been commonly observed that the country is receiving less snow compared to the past.

The NCHM official said snowfall during winter was crucial as it played a significant role in recharging groundwater, serving as a source of water, maintaining river flow, and contributing to snow coverage. “However, to understand the role of climate change in snow coverage, we require at least 30 years of climatological data for accurate assessment.”

The NCHM has been maintaining data since 1996 and updates it annually by adding data from the preceding year to calculate normal values.

Currently, NCHM has 27 years of climatological data.