Yangyel Lhaden
The National Centre for Hydrology and Meteorology (NCHM) predicts slightly above normal rainfall with potential for extreme weather events for the remainder of the monsoon season.
This is according to the NCHM’s latest weather outlook for this season.
The forecast is based on data spanning from 1996 to 2023. The average temperature and rainfall of this period is termed ‘normal’. When figures deviate by up to 10 percent from these averages, they are classified as either ‘slightly above normal’ or ‘slightly below normal’.
This year’s predictions indicate a trend towards slightly above-normal rainfall and temperatures, driven by climate influences such as the La Niña condition and the Indian Ocean Dipole (IOD).
Earlier in the year, during the 10th National Climate Outlook Forum, NCHM had warned of a challenging summer ahead, with expectations of increased rainfall and higher temperatures due to ongoing climate drivers.
The El Niño-Southern Oscillation is currently neutral. La Niña conditions are anticipated to develop in the following months of September, October, and November, potentially intensifying rainfall. The IOD remains neutral and likely to remain so until November.
The monsoon season in Bhutan typically starts around June 5, with some variation. This year, while some dzongkhags started receiving rainfall in the first week of June, the official onset of the monsoon occurred on June 12, 2024.
In June, the country experienced average rainfall during the first week, with amounts gradually increasing over the following weeks until mid-July. However, rainfall fell below the climatological normal during the last two weeks of July.
By the first two weeks of August, rainfall had returned to normal levels. Average temperatures were typical at the start of the monsoon but rose from the last week of July through early August.
Recent months have witnessed several extreme weather events.
Notable extreme weather events between July and August include a flash flood at Begana Guru Lhakhang stream in Thimphu on July 15, at 3:05 p.m. On August 5, a flash flood occurred at Bumthang Lamay Gonpa stream around 5:00 p.m.
Another flash flood hit Dechenphu stream on August 10 between 2:30pm and 3:00pm. On August 17, heavy rainfall affected Isuna, Paro and Gidakom areas, Thimphu between 2:30pm and 3:00pm.
On August 18, a flash flood in Gangtey, caused by heavy rainfall from Bayta Chhu at 2:00pm, impacted Beta, Gela, and Tokha villages in Gangtey gewog.
An official from the NCHM said that August and September were still monsoon months in the country and due to the country’s geologically young and fragile mountain ecosystem, as well as settlements in river valleys, there is a high vulnerability to landslides, flash floods, and Glacial Lake Outburst Floods (GLOFs). “Continuous rainfall during the monsoon and heavy rainfall from convective thunderstorms, as seen in recent events, can trigger flash floods.”
Extreme weather events are a potential risk across the country, the official said. “While GLOFs are more common in northern high-altitude areas, heavy rainfall predominantly affects the southern regions. We urge everyone to remain vigilant, stay informed about weather conditions, and take necessary precautions to ensure safety.”