According to the Department of Hydro-Met Services under Ministry of Economic Affairs (MoEA) the forecast for monsoon rainfall from June to September is to be 5.1% below the normal rainfall range. This would also mean that the annual total rainfall is forecast to be below normal.
For June and July, the monthly rainfall is forecast to be below normal but it will again be above normal for the August and September month which normally does not see as much rain.
The country’s normal rain for the month of June, July, August, September from 1996-2013 is 1308.3mm and this year’s forecast of rain anomaly for the months of June to September is 1241mm.
From the Climatic Predictability Tool (CPT) outputs the rainfall forecasts for June is about 17% below normal, about 7% below normal in July and about 30% above normal in August. September is about 7% above the normal rainfall.
This year’s monsoon season, which started on June 9, is projected to be at 1241.2mm as per the forecast made by the Department. The total amount of monsoon rainfall the country last year was recorded at 1087.03mm.
The senior meteorologist, Department of Hydro-Met Services, Tayba Buddha Tamang, said the onset of monsoon in Bhutan is normally on June 5, with plus or minus 5 days, and will start from the South and advance towards the central and northern parts of the country.
As in the past record, more rain is expected in Phuentsholing, Samdrupjongkhar, Gelephu and Samtse.
Tamang said considering the 20 meteorological stations from 20 dzongkhags, the maximum amount of monsoon rainfall recorded from 1996 to 2013 was in the year 1998 with 1790.6mm and lowest recorded with 1025.6mm in 2006.
When it comes to a region wise breakup, he said the southern region receives more rainfall than other regions and among 20 dzongkhags, it is Samtse that receives the highest rainfall during the monsoons as well as annual rainfall.
The station-wise distribution shows that the highest amount of annual total rainfall occurred at Sipsu south-western part of Bhutan with 5492mm and the lowest occurred at Thimphu with 602mm and Paro accounts for 599mm. Sipsu, Phuentsholing, Bhur, and Deothang in south Bhutan received the highest amounts of rainfall compared with the rest of the country.
From the observational records, July has been as the month with the highest amount of the monthly total rainfall followed by June and August, and the lowest is in December. The monsoon rain in the months of June-September accounts for 72% of the total annual rainfall.