April 2013 Macao, China Country Report Ranjit Tamang Assistant Weather forecaster Meteorology Division Department of Hydro-Met Services Thimphu : Bhutan Training Workshop on Severe Weather forecasting and warning services

2  Total area:38,394 Sq. Km  Population: 672,000  Elevation: 100m-7000m About Bhutan

Network and Current Status 1. Meteorological Network: 90 –Class A Met Station 20 –Real-time AWS09 –Class C Met Station Hydrological Network: 25 –Principal Station 16 –Secondary Station 9 –Sediment Sampling Station Flood Warning Network: 12 –Flood Warning Station 12 3

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5 Flood warning activity is undertaken by the RGoB in collaboration between the Central Water Commission (CWC) of India; Flood warning network stations are established on the north–south rivers that are common to India and Bhutan;

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The existing Weather Forecasting System in Bhutan 1. Developed format in excel basically for temperature forecast. The format is developed to make short range forecast but it can be also use for medium range forecast. 2. MetGIS (weather forecasting software tool): MetGIS was developed with the collaboration of Vienna University, Department of Meteorology and Geophysics, Austria in the year It is a combined, Java-based, Meteorological and Geographic Information System that uses the latest forecast technologies. MetGIS is specialized in mountain weather predictions, since it combines meteorological forecast models with high-resolution geographic information systems (a completely new approach in meteorological forecast technology!), using so-called “downscaling-techniques”. Met GIS model, Data input: Global Forecast System (GFS) of the US National Weather Service. It has a parameters like, 3 hourly rainfall, snowfall and Relative Humidity at a height 3000m. All output in graphic forms, it also has provision of a weeklong forecast in text format. 3. Other websites (South Asian Region) 7

Here are some sample of Met GIS graphics outputs 8

IMD Satellite kalpana-1 9

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11 Climatic Condition Bhutan Climate is generally dominated by monsoon winds –Dry winter and wet summer monsoon Factors that governs the Climate of Bhutan Latitude Altitude Prevailing Wind Direction Orientation of Mountain Ranges Local Winds

Temperatures in degree celsius (max and Min) Mean ( ) 12 JanFebMarAprMayJunJulAugSepOctNovDec StationsMax/Min Deothang20.5/1021.9/ / / / / / / / / / /11.4 Bhur22.2/1323.8/ / / / / / / / / / /14.6 P/ling23.4/ / / / / / / / / / / /14.8 Samtse20.7/ / / / / / / / / / / /15.3 Pemagatshel16.0/ / / / / / / / / / / /6.4 Zemgang12.7/ / / / / / / / / / / /6.1 Tsirang14.5/ / / / / / / / / / / /5.9 Dagana11.6/ / / / / / / / / / / /8.3 Chukha13.3/ / / / / / / / / / / /6.7 Tashigang14.0/ / / / / / / / / / / /4.6 Mongar16.3/ / / / / / / / / / / /7.0 Bhumthang11.1/ / / / / / / / / / / /-3.0 Trongsa14.4/ / / / / / / / / / / /3.7 Wangdi18.2/ / / / / / / / / / / /6.0 Punakha17.9/ / / / / / / / / / / /7.5 Thimphu14.7/ / / / / / / / / / / /-1.5 Paro13.4/ / / / / / / / / / / /1.5 Haa10.8/ / / / / / / / / / / /-3.6 Trashiyangtse13.0/ / / / / / / / / / / /4.0 Lhuentse17.1/ / / / / / / / / / / /8.3 Gasa9.5/ / / / / / / / / / / /0.2

Stations Annual TRF mean ( ) 13 Sations NameAltitudeRF in mm Deothang mtrs Bhur mtrs P/ling220.0 mtrs Samtse550.0 mtrs Pemagatshel mtrs Zemgang mtrs Tsirang mtrs1718 Dagana mtrs Chukha mtrs1525 Tashigang mtrs Mongar mtrs890.3 Bhumthang mtrs750.6 Wangdue mtrs669.9 Punakha mtrs671.6 Thimphu mtrs660.4 Paro mtrs605.6 Haa mtrs871.4 Trashiyangtse mtrs Lhuentse mtrs775.2

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Bhutan Seasonal RF distribution annual rainfall received in different seasons 15

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Major factors contribution for Heavy rainfall in Bhutan 18  SW Monsoon Bhutan received 72% of the annual total rainfall from SW monsoon  Cyclone In the year 2009 cyclone Aila, which hit the Bay of Bengal in May, had a disastrous impact in Bhutan, impacting power and water supplies and damaging roads, bridges and other infrastructure.  Short duration high intensity rainfall

Simulation of RF during Cyclone Aila across the country in the year

Hazards associated with Heavy Rainfall in Bhutan 1.Flash Floods 2.Floods 3.Landsides

Flash Flood Events in Bhutan In August 2000 flood killed 49 people and destroyed 17 houses in Pasakha, in Southern Bhutan 21

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3. Land slides  Young fragile geology and steep slopes of the country is highly susceptible to landslides during rainy season.  Most landslides occur in the eastern and southern foothills where the terrain is steep and rocks underlying the soil cover are highly fractured, allowing easy seepage of water.  Scores of landslides across the National Highway occurred every year during the monsoon, hampering moment of transport for several weeks. 23

 Long range and seasonal forecast, specially monsoon forecast will be carried out in Bhutan in near future.  WRF Model was installed in Meteorology Division,Department of Hydro met. Services under the guidance of Expert from SMRC, Dhaka (Mr. Sujit Kumar Debsarma) in May Conclusion

25 Thank you & TASHI DELEK!