Meteorological Conditions in South East Asia: 23 April 1999

Meteorological Conditions in SouthEast Asia

23 April 1999

The Meteorological Service of Singapore reports on 23 April 1999 for the South East Asian region: “Some hot spots were observed over central and southern Sumatra. Slightly hazy conditions over Singapore”.

“Monitoring of satellite images and weather reports in the region shows that the region continues to be clear of significant forest fires and smoke haze. Only isolated and occasional hot spots and small smoke haze areas are being detected over central and northern parts of Sumatra”. “Latest reports and analyses have shown that the El Nino event which has brought the region severe dry condition since mid 1997 has weakened considerably. Areas of colder-than-normal sea surface temperature have appeared over parts of central Pacific Ocean, which when taken together with other information points to an increased chance of a La Nina event later in the year. In view of the above, rainfall in the region is expected to be near or above normal for the next few months. However, it should be noted that many parts of Indonesia (Kalimantan and parts of Sumatra) would be in their traditionally dry season in the next few months. As such, though extensive and prolonged smoke haze is unlikely for this period, occasional short periods (e.g. a few days) of slight to moderate haze in a more localized manner remain probable.

Fig.1. Regional Surface Winds and Haze/Hot Spot Map, 23 April 1999
(Source: Meteorological Service of Singapore)

The Indonesian government was investigating the cause of recent forest fires that have spread haze over neighboring Singapore and Malaysia. Several forest fires were detected in Riau province on Sumatra Island last week. The following satellite image shows hot spots in Sumatra as. Mild haze from Sumatra has drift over the city-state of Singapore in recent days.

Fig.2. Latest NOAA Satellite image for Sumatra of 23 April 1999
(source: http://www.gov.sg/metsin/hazed.html#sumatra)

The ASEAN Fire Weather Information System (ASFWIS) is a co-operation between ASEAN and the Canadian Forest Service. It provides maps describing the current fire weather situation in South East Asia. This system is based upon the Canadian Forest Fire Danger Rating System (CFFDRS) (for further infomation to the CFFDRS refer to ASFWIS). Studies have shown that the CFFDRS is applicable outside of Canada. Currently it is also used in a modified form in New Zealand (see References). In New Zealand the Fire Weather Indices Fine Fuel Moisture Code (FFMC) and the Initial Spread Index (ISI) represent the fire danger in the scrublands. The Duff Moisture Code (DMC) is also applicable in South East Asia, because it potentially describes the moisture state of the upper peat layers in peat and peat swamp forests. All three parameters may serve as a suitable indicator of forest fire danger in South East Asia.

According to the ASFWIS for 22 April 1999 these parameters show various fire weather conditions over South East Asia. The highest FFMC readings are recorded for northern Thailand, Sumatra and Java, with the FFMC values between 85 to 89. The DMC readings are also high in the north-western part of Thailand. Recent observations in neighbouring countries of South East Asia reveal that the fire danger situation in these countries is for the moment not so high.

Fig.3.,4. and 5. FFMC, ISI and DMC output of the ASFWIS

The Indonesian Meteorological Agency Badan Meteorologi dan Geofisika forecasts rainy and cloudy conditions for Indonesia with maximum temperatures between 28°C (Bandung), 30°C (Samarinda), 27°C (Ujung Pandang) and 31°C (Dili), 34°C (Palembang) and relative humidity ranging from 50% up to 99%.

The Forest Fire Prevention and Control Project (FFPCP) in Palembang (Sumatra) shows an updated fire overview of Sumatra.

Fig.5. Fire Overview Map for 20 April 1999 of the FFPCP project in Palembang
(source: http://www.mdp.co.id/ffpcp/overview.htm)

No fire update information is currently provided by the Integrated Forest Fire Management (IFFM) project in Samarinda (East Kalimantan).

Summary: Although the current fire weather conditions do under normal conditions not favour extensive land clearing by fire or escaping wildfires in Indonesia, the consequences of the large wildfires of 1997-98 must been taken into consideration. These fires had caused extensive degradation of primary and secondary forests along with the spreading of “alang-alang” (Imperata cylindrica) grasslands. These grasslands facilitate the spread of uncontrolled fires over large areas.