BMKG Weather Forecast Friday, 18 September 2026: North Sumatra and West Java on Alert for Heavy Rain
The Meteorology, Climatology, and Geophysics Agency (BMKG) has released the weather forecast for Friday (18/09). Based on data and atmospheric dynamics analysis, several regions have been advised by BMKG to remain on alert due to the potential for rainfall growth around existing cyclonic circulation.
Analysing atmospheric dynamics, BMKG has issued warnings to residents of North Sumatra and West Java to prepare for heavy to very heavy rain. A cyclonic circulation has formed in the South China Sea; this formation is predicted to increase the potential for rain around Northern to Central Sumatra, the North Natuna Sea, and Northern Kalimantan.
An increased potential for rain is also expected around West Java to Banten, as well as the Central Papua region and the Northern waters of Papua. Furthermore, an increase in surface wind speeds should be anticipated in Bali, Maluku, East Nusa Tenggara, South Sulawesi, North Sulawesi, and South Papua. The potential for strong winds in maritime areas may also increase wave heights in the surrounding regions.
BMKG stated that these atmospheric dynamics are causing significant weather potential in several parts of Indonesia. Residents in certain areas are expected to be prepared for moderate to heavy rain, particularly in regions marked in yellow on the BMKG forecast map.
Additionally, surface wind speeds of over 25 knots have been observed in several maritime areas, a condition that could lead to higher waves. Current atmospheric analysis indicates the potential for extreme weather in northern Sumatra, which is currently in a high-alert zone, alongside increased wind speeds.
Moving to Java Island, several cities are predicted to be dominated by thick cloudy conditions. Jakarta is forecasted to have temperatures between 27-32 degrees Celsius. Recent monitoring of atmospheric dynamics confirms an increase in surface wind speeds across the majority of Indonesia’s maritime territories, which has the potential to trigger high waves.
BMKG also released a forecast regarding the potential for very heavy rain in Aceh due to the development of Tropical Cyclone Seed 98W in the South China Sea. The agency has urged the public, particularly those in disaster-prone areas such as the Cibeber, Campaka, and Mande districts, as well as several areas in southern Cianjur, to remain vigilant.