North Sumatra Braces for Extreme Precipitation
The Indonesian Meteorology, Climatology, and Geophysics Agency (BMKG) has issued a high-level alert for North Sumatra, warning of extreme precipitation between November 9 and 12, 2026.
This “Awas” (caution) status anchors a broader weather warning covering the nation from November 6 through November 12, as varied atmospheric conditions challenge typical seasonal expectations.
The agency’s monitoring, updated through early November, highlights that the current weather occurs despite the ongoing influence of a strong El Niño and a positive Indian Ocean Dipole (IOD). These phenomena, confirmed by data from the third ten-day period of October 2026, typically suppress cloud formation.
However, recent records from November 1 to 4 showed significant rainfall, with the highest daily intensity recorded in East Java at 358 mm, followed by Bali at 300 mm, Aceh at 167 mm, and West Kalimantan at 101 mm.
Aceh and West Sumatra Face Heavy Rainfall Risks
While the majority of the archipelago is expected to see only light rain, localized threats are intensifying. Aceh and West Sumatra remain under “Siaga” (alert) status due to the risk of heavy rainfall, according to CNBC Indonesia. Meanwhile, in southern Papua, officials are tracking potential high winds.
On Monday, November 9, the agency specifically flagged Sumatra Island for immediate concern. “Starting from Sumatra Island, be alert for potential rain accompanied by lightning in Padang and Tanjung Pinang,” said BMKG forecaster Muh. Rizky in an official broadcast cited by ANTARA News.
For November 9 to 10, the BMKG has identified specific regions with potential for heavy rain, including Aceh, West Java, Central Papua, Highland Papua, and Papua. Strong winds are anticipated in Lampung, West Java, East Nusa Tenggara, and South Sulawesi.
In the context of daily warnings issued on November 9, the agency placed several provinces—including Banten, Central Java, and East Java—under a “Waspada” (vigilance) status, noting risks of localized flooding. Specifically, the “Awas” classification for North Sumatra covers Humbang Hasundutan and Tapanuli Tengah regencies.
Atmospheric Dynamics Overriding El Niño
Weather in several regions of Indonesia still allows for significant rainfall due to regional atmospheric dynamics, although the strong El Niño phenomenon and positive Indian Ocean Dipole tend to reduce the potential for rain cloud formation. The BMKG attributes the moisture influx to regional atmospheric dynamics, specifically the Madden-Julian Oscillation (MJO)—currently in phases 2 and 3—alongside Rossby and Kelvin waves.
“The activity of these waves, accompanied by wind deceleration and convergence patterns in several regions, can support the growth of rain clouds,” the agency stated in a release reported by Kompas.com. Spatially, the MJO is active across southern Kalimantan, central to southern Sulawesi, Maluku, East Java, Bali, and the Nusa Tenggara islands.
Drought Persists Alongside Flood Threats
Despite the incoming rain, large swaths of Indonesia remain gripped by drought. Monitoring data identifies 543 observation points that have experienced an “Extremely Long” period without rain.
This dryness has heightened the risk of forest and land fires, with satellite imagery currently detecting high concentrations of hotspots across South Papua, East Kalimantan, and Central Kalimantan. Specifically, South Papua has recorded 615 hotspots, while East Kalimantan and Central Kalimantan have reported 223 and 255 hotspots, respectively.
Safety Protocols for Residents
Residents in areas expecting heavy rain are advised to prepare for potential flooding, landslides, and lightning strikes. Simultaneously, the agency urges citizens to avoid burning waste or using fire for land clearing to mitigate the risk of forest fires. Officials recommend that the public monitor the InfoBMKG mobile application for real-time updates as the weather develops.
As forecaster Muh. Rizky noted regarding the varied conditions across the country, For the Maluku and Papua regions, be alert for the potential for light rain in Ternate, Ambon, Sorong, Nabire, Jayapura, Jayawijaya, and Merauke, as well as potential smoke or fog in Manokwari.
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