BMKG Warns of High Waves Around Bali’s Southern Waters

Denpasar — Indonesia’s meteorological agency has warned of waves reaching 2.5 to 4 metres in southern waters around Bali and nearby straits over several days in mid-September 2026, advising extra caution for shipping and coastal activities.

According to the Meteorology, Climatology and Geophysics Agency (BMKG) regional office in Denpasar, a high-wave early warning applies to multiple southern maritime zones around Bali over the period from 9 to 12 September 2026. The agency categorises wave heights of 2.5–4 metres as “high wave” conditions and urges maritime users to be vigilant in affected areas.

BMKG’s Denpasar office identified four maritime areas as having potential wave heights of 2.5–4 metres during the warning period: the southern Bali Strait, the waters south of Bali, the Badung Strait and the southern Lombok Strait. A separate report highlighted similar 2.5–4 metre wave potential in the southern Bali Strait, waters south of Bali and the southern Lombok Strait later in the month, underscoring a continued period of heightened sea conditions around southern Bali.

Conditions in northern waters were expected to be milder but still require attention. BMKG data cited in local coverage indicated wave heights of 1.25–2.5 metres in northern Bali waters and the northern Lombok Strait during high-wave episodes, a range the agency classifies as “moderate”.

Areas under the warning

BMKG’s high-wave category of 2.5–4 metres applied to key southern sea lanes used by fishing vessels and inter-island traffic. These included:

• Southern Bali Strait
• Waters south of Bali
• Badung Strait
• Southern Lombok Strait

Moderate waves of 1.25–2.5 metres were forecast for northern Bali waters and the northern Lombok Strait, as well as parts of the southern Bali Strait, depending on the specific warning period. While lower than the southern forecasts, BMKG and local media noted that these conditions can still pose risks for smaller vessels such as fishing boats and barges.

The agency’s marine bulletins also describe how risk varies by vessel type. Local reports using BMKG guidance noted that fishing boats are exposed to hazards from waves starting around 1.25 metres when accompanied by winds of about 15 knots, barges at around 1.5-metre waves and 16-knot winds, and ferries when waves reach roughly 2.5 metres and winds around 21 knots.

Wind, currents and practical precautions

BMKG’s synoptic analysis for the high-wave warning period indicated changing wind patterns across Bali’s northern and southern waters. In northern Bali, winds were expected to blow from the northeast to south at speeds between about 4 and 30 knots, while in southern waters winds tended to come from the east to south at roughly 4–25 knots.

Currents also contributed to sea conditions. For example, current forecasts for the southern Lombok Strait during the warning window showed speeds that could exceed 3 knots, making navigation more challenging when combined with higher waves. Other areas, including the Badung Strait, northern Bali waters and the southern Bali Strait, were expected to experience weaker but still significant currents in the range of roughly 1–2.5 knots.

Mariners are advised to closely follow BMKG’s latest marine bulletins and heed any instructions from harbour authorities or vessel operators before sailing. For passengers, the presence of a high-wave warning does not automatically mean that a particular ferry or fast-boat service is suspended, as decisions are taken by operators based on vessel capabilities and real-time conditions.

People planning coastal activities on southern-facing beaches and straits are encouraged to be cautious during the warning period, paying attention to local advisories, flag systems and any temporary closures issued by beach management or local authorities.

BMKG’s guidance stresses that its wind, wave and current thresholds are risk indicators rather than permissions to sail, and that final operational decisions depend on individual vessels, routes and up-to-date marine forecasts.

Sources

• Denpasar24
• BMKG – High Wave Warning (Peringatan Gelombang Tinggi)
• Balipost – Peringatan Dini Angin Kencang, Cek Prakiraan Cuaca Bali
• IDN Times – BMKG Denpasar Peringatkan Gelombang 4 Meter di Perairan Bali
• NusaBali.com – Gelombang 4 Meter Mengintai Selatan Bali