BMKG Flags Moderate Waves in Southern Sape Strait and NTT Waters

Labuan Bajo — Indonesia’s Meteorology, Climatology and Geophysics Agency (BMKG) has advised small craft, fishermen and marine-tourism operators in the waters around West Manggarai and the wider Nusa Tenggara region to be alert for moderate waves, with seas in the southern Sape Strait and nearby areas forecast in the coming days at around 1.25–2.5 metres.

The advisory forms part of a regional outlook issued by BMKG’s Maritime Meteorology Station in Tenau, Kupang, covering Nusa Tenggara Timur (NTT) waters from 17 to 20 September 2026, including the southern part of the Sape Strait and marine areas bordering Komodo National Park.

According to BMKG’s information relayed by the Kupang-based public broadcaster RRI, waves in the southern Sape Strait and adjacent seas are expected to reach the agency’s moderate category, defined as more than 1.25 metres and up to 2.5 metres. These conditions are forecast for several stretches of water commonly used by inter-island ferries, fishing boats and dive-tourism vessels, including the southern Sape Strait, Flores Sea and the waters around Komodo.

RRI reported that BMKG’s outlook is valid from 17 September at 08:00 WITA to 20 September at 08:00 WITA, with moderate waves expected on 17–18 September in the southern Sape Strait and continuing across 18–19 and 19–20 September in combination with other NTT sea areas. The agency’s marine bulletin classifies such seas as requiring heightened caution for small vessels, including traditional fishing boats and tourism craft.

Wave and wind conditions

In its national marine bulletin for shipping, BMKG defines wave categories from calm, with ripples below 0.1 metres, up through smooth and slight seas, to moderate conditions between 1.25 and 2.5 metres. The southern Sape Strait and neighbouring waters of Flores, Komodo and southern Alor–Pantar are all listed in recent advisories as areas where moderate waves may develop during the 18–20 September period.

A separate forecast highlighted by regional media outlet Akurat.co also cites BMKG data for NTT seas between 18 and 20 September, noting moderate waves in the southern Sape Strait, Flores Sea, Komodo waters and several other channels during that three-day window. The report attributes the conditions to prevailing trade winds and advises operators to monitor BMKG updates before sailing.

BMKG’s maritime guidance notes that stronger winds can rapidly increase sea state, with the Sape Strait and surrounding waters among areas where elevated wind speeds are capable of driving wave heights into the moderate band. According to the regional advisories, wind over NTT waters during the period is predominantly from the east to southeast, at speeds broadly within the range BMKG associates with moderate seas.

Implications for Labuan Bajo and Komodo routes

While the BMKG bulletins do not specifically single out individual operators or routes, the southern Sape Strait and Komodo waters form part of common itineraries for Labuan Bajo-based liveaboards, fast boats and day-trip vessels serving Komodo National Park. The presence of moderate waves can affect comfort, scheduling and safety margins for small craft, particularly during open-water crossings.

RRI’s summary of the Tenau maritime station’s advisory states that BMKG urges marine users across NTT to remain vigilant, follow official forecasts and consider the limitations of their vessels when planning trips in areas with moderate waves. The bulletin emphasises that traditional wooden boats and smaller speedboats are more vulnerable to rougher seas than larger ships.

For travellers and operators, BMKG’s definition of moderate waves—up to 2.5 metres—serves as a reference for conditions under which extra caution is advised, but not necessarily a closure of routes. Both BMKG and regional media recommend checking the latest marine forecast immediately before departure and coordinating with port authorities when seas are in the moderate or higher categories.

BMKG’s wider dry-season guidance for NTT also reminds residents and visitors to conserve water, avoid unsupervised land burning and take protective measures against sun exposure, highlighting that the period of elevated waves in southern Sape Strait coincides with typically sunny to partly cloudy weather over much of the province.

Sources

• BMKG Marine Weather – Maritime section
• RRI Kupang – Gelombang Tinggi Mengancam Perairan NTT hingga 20 September 2026
• Akurat.co – Waspada Kecepatan Angin dan Tinggi Gelombang di Perairan NTT Tiga Hari Kedepan