El Nino Watch
The forecast height of waves off Samui, in metres. Around 2 m, small boats are told to stay ashore and fast ferries start to be cancelled; at 3 m car ferries are likely suspended.
Ocean
Wave forecasts give the significant wave height: roughly the average height of the highest third of the waves. Individual waves are often higher than this average, so expect some bigger waves.
The app uses the Open-Meteo marine forecast for open water near Samui, plus TMD wind-wave warnings for the Gulf of Thailand. Only Gulf warnings count: Andaman Sea warnings do not concern Samui.
Why it matters: Samui is an island. The car ferries (Seatran, Raja) and passenger boats (Lomprayah) are how most food, fuel and people arrive. In rough seas the crossings are cut back or cancelled, and the high-speed catamarans are the first to stop.
When the ferries stop, the island is cut off: supplies, fuel and evacuation depend on the sea. Only the airport remains, with limited seats. Shop and refuel before the seas rise.
| Max wave height (72 h) | Sea state factor | Exit plan (ferry) |
|---|---|---|
| below 1.5 m | 0 Normal | ok |
| 1.5 to 2 m | 1 Watch | ok |
| 2 to 3 m | 2 Prepare (small boats stay in port) | caution |
| 3 m or more | 3 Act | blocked |
A TMD Gulf rough-sea warning in force raises the sea state factor to at least 1. For departure windows, a TMD bulletin saying small boats should stay ashore counts as blocked.