Separate the parts
| Forecast term | Question to ask |
|---|---|
| Wind | What direction, strength and changes are expected? Where will the route be exposed? |
| Sea | What waves are being generated by the local wind? |
| Swell | What wave energy is arriving from elsewhere, and from which direction? |
| Tides and currents | How could flow, depth and timing affect this part of the route? |
| Warnings | Is the forecast area correct, and are warnings or changes expected during the passage? |
A forecast is not a wave-height ceiling
Wave-height forecasts commonly use significant wave height, a statistical description of the wave field. Individual waves can be higher. Read the Bureau’s explanation rather than treating one forecast number as the largest wave you will encounter.
Classroom scenario
North-east winds 10–15 kn, tending south-west 20–25 kn during the afternoon. Seas increasing from 1 m to 2 m. Southerly swell 1.5 m. A planned return passage is exposed to the south-west.
Identify the expected change, the exposed leg and the information missing from this exercise. Consider how an earlier change would affect the return. There is no universal “go” answer without knowing the boat, crew, local conditions and operating limits.
Discussion prompts
- Check forecast issue time, warning updates and the timing uncertainty.
- Compare the forecast with observations, tide information and local knowledge.
- Identify alternate shelter and the points where the plan can be changed.
- Check the vessel’s and operator’s limits, then brief the crew on reassessment.
Keep checking after departure
Conditions can change before a forecast is updated. A departure decision is only the start: keep watching, compare observations with the plan and reassess within your operator’s procedures.