Module 13 - Meteorology
Local Wind Effects
What you will learn
Anticipate sea-breeze, land-breeze, funnelling, headland and downslope effects as modifiers of the regional forecast, not fixed daily rules.
Local winds arise from temperature contrast and terrain. Their strength and direction depend on gradient wind, stability, coastline shape, time and topography.
A sea breeze can develop when sunny land heats faster than the sea, air rises inland and cooler marine air moves onshore. A land breeze can develop from the reverse night-time temperature contrast. Neither is guaranteed or tied to one fixed Beaufort force or clock time.
The gradient wind can reinforce, oppose, delay or overwhelm a thermal circulation. Coastline shape, stability, cloud and inland heating also matter. A convergence zone can form where flows meet and may support a band of cloud or showers.
Cold dense air can drain downslope as a katabatic flow, while valleys, gaps and headlands can funnel or accelerate wind. Treat topographic effects as location-specific risks verified by forecasts, pilot information and observation, not as universal claims about a whole region.
Combine regional and local wind evidence
The regional forecast is a light offshore wind on a sunny afternoon, but the route passes a headland and then enters a narrow inlet.
1. Keep the gradient wind
Start with the official direction and force; do not erase it.
2. Add thermal potential
Consider whether strong land heating and coastline orientation can oppose or modify it.
3. Add terrain
Allow for acceleration around the headland and funnelling in the inlet.
4. Observe
Use water texture, cloud, nearby reports and the yacht’s true-wind trend to verify the effect.
Sense check: An offshore gradient wind does not guarantee an onshore sea breeze, and a thermal effect does not cancel the regional system everywhere.
Common mistake or limitation
- Memorising that a sea breeze always reaches Force 3–4 and peaks at one fixed time.
- Adding a sea breeze arithmetically to the gradient wind without considering direction, stability and coastline.
- Assuming every strong gust below high ground is katabatic rather than checking funnelling, gradient and convective effects.
Recap
- Sea and land breezes depend on temperature contrast and the surrounding weather.
- Gradient wind, stability, coastline and terrain can reshape or suppress them.
- Use local effects as forecast modifiers verified by observation.
Optional quick check
Section 10 of 13
Why is an afternoon sea breeze not guaranteed?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
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