Coastal Orographic Lift – How 100 m Hills Add 20% to Gradient Wind
You are sailing past a flat beach. The wind is 12 knots. Then you pass a section of coast with a 100-meter ridge or cliff. Suddenly, you are powered on your foil. The wind speed jumps to 15 knots.
You found "Orographic Lift." This is the compression of air over terrain. It is one of the most reliable ways to find 15–25 knots of power when the forecast looks weak.
The Compression Zone
Air acts like a fluid. When it hits an obstacle (like a coastal hill), it must go over it. The column of air is squeezed between the hill and the atmosphere above.
According to the Bernoulli Principle, as the fluid is squeezed into a smaller space, it must speed up. This acceleration happens not just at the top of the hill, but at the "foot" of the slope on the water.
- Flat Coast: Air stream is 1000m deep. Speed = 12 knots.
- Hilly Coast: Air stream compressed to 800m. Speed = 15 knots.
Wind Direction Sensitivity
Orographic lift only works if the wind direction is perpendicular (or close to it) to the ridge.
- Onshore / Side-Onshore: The wind hits the hill and accelerates. Boost.
- Side-Shore: The wind slides along the wall. Minimal boost.
- Offshore: The wind tumbles over the hill. Turbulence. (Avoid this).
The "Cap Cloud" Sign
How do you identify these spots from the water? Look for a "Cap Cloud." As the air rises over the coastal hill, it cools. If it reaches the dewpoint, a stationary cloud forms right on the ridge line. If you see a cap cloud, the orographic engine is running. The wingfoil wind underneath that hill will be significantly stronger than the open ocean.
100 Meters is Enough
You do not need a mountain. A ridge of just 50 to 100 meters is enough to create a noticeable compression zone. Check your map for "High Cliff" areas or coastal roads that climb up. The water directly in front of these features is often a hidden gem for light wind days.
Summary
When the forecast is marginal, head for the hills. Find a coastline with a ridge facing the wind. The physics of compression will give you the extra 20% power you need to get on foil while the flat-beach riders are stuck pumping.