10-Meter vs 2-Meter Wind Discrepancy – The Real Number Your Wing Actually Feels
There is a fundamental disconnect between the wind forecast and the wingfoiler. Weather models like GFS and ECMWF output wind data at a standard height of 10 meters (33 feet).
You do not ride at 10 meters. You ride at 2 meters.
Due to surface friction, the wind at your board height is significantly slower than the wind on the map. This "Wind Shear" is the reason you often feel underpowered on days that look perfect on paper.
The Friction Equation
Wind moves over the water like water moves over a riverbed. The bottom is slow; the top is fast. This is the Wind Gradient.
Over open water, the drop-off follows a logarithmic curve.
- Forecast (10m): 15 knots.
- Reality (2m): ~11–12 knots.
That is a 20% loss in power. In the light wind zone, this is catastrophic. A forecast of 12 knots (10m) might result in only 9 knots (2m) hitting your wing. You pump, but you cannot fly.
Sea State Amplification
The rougher the water, the worse the discrepancy.
- Flat Water: Low friction. The wind at 2m is close to the wind at 10m.
- High Swell/Chop: High friction. The waves act like trees, creating a "roughness layer" that slows the air near the surface.
In high wind (30 knots forecast), the chaotic sea state can reduce the surface wind to 22 knots. However, if you lift your wing high for a tack, you suddenly hit the 30-knot stream. This shear destabilizes your ride.
Correction Factor
When you read a meteogram, you must apply a mental correction factor based on the wind speed.
- Light Wind (8–15 kts): Subtract 2–3 knots.
- Sweet Spot (15–25 kts): Subtract 3–5 knots.
- Storm (30+ kts): Subtract 5–8 knots.
Summary
The map is not the territory. The GFS model assumes you are 33 feet tall. You are not. Rig your gear for the 2-meter reality, not the 10-meter prediction. If the forecast looks borderline, bring the big wing.