Reading a wind chart

A wind chart tells you two things: how hard it blows and where from. Here's how to read barbs, colours and direction without going wrong.

The colour field: the strength

The background colour represents wind speed. The scale generally runs from blue (calm) to red/purple (storm), passing through green and yellow. A single glance is enough to spot the strong zones and the light ones. Always check the unit: at sea we think in knots (1 knot ≈ 1.85 km/h).

Wind barbs: strength + direction in a single symbol

The little "flags" are wind barbs. The shaft shows the direction, and the feathers encode the strength:

• a half-barb = 5 knots,
• a full barb = 10 knots,
• a pennant (solid triangle) = 50 knots.

You add them up: a shaft with a full barb and a half-barb = 15 knots.

From mean wind to gusts

The chart most often shows the mean wind. But it's the gust that knocks the boat down and dictates the sail choice. Count on 30 to 40% more than the mean wind, often more in unstable weather (showers, thunderstorms, high CAPE). Turn on the "gusts" layer before taking a reef.

Anticipating the shift

Wind doesn't only change in strength: it shifts. Scroll through the hours to see how it evolves. A shift in direction changes your points of sail, your tacks, and can turn a tight beat into a comfortable reach — or the reverse. It's also what creates or removes shelter under a coast.

The coastal reflex

Near the coast, terrain, headlands and thermal breezes distort the synoptic wind. A fine-mesh model (such as AROME) renders these local effects far better than a global model. When in doubt, compare several models.

On SailMeteo, tap any point on the map: the banner shows the exact wind, gusts and direction at the chosen time.