Wind forecast — how to read it

The wind map shows forecast wind speed and direction at four altitudes: surface (10 m), 850 hPa (~5,000 ft), 700 hPa (~10,000 ft), and 500 hPa (~18,000 ft). Switch layers with the selector above the legend.

The layer selector

Above the wind legend, an Altitude dropdown lets you switch the raster between the mean-wind field at four altitudes plus the surface gust field:

• Surface (10 m) — mean 10 m wind. What tower reports and what determines your crosswind on landing.
• GUST (10 m) — the model's forecast peak-gust field, still at 10 m. See below for why you plan against this, not the mean.
• 850 hPa (~5,000 ft AMSL) — typical low-VFR cruise altitude for piston GA.
• 700 hPa (~10,000 ft AMSL) — top-of-VFR cruise, and the altitude glider pilots wave-fly at.
• 500 hPa (~18,000 ft AMSL) — above VFR, but useful for reading the synoptic pattern (jet-stream position, upper-level trough / ridge structure).

Switching between layers is what makes this map more than a wind arrow: you get a compact vertical wind profile plus a peak-gust view for every point in the domain, animated across 48 forecast hours. Comparing the surface layer to 850 hPa is how you spot the classic surface-friction inversion; comparing 850 to 700 tells you whether a climb buys you tailwind; comparing 700 to 500 shows the wave structure above; flipping between Surface and GUST tells you how peaky the wind day actually is.

Reading wind barbs

Each barb shows two things at once:

• Direction: the barb points into the wind — a barb pointing north is wind from the north.
• Speed: counted from the little lines on the tail.
  • Short line = 5 kt
  • Long line = 10 kt
  • Filled triangle = 50 kt

A barb with two long lines and one short line = 25 kt. Two triangles plus a long line = 110 kt.

Color intensity reinforces the speed — deeper blue / purple means stronger wind at that layer. It's for at-a-glance scanning; use the barb count for the actual number.

Decision 1 — crosswind at destination

Look at the surface layer. Combine the wind direction with the runway orientation at your destination. ClearToFly's per-airfield meteogram does this calculation for you automatically and shows crosswind per runway.

Wind vs. gust — mean and worst-case

The wind map shows the model's mean 10 m wind — the ten-minute-average value you'd see on a windsock or in the “wind” part of a METAR. But airplanes don't fly the mean; they fly through the peaks. On a gusty day the value that actually matters for the crosswind limit is the gust — the peak short-term speed the aircraft will experience during the approach or takeoff roll.

ClearToFly surfaces gusts on the meteogram wind panel (dashed red line and the SGGG part of the direction annotation, e.g. 240° / 12G22). When planning against a limit like “max demonstrated crosswind 15 kt”, compare it to the gust, not the mean. A day with 10 kt mean wind but gusts to 25 kt is a day above the demonstrated crosswind of most trainers.

On this map, the mean-wind view (Surface, 850, 700, 500) shows the ten-minute-average wind, while the GUST (10 m) layer shows the forecast peak gust at 10 m — swap between the two to see how peaky the wind day is. For a hour-by-hour gust curve at one airfield, use the meteogram's Wind panel: the dashed red curve is the gust and the annotation 240° / 12G22 reads as “from 240° at 12 kt gusting 22 kt”.

Decision 2 — cruise altitude selection

Switch between the 850 hPa (~5,000 ft) and 700 hPa (~10,000 ft) layers. If the tailwind is stronger higher up and the terrain and ceiling allow it, climbing pays. ClearToFly's cross-section has a head/tailwind analysis table that scores every leg × altitude combination automatically.

Decision 3 — wind shear between layers

Model caveats

ICON-D2 resolves ridge/valley wind acceleration reasonably well at 2.1 km, but it will still under-forecast local peaks near terrain (rotor zones, mountain waves). For flying near the Alps or the Erzgebirge, always combine the wind map with a cross-section and local knowledge.