Wind Shear, Gusts and Variable Wind

Updated: 2026-09-27 · First published: 2026-09-27 · About this site

The wind group looks simple — direction, speed, gust — but the way it is measured and rounded hides the things that actually bother an aircraft on final. This guide explains what the group measures, what it leaves out, what the variability and shear groups add, and how to see low-level wind shear coming from the reports and forecasts around you before anyone puts WS in a METAR.

What the wind group measures

24018G28KT 200V270:

• 240 — mean direction in degrees true, rounded to 10°, averaged over 10 minutes (2 minutes in ATIS and tower reports). Tower and ATIS winds are in magnetic.
• 18 — mean speed over the same 10 minutes, in knots (KT). Some countries use metres per second (MPS): 08MPS is about 16 kt.
• G28 — the peak 3-second gust in that period, reported only if it exceeds the mean by 10 kt or more.
• 200V270 — the range of direction, reported when it spans 60° or more and the mean speed is above 3 kt.

Two things are hidden. First, a peak of 27 kt on an 18 kt mean is not reported as a gust at all, so a report without a G is not a report of steady wind. Second, 10-minute averaging smooths out the squall that arrived four minutes ago. The remarks may help — PK WND gives the peak since the last routine report — and the remarks guide decodes it.

Gusts on the approach

A gust is an increase in wind speed; the hazard is the decrease that follows it. On final at V_REF in a 28 kt gust, the airspeed is fine; when the gust collapses back to 18 kt the aircraft loses 10 kt of airspeed in a second or two, at 200 ft, with the power already at approach setting. The standard answer is to fly faster: add half the gust factor (here 5 kt) to the approach speed, up to a limit set by your aircraft's landing distance. The crosswind guide explains how the gust also changes the crosswind component you must plan for.

Variable wind

VRB05KT — the direction is undefined, either because the speed is below 3 kt or because it varied by 180° or more (a thunderstorm nearby, a sea breeze arriving). At 5 kt this is harmless. VRB15KT, which does occur under a convective cell, is a warning: any runway can have a 15 kt tailwind for part of the approach. 24012KT 200V270 is less dramatic but for runway selection you should compute the crosswind for the worst extreme of the range, not for the mean.

The wind shear group

In ICAO reports a wind shear warning can appear after the temperature and pressure: WS ALL RWY or WS R24. It records that low-level wind shear — a sudden change of wind speed or direction with height — has been reported in the lowest 1,600 ft (500 m) of the climb-out or approach, by an aircraft or by a ground-based detection system. Its absence proves nothing: it depends on someone having encountered the shear and said so. When it is present, expect airspeed excursions of 10–20 kt on final and plan a go-around decision at a height where a go-around is still comfortable.

Seeing shear before it is reported

Low-level wind shear has a small number of causes, and each one leaves a fingerprint in the reports and forecasts:

• Thunderstorms. A downburst produces a headwind that becomes a tailwind within a mile. Any TS, CB or TCU in the METAR, or a PROB/TEMPO TSRA in the TAF, is a shear forecast. The gust front can be 10 NM ahead of the cell.
• Fronts. A wind shift of 90° or more across a front, with speeds of 20 kt or more on either side, gives shear at the frontal surface. Look for WSHFT … FROPA in the remarks and for a TAF with an FM group changing the wind direction sharply.
• Nocturnal inversion. Calm at the surface on a clear night while the pressure gradient is strong. The wind just above the inversion — 300 to 1,000 ft — can be 30–40 kt. The signature is 00000KT at the surface and 25 kt at the nearest hilltop station, or a large difference between the surface wind and the 1,000 ft forecast on the winds-aloft panel of the meteogram.
• Sea breeze fronts. An afternoon wind reversal at coastal fields, often 15–20 kt onshore arriving within minutes. Compare the coastal station with one 20 km inland.
• Terrain. Rotor and downslope wind on the lee side of ridges. The METAR at LTBS Dalaman on a northerly day, or at LOWI Innsbruck in föhn, shows gusts that the synoptic wind does not explain; the terrain does.

Reading the winds-aloft profile

The most direct way to see shear in advance is to compare the surface wind with the wind a few hundred feet up. Every airport page on this site shows a winds-aloft panel from the model consensus in 1,000 ft steps, alongside the surface METAR. A surface wind of 5 kt with 35 kt at 2,000 ft is a shear layer somewhere in between, and on a stable night it will be sharp. That comparison — surface observation against the lowest model levels — is available for every reporting airport, and it is worth a look on any night when the surface is calm and the forecast is not.

Frequently asked questions

When is a gust reported in a METAR?

When the peak 3-second wind in the 10 minutes before the observation exceeds the mean by 10 kt or more. 24018G28KT is a mean of 18 kt with a peak of 28 kt. If the peak was 27 kt, no gust is reported — which does not mean the air was smooth.

What does 200V270 mean after the wind?

The direction varied between 200° and 270° during the 10-minute period. The range is reported when it spans 60° or more with a mean speed above 3 kt. Below 3 kt with a range of 60° or more the wind is reported as VRB.

What is WS ALL RWY?

Wind shear reported on all runways in the lowest 1,600 ft of the approach or take-off path, from pilot reports or a shear-detection system. WS R24 means shear reported on runway 24 only. It appears after the cloud and temperature groups in ICAO reports.

What is a gust factor and why does it matter?

The difference between the gust and the mean wind — 10 kt in 24018G28KT. It is the amount of airspeed you can lose in a second when a gust ends. Many pilots add half the gust factor to their approach speed to keep a margin above the stall in the lull.

Is 00000KT the same as calm?

Yes — a mean speed below 1 kt is reported as 00000KT, direction zero. It is not the same as a light and variable wind (VRB03KT), which still has a 3 kt wind from an undefined direction, and it is not a guarantee of no shear: calm at the surface with a 40 kt wind at 500 ft is a classic nocturnal inversion shear.

Read next

• How to Read METAR Reports: A Pilot's Guide — Learn to decode a METAR line by line: station, time, wind, visibility, weather, clouds, temperature, QNH and trend. Worked example plus the mistakes that catch pilots out.
• VFR vs IFR Flight Categories Explained — What the four flight categories mean, the exact ceiling and visibility thresholds, how to derive them from a METAR or TAF, and how they differ from flight rules and European colour states.
• How to Read a TAF Forecast — Decode a TAF: validity period, FM, BECMG, TEMPO and PROB groups, what each change group promises, and how to pick the worst period for alternate planning. Worked example included.
• Crosswind Component and Runway Selection — The sine rule, the clock-face shortcut, gust handling and a worked example. How crosswind, headwind and tailwind components decide which runway to use and when to divert.
• QNH, QFE and QNE: Altimeter Settings Explained — What each altimeter setting measures, when to use which, how to convert hPa and inHg, what a wrong setting does to your altitude, and how transition altitude and level work.
• All pilot guides — the full library, 15 articles.
• Airports by country — live METAR and TAF for every reporting station
• World weather rankings from the observation archive