The winds aloft forecast is six digits per altitude and no punctuation, and it hides two special cases that look like ordinary numbers but are not.

A winds aloft decoder handles those cases for you. Knowing them yourself takes about five minutes and stops you reading a 99 knot wind as something calm.

Each group is six digits: two for direction in tens of degrees, two for speed in knots, two for temperature in Celsius. So 2712-04 is wind from 270 at 12 knots, minus 4. Two exceptions matter. 9900 means light and variable. A direction of 51 through 86 means the speed is over 100 knots, and you subtract 50 from the direction and add 100 to the speed.

What's New in Winds Aloft Products for 2026

The FB forecast itself has not changed format. What has changed is what sits beside it.

Gridded forecast products now give wind and temperature at any point. The FB covers only a handful of stations. That is better for route planning, because the FB was always a station product doing an area job.

The FB has not gone away, and it remains what you get in a standard briefing and what checkride questions are written around. It is also small enough to read on a phone with no signal. The gridded products are not.

What a Winds Aloft Decoder Has to Handle

Each altitude gets one group. A full line for a station looks like this:

FT 3000 6000 9000 12000 18000 24000 30000 DFW 2113 2325+07 2434+02 2542-04 2653-16 2771-28 279440

Reading one group at a time:

• 2113 at 3,000 feet: wind from 210 at 13 knots. No temperature, because temperatures are not forecast within 2,500 feet of the station elevation
• 2325+07 at 6,000: from 230 at 25 knots, plus 7 Celsius
• 2542-04 at 12,000: from 250 at 42 knots, minus 4

The direction is the first two digits times ten, and it is true, not magnetic. The speed is the next two in knots. The temperature is the last two with its sign.

Above 24,000 feet the sign disappears, because temperatures up there are always negative. 279440 is from 270 at 94 knots, minus 40.

The 9900 Group

9900 is not a direction of 990 degrees, which is the first thing that should tell you it is special.

It means light and variable. The forecast wind is under 5 knots, and the direction is not worth predicting. You will see it most at the lowest levels and on calm days.

For planning, treat it as no useful wind, not as zero wind. Five knots from an unknown direction still adds up over a long leg. The forecast just will not commit to a direction.

Winds Over 100 Knots

This is the case that catches people, because the encoded group looks completely ordinary.

Direction is normally 01 through 36. When the wind goes over 99 knots, the encoder adds 50 to the direction and takes 100 off the speed. That way the group still fits in four digits.

To decode it:

• If the first two digits are 51 through 86, subtract 50 from them and add 100 to the speed
• 731960 becomes direction 73 minus 50, so 230 degrees, and speed 19 plus 100, so 119 knots, at minus 60
• 831950 becomes 330 degrees at 119 knots, minus 50

The clue is the first two digits. Anything above 36 cannot be a direction in tens of degrees, so it has to be the shifted form.

One more special case sits at the top of the range. A speed of exactly 199 knots or more is encoded as 99, so 7799 is 270 degrees at 199 knots or greater.

Which Altitudes You Get

The forecast levels are fixed, and which ones appear depends on the station.

• 3,000, 6,000, 9,000, 12,000, 18,000, 24,000, 30,000, 34,000 and 39,000 feet
• Levels within 1,500 feet of the station elevation are omitted entirely
• Temperatures are omitted for any level within 2,500 feet of station elevation

So a station at 5,000 feet gets no 3,000 or 6,000 foot group. A mountain station may start at 12,000. A missing level is not a missing forecast. It is a level that would sit underground, or too close to the surface to forecast.

All altitudes are MSL, and all winds are true.

Using It for a Route

Two things the forecast is good for and one it is not.

It is good for choosing a cruise altitude. Read one station down the column and you can see where the tailwind is. The gap between 6,000 and 12,000 feet is often bigger than pilots expect.

It is good for finding the freezing level, roughly. The temperature column crosses zero somewhere. Interpolate between two levels and you know whether the cloud ahead sits above it or below it.

It is not good for the air between stations. The FB covers named locations. On a long leg, the wind between two of them is your interpolation, not a forecast anybody issued.

Reading a Full Station Line

The layout only clicks once you take one line apart end to end.

DFW 2113 2325+07 2434+02 2542-04 2653-16 2771-28 279440

• 3,000 feet: from 210 at 13 knots. No temperature, because the level is close to the station elevation
• 6,000 feet: from 230 at 25 knots, plus 7
• 9,000 feet: from 240 at 34 knots, plus 2
• 12,000 feet: from 250 at 42 knots, minus 4
• 18,000 feet: from 260 at 53 knots, minus 16
• 24,000 feet: from 270 at 71 knots, minus 28
• 30,000 feet: from 270 at 94 knots, minus 40

Two things jump out of that column. The wind veers slightly and strengthens all the way up, which is the ordinary picture. And the freezing level sits between 9,000 and 12,000 feet, because that is where the temperature crosses zero.

For a light aircraft planning to cruise at the 9,000 foot level with cloud around, that second fact is the more useful of the two.

Where Winds Aloft Fit Against Other Products

The FB is one of three ways to answer the same question, and they disagree in useful ways.

• The FB is a forecast, issued a few times a day, for named stations at fixed levels
• A PIREP is an observation. Somebody flew there and reported the wind, so it beats a forecast for the level and place it covers
• Gridded products interpolate a model to any point, which is convenient and is still a model

When a PIREP and the FB disagree at the same level, the PIREP wins for that place and that hour. When they agree, you can lean harder on the rest of the FB column.

The FB also ages. Read the valid period on the product, not just the numbers. A forecast issued for a window that has already closed is describing a wind somebody expected several hours ago.

Common Mistakes With the FB Forecast

Mistake 1: reading the direction as degrees. The first two digits are tens of degrees. 21 is 210, not 21. It sounds obvious until you are tired and the number looks like a heading.

Mistake 2: treating a missing level as calm. A level that is not there was not forecast, usually because it sits too close to the station elevation. There is no wind information hiding in a blank.

Mistake 3: using the numbers as magnetic. They are true. So is the wind in a METAR and a TAF. The tower is the odd one out, and it is the one you hear most often, which is why the habit slips.

Mistake 4: forgetting the shifted form. A group like 7320 looks perfectly normal. It is 230 degrees at 120 knots, and if you read it as 730 degrees you will notice, but if you read it as a light wind you will not.

Mistake 5: interpolating across stations without thinking. Two stations 300 miles apart with different winds do not imply a smooth gradient between them. Terrain and fronts sit in the gap.

When to Trust It and When Not To

The FB is a forecast, so its reliability behaves like any other forecast.

The near term is strong. A few hours out, over flat terrain, at a station the product actually covers, the FB is usually close enough to plan fuel around.

It weakens with time, with terrain, and with distance from a forecast point. Mountain waves, local channelling and sea breezes all happen at scales the product does not resolve, and none of them will appear as anything unusual in the digits.

The check that costs nothing: look for a PIREP near your route and level. If one exists and it matches, you have a forecast and an observation agreeing. If it does not match, you have learned something the numbers alone could not tell you.

FAQ

What does 9900 mean in a winds aloft forecast?

Light and variable. The forecast wind is under 5 knots and the direction is not predictable enough to state. It appears most often at low levels and on calm days, and it means no useful wind rather than exactly zero wind.

How do you decode a winds aloft group over 100 knots?

If the direction digits are 51 through 86, subtract 50 from the direction and add 100 to the speed. So 731960 is 230 degrees at 119 knots, minus 60. Direction digits above 36 are impossible normally, which is the clue.

Are winds aloft true or magnetic?

True, like the wind in a METAR or TAF. A tower gives you magnetic over the radio. Convert before you use an FB wind for a heading, or you will be off by the local variation.

Why is there no temperature on some groups?

Temperature is not forecast for any level within 2,500 feet of the station elevation. Above 24,000 feet the sign is dropped instead, because temperatures that high are always below zero and the minus adds nothing.

Are the altitudes MSL or AGL?

MSL. Levels within 1,500 feet of the station elevation are left out completely, which is why a mountain station's forecast may not start until 12,000 feet.

Verdict on the Winds Aloft Decoder

A winds aloft decoder earns its place on exactly two groups: 9900 and anything with a direction above 36. Everything else in the format is four digits you can read at a glance once you know the layout.

Learn those two exceptions and you can read an FB without a tool, which is worth something on a day when you are looking at a printout or a phone with no signal.

The one habit to carry into it: read down the column, not across the row. The FB answers the question of what altitude to fly at, and it answers it best when you compare the levels at one station rather than the stations at one level.

If you would rather not do the arithmetic, paste a whole FB bulletin into the WxDecoder decoder. It reads the column header, aligns each station's groups to their altitudes, and applies both exceptions for you, with the raw group beside the decode so you can check it.

Last updated August 30, 2026