# How to Read Winds Aloft: Codes and Temperatures

> Decode the FB winds and temperatures aloft table, keep true direction and altitude references straight, and work explained practice codes.

- Source: https://firstsolo.ai/blog/how-to-read-winds-aloft
- Author: Sam Whitaker, Student Pilot
- Published: 2026-10-23
- Updated: 2026-10-23
- Last reviewed: 2026-10-23

To read winds aloft in a coded FB table, first match the forecast's location, altitude and time to your flight. Decode ordinary groups as wind direction in tens of degrees true, speed in knots and temperature in Celsius. Check the special codes for light wind, speeds of 100 knots or more and temperatures above 24,000 feet before using the result for planning.

## What are the key winds-aloft decoding rules?

The column and header provide context that the number group cannot supply by itself.

| Key fact | Reading rule | Official source |
| --- | --- | --- |
| Direction | Wind is from the coded direction, referenced to true north | [FAA Aviation Weather Handbook, 27.2](https://www.faa.gov/sites/faa.gov/files/FAA-H-8083-28B.pdf) |
| Ordinary group | DD × 10 gives degrees; ff gives knots; signed TT gives °C | [NWS Instruction 10-812, section 6](https://www.weather.gov/media/directives/010_pdfs/pd01008012curr.pdf) |
| 9900 | Light and variable, or speed below 5 knots | [FAA handbook, 27.2.1.1.1](https://www.faa.gov/sites/faa.gov/files/FAA-H-8083-28B.pdf) |
| High-speed encoding | For 100–199 knots, subtract 50 from DD and add 100 to ff when decoding | [NWS Instruction 10-812](https://www.weather.gov/media/directives/010_pdfs/pd01008012curr.pdf) |
| Temperature sign | Explicit from 6,000 through 24,000 feet; omitted above 24,000 because negative | [FAA handbook, 27.2.1.1.1](https://www.faa.gov/sites/faa.gov/files/FAA-H-8083-28B.pdf) |

These are the traditional US FB text conventions, sometimes called FD winds. They do not mean every graphical or app-based winds product uses this code.

## Where do you find the table and choose its time?

Use the current text product and read its header before choosing a row.

The [AWC Wind/Temp data page](https://aviationweather.gov/data/windtemp/) provides the coded product. Its [product guide](https://aviationweather.gov/help/data/) identifies this as NCEP's FB winds product, grouped by region, with 6-, 12- and 24-hour forecasts. Your flight-planning app may instead draw from another model or grid; confirm its product and units rather than assuming its values came from the text table.

Read three separate ideas in the header: **DATA BASED ON**, **VALID** and **FOR USE**. The first identifies the forecast's data basis, the second its forecast valid time and the third the intended use window. Z means UTC. A forecast downloaded now can still be the wrong forecast for a later flight.

For a study exercise, imagine a header marked **VALID 231800Z FOR USE 1700-2100Z**. It describes a valid time on the 23rd at 1800 UTC and a use window from 1700 to 2100 UTC. This invented header teaches the fields; it is not a current bulletin or a promise that every product has that window. Check the actual date, including any midnight crossing.

## How do you decode an ordinary wind-and-temperature group?

Split the group into direction, speed and temperature, then carry the column altitude into your answer.

Take the original practice code **2422-08** at **9,000 feet**:

- **24** means wind from **240° true**.
- **22** means **22 knots**.
- **-08** means **-8°C**.

Say the complete answer: “At the selected time and location, the 9,000-foot forecast is wind from 240° true at 22 knots, temperature minus 8 Celsius.” Avoid saying only “240 at 22,” because it loses the product context and reference.

![A practice winds-aloft group 2422-08 is split into 240 degrees true, 22 knots and minus 8 Celsius](https://s3.doublegis.com/firstsolo/blog/how-to-read-winds-aloft/winds-aloft-group-decoder.svg?v=b7850201)

*Original fictional example. The altitude comes from the column, not from the code; the values are not current weather.*

At the ordinary 3,000-foot column, the text table supplies wind without a temperature. A four-digit group there is not missing a temperature sign you should guess. The FAA handbook's decoding example explicitly lists temperature at that level as not forecast.

## How do 9900 and high-speed groups change the method?

Recognize a special code before multiplying its first two digits by ten.

**9900** is not a direction of 990° and does not establish zero wind. It communicates light and variable wind or a forecast speed under 5 knots. At a level that includes temperature, a temperature suffix may follow that wind code.

After excluding 9900, direction fields **51 through 86** identify the high-speed form. For a practice group, use **762548** at **30,000 feet**. Subtract 50 from 76, giving 26: the direction is **260° true**. Add 100 to 25: the speed is **125 knots**. At that altitude the unsigned 48 means **-48°C**. It is not positive 48 Celsius and the wind is not from 760°.

![A reading sequence checks 9900 first, then high-speed direction encoding and the column's temperature convention](https://s3.doublegis.com/firstsolo/blog/how-to-read-winds-aloft/winds-aloft-special-code-checks.svg?v=bcf67202)

*A decoding aid for the FB text format. Treat 9900 separately before applying the high-speed arithmetic.*

The speed encoding has an upper limit: the [FAA handbook](https://www.faa.gov/sites/faa.gov/files/FAA-H-8083-28B.pdf) explains that 200 knots or more is represented as 199 knots. Its **7799** example therefore means wind from 270° true at **199 knots or greater**, not a precise measurement of 199 knots. You do not need those altitudes for an ordinary student flight to understand the coding exception.

## Why are some cells blank, and are the heights AGL?

A blank cell does not mean calm wind, and these table levels are not heights above local terrain.

[NWS Instruction 10-812, section 4](https://www.weather.gov/media/directives/010_pdfs/pd01008012curr.pdf) excludes wind forecasts within 1,500 feet of a location's elevation and temperature forecasts within 2,500 feet; it specifies exceptions for certain added Hawaii/Pacific levels. It distinguishes actual-altitude lower levels from pressure-altitude upper levels, using an MSL reference. Never relabel a 6,000-foot column as 6,000 feet AGL.

Keep your eye on the column labels when a station row starts farther to the right. Copying the first visible group into the first printed column can put the right code at the wrong altitude. Recheck both the row identifier and the column after writing a value into a navigation log.

| Fictional table entry | Correct interpretation | Error to catch |
| --- | --- | --- |
| 3,000 ft: 2316 | From 230° true at 16 kt; temperature not supplied | Adding an invented temperature |
| 6,000 ft: 1908+05 | From 190° true at 8 kt, +5°C | Calling the height 6,000 ft AGL |
| 12,000 ft: 9900-03 | Light/variable or under 5 kt, -3°C | Reading 990° or assuming exactly zero wind |

*Original codes for study, not a real station row. Decode each with its stated column.*

## How do you turn a decoded wind into useful planning?

Apply it to the correct route leg and time, while keeping the forecast separate from a guarantee.

For an elementary arithmetic exercise, assume a **100-knot true airspeed** and a **20-knot wind directly opposing the track**, with no crosswind. The resulting groundspeed is **80 knots**. A hypothetical **80 NM** leg then takes **one hour**. These are invented inputs, not a route, aircraft performance claim or fuel plan. A crosswind requires a wind-triangle calculation rather than simple subtraction.

Write the units beside each input. True course, true wind and magnetic heading are different quantities; keep references consistent while solving, then make the appropriate navigation corrections. Check actual progress and revise estimates rather than expecting the forecast wind to occur exactly.

The [AIM preflight-briefing guidance](https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap7_section_1.html) describes winds aloft as part of a broader briefing. [Section 91.103](https://www.ecfr.gov/current/title-14/section-91.103) includes weather, fuel requirements and alternatives for IFR flights or flights away from an airport's vicinity. Choosing a favorable wind does not answer questions about clouds, icing, turbulence, terrain, airspace or aircraft limitations.

## Check yourself

These original questions practise interpretation; they are not released FAA test questions.

**1. At 9,000 feet, what does 2817-06 mean?**

Wind from 280° true at 17 knots, temperature -6°C. The 9,000-foot context comes from the column; the first digits give direction, not altitude.

**2. At 30,000 feet, does 741552 mean 740° at 15 knots and +52°C?**

No. Subtract 50 from 74 and multiply by ten: 240° true. Add 100 to 15: 115 knots. Above 24,000 feet, the unsigned temperature is negative, so -52°C.

**3. Does 9900 justify planning with a guaranteed zero wind?**

No. It covers light and variable wind or a speed under 5 knots. It is a forecast convention, not a promise of still air or a reason to stop monitoring progress.

## Frequently asked questions

**Are winds aloft true or magnetic?**

The coded FB table uses true north. Preserve that reference when combining it with other navigation inputs.

**Is a winds-aloft forecast an observation?**

No. It predicts conditions at specified locations, levels and times. The observation basis in the header does not turn the forecast into an encountered-weather report.

**Can I assume a blank cell means 9900?**

No. Missing or omitted data and a coded light-wind forecast have different meanings. Check the column and product instructions.

**Does every app use the same FB table?**

No. The FAA handbook describes multiple model-based winds products. Read the app's source, level, time and units before comparing it with a text bulletin.

## What should you practise next?

Return to the [METAR weather-reports hub](https://firstsolo.ai/blog/how-to-read-a-metar), then use the [GFA walkthrough](https://firstsolo.ai/blog/gfa-aviation-weather) and [TAF guide](https://firstsolo.ai/blog/how-to-read-a-taf) to compare the time and purpose of different weather products. Practise decoding a group, stating its full context, then identifying what it cannot tell you.

FirstSolo.ai is solely a study tool. It does not issue knowledge-test endorsements now or in the future. Use current official weather and instructor guidance for flight preparation.

## Sources and review notes

- [FAA Aviation Weather Handbook, FAA-H-8083-28B](https://www.faa.gov/sites/faa.gov/files/FAA-H-8083-28B.pdf), 27.2, especially pages 27-4 and 27-5: format, exceptions and header context.
- [NWS Instruction 10-812](https://www.weather.gov/media/directives/010_pdfs/pd01008012curr.pdf), sections 4 and 6: levels, omissions and encoding.
- [AWC product guide](https://aviationweather.gov/help/data/) and [Wind/Temp data](https://aviationweather.gov/data/windtemp/): current product access and scope.
- [FAA AIM 7-1-5](https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap7_section_1.html) and [14 CFR 91.103](https://www.ecfr.gov/current/title-14/section-91.103): briefing and preflight context.

Facts checked October 23, 2026 for the October 22 calendar entry. All practice codes and calculations are explicitly instructional. Human pilot/author approval remains pending before publication.

*FirstSolo.ai is independent and is not affiliated with or endorsed by the FAA.*