How to Read Winds Aloft: Codes and Temperatures

What are the key winds-aloft decoding rules?

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

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 provides the coded product. Its product guide 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.

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 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 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 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.

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 describes winds aloft as part of a broader briefing. 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.

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, then use the GFA walkthrough and TAF guide 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, 27.2, especially pages 27-4 and 27-5: format, exceptions and header context.
• NWS Instruction 10-812, sections 4 and 6: levels, omissions and encoding.
• AWC product guide and Wind/Temp data: current product access and scope.
• FAA AIM 7-1-5 and 14 CFR 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.

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