Winds aloft (FB) decoder

Model: FB winds and temperatures aloft coding: direction in tens of degrees true, 51-86 means add 100 kt, a coded 199 kt means 199 kt or greater, 9900 is light and variable, and signs are omitted above 24,000 ft (all negative)

Accuracy: Decodes the text as written. Levels missing at the left of a station line are the ones within 1,500 ft of the station (winds) or at 3,000 ft (temperature).

When to use this: Use this when you have an FB winds and temperatures aloft product and want a level read in plain language: the wind direction and speed and the temperature at a flight level, either from a single coded group or from a whole station line. It is the quickest way to get the wind for a cruising altitude into the wind triangle or a fuel plan.

Limitations: It decodes the text you paste and nothing else: it does not fetch the product, check it against the station, or interpolate between levels. Levels near the station are omitted by the coding itself, so a station line may not carry the altitude you want. Forecast winds aloft are a forecast, and the temperature sign is implied above 24,000 ft, which this tool applies rather than guesses.

Worked example: The group 731960 at FL340. Source: add-practitioner-essentials FB scenario: 230° true at 119 kt, -60 °C. It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.

Review: Not yet independently reviewed by a flight instructor (CFI).

Last verified: 2026-09-23, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.

Status: version 1.1.0, core 0.1.0. See this tool in the verification report.

Changes

• 2026-09-23, fixed: The winds aloft code 7799 decoded as "270° true at 199 kt". FB forecasts code 200 kt and more as 199 kt (FAA-H-8083-28B section 27.2.1.1.1), so it now reads "270° true at 199 kt or greater", the row carries speed_bound "at-least", and the result has a SPEED_AT_LEAST note. The decoder is now version 1.1.0. Changelog
• 2026-09-19, fixed: A differential against python-metar on 612 live reports found three METAR defects, now fixed: cloud layers with /// (type not determined by an automated station) were dropped, BECMG and TEMPO trend groups were applied to the current observation (a forecast wind could replace the observed one), and 9999NDV visibility was not read. The winds-aloft decoder now accepts a whole pasted FB product and takes its levels from the FT header. Changelog

Checked against: 24 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.

Sources

• Aviation Weather Handbook, FAA-H-8083-28B, Federal Aviation Administration, FAA-H-8083-28B. Section 8.4 (altimetry), section 3.4.2.14 and tables 3-17 and 3-18 (flight categories), section 24.4 (METAR and SPECI), section 27.2 (FB winds and temperatures aloft), and section 27.4 (TAF). Read free.

Terms

FB: winds and temperatures aloft forecast

The US text forecast of wind direction, wind speed, and temperature at standard altitudes, coded in groups like 2635-08. Source: Aviation Weather Handbook