[{"data":1,"prerenderedAt":475},["ShallowReactive",2],{"learn-\u002Flearn\u002Freading-winds-and-temperatures-aloft":3,"learn-nav-\u002Flearn\u002Freading-winds-and-temperatures-aloft":443},{"id":4,"title":5,"body":6,"date":369,"description":370,"draft":371,"extension":372,"faqs":373,"howTo":383,"keyTakeaways":391,"meta":397,"navigation":398,"path":399,"quiz":400,"seo":427,"series":428,"seriesOrder":428,"sources":429,"stem":440,"topic":441,"__hash__":442},"learn\u002Flearn\u002Freading-winds-and-temperatures-aloft.md","Reading winds and temperatures aloft",{"type":7,"value":8,"toc":357},"minimark",[9,13,19,24,41,44,48,51,90,93,116,120,123,128,131,169,173,176,214,218,227,233,251,258,275,279,290,305,308,312,350,354],[10,11,12],"p",{},"A winds and temperatures aloft forecast tells you what the wind and air temperature will be at a range of levels, and reading one lets you pick a cruising level and work out your real ground speed before you ever start the engine.",[14,15,16],"blockquote",{},[10,17,18],{},"This is general educational information, not operational, legal, or regulatory advice. Rules differ by authority and change over time. Always verify against current official sources and follow your operator's approved procedures.",[20,21,23],"h2",{"id":22},"what-the-forecast-is","What the forecast is",[10,25,26,27,34,35,40],{},"The winds and temperatures aloft forecast, known in the United States as the FB or FD product, gives the forecast wind direction, wind speed, and air temperature at a set of standard levels above a station. In the US it is produced by the ",[28,29,33],"a",{"href":30,"rel":31},"https:\u002F\u002Faviationweather.gov\u002F",[32],"nofollow","NOAA\u002FNWS Aviation Weather Center",", and the coding and decoding rules are set out in the ",[28,36,39],{"href":37,"rel":38},"https:\u002F\u002Fwww.faa.gov\u002Fregulationspolicies\u002Fhandbooksmanuals\u002Faviation\u002Ffaa-h-8083-28b-aviation-weather-handbook",[32],"FAA Aviation Weather Handbook (FAA-H-8083-28)",", the modern home of the material that older pilots will know from Advisory Circular AC 00-45. Other authorities publish the same information graphically as wind and temperature charts, often called spot wind or significant weather charts.",[10,42,43],{},"The standard levels in the US forecast are 3000, 6000, 9000, 12000, 18000, 24000, 30000, 34000, and 39000 feet. There are two sensible omissions: no wind is forecast for a level within 1500 feet of the station elevation, and no temperature is forecast for the 3000 foot level or for any level within 2500 feet of the station elevation.",[20,45,47],{"id":46},"how-a-group-is-built","How a group is built",[10,49,50],{},"Each level is given as a short coded group. A full group has six characters: two for direction, two for speed, and two for temperature.",[52,53,54,78,84],"ul",{},[55,56,57,61,62,65,66,70,71,77],"li",{},[58,59,60],"strong",{},"Direction"," is the first two digits, in tens of degrees ",[58,63,64],{},"true",". So ",[67,68,69],"code",{},"24"," is 240 degrees. This is the same true reference used by the written wind in a ",[28,72,76],{"href":73,"className":74},"\u002Flearn\u002Fglossary#gt-metar",[75],"glossary-link","METAR",", not the magnetic wind you hear on the radio.",[55,79,80,83],{},[58,81,82],{},"Speed"," is the next two digits, in knots.",[55,85,86,89],{},[58,87,88],{},"Temperature"," is the last group, in Celsius. From 6000 feet up to and including 24000 feet the sign is shown. Above 24000 feet the temperature is always negative, so the sign is left off.",[10,91,92],{},"Two special cases are worth committing to memory:",[52,94,95,105],{},[55,96,97,100,101,104],{},[67,98,99],{},"9900"," means the wind is ",[58,102,103],{},"light and variable",", less than 5 knots.",[55,106,107,108,111,112,115],{},"When the forecast speed is ",[58,109,110],{},"100 knots or more",", the coders add 50 to the direction and subtract 100 from the speed so the numbers still fit two digits each. A direction figure between 51 and 86 is your clue. To decode, subtract 50 from the direction and add 100 back to the speed. A speed of 200 knots or more is always coded as 199, which appears as a speed of ",[67,113,114],{},"99"," after the addition.",[20,117,119],{"id":118},"a-worked-example","A worked example",[10,121,122],{},"Here is a forecast for one station, level by level:",[10,124,125],{},[67,126,127],{},"3000 2113   6000 2125+05   9000 2235-01   12000 2348-07   24000 2576-30   39000 731950",[10,129,130],{},"Reading it across:",[52,132,133,139,145,151,157,163],{},[55,134,135,138],{},[67,136,137],{},"2113"," at 3000 ft: wind from 210 degrees true at 13 knots. No temperature is given at 3000 ft.",[55,140,141,144],{},[67,142,143],{},"2125+05"," at 6000 ft: wind 210 at 25 knots, temperature plus 5 Celsius.",[55,146,147,150],{},[67,148,149],{},"2235-01"," at 9000 ft: wind 220 at 35 knots, temperature minus 1 Celsius. This is close to the freezing level, which matters for icing.",[55,152,153,156],{},[67,154,155],{},"2348-07"," at 12000 ft: wind 230 at 48 knots, temperature minus 7.",[55,158,159,162],{},[67,160,161],{},"2576-30"," at 24000 ft: wind 250 at 76 knots, temperature minus 30.",[55,164,165,168],{},[67,166,167],{},"731950"," at 39000 ft: the direction code 73 is above 36, so subtract 50 to get 23, meaning 230 degrees true; add 100 to the speed of 19 to get 119 knots; the temperature is minus 50, with the sign assumed because the level is above 24000 ft. This is the kind of fast, cold flow you find near a jet stream.",[20,170,172],{"id":171},"what-you-do-with-it","What you do with it",[10,174,175],{},"A winds aloft forecast earns its keep in planning:",[52,177,178,184,196,202],{},[55,179,180,183],{},[58,181,182],{},"Choosing a level."," Compare the wind at adjacent levels and pick the one that gives you the best tailwind or the smallest headwind for your route. A few thousand feet can be worth ten or twenty knots of ground speed.",[55,185,186,189,190,195],{},[58,187,188],{},"Ground speed, time, and fuel."," The forecast wind is what turns your ",[28,191,194],{"href":192,"className":193},"\u002Flearn\u002Fglossary#gt-true-airspeed",[75],"true airspeed"," into a ground speed, and ground speed is what sets your time en route and your fuel burn.",[55,197,198,201],{},[58,199,200],{},"Icing and the freezing level."," Watch for levels where the temperature is near zero and the air is moist; that is where airframe icing lives. The level where the forecast crosses zero is a useful estimate of the freezing level.",[55,203,204,207,208,213],{},[58,205,206],{},"Turbulence and shear."," A large change of wind speed or direction between adjacent levels is a hint of ",[28,209,212],{"href":210,"className":211},"\u002Flearn\u002Fglossary#gt-wind-shear",[75],"wind shear"," and possible turbulence, and very strong high-level winds point to the jet stream.",[20,215,217],{"id":216},"turning-the-wind-into-a-ground-speed","Turning the wind into a ground speed",[10,219,220,221,226],{},"The reason a winds aloft forecast is worth decoding is that it lets you turn your true airspeed into a ground speed before you fly, which is what sets your time en route and your fuel. The tool for this is the wind triangle, described in the navigation chapter of the ",[28,222,225],{"href":223,"rel":224},"https:\u002F\u002Fwww.faa.gov\u002Fregulations_policies\u002Fhandbooks_manuals\u002Faviation\u002Fphak",[32],"Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25)",".",[10,228,229,230,232],{},"Take a worked example. You plan to cruise at 9000 feet on a track of 090 degrees true, at a true airspeed of 120 knots. The decoded forecast for 9000 feet is ",[67,231,149],{},", a wind from 220 degrees true at 35 knots. The wind is blowing from your right and slightly behind you, so part of it pushes you along and part of it pushes you sideways.",[52,234,235,242],{},[55,236,237,238,241],{},"The angle between the wind direction (220) and your track (090) is 130 degrees. Because that is more than 90 degrees, the wind has a ",[58,239,240],{},"tailwind"," component: it is helping.",[55,243,244,245,250],{},"A rough mental estimate splits the wind into along-track and across-track parts. With the wind well behind the beam, a useful chunk of those 35 knots adds to your ground speed, so a 120-",[28,246,249],{"href":247,"className":248},"\u002Flearn\u002Fglossary#gt-knot",[75],"knot"," true airspeed might give a ground speed nearer 140 knots, while the crosswind part is what you cancel with a small drift correction to hold the track.",[10,252,253,254,257],{},"Now switch the track to 270 degrees, flying the reverse route, and the same wind comes from ahead of the beam. The along-track part now ",[58,255,256],{},"subtracts",", so the ground speed drops below the true airspeed, perhaps to around 100 knots, and the leg takes noticeably longer on the same fuel flow. The wind did not change; your direction relative to it did.",[10,259,260,261,264,265,268,269,274],{},"Two conventions are worth pinning down while you are at it. The forecast levels are referenced to ",[58,262,263],{},"mean sea level",", and above 18000 feet in the United States they are expressed as ",[58,266,267],{},"flight levels"," (FL180, FL240) flown on the standard altimeter setting, not as feet on the local ",[28,270,273],{"href":271,"className":272},"\u002Flearn\u002Fglossary#gt-qnh",[75],"QNH",". And the freezing level is wherever the forecast temperature passes through zero, which is the first place to look for airframe icing if there is moisture about.",[20,276,278],{"id":277},"a-forecast-not-an-observation","A forecast, not an observation",[10,280,281,282,285,286,289],{},"It is worth remembering what kind of data this is. A winds and temperatures aloft forecast is exactly that, a ",[58,283,284],{},"forecast",", generated from a numerical weather model for fixed valid periods and use-windows. The actual wind you find at a level can differ from the forecast, sometimes by a useful margin, especially around fronts, jet streams, and terrain where models struggle. The ",[28,287,33],{"href":30,"rel":288},[32]," issues the product in cycles, each valid for a stated window, so the version you use should be the current one for your planned departure.",[10,291,292,293,296,297,300,301,304],{},"Two refinements help you read it sensibly. ",[58,294,295],{},"Pilot reports"," of the actual wind and temperature at a level are a direct check on the forecast, and a string of reports showing the wind running stronger than forecast is worth more than the printed figure. And the winds aloft forecast is usually read alongside the ",[58,298,299],{},"significant weather chart"," and any ",[58,302,303],{},"freezing-level chart",", which together show the fronts, the jet stream, and the icing layers that explain why the wind and temperature change between levels.",[10,306,307],{},"The practical habit, then, is to treat the forecast as your planning baseline, the best estimate of the wind that turns your true airspeed into a ground speed, while staying ready for the real wind to differ and updating your time and fuel against the ground speed you actually achieve once airborne.",[20,309,311],{"id":310},"common-pitfalls","Common pitfalls",[52,313,314,326,332,338,344],{},[55,315,316,319,320,325],{},[58,317,318],{},"Reading the direction as magnetic."," Forecast winds are true. Only spoken winds from ATC or the ",[28,321,324],{"href":322,"className":323},"\u002Flearn\u002Fglossary#gt-atis",[75],"ATIS"," are magnetic.",[55,327,328,331],{},[58,329,330],{},"Missing the strong-wind code."," A direction over 36 is not a real heading; it means 50 was added and the wind is 100 knots or more.",[55,333,334,337],{},[58,335,336],{},"Forgetting the temperature sign."," Above 24000 feet the temperature is always negative even though no minus sign is printed.",[55,339,340,343],{},[58,341,342],{},"Expecting a temperature near the surface."," There is none at 3000 feet or within 2500 feet of the station.",[55,345,346,349],{},[58,347,348],{},"Treating the levels as height above ground."," They are referenced to mean sea level, like all forecast levels.",[20,351,353],{"id":352},"in-pilot-efb","In Pilot EFB",[10,355,356],{},"Pilot EFB fetches and displays the winds and temperatures aloft for the airports you have selected, at the standard levels, showing wind direction, speed, and temperature so you can compare levels at a glance when you plan a cruise. It presents the forecast; it does not choose your level or compute your fuel for you, so apply your own judgement and your aircraft's data. Forecasts you have already pulled stay readable offline, because your device is the source of truth for what you have saved, while fetching a fresh forecast needs a connection. Pilot EFB is offline-first and is not a certified Electronic Flight Bag.",{"title":358,"searchDepth":359,"depth":359,"links":360},"",2,[361,362,363,364,365,366,367,368],{"id":22,"depth":359,"text":23},{"id":46,"depth":359,"text":47},{"id":118,"depth":359,"text":119},{"id":171,"depth":359,"text":172},{"id":216,"depth":359,"text":217},{"id":277,"depth":359,"text":278},{"id":310,"depth":359,"text":311},{"id":352,"depth":359,"text":353},"2026-04-13","How to decode a winds and temperatures aloft forecast field by field, including the coding trick for strong winds, with a worked example and how to use it for cruise planning.",false,"md",[374,377,380],{"q":375,"a":376},"Is the wind in a winds aloft forecast true or magnetic?","It is degrees true, the same as the written wind in a METAR or TAF. The magnetic wind you hear from the tower or the ATIS is a separate, spoken convention. Forecast and reported written winds are always referenced to true north.",{"q":378,"a":379},"Why does a winds aloft group sometimes have a direction greater than 360?","It is a coding trick for strong winds. When the forecast speed is 100 knots or more, 50 is added to the two-digit direction and 100 is subtracted from the speed so the group still fits. To decode it, subtract 50 from the direction and add 100 back to the speed. A direction code from 51 to 86 is the signal that this has been done.",{"q":381,"a":382},"Why is there no temperature at the lower levels?","No temperature is forecast for the 3000 foot level or for any level within 2500 feet of the station elevation, because it is too close to the surface to be useful. Above 24000 feet the temperature is always negative, so the sign is left off to save space.",{"name":384,"steps":385},"How to decode a winds and temperatures aloft group",[386,387,388,389,390],"Take the first two digits as the wind direction in tens of degrees true, so 24 means 240 degrees.","If the direction code is between 51 and 86, subtract 50 from it and add 100 to the speed, because the wind is 100 knots or more.","Take the next two digits as the wind speed in knots.","Read 9900 as light and variable, meaning less than 5 knots.","Take the final digits as the temperature in Celsius, with the sign shown up to and including 24000 feet and assumed negative above it.",[392,393,394,395,396],"A winds and temperatures aloft forecast gives wind direction, wind speed and air temperature at a set of standard levels above a station.","Direction is the first two digits in tens of degrees true, the same true reference as the written wind in a METAR, not the magnetic wind from ATC.","A direction code between 51 and 86 means 50 was added to the direction and 100 subtracted from the speed because the wind is 100 knots or more; subtract 50 and add 100 back to decode it.","9900 means the wind is light and variable, less than 5 knots.","No temperature is forecast within 2500 feet of the station elevation, and above 24000 feet the temperature is always negative so the sign is left off.",{},true,"\u002Flearn\u002Freading-winds-and-temperatures-aloft",[401,410,418],{"q":402,"options":403,"answer":408,"explanation":409},"In a winds aloft group such as 2113, the first two digits give the wind direction in tens of degrees referenced to which north?",[404,405,406,407],"Magnetic north, like the wind from ATC or the ATIS","True north, like the written wind in a METAR","Grid north","Whichever north the chart legend specifies",1,"Direction is the first two digits in tens of degrees true, the same true reference used by the written wind in a METAR, not the magnetic wind you hear on the radio.",{"q":411,"options":412,"answer":359,"explanation":417},"A winds aloft group shows a direction code of 73. What does this tell you?",[413,414,415,416],"The wind is light and variable","The temperature reading should be treated as positive","50 was added to the direction and the wind is 100 knots or more","The level is below the station elevation","A direction figure between 51 and 86 is the clue that 50 was added to the direction and 100 subtracted from the speed because the forecast speed is 100 knots or more; you subtract 50 and add 100 back to decode it.",{"q":419,"options":420,"answer":425,"explanation":426},"Why is no temperature forecast for the 3000 foot level?",[421,422,423,424],"It is too close to the surface to be useful, within 2500 feet of the station elevation","The temperature there is always negative so the sign is left off","The wind there is light and variable","The level is expressed as a flight level",0,"No temperature is forecast for the 3000 foot level or for any level within 2500 feet of the station elevation, because it is too close to the surface to be useful.",{"title":5,"description":370},null,[430,431,433,436,439],{"label":39,"url":37},{"label":432,"url":223},"FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25)",{"label":434,"url":435},"FAA Aeronautical Information Manual, Chapter 7 Section 1 (Meteorology)","https:\u002F\u002Fwww.faa.gov\u002Fair_traffic\u002Fpublications\u002Fatpubs\u002Faim_html\u002Fchap7_section_1.html",{"label":437,"url":438},"UK Met Office: aviation forecasts and charts","https:\u002F\u002Fwww.metoffice.gov.uk\u002Fservices\u002Ftransport\u002Faviation\u002Fregulated",{"label":33,"url":30},"learn\u002Freading-winds-and-temperatures-aloft","Weather","3SNR90QexXFDmgc_Evupk8JbmgxFQkxC9hw75hRQ-NY",{"related":444,"newer":463,"older":470,"series":428},[445,451,455],{"path":446,"title":447,"description":448,"date":449,"topic":441,"draft":371,"minutes":450,"series":428,"seriesOrder":428},"\u002Flearn\u002Freading-a-surface-analysis-chart","How to read a surface analysis chart","Decode a surface analysis chart: isobars and the pressure gradient, highs and lows, warm, cold and occluded fronts, and what the big picture tells you before you read the METAR.","2026-06-20",3,{"path":452,"title":453,"description":454,"date":449,"topic":441,"draft":371,"minutes":450,"series":428,"seriesOrder":428},"\u002Flearn\u002Fthe-international-standard-atmosphere","The International Standard Atmosphere (ISA)","What the ICAO International Standard Atmosphere is, its sea-level values and lapse rate, and how ISA deviation underpins altimetry, performance and density altitude.",{"path":456,"title":457,"description":458,"date":459,"topic":441,"draft":371,"minutes":460,"series":461,"seriesOrder":462},"\u002Flearn\u002Fhow-to-read-a-sigmet-and-airmet","How to read a SIGMET and an AIRMET","What SIGMETs and AIRMETs warn of, the phenomena codes, how long each stays valid, and a worked SIGMET decoded field by field, with the ICAO baseline and the US differences.","2026-06-18",5,"decode-the-weather",4,{"path":464,"title":465,"description":466,"date":467,"topic":468,"draft":371,"minutes":469,"series":428,"seriesOrder":428},"\u002Flearn\u002Fnotam-categories-and-time-windows","NOTAM categories and time windows","How NOTAMs are sorted by scope and subject, how the validity fields B, C and D set the time window, and what PERM and EST mean, so you can triage a long briefing package.","2026-04-16","Briefing",8,{"path":471,"title":472,"description":473,"date":474,"topic":468,"draft":371,"minutes":469,"series":428,"seriesOrder":428},"\u002Flearn\u002Fdecoding-notam-q-codes","Decoding NOTAM Q-codes and abbreviations","A deeper guide to the NOTAM Q-line: the five-letter Q-code, the traffic, purpose and scope qualifiers, the height and coordinate fields, and the contractions NOTAMs are written in.","2026-04-10",1781989193861]