1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

ATIS Winds - True or Magnetic?

Discussion in 'Pilot-Controller Questions' started by Dazzler, Jun 30, 2009.

  1. Dazzler

    Dazzler Well-Known Member

    Joined:
    Jan 24, 2004
    Messages:
    1,152
    Likes Received:
    0
    METARs give wind direction in relation to TRUE north.

    Now, when recording ATIS, which is sourced from the METARs, is the wind direction converted to relate to MAGNETIC north instead of TRUE? This certainly would be useful seeing as Runway Designations are assigned with reference to MAGNETIC north.
     
  2. nocturnalaviator

    nocturnalaviator FNG

    Joined:
    Oct 30, 2007
    Messages:
    973
    Likes Received:
    273
    Call the tower, or go up and see them with your questions. They encourage it!
     
  3. dc3flyer

    dc3flyer Well-Known Member

    Joined:
    Aug 15, 2006
    Messages:
    1,805
    Likes Received:
    20
    In most places I don't think it really matters THAT much. Winds are also given 10's of degrees (such as 180 or 190) instead of actual degress (such as 183 or 187). So are a few degrees going to matter? Not to mention the winds change a little more often than the reports.

    In the lower 48, what is the maximum difference, 18 degrees?
     
  4. n6149s

    n6149s New Member

    Joined:
    Jun 16, 2009
    Messages:
    108
    Likes Received:
    0
    When I was a developmental working on GC, I told my instructor that they were magnetic. He insisted that I was wrong, and he had been converting them 20 degrees for about 19 years. He was wrong, they are magnetic. That does help when looking down a magnetic heading of a runway.
     
  5. Greg01

    Greg01 Well-Known Member

    Joined:
    Dec 10, 2007
    Messages:
    124
    Likes Received:
    5
    Magnetic. At BUF they take the METAR reading and tack on 10 degrees and type it into the ATIS computer.
     
  6. OldTownPilot

    OldTownPilot Well-Known Member

    Joined:
    May 3, 2005
    Messages:
    4,860
    Likes Received:
    9
    Its magnetic.

    Maine is just under 19 west, and NW Washington is just under 19 east. The difference between the METARs and the ATIS' here is 20 degrees.

    In the corners of the country its something that you have to concern yourself with, especially in XC planning. The difference between a 30 and a 50 degree crosswind can be substantial too, especially for a low time private pilot.
     
  7. Fandango Flyer

    Fandango Flyer Well-Known Member

    Joined:
    Aug 1, 2006
    Messages:
    22
    Likes Received:
    0
    It's pretty far in the back of my head, but I sorta remember something about that if the winds are written they are true, and that if they are spoken they are magnetic.
     
  8. 7700

    7700 Well-Known Member

    Joined:
    Mar 23, 2009
    Messages:
    258
    Likes Received:
    30
    Here's a good way to remember True vs Mag Winds:

    Anything you read (METAR's, TAF's, FD's, Wx Charts) is True

    Anything your hear (ATIS, ASOS) is Magnetic
     
  9. 400A

    400A New Member

    Joined:
    Mar 22, 2008
    Messages:
    677
    Likes Received:
    0
    Text is True, all else is magnetic
     
  10. Dazzler

    Dazzler Well-Known Member

    Joined:
    Jan 24, 2004
    Messages:
    1,152
    Likes Received:
    0
    Not true - you read the numbers on the runway, which is text, but that's MAGNETIC not TRUE ;)
     
  11. 400A

    400A New Member

    Joined:
    Mar 22, 2008
    Messages:
    677
    Likes Received:
    0

    Paint doesn't count, see my invisible disclaimer in above post.


    :cwm27:
     
  12. Beehive

    Beehive Well-Known Member

    Joined:
    Jan 6, 2008
    Messages:
    333
    Likes Received:
    0
    Our metar gets a copy and paste to ATIS. It sounds like I read it.
    Maybe that's why tower gives the wind on takeoff and landing clearance.
    -13 degrees variation.
     
  13. Sunburn

    Sunburn Well-Known Member

    Joined:
    Aug 3, 2008
    Messages:
    525
    Likes Received:
    5
    7110.65 says that the ATIS winds shall be in magnetic
     
  14. Inverted

    Inverted You can snap roll anything, once...

    Joined:
    Sep 28, 2008
    Messages:
    3,345
    Likes Received:
    1,418
    I asked the tower this at KLVK and they give winds in Magnetic. It only makes sense it takes the work out of converting.
     
  15. nocturnalaviator

    nocturnalaviator FNG

    Joined:
    Oct 30, 2007
    Messages:
    973
    Likes Received:
    273
    LOL you ask a question, you get an answer, and then tell the guy he's wrong on a technicality, lol good one! If you gave me that answer in person i'd tell you I rest my case, inform you that you know it all, and walk away. But hey give someone a jerk answer, get a jerk response.
     
  16. atcbrownie

    atcbrownie New Member

    Joined:
    Oct 30, 2008
    Messages:
    18
    Likes Received:
    0
    I have never read anything other than what comes out on the metar nor have I ever heard of anyone else doing so. The AFB I was at our atis was automated directly from the metar. Whatever the metar says is what the controller is going to tell you.
     
  17. sdfcvoh

    sdfcvoh This is my Custom Title

    Joined:
    Apr 2, 2007
    Messages:
    1,812
    Likes Received:
    36
    To put this into further perspective, what are you doing when you READ numbers?... You are flight planning....

    Flight planning begins with TRUE courses and headings, and that is the reason printed material is true and not magnetic. Just in case you were wondering...
     
  18. clestudentpilot

    clestudentpilot Well-Known Member

    Joined:
    May 19, 2007
    Messages:
    164
    Likes Received:
    0
    It is not always true in print that the winds are true. Where I was at, it was a manual weather reporting station. The instruments they read the winds from were the same whether you were writing down the METAR information to record the ATIS, and to call FSS with, or giving it to pilots in a takeoff or landing clearance. While this contradicts things, I asked some people who are much more knowledgable than I am when it comes to being a whether observer, since I am not one, I received the answer that the NWS prefers true, the FAA prefers magnetic. The NWS has won out in these scenarios. To obtain a wind reading, you observe the wind for 2 minutes, and take the average of the 2 minute reading. I won't get into details on gusts factors, or variable wind directions. When an automated station give the winds, whether on a frequency on ASOS or AWOS, or in a METAR, the same is true, a 2 minute average. The automated stations are obviously much more accurate, and the machine can automatically change the direction for magnetic direction in an AWOS or ASOS recording you listen to. At controlled fields, they may have to look at the METAR readout from the AWOS, and convert before recording the ATIS. For all intents and purposes, a human weather observer just is not good enough to get the very precise winds when observing them. If the winds cary between 176 and 224 in the 2 minute interval, the observer may to average it say it varied between 170 and 230 to give a wind of 220, while someone else may see this as between 180, and 230 for 225, which would round to 230. What I'm saying is that humans just aren't good enough at the manual stations to get it as accurate as the automated stations can. That is why we didn't add or subtract anything when calling FSS with the METAR, it was so close that it was impracticle. Stations in Maine or Washington may do things differently though
     
  19. Guy

    Guy Well-Known Member

    Joined:
    May 20, 2009
    Messages:
    847
    Likes Received:
    4
    Give that man a cigar. He is right.
     
  20. Sunburn

    Sunburn Well-Known Member

    Joined:
    Aug 3, 2008
    Messages:
    525
    Likes Received:
    5
    This is the reference I was looking for

    7110.65 2-9-3
    Include the following in ATIS broadcast as
    appropriate:
    a. Airport/facility name, phonetic letter code, time
    of weather sequence (UTC). Weather information
    consisting of wind direction and velocity, visibility,
    obstructions to vision, present weather, sky condition,
    temperature, dew point, altimeter, a density
    altitude advisory when appropriate and other
    pertinent remarks included in the official weather
    observation. Wind direction, velocity, and altimeter
    shall be reported from certified direct reading
    instruments. Temperature and dew point should be
    reported from certified direct reading sensors when
    available. Always include weather observation
    remarks of lightning, cumulonimbus, and towering
    cumulus clouds.
    NOTE ASOS/AWOS is to be considered the primary source of
    wind direction, velocity, and altimeter data for weather
    observation purposes at those locations that are so
    equipped. The ASOS Operator Interface Device (OID)
    displays the magnetic wind as “MAG WND” in the
    auxiliary data location in the lower left-hand portion of the
    screen. Other OID displayed winds are true and are not to
    be used for operational purposes.
     

Share This Page