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  • Veer or Back

    HI
    in N.H wind Veer or Back?

  • #2
    Re: Veer or Back

    Both, depends which wind they're talking about

    If wind is 250 on surface it will veer once it becomes free stream wind around 2000ft

    If wind is 250 around 2000ft, it will back at the surface.

    Damir

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    • #3
      Re: Veer or Back

      Question: Friction between the air and the ground results in the northern hemisphere in:
      a/backing of the wind and decrease of wind speed at the surface.
      b/veering of the wind and decrease of wind speed at the surface.
      c/veering of the wind and increase of wind speed at the surface.
      d/backing of the wind and increase of wind speed at the surface.


      Question: In the Northern Hemisphere a man observes a low pressure system passing him to the south, from west to east. What wind will he experience?
      a/Backs then veers.
      b/Constantly backs.
      c/Backs then steady.
      d/Veers then backs.

      Question: After passing at right angles through a very active cold front in the direction towards the cold air, what will you encounter at FL 50, in the northern hemisphere immediately after a marked change in temperature?
      a/A backing in the wind direction.
      b/A decrease in tailwind.
      c/An increase in tailwind.
      d/A veering in the wind direction.


      Question: During a descent from 2000 FT above the surface to the surface (no front present, northern hemisphere), the wind normally
      a/backs and increases
      b/veers and increases
      c/veers and decreases
      d/backs and decreases

      Question: At the approach of a warm front (Northern Hemisphere) the wind direction changes from the surface up to the tropopause. The effect if this change is that the wind:
      a/Backs in the friction layer and veers above the friction layer.
      b/Veers in the friction layer and backs above the friction layer.
      c/Backs in the friction layer and backs above the friction layer.
      d/Veers in the friction layer and veers above the friction layer.


      Question: With the passage of an active polar front depression the surface winds will ? and the upper winds will ? in the northern hemisphere:
      a/Back; back
      b/Back; veer
      c/Veer; veer
      d/Veer; back

      Question: When compared to the geostrophic wind in the northern hemisphere, surface friction will cause the surface wind to
      a/veer and increase
      b/back and decrease
      c/back and increase
      /veer and decrease



      Question: In relation to the wind speed and direction at the top of the friction layer, which change in wind will a pilot normally experience during descent to the surface over land in the northern hemisphere?
      a/Backing ca. 30 degrees, speed is reduced by ca. 50%.

      b/Veering ca. 30 degrees, speed is reduced by ca. 50%.
      c/Backing ca. 10 degrees, speed is reduced by ca. 30%.
      d/Veering ca. 10 degrees, speed is reduced by ca. 30%.

      Comment


      • #4
        Re: Veer or Back

        Question: What is the relationship between the 5000 ft wind and the surface wind in the southern hemisphere?
        a/Surface winds are backed from the 5000ft and have a slower speed.
        b/Surface winds are veered from the 5000ft and have the same speed.
        c/Surface winds are veered from the 5000ft and have a slower speed.
        d/Surface winds are backed from the 5000ft and have a faster speed.

        Question: Which statement is correct for the southern hemisphere?
        If the wind veers with increasing height then warm air is advected
        The jet streams are easterly
        The wind veers at the passage of a cold front
        In the friction layer the wind backs with increasing height

        Comment


        • #5
          Re: Veer or Back

          Hi Laith,

          This series of questions is examining two different phenomena:

          1. The freestream wind follows the isobars

          2. The low level or "surface" wind is modified by surface friction

          When, for example a low pressure system in the NH passes north of you the isobars will give you an observed frestream wind that goes from SW through W to NW. This is a "veer" over time. Meanwhile, at any chosen point the surface wind will be slower than the freestream and as a consequence will have backed in relation to the freestream.

          For the freestream wind, N or S hemi, just follow the isobars. For the surface winds, coming down from the freestream to the surface wind is:

          Slack and back but slack and veer in the S hemisphere

          Dick

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          • #6
            Re: Veer or Back

            thanks damirhusic
            thanks Dick

            Comment


            • #7
              Originally posted by laith View Post
              Re: Veer or Back
              Question: In relation to the wind speed and direction at the top of the friction layer, which change in wind will a pilot normally experience during descent to the surface over land in the northern hemisphere?
              a/Backing ca. 30 degrees, speed is reduced by ca. 50%.

              b/Veering ca. 30 degrees, speed is reduced by ca. 50%.
              c/Backing ca. 10 degrees, speed is reduced by ca. 30%.
              d/Veering ca. 10 degrees, speed is reduced by ca. 30%.
              I still don't understand this . Also what's "ca." ?

              Sorry to bring this up again!

              Comment


              • #8
                ca is an abbreviation for circa . It is a word of Latin origin and means "about" or "around".

                The numbers are a direct quote from the learning objectives.
                You can find these by googling "Annex II to ED Decision 2016/008/R"

                Relative to the freeflow wind at height the wind will back and slacken off as you descend to the surface in the Northern Hemisphere due to the friction effect. Backing means the direction from which the wind is coming will move anticlockwise round the compass rose. As an example a freeflow wind of 270 at 20 knots will back to 240 at 10 kts.

                In the Southern Hemisphere the wind veers and slackens off as you descend to the surface. Veering means the direction from which the wind is coming will move clockwise round the compass rose. As an example a freeflow wind of 270 at 20 knots will veer to 300 at 10 kts

                JJ

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