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Wind vectors �(velocity, speed, shear)

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Wind direction, speed & wind shear

  • Wind direction is the direction from which the wind is blowing
    • West wind: blows from west to east
    • South wind: blows from south to north
    • Eastward: means a west wind
    • Easterly: means an east wind
  • Wind speed: Magnitude of the wind vector
  • Isotach: lines with equal wind speed
  • Wind shear: difference between the wind directions and speeds at two different heights (subtract the two wind vectors)

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Wind direction

  • Cardinal directions (NESW) and azimuth degrees

0º

90º

180º

270º

45º

135º

225º

315º

Azimuth:�increases�counterclockwise

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How to draw wind vectors

Length of a wind vector indicates the speed

Draw (in-class exercise together on the white board):

  • Wind vector with speed 10 m/s and wind vector with speed 20 m/s (identical direction)
  • Westerly wind
  • West wind
  • Westward wind
  • SSE wind
  • Wind from 30°
  • Wind shear between a NW wind at 10 km and NE wind at 5 km. Both wind speeds are identical.

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Wind symbols on weather maps

Zoom into some surface�measurements (station�reports)

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Wind barbs

  • International convention
  • Indicate wind direction � and speed in knots
  • 1 knot = 0.51 m/s