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ELI5 Yahaaa

Named for where it starts

Where Does the Wind Come From?

A north wind blows from the north, and it carries whatever the north was like.

1 The arrowpoints into thewind2 That directionnames it3 And tells youwhat air iscoming
A north wind is not going north. It is coming from there.
  1. Step 1 of 5

    Wind is air moving to even out pressure.

    Air between two placesHigherpressurepushes outLower pressurepulls in

    Where air presses harder it pushes toward where it presses less. That flow is all wind is — the atmosphere trying to flatten a difference.

  2. Step 2 of 5

    A vane turns to face where it comes from.

    A weather vane on aroof Big tail downwind, smallpoint upwind

    The tail is large, so wind pushes it downwind. That swings the small pointed end round to aim directly into the oncoming air.

  3. Step 3 of 5

    Naming by origin is the useful convention.

    Northerly Air from the pole —coldSoutherly Air from the tropics —warm

    What you want to know is what sort of air is arriving. Naming a wind for where it started tells you that immediately.

  4. Step 4 of 5

    The origin explains the humidity too.

    From the sea Damp — cloud anddrizzleFrom the land Dry — clear skies

    Air that crossed an ocean arrives damp; air that crossed a continent arrives dry. Direction predicts moisture as reliably as it predicts temperature.

  5. Step 5 of 5

    A change of direction is a change of weather.

    1 The vane swingsround2 A front ispassing3 The weatherchanges

    When the wind swings round, a different air mass has arrived. That shift is often the first sign of a front, before any cloud appears.

    Around a low-pressure system in the northern hemisphere the wind circles anticlockwise, so its direction tells you where the centre is.

The short version

Wind is air flowing from high to low pressure, and naming it for its origin tells you the temperature and moisture arriving.

Try it yourself

Tie a ribbon to a stick and hold it up. Face into the wind — the direction you are facing is the wind's name.

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