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Weather Lab 6-8 / Week 04 / Wednesday
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Week 04 · Where Wind Comes From

Wednesday

Station Lab: Wind flag and compass
// Air on the move, from high pressure to low
⏱ about 20 min

Wednesday: Station Lab: Wind Flag and Compass

Rocket arrives at Station Rooftop with a broom handle, a strip of old cloth and a roll of tape. "Wind flag!" he announces.

Raven holds up a paper circle with N, E, S and W drawn on it. "And a compass. We line up north with the real north."

"How do we know where real north is?" Rocket asks, already taping cloth to the handle.

Nova turns slowly until her light points one way. "A grown-up or a map of your area can show you north," she says. "Then everything else lines up."

Raven sets the compass on the railing and tapes it down. "The flag tells us direction. What tells us speed?"

"How hard it flaps?" Rocket says. Nova hums. "Sailors solved that problem long ago," she says. "Watch what the wind does to leaves and twigs."

Your mission

You will build a wind flag and a paper compass and set them at your station. Then you will record wind direction and strength three times today.

Estimated wind strength comes from the Beaufort scale, a scale sailors have used for more than two hundred years. The National Weather Service still lists it.

  • A strip of light cloth or ribbon, about the length of your arm
  • A stick, dowel or old broom handle
  • Tape or string
  • A paper plate or card, a marker, and a ruler
  • A spot on the ground, a railing or a windowsill that is open to the wind
  • Your station log
Safety first
A grown-up handles anything sharp, such as trimming the cloth or the stick.
Your station sits on the ground, a railing or a windowsill. Nobody goes on a roof or a ladder.
Never take a reading during a thunderstorm, a flood or very high wind. Wait indoors until it passes.
Never look at the Sun.
  1. Tie or tape one end of the cloth strip to the top of the stick so it can swing freely.
  2. Draw a cross on the paper plate and label the ends N, E, S and W, clockwise from the top.
  3. Add NE, SE, SW and NW between the letters.
  4. Find north. Ask a grown-up, or check a map of your area. Maps mark north on them.
  5. Set the plate flat with N pointing north, and tape it down. Push or prop the stick upright beside it.
  6. Read the wind: the flag points away from the wind, so the wind comes from the opposite side of the plate.
  7. Estimate strength from the Beaufort table below by watching leaves, twigs and the flag.
  8. Record the time, the direction and the Beaufort force in the data table. Repeat two more times today.

The Beaufort scale on land

The Beaufort scale runs from force 0 to force 12. Each force has a description of what the wind does to things around you.

Here are the first seven forces, with the National Weather Service's land descriptions and speed ranges in miles per hour.

Stay indoors at force 7 or higher. Those winds move whole trees and make walking hard.

ForceNameSpeed (mph)What you see on land
0Calm0 to 1Smoke rises straight up
1Light air1 to 3Smoke drifts; wind vanes do not move
2Light breeze4 to 7Wind felt on face; leaves rustle; vanes move
3Gentle breeze8 to 12Leaves and small twigs keep moving; a light flag extends
4Moderate breeze13 to 18Dust and loose paper lift; small branches move
5Fresh breeze19 to 24Small leafy trees begin to sway
6Strong breeze25 to 31Large branches move; umbrellas are hard to use
PREDICT BEFORE YOU READ
  • Read the question.
  • Tap your answer.
Your flag hangs limp and smoke from a chimney rises straight up. What force is that?
Leaves and small twigs keep moving and your light cloth flag stands out. What force is that?
Dust and loose paper lift off the ground. About how fast is the wind?
TimeWind from (N, NE, E...)Beaufort forceWhat I saw
Morning
Midday
Late afternoon
What the lab showsTrue or false?
The flag points away from the wind.?
The wind comes from the side of the compass the flag points toward.?
Force 2 means you can feel the wind on your face.?
You should go outside at force 7 to get a better reading.?
WHY THIS EXERCISEA reading is only useful if the direction rule and the strength scale are applied the same way every time.
Your flag points south. The wind is from the ____.
What is the highest Beaufort force on the scale? Type a number.
Sketch your station from above. Label the compass plate, the wind flag, north, and the direction of today's wind.

Great building. Tomorrow you will read the National Weather Service's map of the whole planet's winds.

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