Lesson 3 - Understanding Wind at Sea

Key Takeaways:

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• Global Wind Systems:

  • Trade Winds: Steady easterlies near equator.

  • Westerlies: Prevail in temperate latitudes.

  • Polar Easterlies: Less stable, cold, from poles.

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• Local Wind Effects:

  • Sea Breeze: Onshore wind during the day due to land heating faster.

  • Land Breeze: Offshore wind at night from cooling land.

  • Katabatic Winds: Cold, dense air rushing downhill (e.g., Bora).

  • Anabatic Winds: Warm air rising during daytime.

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• Wind & Geography:

  • Wind bends and accelerates around headlands and through valleys.

  • Funneling increases wind speed in narrow passages.

  • Wind shadows create turbulence and lulls downwind of land masses.

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• Gusts, Squalls, and Shifts:

  • Gusts: Short increases in wind speed.

  • Squalls: Strong, often wet, sudden wind events—prepare early.

  • Shifts: Changes in wind direction—often ahead of a front or terrain-driven.

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• Practical Wind Reading:

  • Combine forecast, visual indicators (flags, telltales), and instruments.

  • Apparent wind vs. true wind—both matter for sail trim.

  • Learn to anticipate—not just react.