The focus of this lesson is to provide students with an understanding why winds blow the directions they do–general east-west movements, and in spirals–and major consequences, hurricanes and rain shadows. Begin with a review of Lessons A-18, Convection Currents: Observation and Interpretation and D-13 Weather I: Wet tropics and Dry Deserts, D-13
Trade winds and wind blowing in a spiral
Understanding global convection currents (D-13) logically leads to the conclusion that prevailing winds should blow north or south. However navigators exploring the world in the 15 and 16th centuries, discovered winds at equatorial latitudes blowing consistently westward and at temperate latitudes winds blowing consistently eastward. These became known as trade winds.
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Also, it became clear that winds around storm centers were blowing in a circle. This is now visually evident from satellite images.
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Despite this spiral motion, however, storm systems themselves moved in the same pattern as trade winds. Type into your browser: hurricane tracks images