2. Prevailing Wind A wind that consistently blows from one direction more than from another.
3. Anemometer An instrument used to determine wind speed.
4. El Nino The name given to the periodic warming of the ocean that occurs in the central and eastern Pacific; A major El Nino episode can cause extreme weather in many parts of the world.
5. Key Concept What causes local winds? The local winds are caused either by topographic effects or by variations in surface composition—land and water—in the immediate area.
6. Key Concept Describe the general movement of weather in the United States. In the United States, the westerlies consistently move weather from west to east across the continent.
7. Key Concept What happens when unusually strong, warm ocean currents flow along the coasts of Ecuador and Peru? At irregular intervals of three to seven years, these warm countercurrents become unusually strong and replace normally cold offshore waters with warm equatorial waters.
8. Key Concept How is a La Nina event triggered? Researchers have come to recognize that when surface temperature in the eastern Pacific are colder than average, a La Nina event is triggered that has a distinctive set of weather patterns.
