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Why Do Hurricanes Swirl Around in a Circle? myNotes
Winds start blowing in a straight direction. But they curve because
the Earth moves as it spins on its axis. This is known as Coriolis effect.
The faster the winds blow, the more they curve. In a hurricane, winds
blow so fast, they form spirals. In the Northern Hemisphere, the winds
in a hurricane blow counterclockwise. In the Southern Hemisphere,
they move clockwise.
Where Do Hurricanes Start?
The winds that blow over the tropical oceans are typically
“easterlies”—winds that blow from east to west. Thunderstorms that
develop in low-pressure areas disturb this wind flow, producing a
wavelike movement. Meteorologists call it an easterly wave, or a
tropical wave. About 80 percent of hurricanes in the Atlantic Ocean
start in easterly waves over western Africa.
ARCTIC OCEAN
NORTH
ASIA AMERICA
PACIFIC OCEAN
ATLANTIC OCEAN
Tropic of Cancer
INDIAN OCEAN PACIFIC OCEAN SOUTH
AMERICA
Tropic of Capricorn
AUSTRALIA
The shaded areas show where hurricanes form. The arrows
represent paths that they often take. The lighter the color of
the ocean, the higher the sea-surface temperature.
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