Hurricanes Facts
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Hurricanes are areas of low air pressure that form over oceans in tropical climate regions.
Hurricanes are large storms with rotating winds. They form over the warm waters of the
ocean when there are large pressure and temperature differences between the warm water and
the clouds. The clouds pull the moisture and the air near the surface of the water up, toward
the clouds, which creates a column of fast-moving air.
Sometimes the air in one place is warmer than the air in another place near it. Warm air is
thinner and lighter than cool air. When heavier cool air touches warm air, it presses against it
and pushes. Some of the warm air moves sideways, and some of it moves up. As the warm
air keeps moving to the side and up and out of the way, the cool air flows in to take its place.
This movement of the air is the wind. Most of the air all over the surface of the earth is
moving, a little or a lot, most of the time.
In the beginning, the ocean storm is called a “tropical disturbance”, which is like a bunch of
thunderstorms with very little wind circulation. When wind speeds up to 20 to 34 miles per
hour, the ocean storm becomes a tropical depression. A tropical depression can quickly
become a tropical storm if the wind speeds reach 35-64 miles per hour. Once the whirling
mass of air grows and continues to spin around a center of low pressure, wind speeds
increase. When wind speeds reach 74 miles per hour or greater, the storm is considered a
hurricane and given an official name.
Hurricanes may have a diameter of 400 to 500 miles (640-800 kilometers).
The “eye” (center) of a hurricane can be up to 20 miles (32 km) across. The weather in the
“eye” is surprisingly calm with low winds and clear skies.
Hurricanes hit land with tremendous force, bringing huge waves and heavy rain.
Many hurricanes cause severe flooding.
About 90 percent of the deaths that occur during hurricanes result from drowning in floods.
The world’s worst hurricane (for loss of life) took place in 1970 in Bangladesh. That
hurricane created a flood that killed more than one million people.
Thunderstorms often form within hurricanes and produce tornadoes.
A hurricane weakens rapidly after it strikes land.
Most hurricanes in North America hit areas near the Atlantic Ocean and the Gulf of Mexico.
The warm water of the West Atlantic and the Gulf of Mexico create more favorable
conditions for hurricanes.
The words hurricane, cyclone and typhoon are all names for the same type of storm. The
name tells you where the storm occurred. Hurricanes are defined as storms over the North
Atlantic or the Caribbean. In the western Pacific Ocean, hurricanes are known as typhoons.
Cyclones are hurricanes over the Indian Ocean.
For a hurricane to survive, the water temperature must be at least 75-80 degrees Fahrenheit
and the surface winds must converge.
Cold water off North America’s West Coast prevents hurricanes from surviving there.
Because hurricanes need warm, moist air, they usually begin in late summer or early fall.
In 1992, Hurricane Andrew blew across southern Florida at speeds of 140-160 mph (225-258
kph). In terms of property loss, Andrew was one of the worst hurricanes to ever hit North
America. The property devastation was massive. Entire communities were wiped out and had
to be rebuilt. Hurricane Andrew left 50 people dead and caused over $25 billion in damages.
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Hurricanes were first given names in the 19th century by Clement Wragge, an Australian
weatherman. Nicknamed “Wet Wragge”, he named very violent storms after people he
disliked.
Today, an alphabetical list of names is drawn up each year for the coming year’s hurricanes.
The United States Weather Bureau calls a wind a hurricane when it blows as fast as 74 miles
an hour.
A hurricane spins very fast when it moves across warm water, but it slows down and dies
away if its path takes it over land. A hurricane that turns out to sea will die out when it
reaches colder water or cooler air.
The intensity of a hurricane is measured on the Saffir-Simpson Scale. This scale measures
the wind speed and air pressure of the storm. Based on these characteristics, a hurricane is
ranked with a number between 1 and 5.
Category 3, 4, or 5 hurricanes are considered intense and extremely dangerous.