Hiểu hơn về Hurrican

how-do-hurricanes-form-young-people

Không khí xung quanh hành tinh của chúng ta nặng 5.000.000.000.000 tấn! Nói cách đó, đó là 5 tỷ tỷ tấn và là rất nhiều. Không khí này luôn luôn di chuyển. Nó quay cuồng, thổi lượn, chìm, và tăng lên. Vào mùa hè và đầu mùa thu, những không khí tuyệt vời trên các đại dương ấm áp. Trpoical Oceans. Nếu một khối không khí ấm hơn và lấy rất nhiều độ ẩm, nó có thể bắt đầu xoáy tròn. Khi điều này xảy ra, một HURRICANE hoặc ONE-EYED MONSTER ra đời. Nếu cơn bão đi đến lục địa, nó có thể quét sạch mọi thứ trên con đường của nó.

The air that surrounds our planet weighs 5,000,000,000,000,000 tons! In words, that is 5 quadrillion tons and that’s a lot. This air is always moving. It swirls, blows, sinks, and rises. In summer and early fall, great masses of air sit over the warm, tropical oceans. If a mass of air gets warmer and picks up lots of moisture, it can start swirling. When this happens, a HURRICANE or a ONE-EYED MONSTER is born. If the hurricane moves toward the continent, it could wipe out everything in its path.

Animation is brought to you with special permission by AccuWeather.com
Hurricanes are tropical cyclones that can cover thousands of square miles. The winds in a hurricane exceed 74 miles per hour and circulate counter-clockwise about its center in the Northern Hemisphere or clockwise in the Southern Hemisphere. Hurricane-like storms are called by different names in the different regions of the world. Wind belts and highs and lows all help direct the journeys of tropical cyclones.

How does a “one-eyed monster” form? Actually, there are several ingredients needed for a hurricane to form.

  • Tropical Ocean Water (at least 500 kilometers or 300 miles from the Equator)


  • Heat from the Sun


  • Air


  • Wind


  • The Spin of the Earth

Follow the steps below through the life cycle of a hurrricane.

A Monster is Born

Step 1. The sun warms the ocean water to 81 degrees Fahrenheit or 26.5 degrees Celsius. Step 2. The ocean water evaporates caused by the heat from the sun. The evaporatingwater forms a cloud of warm, moist air that moves upward.
Step 3. As the warm, moist air rises, more air rushes in to replace it. This air is also heated and moistened by the ocean surface.It begins to rise and form clouds,heating the air around it. Step 4. Eventually, a large mass of warm, moist air with rain clouds is formed over the ocean. The warm air expands and becomes less dense and lighter and forms an area of low pressure.
Step 5. More warm, moist air rushes in from the ocean surface. The air begins to spin because of the rotation of the earth. The air goes faster and faster as it spirals inward. Step 6. The whole storm, now spinning like a top, is carried across the ocean by the wind.As it moves across the warm ocean waters, it will continue to become stronger and stronger.
Step 7. Finally, it moves over land or cold water. It loses its fuel source, warm ocean, and begins to die out.

Stages of a Hurricane

A TROPICAL DISTURBANCE is the first stage of development of a hurricane. It consists of a mass of thunderstorms that have only a slight wind circulation. The tropical disturbance becomes a tropical depression when the winds increase to more than 20 knots or 23 miles per hour.

A TROPICAL DEPRESSION forms when a group of thunderstorms comes together under the right atmospheric conditions for a certain length of time. Winds near the center of the tropical depression are constantly between 20 and 34 knots (23 – 39 mph). Lowered pressure is indicated with at least one closed isobar on a surface pressure chart. Also, the organized circulation of wind in the center of the thunderstorms is detected.

This is a satellite picture of a tropical depression.
Tropical depressions look like individual thunderstorms that are grouped together.

A TROPICAL STORM forms when the maximum sustained winds have intensified to between 35-64 knots (39-73 mph). It becomes better organized and begins to look like a hurricane with a circular shape. At this point, the storm is given aname. Most of the problems from tropical storms come from heavy rainfall.

This is a satellite picture of tropical storm Charlie in 1998 over Texas. This storm dumped between 5-10 inches of rain over many southern Texas cities.

A HURRICANE finally forms when surface pressures continue to drop and when sustained wind speeds reach 64 knots (74 mph). There is also a definite rotation about the eye.

Hurricanes have definite parts that are easily recognized in this satellite animation.

 

Hurricane Categories

Hurricane intensity is measured using the Saffir-Simpson damage potential scale. It is named after Herbert Saffir, a consulting engineer in Coral Gables, Florida, and Robert Simpson, who was director of the National Hurricane Center from 1967 through 1973.Mr. Saffir developed the first version of the scale in 1971 for a United Nations report on construction that could stand up to high winds. It used wind speeds as a guide to the damage to expect. Hurricane Camille that hit the Mississippi Coast on August 17, 1969, was the reason the scale was devised. On the Saffir-Simpson scale hurricanes are rated by their potential for damage on a scale of one to five.
Saffir-Simpson Hurricane Scale
Category
Wind Speed
Storm Surge
Damage
Example
1
74-95 mph
4-5 feet
Minimal
Irene, 1999
2
96-110 mph
6-8 feet
Moderate
Floyd, 1999
3
111-130 mph
9-12 feet
Extensive
Fran, 1996
4
131-155 mph
13-18
Extreme
Andrew, 1992
5
Over 155 mph
Greater than 18 feet
Catastrophic
Camille, 1969

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