How do hurricanes or tropical cyclones form?« Back to Questions List

Hurricanes are born at sea. They are massive, rotating tropical storms followed by powerful winds and rains. They consist of high winds and lines of clouds that spiral in towards a common center known as eye. The eye is about 15 miles in diameter surrounded by a towering wall of clouds that are responsible for the heavy rains. Winds start to blow at a minimum speed of 75 miles per hour and speed around the eye exceeds 150 miles per hour. Such high speeds can easily uproot trees, overturn cars and lift the roofs off buildings.

Hurricanes are also called by other names like typhoons or cyclones. The names are given based on where they occur. The common scientific name for all these violent storms is tropical cyclone.  Hurricane is the name used for tropical cyclones formed over the Atlantic Ocean or eastern Pacific Ocean. The tropical cyclones in the western Pacific and China Sea area are known as typhoons. In Bangladesh, Pakistan, India, and Australia, they are called cyclones and in the Philippines, they are named  bagyo.

Tropical cyclones begin as small areas of low pressure over tropical seas. Warm, moist air rises rapidly and as tons of water vapor condenses, great quantities of heat are released to further fuel the upward rush of air. Soon moist surface winds start spiraling in from all directions. As winds intensify, tropical cyclone takes its shape. The fury continues until it moves over land or colder region of the sea, where its supply of heat and moisture is finally cut off. 

Hurricane, tropical cyclone, storm, typhoon, cyclone, tropical, sea, warm, moist air,

In another way, tropical cyclone can be imagined as a giant engine which uses warm, moist air as fuel. As warm air rises, it creates an area of low air pressure below.  Air with higher air pressure in the surrounding areas pushes fresh air to the low pressure area. This fresh air too becomes warm and moist and rises causing air swirls in surrounding areas. Once the risen air cools off, they become clouds leading to heavy rains. The tropical cyclones become weak when they hit land as the fresh supply of warm moist air from sea is stopped.    

When the speed of winds in the rotating storm crosses 39 mph, the storm is called a tropical storm. Once the wind speed crosses 74 mph, it is classified as category 1-5 storm, based on the Saffir–Simpson hurricane wind scale (SSHWS). .

The two GOES satellites built by NASA keep their eyes on hurricanes from  a height of 22,300 miles above  Earth, sending warning signals. How does Saffir-Simpson Hurricane Wind Scale (SSHWS) classify hurricanes?

 

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Posted by attemptnwin
Asked on September 12, 2017 2:53 am