As Cyclone Fani starts its descend in India, hitting its eastern coast and making landfall in Odisha, the might of nature's fury is well in the display.
Cyclones, typhoons, tornadoes and hurricanes are all violent furies of the sea which when combined with whirlwind air pressure create havoc, and they have been cited across the globe. But are they all names of the same phenomenon or differ in type and form? Let's find out:
Hurricane, Cyclone and Typhoon
The only difference between a hurricane, a cyclone, and a typhoon is the location where the storm occurs. They are categorised under the same weather phenomenon, but different names are used to describe these storms in different places. In the Atlantic and Northeast Pacific, the term “hurricane” is used. Whereas, the same type of disturbance in the Northwest Pacific is called a “typhoon” and “cyclones” occur in the South Pacific and the Indian Ocean; regardless of the strength of the wind associated with the weather system. Thus, explaining why India always faces the wrath of a cyclone and not a hurricane or a typhoon.
Hurricanes are defined by a five-category system based on maximum sustained wind speed in many countries, like Australia.
The weakest tropical cyclones are called tropical depressions. If a depression intensifies such that its maximum sustained winds reach 39 miles per hour, the tropical cyclone becomes a tropical storm. Ans once a tropical cyclone reaches maximum sustained winds of 74 miles per hour or higher, it is then classified as a hurricane, typhoon, or tropical cyclone, depending upon where the storm originates in the world.
Tropical cyclone and cyclone
A tropical cyclone is a generic term used by meteorologists to describe a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has closed, low-level circulation. Once a tropical cyclone reaches maximum sustained winds of 74 miles per hour or higher, it is then classified as a hurricane, typhoon, or cyclone depending upon where the storm originates in the world.
Tropical cyclones rotate counterclockwise in the Northern Hemisphere. They are classified as follows:
Tropical Depression: A tropical cyclone with maximum sustained winds of 38 mph (33 knots) or less
Tropical Storm: A tropical cyclone with maximum sustained winds of 39 to 73 mph (34 to 63 knots)
Hurricane: A tropical cyclone with maximum sustained winds of 74 mph (64 knots) or higher. In the western North Pacific, hurricanes are called typhoons; similar storms in the Indian Ocean and South Pacific Ocean are called cyclones.
Major Hurricane: A tropical cyclone with maximum sustained winds of 111 mph (96 knots) or higher, corresponding to a Category 3, 4 or 5 on the Saffir-Simpson Hurricane Wind Scale.
Tornadoes, unlike hurricanes, are different storm game altogether. They form spontaneously, are short-lived and traverse a much smaller land mass by comparison.
Many atmospheric conditions need to converge at the right time for tornadoes to form. They need hot, humid air near the ground with a cool air mass above them. They also need strong wind velocity at higher altitudes, known as wind shear, to get them spinning. A tornado is basically a violently spiralling funnel cloud that extends from the bottom of a thunderstorm to the ground.
The only similarity between a tornado and hurricanes or cyclones is that they both contain strong rotating winds that can cause damage. Tornadoes usually occur over land, while hurricanes almost always form over the ocean.
They also differ in size. The largest tornado every observed was 4 km wide, but most tornadoes are about 0.8 km wide. Hurricanes are much larger, ranging from about 160 km to 1,600 km wide. Also, a tornado’s lifetime is short, ranging from a few seconds to a few hours, while a hurricane’s life cycle can last from days to weeks.
The strongest tornadoes can have recorded wind speeds of over 483 kph, but even the strongest hurricanes rarely produce wind speeds over 322 kph.
Tornadoes and twisters
A tornado and a twister are different names for the same type of storm — a violently rotating column of air over land associated with a severe thunderstorm. Tornadoes have an intense updraught near their centre, capable of lifting heavy objects such as cars and trees and causing enormous destruction.
Typhoons are classified as 'typhoon', 'very strong typhoon', or 'violent typhoon' by the Japan Meteorological Agency. It is a mature tropical cyclone that develops between 180° and 100°E in the Northern Hemisphere. This region is referred to as the Northwestern Pacific Basin, and is the most active tropical cyclone basin on Earth, accounting for almost one-third of the world's annual tropical cyclones.
While a hurricane occurs in the Atlantic Ocean or the northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a tropical cyclone occurs in the South Pacific or the Indian Ocean.
Within the northwestern Pacific, there are no official typhoon seasons as tropical cyclones form throughout the year. But like any tropical cyclone, there are a few main requirements for typhoon formation and development, such as:
— Sufficiently warm sea surface temperatures
— Atmospheric instability
— High humidity in the lower to middle levels of the troposphere
— Enough Coriolis effect to develop a low-pressure center
— A pre-existing low-level focus or disturbance, and
— A low vertical wind shear
On average, the northwestern Pacific features the most numerous and intense tropical cyclones globally. Like other basins, they are steered by the subtropical ridge towards the west or northwest, with some systems recurving near and east of Japan.
Some of the deadliest typhoons in history have struck China. Southern China has the longest record of typhoon impacts for the region, with a thousand-year sample via documents within their archives. Taiwan has received the wettest known typhoon on record for the northwest Pacific tropical cyclone basins.
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Updated Date: May 03, 2019 11:10:00 IST