Cyclone facts for kids
In meteorology, a cyclone is a huge swirling mass of air. It spins around a strong center of low pressure. In the Northern Hemisphere, cyclones spin counterclockwise. In the Southern Hemisphere, they spin clockwise. Think of it like water going down a drain!
Cyclones have winds that spiral inwards towards their low-pressure center. The biggest low-pressure systems are polar vortices and large extratropical cyclones. Tropical cyclones and subtropical cyclones are also big cyclones. Smaller ones include mesocyclones, tornadoes, and dust devils.
Cyclones can even form on other planets like Mars, Jupiter, and Neptune.
The process of a cyclone forming and getting stronger is called cyclogenesis. Extratropical cyclones often start as waves where cold and warm air meet. As they grow, they form weather fronts. These fronts are like boundaries between different air masses.
Weather fronts show where two air masses with different temperatures, humidity, and densities meet. They cause most of our weather. Strong cold fronts often bring thunderstorms. Warm fronts usually bring rain and fog.
Tropical cyclones form from lots of thunderstorm activity. They get their energy from the heat released when moist air rises. Cyclones can change between being extratropical, subtropical, or tropical. Mesocyclones form over land and can create tornadoes. Waterspouts are like tornadoes over water.
In different parts of the world, tropical cyclones have different names:
- In the Atlantic and northeastern Pacific oceans, they are called hurricanes.
- In the Indian and south Pacific oceans, they are called cyclones.
- In the northwestern Pacific, they are called typhoons.
Contents
What is a Cyclone Called?
Henry Piddington was a scientist who studied tropical storms in India in the 1800s. He invented the word cyclone. It means "the coil of a snake," because of how the storms spiral. In 1842, he wrote an important book called Laws of the Storms.
How is a Cyclone Built?
All cyclones share some common features. A cyclone is always a low-pressure area. The very center of a cyclone, often called the eye in a strong tropical cyclone, has the lowest air pressure.
Because of the Coriolis effect (a force caused by Earth's rotation), winds around a large cyclone spin counterclockwise in the Northern Hemisphere. They spin clockwise in the Southern Hemisphere. This is the opposite of how winds spin around high-pressure systems, which are called anticyclones.
How Do Cyclones Form?
Cyclogenesis is the process where cyclones develop or get stronger. This can happen in many different ways and at different sizes.
- Extratropical cyclones start as waves along weather fronts. They become "cold-core" systems later on.
- Tropical cyclones form from lots of thunderstorm activity and are "warm-core" systems.
- Mesocyclones are warm-core cyclones that form over land. They can lead to tornadoes.
- Waterspout]]s can also form from mesocyclones, but often develop in areas with unstable air and low wind shear (changes in wind speed or direction).
The opposite of cyclogenesis is cyclolysis, which is when a cyclone weakens or disappears.
A low-pressure area can form in several ways. Sometimes, mountains can help create one. Large groups of thunderstorms can also create low-pressure areas. This disturbance can grow into a wave along a front. The low pressure sits at the top of this wave.
Around the low, the air starts to spin like a cyclone. This spinning air moves cold air towards the equator on one side and warm air towards the poles on the other. A cold front forms on the cold side, and a warm front forms on the warm side. The cold front usually moves faster and "catches up" to the warm front. When this happens, an occluded front forms.
Tropical cyclogenesis is how tropical cyclones develop and get stronger. This process is very different from how mid-latitude cyclones form. For a tropical cyclone to form, six main things are needed: 1. Warm enough sea surface temperatures. 2. Unstable air in the atmosphere. 3. Lots of humidity (moisture) in the lower and middle parts of the troposphere. 4. Enough Coriolis force to create a low-pressure center. 5. An existing small disturbance or low-pressure area. 6. Low vertical wind shear (meaning winds don't change much with height).
About 86 tropical cyclones form worldwide each year. Around 47 of these become strong enough to be called hurricanes or typhoons. About 20 become very intense, like Category 3 or higher on the Saffir–Simpson hurricane scale.
Different Kinds of Cyclones
Here are the main types of cyclones you might see on weather maps:
Surface Cyclones
These cyclones affect the weather at the Earth's surface.
Extratropical Cyclones
An extratropical cyclone is a large low-pressure weather system. It is found outside the tropics, in the middle latitudes. These cyclones are linked to fronts and changes in temperature and dew point across horizontal distances. They are often called "mid-latitude cyclones." Weather forecasters and the public often call them "depressions" or "lows." These are the common weather systems that, along with anticyclones, control much of Earth's weather.
Sometimes, an extratropical cyclone can become a subtropical storm. If it stays over warm waters long enough, its center can warm up, and it might even turn into a tropical cyclone. A very strong extratropical cyclone that hits in winter is sometimes called a nor'easter.
Polar Low
A polar low is a small, short-lived low-pressure system that forms over the ocean near the poles. Scientists first saw them on satellite images in the 1960s. The strongest polar lows form over ice-free parts of the Arctic during winter. They quickly disappear when they move over land. These systems are usually less than 1,000 kilometers (620 miles) wide and last only a couple of days. They can be hard to spot with regular weather reports and can be dangerous for ships and oil platforms.
Subtropical Cyclones
A subtropical cyclone has some features of a tropical cyclone and some of an extratropical cyclone. They can form between the equator and 50 degrees latitude. Meteorologists officially recognized this type of cyclone in 1972.
Since they often start from extratropical cyclones, they don't need super warm ocean temperatures. They can form when the water is around 23 degrees Celsius (73 degrees Fahrenheit). This is a few degrees cooler than what tropical cyclones need. This means subtropical cyclones can form outside the usual hurricane season. While they rarely have hurricane-force winds, they can sometimes become tropical storms as their centers warm up.
Tropical Cyclones
A tropical cyclone is a powerful storm system with a low-pressure center and many thunderstorms. These storms bring strong winds and heavy rain. A tropical cyclone gets its energy from the heat released when moist air rises and its water vapor turns into rain. This is why they are called "warm core" storms.
The word "tropical" refers to where these storms usually form: in tropical parts of the world. It also refers to how they depend on warm, moist air masses. The word "cyclone" describes their spinning nature: counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
Tropical cyclones can cause very strong winds and huge amounts of rain. They also create high waves and dangerous storm surges. Storm surges are rises in sea level caused by the storm's low pressure and strong winds pushing water towards the coast. These surges can cause major coastal flooding far inland.
Tropical cyclones lose strength when they move over land because they no longer have warm ocean water to feed them. This is why coastal areas often get the worst damage. However, heavy rains can cause serious flooding even far inland.
Even though they can be destructive, tropical cyclones also help the Earth. They carry heat and energy away from the tropics towards cooler temperate areas. This helps keep the Earth's atmospheric circulation balanced.
Many tropical cyclones start from small disturbances in the atmosphere when conditions are right. Others form when different types of cyclones gain tropical features. These systems are then moved by steering winds in the troposphere. If conditions stay good, the storm gets stronger and can even develop an eye. If conditions get worse or the storm moves over land, it weakens and eventually disappears.
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Australian region cyclone
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South-West Indian Ocean cyclone
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Upper Level Cyclones
Polar Cyclone
A polar cyclone (also called a polar vortex) is a huge area of low pressure. It gets stronger in winter and weaker in summer. A polar cyclone is a low-pressure weather system, usually 1,000 to 2,000 kilometers (620 to 1,240 miles) wide. The air spins counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. These cyclones are not caused by thunderstorms or by cold and warm air masses meeting. They are part of the Earth's global air movement. The main part of a polar cyclone is high up in the atmosphere.
TUTT Cell
Sometimes, high-level cold low-pressure areas can break off from a larger trough of low pressure in the tropics. These are called TUTT cells. They usually move slowly from east to west. They don't usually reach down to the surface. In rare cases, they can become warm-core tropical cyclones.
Smaller Cyclones (Mesoscale)
These types of cyclones are too small to see on regular weather maps.
Mesocyclone
A mesocyclone is a spinning column of air, about 2 to 10 kilometers (1.2 to 6.2 miles) wide, inside a thunderstorm. Air rises and spins around a vertical axis. They are usually linked to a low-pressure area within a supercell thunderstorm. These storms can have strong surface winds and large hail. Mesocyclones often happen with strong updrafts in supercells, where tornadoes can form. About 1,700 mesocyclones form in the United States each year, but only about half of them produce tornadoes.
Tornado
A tornado is a violently spinning column of air that touches both the ground and a cumulonimbus cloud (or sometimes a cumulus cloud). They are also called twisters.
Dust Devil
A dust devil is a strong, well-formed, and long-lasting whirlwind. They can be small (half a meter wide and a few meters tall) or very large (more than 10 meters wide and over 1,000 meters tall). The air inside them mainly moves upwards. Dust devils are usually harmless, but very large ones can sometimes be a threat to people and property.
Waterspout
A waterspout is a spinning column of air that forms over water. Most waterspouts are like a non-supercell tornado over water, connected to a cumulus cloud. They are often weaker than tornadoes over land, but stronger ones can form from mesocyclones.
Steam Devil
A gentle spinning column of air over calm water or wet land. You can see it because of rising water vapor.
Fire Whirl
A fire whirl, also called a fire devil or fire tornado, is a whirlwind caused by a fire. It is often made of flames or ash.
Cyclones on Other Planets
Cyclones are not just found on Earth! Spinning storms are common on gas giant planets like Jupiter and Neptune. For example, the Small Dark Spot on Neptune is a cyclone. Mars has also shown cyclonic storms. However, giant storms like Jupiter's Great Red Spot are actually the opposite of cyclones; they are anticyclones.
See also
In Spanish: Ciclón para niños
