Tropical cyclone

A tropical cyclone is a powerful storm system that forms over warm ocean waters. It has strong winds, heavy rain, and thunderstorms arranged in a spiral. Depending on where it happens and how strong it is, a tropical cyclone may be called a hurricane (/ˈhʌrɪkən, -keɪn/) in the Atlantic Ocean or northeastern Pacific Ocean, a typhoon (/taɪˈfuːn/) in the northwestern Pacific Ocean, or simply a tropical cyclone in the Indian Ocean and South Pacific.

These storms get their energy from the heat of the ocean. Warm water evaporates into the air, which then rises and cools, forming clouds and rain. This process gives the storm its power. Tropical cyclones usually form far from the equator because they need the Earth's rotation to spin.

When a tropical cyclone reaches the coast, it can cause damage with strong winds, heavy rain, big waves, and storm surges. While areas near the coast often face the most impact, heavy rain can cause flooding far inland. Scientists have noticed that climate change affects tropical cyclones, potentially making these storms stronger and more frequent as ocean waters get warmer.

Definition and terminology

A tropical cyclone is a big storm with strong winds and heavy rain. It forms over warm ocean water. The storm has a center with very low pressure and thunderstorms around it. When the winds blow faster than 35 kilometers per hour, we call it a tropical cyclone.

These storms have different names depending on where they happen. In the Atlantic Ocean or northeastern Pacific Ocean, they are called hurricanes. In the northwestern Pacific Ocean, they are called typhoons. In the Indian Ocean and South Pacific, they are usually called tropical cyclones. The word "tropical" means the storm starts near the equator, and "cyclone" means the winds spin in a circle.

Formation

Main article: Tropical cyclogenesis

Tropical cyclones often form in the summer, but they can appear any time in warm areas. They usually start near the Intertropical Convergence Zone, where warm air rises and makes thunderstorms. These thunderstorms can come together and start to spin, helped by the Earth's rotation.

For a tropical cyclone to become stronger, it needs warm ocean water, steady winds, moist air, and enough spin from the Earth. The ocean's temperature and weather patterns like the El Niño–Southern Oscillation can affect when and where these storms form. Special centers around the world watch for these storms and give warnings to help keep people safe.

Interactions with climate

Each year, many named tropical cyclones form around the world. Most storms happen in late summer when the difference between the air high up and the ocean surface is the biggest. Every ocean area has its own storm season. For example, the Atlantic Ocean has the most storms from June to November, with the peak in early September.

Climate change can change tropical cyclones in several ways. Warmer ocean temperatures can give storms more energy, possibly making them stronger and bringing more rain. Scientists have noticed that very strong storms, especially those rated Category 4 or 5, have become more common in recent years. Warmer air can also hold more water, meaning storms can bring even heavier rain. Rising sea levels can also make coastal flooding from storms worse. Scientists are still learning exactly how climate change will change the total number of storms each year. Some studies suggest there may be fewer storms overall, but those that form could be more powerful and affect areas farther from the equator.

Intensity

Tropical cyclones change in strength based on their wind speeds and pressure. Scientists use tools like satellites and special airplanes to measure how strong these storms are.

The strongest storm ever recorded was Typhoon Tip in 1979. It had very low pressure and very fast winds.

Warm ocean water helps tropical cyclones grow. When the water is extra warm, storms can get stronger quickly. But if the storm moves over cooler water or land, it can weaken. Scientists have many ways to measure a storm’s strength, including looking at satellite pictures and using special numbers to guess how powerful it is.

Classification and naming

Tropical cyclones have different names depending on where they occur and how strong they are. In the Atlantic Ocean and northeastern Pacific, they are called hurricanes when their winds are very strong. In the western Pacific and Indian Ocean, they are called typhoons or severe cyclonic storms. Weaker storms might be called tropical storms, cyclonic storms, or tropical depressions.

These storms are given names to help people remember them and stay safe during warnings. Naming storms helps avoid confusion, especially when many storms happen at the same time. The names come from lists made by weather services around the world. If a storm causes a lot of damage, its name is retired and replaced with a new one.

Structure

Eye and center

Main article: Eye (cyclone)

At the center of a strong tropical cyclone, there is a calm area called the "eye." This eye is usually clear of clouds and about 30 to 65 kilometers wide, though it can be smaller or much larger. Around the eye is the "eyewall," where the strongest winds and heaviest rain happen.

Size

Tropical cyclones come in many sizes. They can be as small as 100 kilometers across or as large as 2,000 kilometers. The largest ones are usually found in the northwest Pacific Ocean, while the smallest are in the northeastern Pacific Ocean. For example, Typhoon Tip was one of the largest ever recorded.

Movement

The movement of a tropical cyclone, also called its track, is mainly guided by two things: winds around it and beta drift.

Winds in the area can push the storm along, like leaves moving in a stream. This is the main way the storm moves.

Beta drift is another factor. It makes the storm slowly move toward the poles and westward because of the Earth's rotation. This effect is stronger for bigger and more powerful storms. Sometimes, when two tropical cyclones get close, they can affect each other's movement and move around a point between them. As a storm moves to higher latitudes, it may also begin to move poleward and eastward, a change known as recurvature.

Effects

Tropical cyclones can create big waves, heavy rain, and strong winds. These can disrupt ships far out at sea. On land, powerful winds can damage buildings, vehicles, and trees. The most serious effect is the storm surge, where the sea level rises dramatically, often causing the worst damage.

These storms also bring other hazards like rip currents, tornadoes, and heavy rain that can cause flooding. They can bring needed rain to dry areas but can also worsen wildfires by fanning flames with their strong winds. The rain and wind can damage farms, homes, and infrastructure.

Observation and forecasting

Observation

Tropical cyclones have been around the world for thousands of years. Scientists study old records and natural clues like sand to learn about past storms. Before satellites, many storms were not noticed unless they hit land or ships.

Today, we watch storms using weather satellites that take pictures every 15 to 30 minutes. When a storm gets close to land, Doppler radar gives updates every few minutes. Special airplanes, called hurricane hunters, fly into storms to measure wind and weather.

Forecasting

See also: Tropical cyclone track forecasting, Tropical cyclone prediction model, and Tropical cyclone rainfall forecasting

Computers help scientists guess where storms will go by looking at air pressure and other things. While we can guess a storm's path fairly well, it's still hard to know how strong a storm will become. Forecasters update their guesses every six hours.

Geopotential height

Main article: Geopotential height

Scientists use something called geopotential height to understand air pressure and predict weather. They look at several levels high in the sky to see where moisture and movement might cause rain. The lowest level they watch is about 1,500 meters above sea level, and the highest they track is around 12,000 meters up.

Awareness and response

Before tropical cyclone seasons start, people get ready. They think about their risks, check insurance, and gather supplies for emergencies. If a tropical cyclone is coming, weather offices give warnings to help people stay safe.

After a hurricane, workers help clean up and fix things. They work with many groups to restore buildings, clear away waste, and repair roads. It’s important to work with trained groups for safety. Responders can face dangers like unsafe buildings and bad weather, so they need to stay careful and well-rested.

Extraterrestrial tropical cyclones

Scientists have wondered if tropical cyclones can form on planets far from Earth. Big storm systems have been seen on Venus and Saturn, but they are not the same as Earth's tropical cyclones. On Titan, Saturn's biggest moon, scientists have not found tropical cyclones. However, Titan has weather patterns that look a bit like Earth's because of its methane cycle.

Some studies suggest that tropical cyclones might exist on planets like Earth that orbit distant stars. These planets might have such storms if they spin at the right speed and are close enough to their star to keep liquid water.