What is a Tropical Cyclone, how do they originate, and what are their consequences?

Even in their early phases of development, tropical cyclones pose a hazard to life and property. Storm surge, flooding, strong winds, tornadoes, and lighting are all risks that can have a severe impact on life and property.

Tropical cyclones are powerful circular storms that form over warm tropical oceans and bring torrential precipitation and winds of more than 119 kilometers per hour.

Tropical cyclones, often known as typhoons or hurricanes, are among the most damaging weather occurrences.

Tropical cyclones are recognized by several names around the world depending on their origin.

- Hurricanes are named after them in the Atlantic Ocean and the eastern North Pacific Ocean.

- Typhoons are what they're called in the western Pacific Ocean.

- Tropical cyclones are what they're called in the South Pacific and Indian Oceans.

Low air pressure, strong winds, and heavy rain characterize tropical cyclones. Winds up to 240 km/hr and gusts up to 320 km/hr are possible in extreme conditions. These powerful winds may result in torrential rains and a potentially disastrous phenomenon known as storm surge. It is essentially a 6 meter increase of the water surface above typical levels. Such cyclones, which combine powerful winds and water, pose a major threat to coastal areas in tropical and subtropical portions of the world.

Tropical cyclones are classified as follows based on the greatest sustained wind:

A tropical depression occurs when the maximum sustained speed is less than 63 km/h.

- A tropical storm is defined as a storm with a maximum sustained speed of greater than 63 km/h. After then, it is given a name.

When the maximum sustained speed exceeds 116 km/h, it is classified as a hurricane, typhoon, severe tropical cyclone, severe storm, or tropical cyclone, depending on the basin.

In actuality, the Saffir-Simpson Hurricane Wind Scale, which is used in the Caribbean Sea, the Gulf of Mexico, the North Atlantic Ocean, and thus the eastern and central North Pacific Ocean, classifies hurricanes from Category 1 to 5

- Category 1: Hurricanes with sustained wind speeds of 119-153 km/h were mentioned.

- Category 2: Hurricanes with sustained wind speeds of 154-177 km/h were mentioned.

- Category 3: Hurricanes with sustained wind speeds of 178-209 km/h were mentioned.

- Category 4: Hurricanes with maximum sustained wind speeds of 210-249 km/h were mentioned.

- Category 5: Hurricanes with sustained wind gusts reaching 249 km/h were mentioned.

Everything you need to know about Amphan Cyclone

Tropical Cyclone Effects

As previously stated, the impact of a tropical cyclone and the expected damage are dependent on a variety of factors, including moving speed, the duration of strong winds and accumulated rainfall during and after landfall, sudden changes in moving direction and intensity, the structure of the tropical cyclone, such as size and intensity, and the human response to tropical cyclone disasters.

Tropical cyclones have an impact on health in a number of ways, both directly and indirectly:

- It raises the risk of drowning and other forms of physical harm.

- It also raises the risk of water-borne and vector-borne infections.

- Has an effect on the psychological condition that is also related to emergency situations.

- Cause havoc with health-care systems, facilities, and services. It also left communities without health services when they were most needed.

- Causes harm to basic infrastructure, such as food and water supply, as well as safe shelter.

The impact of a tropical cyclone is also considered to be dependent on the amount of people living in low-lying coastal areas along the storm's direct path, the built environment, such as building design, and sufficient time for warning and escape.

When tropical storms create floods and sea surges, the danger of drowning and water-borne or vector-borne diseases increases. Flood water may include sewage and chemicals, conceal sharp metal or glass objects and electrical lines, or harbour poisonous snakes or reptiles that can cause injuries, electrocution, bites, and disease transmission. Storms harmed about 726 million people worldwide between 1998 and 2017, according to the WHO.

What is the mechanism of a tropical cyclone?

Tropical cyclone winds swirl around a low-pressure area in the centre. The wind is created by the Earth's low-pressure core and rotation, which deflects the wind's path through a phenomena known as the Coriolis force. Tropical cyclones revolve in a counter-clockwise or cyclonic direction in the Northern Hemisphere, and in a clockwise or anticyclonic direction in the Southern Hemisphere.

The wind field of a tropical storm can be classified into three categories:

1. A ring-shaped outer zone with a 30 to 50-kilometer inner radius. The wind speed increases consistently toward the centre in this location.

2. Wind speeds reach their maximum value at the second region, the eyewall, which is typically 15 to 30 kilometres from the storm's centre.

3. In turn, the eyewall surrounds the interior region known as the eye, where the wind speed drops rapidly and the air is usually calm.

Do you understand the distinction between a Tropical Cyclone and an Extra-tropical Cyclone?

What causes a tropical cyclone to form?

The tropical cyclone is generated when a transfer of water vapour and heat from the warm ocean to the overlying air happened predominantly by evaporation from the surface of the sea. As we know that warm, wet air rises, expands and cools, fast and become saturated and releases latent heat due to the condensation of water vapour. By this process, the column of air in the centre of the forming disturbance is warmed and wet. The temperature difference between the warm, rising air and the cooler environment causes air to become buoyant, allowing it to rise faster.

If the surface of the water is too cool then there will not be enough heat available and the rate of evaporation will be low to supply fuel to the tropical cyclone. Even the supply of energy will also be shut off owing to the warm surface water layer is not enough deep.

Because the tropical system alters the underlying ocean, this occurs. Because of the rain coming from the deep convective clouds, the sea surface cools, and the high winds in the storm's centre increase turbulence. The fuel supply for the tropical system will be eliminated if the resultant mixing brings cool water from below the surface layer to the surface.

Let us inform you that the vertical movement of warm air alone is insufficient to commence the creation of a tropical cyclone. As a result, if warm, moist air enters into an already disturbed environment, only development will occur.

The rising air warms the core of the disturbance by releasing both latent and direct heat transfer from the sea's surface, and the atmospheric pressure in the disturbance's centre decreases. As a result, the pressure drops, causing the surface winds to pick up, increasing the vapour and heat transfer and contributing to the air rising even further. In a positive feedback mechanism, the core warms up and the increasing surface winds strengthen or encourage each other.

So now you know what a tropical cyclone is, what it looks like, how it forms, and how it affects people.