The formation of tropical storms

• Tropical storms form over warm oceans and travel from east to west.
• Tropical storms bring with them high winds, rain and storm surges.
• Tropical storms can cause large-scale damage and danger to life.

Hurricanes, typhoons and cyclones are all names used to refer to violent, rotating, tropical storms.

The term for these storms changes, depending on where they occur. If they form over the Atlantic Ocean or the Eastern Pacific Ocean, they are called hurricanes.

If they occur in the Far East, near places such as Japan, they are known as typhoons and if they occur in the Indian Ocean they are known as cyclones.

For a tropical storm to form, there needs to be a warm ocean (27 °C or above) and light winds.

As tropical storms require warm oceans, they are normally found in tropical regions between 5° and 30° north and south of the equator where the water is warmest.

They usually form in the late summer when sea temperatures are at their highest.

• Step 1: Warm air rises from the ocean. As the warm air rises it leaves a space below it called an area of low pressure. This space is instantly filled by surrounding air rushing in causing strong winds.
• Step 2: The air that has rushed in now warms up and rises too. This rising air brings with it moisture. This moisture cools and condenses to form towering storm clouds. This forms the eye wall.

• Step 3 – When the cooled air descends it will form an area of calm in the centre called the eye.
• Step 4 – Due to the winds near the equator the tropical storm starts to move from east to west. The spin of the Earth causes these winds to curve and leads to the storm starting to spin.

Scientists believe that climate change may affect tropical storms.

As the Earth warms so to do the oceans. If more of the oceans are above 27 °C, more places may experience tropical storms. Higher temperatures may also mean more energy for a tropical storm meaning they become more powerful and cause more damage.

A tropical storm can last up to a month and move very slowly, about 15 mph, across the ocean. On average seven hurricanes form each year over the Atlantic Ocean. Not all of these tropical storms make it to land; an average of two a year do.

If a tropical storm does make landfall, it can have devastating effects on both people and the environment. These effects can be divided into primary effects and secondary effects.

Primary effects are caused by the tropical storm itself, usually as a result of high winds and the storm surge that often accompanies a tropical storm.

Primary effects may include:

• Strong winds, heavy rain and storm surges lead to buildings being destroyed or flooded.
  • Hurricane Dorian which hit the Bahamas and mainland USA in 2019 was the most powerful Atlantic hurricane on record with winds at 185 mph (295 km/h).
• Roads, railways, electricity supplies and other infrastructure being damaged.
• People being killed.
  • Hurricane Katrina hit the United States in 2005 and killed more than 1800 people.

Secondary effects are caused by the primary effects and usually happen later on.

Secondary effects may include:

• food and clean water shortages
• jobs being lost as businesses are damaged
• costs of damage
• landslides which can cause people to become homeless and cause evacuation difficulties for the emergency services