Causes of Tropical Storms
Geography: Cambridge International GCSE (2027 Exams), topic 2.4.3
Formation of Tropical Storms
Tropical storms form over water that is 26.5oC or warmer and when there's a small difference in wind speeds between the upper atmosphere and the lower atmosphere.
Form over warm water
- Tropical storms form over water that is 26.5oC or warmer.
- These temperatures are favourable because they mean there's lots of warm, moist air to cause extreme rain. Energy from warm water intensifies cyclones.
- Lots and lots of energy is released when air evaporates, rises or cools. This increases the speed and energy of a storm.
- The strength of a storm falls as they move further away from warm water (so when storms are above land or above cooler parts of the ocean). This is called dissipation.
Move west
- Near the equator, surface winds are mainly trade winds moving east.
- The trade winds and something called the Coriolis Effect mean that tropical storms move from east to west.
Spin
- The rotation of the Earth causes the Coriolis effect, which makes tropical storms spin by deflecting winds.
Source areas
- The source area for most cyclones is between 5o and 30o north and south because the water is below 26.5oC further from the equator.
- Most cyclones form when sea temperatures are warmest, which is June-November in the northern hemisphere, and November-April in the southern hemisphere.
Test yourself on Causes of Tropical Storms
What temperature must water be for a tropical storm to develop over it?
Which direction do tropical storms tend to move?
Which of the following describes tropical storms?