Why Is There A Hurricane Season?

What causes hurricanes?

- Alexandra Franklin-Cheung

Hurricanes are some of the most powerful storms on Earth, drawing their energy from warm tropical waters in the Atlantic or north-eastern Pacific. In other parts of the world, these swirling storms are known as typhoons (in the north-western Pacific) or cyclones (South Pacific and Indian Ocean). These storms form above ocean waters when warm, moist air rises. This draws in more humid air from surrounding areas, and as the air rushes in, the Coriolis effect (created by the Earth’s spin) causes it to follow a curved path, leading the developing storm to spin anticlockwise in the northern hemisphere. As the rising air cools, the moisture condenses out and forms rain clouds. As long as there’s sufficient heat from the oceans, the storm continues to grow, and it may eventually be intense enough to produce the 119km/h winds that officially define a hurricane. As the hurricane rotates faster, a calm ‘eye’ of low air pressure forms at its centre, surrounded by the strongest winds. The Saffir-Simpson hurricane wind scale classifies hurricanes from 1 to 5 based on wind speed, with category 5 hurricanes fostering winds of 250km/h and above.

Most hurricanes in the North Atlantic form off the western coast of Africa, and are carried to North America, the Caribbean and the Gulf of Mexico by the prevailing easterly winds. Once they make landfall, they weaken and dissipate, but not before unleashing devastatingly strong winds and heavy rains on anything in their path, as well as causing storm surges (an abnormal rise in sea level). An average of six hurricanes are produced in the Atlantic every year, but the 2020 season was exceptionally active.