What are hurricanes?

Tropical cyclones are violent weather events formed over the tropical ocean. They are rotating, low-pressure storm systems characterized by strong winds, heavy rain and thunderstorms near their center.

Different names are used to describe these cyclones, depending on the region where they occur and their speed. When wind speeds reach 74 mph (119 km/h), the cyclones are classified as “hurricanes” in the North Atlantic Ocean or East Pacific Ocean, and as “typhoons” in the Northwest Pacific Ocean. At wind speeds between 39 and 74 mph (63 and 119 km/h), they are referred to as “tropical storms.

The North Atlantic hurricane season runs between June and November each year. As hurricanes can have devastating consequences when moving over land, endangering homes and lives, we try to predict whether a low, normal or high hurricane activity is expected in order to prepare adequately for the upcoming hurricane season.

Hurricane Florence, 2018. Source: NASA.

How are hurricanes formed?

Hurricanes are formed when a low-pressure area in the atmosphere moves over warm tropical waters and takes up heat and moisture. This causes a closed rotating system of clouds and thunderstorms to form, with raging winds that reach over 74 mph (119 km/h).

A single hurricane can release enormous amounts of energy, as much as about half of the world’s total electrical generating capacity. More information.

Diagram of surface winds from the east and upper-level winds from the west during the Atlantic hurricane season, causing vertical wind shear and inducing hurricane formation. Source: NOAA Climate.gov.