Winds of more than 200 km/h bring down power lines and flatten buildings. Enormous waves and torrential rain often cause serious flooding.
Hurricanes pick up huge amounts of energy and moisture as they pass over the warm ocean. Some scientists think that global warming may increase the number of hurricanes and make them even more powerful.
The most destructive hurricane of recent years was Katrina, which hit the southern United States in August 2005. Huge waves and driving rain overcame the flood defences of New Orleans, leaving most of the city under water. More than 1,800 lives were lost. Millions of people had to be rescued, and many have never returned.
ESA’s MetOP-A, ERS-2 and Envisat spacecraft are able to watch their unpredictable movements and study them from top to bottom. Envisat’s instruments send back data about the clouds that swirl around the eye in the centre of the storm. They also measure wind speed around the eye.
At the same time, the radar instrument measures winds and waves over the ocean. The satellite also measures the temperature of the upper clouds and the sea surface, as well as changes in sea level.
Last update: 15 November 2010