Take moisture, warm ocean temperatures, then add the Earth’s rotation to stir up a tropical storm. Atlantic hurricanes account for ten of the 90 hurricanes that happen around the world each year, with 85 per cent starting as disturbances in the air off West Africa. But each year only six out of 60 atmospheric disturbances in West Africa graduate into hurricanes.
Researchers now suggest that it might be possible to predict which tropical disturbances in West Africa’s storm nursery will develop into hurricanes.
‘We found that the larger the area covered by the disturbances, the higher the chance they would develop into hurricanes only one to two weeks later,’ says Dr Colin Price, a professor of atmospheric sciences in the Department of Geosciences at Tel Aviv University, who led the research.
‘Some of the Atlantic hurricanes start in the mid-Atlantic or even closer the Caribbean, and cannot be tracked to an origin in the East Atlantic,’ Price tells Geographical.
Geostationary satellites watch cloud cover over Africa, taking a snapshot every 15 minutes. The researchers looked at data for five years, analysing the cloud cover during the June–November hurricane season.
More clouds means more atmospheric disturbance. Infrared cloud-top data from the satellites allowed the researchers to track temperature change.
‘We first showed that the areal coverage of the cold cloud tops in tropical Africa was a good indicator of the monthly number of atmospheric disturbances – or waves – leaving the west coast of tropical Africa,’ says Price. ‘The disturbances that developed into tropical storms had a significantly larger area covered by cold cloud tops compared with non-developing waves.’
Price found that when each storm was looked at alone, larger cloud coverage in West Africa meant more energy built up for a future hurricane.
‘The conclusion, then, is that the spatial coverage of thunderstorms in West Africa can foretell the intensity of a hurricane a week later,’ says Price. This means that it may be possible to predict hurricanes up to one or two weeks in advance.
Over the last ten years four Atlantic hurricanes – Katrina, Sandy, Ike and Wilma – have caused around $262billion in damage to the US, and taken 2,337 lives.