Thursday, October 14, 1999 Published at 01:31 GMT 02:31 UK
Hurricane force revealed
Factors controlling hurricane strength have been poorly understood
A new method of predicting hurricanes could provide vital information for people living in the path of a storm, according to a weather researcher in the United States.
This is because the the factors controlling the intensity of a hurricane have been poorly understood.
Now Dr Kerry Emanuel, from the Massachusetts Institute of Technology, says the strength of a hurricane depends on three things
His new forecasting model looks at the thunderstorms surrounding the eye of the storm, and the hurricane's interaction with the ocean.
Once the path of the hurricane is known, Dr Emanuel says he can now forecast its strength reliably.
"We think we can understand most of the physics that are critical to the intensity of hurricanes," he says.
With a computer program he has designed for use on ordinary PCs, Dr Emanuel says the strength of storms "can be predicted as far in advance as an accurate track prediction can be made".
Even a 1C drop in water temperature can have a significant effect by decreasing the amount of evaporation into the eye of the storm.
Previous, less reliable methods of forecasting hurricane strength did not take the ocean-atmosphere exchange into account, according to Dr Emanuel.
The model has been welcomed by Hugh Willoughby from the National Oceanic and Atmospheric Administration (NOAA).
He is impressed by its accuracy in assessing - retrospectively - the maximum wind strengths of Hurricanes Hugo in 1989, Andrew in 1992, and Opal in 1995.
Hurricanes are tropical storms brought about by heavy evaporation of water from the ocean's surface. The hot wet air is sucked into a tropical depression, and rises in a spiral in which winds can reach 300km/h (200mph).
In addition to violent winds, the impact of heavy rain, waves and storm tides make hurricanes among the most dangerous kind of natural disasters.