Science: Fox to the Rescue

Bermuda was celebrating a narrow escape from a hurricane last week. Hurricane “Easy”* had roared up from the region north of Puerto Rico, curved toward the northeast, and was bearing down on Bermuda with house-smashing 160 m.p.h. winds. Tourists were huddled indoors behind boarded-up windows. Natives, expecting the worst, had battened down all hatches. Then “Easy” swerved sharply toward the east, its center missing Bermuda by 80 miles. At the same time, the force of its winds diminished. Bermuda got only a mild gale that blew down a few banana trees.

The gallant knight that rescued Bermuda was a second hurricane, “Fox,” that followed a converging course to the eastward, farther out in the Atlantic. When the two Storms were 450 miles apart, they began to come under the “Fujihara Effect”—the tendency of two approaching hurricanes to waltz around each other (see diagram).

A hurricane is a great doughnut of wind and cloud that revolves (in the northern hemisphere) in a counterclockwise direction. The winds that race toward and round the calm, low-pressure center of the storm are fed with air from the high-pressure areas outside the whirl.

The Japanese meteorologist Sakuhei Fujihara observed that two hurricanes never collide, but when they come close enough they attract one another and swerve off their former courses. This is because the high-pressure area between them is exhausted by the sucking effect of the two circular storms. So the barometric pressure drops while the pressure outside the storm-pair remains high. This unbalanced condition pushes the two storms closer. At the same time, their violence decreases because of the lack of enough air pressure to keep them spinning as fast as before.

Then another process begins. The two spinning storms begin to move around one another. They never complete a full turn, but the waltzing motion diverts them from their courses. It was this providential swerving that saved Bermuda.

*The U.S. Weather Bureau names hurricanes alphabetically “Able,” “Baker,” “Charlie,” etc., according to the order of their appearance each season.