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In 1921 the Japanese meteorologist Dr. Sakuhei Fujiwara published a scientific paper concerning the movement of vortexes in and over water, one of the effects he described was later named after him as the Fujiwara effect.

Fujiwara described this effect without the benefit of weather satellites, postulating it from experiments in his laboratory. he described how vortexes or whirlpools in water acted when they came into the vicinities of each other, and postulated that air would behave in the same manner. It was not until the first weather satellites were launched in the 1960's that the effect was seen in nature.

During the storm season many tropical lows will form, some of which will go on to form hurricanes, typhoons and cyclones. Sometimes two hurricanes will form close to each other, or move towards each other. When this happens they will begin to circle around a common point between them, gradually spiraling to a meeting point.

For the effect to occur the storms typically have to approach within nine hundred miles of each other, and be at tropical storm intensity already.

Sometimes more than two tropical storm systems will be involved in the interaction, such as in 1995 when hurricane Iris circled firstly hurricane Humberto, and then absorbed the smaller tropical storm Karen.

If the storms are of equal intensity they will tend to circle each other equally, until either splitting apart or merging into one larger storm. If one is smaller than the other it will tend to circle the larger until it is absorbed by it. Luckily the interaction seldom involves two category five systems, as these will seldom develop closely to each other. One example of this happening is with typhoons Ivan and Joan in 1997, in the Pacific. Luckily they continued separately instead of forming one super storm.

The stages of the interaction are broken into four stages:

1.Approach and capture. The stages at which the storms first come within each other's orbits and begin to interact.
2.Mutual orbit. The point where the storms are orbiting around a mutual point of reference.
3.Merger. If one storm is absorbed into the other, as Karen was into Iris.
4.Escape. If one storm leaves on its own track or the storms split to follow different tracks, as Ivan and Joan did.

The effect is seen more commonly in the northwestern Pacific than in the north Atlantic. It happens annually in the Pacific, and once every three years or so in the Atlantic. This is because tropical storms are more common in this region of the Pacific than in the Atlantic.

Further references available from : http://everything2.com/index.p l?node_id=1365614

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