Atmosphere And Weather

Twin Hurricanes the Fujiwara Effect Explained



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The power and destruction of one hurricane is enough to cripple a large city. But imagine what the effect of two hurricanes rotating as one would be. This is the phenomenon called the Fujiwhara effect.

Best described as a stormy waltz, Dr. Sakuhei Fujiwhara wrote a scientific paper in 1921 as he studied vortexes in water. Water vortexes are better known as whirlpools and are common during a hurricane. His paper further looked into the effect that was evident when two hurricanes were less than 900 miles apart. Once within the mentioned 900 miles, the forces would spin around each other.

Dr. Fujiwhara studied the cyclones that often attached Japan and found three cases that could happen when two storms met.

-The most common force he saw was when the hurricanes were of equal size and strength all the while spinning in the same direction. Hurricanes usually spin counter-clockwise. They would lock forces and spin in a large vortex, their strength usually increasing will the rotation.

-If one of the vortexes is larger than the other, then after locking spin cycles the larger one will dominate and eventually the smaller force will be "gobbled" up, joining the larger force.

-If a force is spinning in the opposite direction of the other, the vortexes will repel against each other. This is the most common of the Fujiwhara effect. Many cyclones, hurricanes and typhoons respond to this effect very similarly.

However, the storm does not have to be tropical. Instances have shown that land storms will have the first effect. This is instead an atmospheric vortex instead of the common water vortex. Often the second instance is the most common on land.

The Fujiwhara effect is perhaps best described as two ice skaters joining hands at the center, while continuing to spin quickly in a large circle. Their force continues the movement, but the clasped hands keep the two skaters joined.

After the two storms are "joined" in a single spin revolution, they can then move off in a like direction while maintaining that spin.

Perhaps the best known example of this was August 23, 1995, when a little tropical storm called Iris was coming near the Windward Islands. A hurricane named Humberto was gaining on the tropical storm and eventually came close enough to begin the Fujiwhara dance. They locked forces and began to spin around each other exhibiting the first type of Fujiwhara effect.

Iris strengthened to a hurricane just as the forces met, but the force of keeping the two storms together weakened both of the storms. After a while the storms broke apart with the force of the break throwing them in different directions. Humberto moved towards the north while Iris drifted south.

Fast forward 8 days when Iris gained enough strength to again become a hurricane with sustained winds of 110 mph. As Iris moved east of Bermuda, it met with Tropical Storm Karen and basically swallowed up the smaller storm as in the third effect of the Fujiwhara.

Though many scientists have tried to discredit the theory, the hurricanes themselves have proven the forces are there. Scientists have since allowed the theory, now believing the circumstances must be ripe for the storms to rotate, which is rare. Storms in the effect rotate around each other as if with locked arms. Instead of rotating around the other storm, a center point seems to be the center location of the Fujiwhara effect. Though Dr. Fujiwhara only wrote limited papers on scientific subjects, he brought attention to a potentially massively destructive force of nature.

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