Japan sees three tropical cyclones at once

However difficult it is to forecast the weather, the results will always follow the laws of physics.

At the moment, the forecast paths of three tropical storms, now close to Japan, seems to question logic.


If all three followed similar paths - because all three are being steered by the same wind and sitting over the same warm water - then it would just be a busy period.

Unfortunately, this does not seem to be the case.

At 1200GMT on Saturday, Tropical Storm Mindulle was very close to Iwo Jima and moving north. Tropical Storm Lionrock was 500km south of Osaka and heading west. While Tropical Storm Kompasu was less than 500km east of Tokyo, yet travelling northwestwards.

Tropical storms are steered by winds in the middle atmosphere and are fed by the warmth of the waters beneath them. On first sight, it makes no sense that three storms this close to each other should go in different directions.

Indeed, when any two tropical cyclones are within 2,000km of each other, they may well start "dancing". They interact in what is known as the Fujiwhara Effect and rotate around a point halfway between each other.

These storms fit the bill but show no signs of interacting now or in the forecast future.

The laws of physics clearly cannot be broken, and on closer inspection, the atmosphere shows the cause of this apparent lack of sense: A line of discontinuity in the atmosphere runs across Japan, just to the west of Tokyo, from north to south.

In meteorological terms, this is called a trough and is a common feature in the atmosphere. It can be thought of as a crack, rather like that seen in deeply parched ground.

In the atmosphere, that crack, or trough, can reach from the top of the atmosphere to the ground, and one is developing over Japan.

Tropical storms cannot cross such troughs and on either side the wind blows away, so Storm Lionrock, on the western side, heads west while Storm Kompasu, on the eastern side, will move northeast.

• The only one of these storms to become newsworthy will be Mindulle. It is just to the east of this deepening trough crack and following the side upwards straight towards Tokyo.

It is likely to become a typhoon before it enters Tokyo Bay on Monday.

Satellite evidence suggests that a fourth cyclone is forming to complete the square in the southeast corner.

As yet, this cluster of tropical thunderstorms has not been officially identified.
  [Rob McElwee]
Source: Al Jazeera
20/8/16
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