Photo/Illutration The predicted course of Typhoon No. 10 as of 5 a.m. on Aug. 28 (Captured from the Japan Meteorological Agency’s website)

A confluence of wind and weather factors has resulted in powerful Typhoon No. 10 traveling much slower than expected, increasing the chances of longer-lasting damaging effects. 

The typhoon was traveling south of Japan on Aug. 27, moving northwestward, at a speed equivalent to that of a bicycle.

As of 9 p.m., the storm was traveling approximately 80 kilometers east-northeast of Amami, Kagoshima Prefecture, and was essentially "stationary," according to the Japan Meteorological Agency.

A few hours earlier, Typhoon No. 10 was reported to be moving "slowly." This is defined as less than 9 kph, which is comparable to the speed of a bicycle.

The season’s 10th typhoon, also called Shanshan, is expected to make landfall in the main island of Kyushu and then move northeastward along the Japanese archipelago, slightly increasing its speed.

It is likely to remain over the archipelago from Aug. 29 to Sept. 1, according to a forecast issued at 9:50 p.m. on Aug. 27.

WESTERLIES MISSED TYPHOON

While typhoons are intense rotating vortices that spin counterclockwise, they have little power to move forward on their own and are pushed by surrounding winds.

According to Jun Yoshino, professor of meteorology at Gifu University, the main reason for Typhoon No. 10’s slower speed is the westerly winds.

Initially, the westerly winds, which blow from west to east, were expected to bend southward and catch the typhoon, carrying it eastward with them.

However, this southward bend of the jet stream was less than expected, weakening its influence on the typhoon and slowing it.

"It's as if the westerlies have missed catching the typhoon," Yoshino said.

"If the westerly winds bend significantly again, they may push the typhoon, but it’s unlikely at the moment," he added.

Another factor contributing to the typhoon’s slow speed is that the winds generated by the two high-pressure systems located to the east and west of the Japanese archipelago are canceling each other out.

Currently, there is a Pacific high-pressure system to the east of Japan and a Tibetan high-pressure system to the west, and both have winds blowing clockwise around them.

In the airspace above the archipelago, sandwiched between the two high-pressure systems, the two opposing currents of wind, "south to north" and "north to south," neutralize each other, resulting in a calmer atmosphere.

Additionally, a cold vortex that had been pushing the typhoon westward has also weakened.

“The typhoon is slowing due to the lack of strong winds to propel it forward," explained Yoshino.

“If this pattern persists, the storm could become stationary or meander,” he said. "There is a risk of prolonged heavy rainfall and strong winds, increasing the likelihood of disasters."

For forecast updates, check the JMA website.

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