General News

Typhoon Precursors Form in Succession Over Japan’s Southern Sea; Situation Unlikely to Change Soon

The Yomiuri Shimbun

16:55 JST, August 16, 2024

Four typhoons including the current Typhoon Ampil — also known as Typhoon No. 7 — formed one after another over the sea south of Japan between Aug. 8 and Tuesday.

According to the Japan Meteorological Agency (JMA), the presence of a low-pressure atmospheric vortex — called a monsoon gyre — has increased the likelihood that typhoons will form.

A high-pressure system in the Pacific is currently far to the east over the sea south of Japan, and a nearby low-pressure system is expanding, bringing with it anticlockwise wind circulation, which can easily create updrafts. Accordingly, clusters of cumulonimbus clouds, the precursors of typhoons, are forming one after another.

Additionally, sea surface temperatures in the area this year are about 2 C higher than normal, a situation that is adding a large amount of water vapor to the air. This is another condition that is ripe for typhoons.

Nagoya University Prof. Kazuhisa Tsuboki, who studies typhoons, spoke about the cause of this consecutive development of cumulonimbus clouds: “There have been few typhoons so far this year, and the sea had not been stirred up until recently.”

Typhoon Ampil moved northward along the edge of the high-pressure system in the Pacific. JMA said that the typhoon-prone conditions are not expected to go away any time soon and the agency would keep monitoring the development of subsequent typhoons.