Powerful Typhoon Jebi triggered a historic storm surge of 3.29 meters in Osaka Prefecture in western Japan on Sept. 4, surpassing the previous high of 2.93 meters recorded in 1961 due to Typhoon Nancy, which killed 194 people.
The storm tide and huge waves flooded Kansai International Airport with seawater, and the airport remains closed for the time being. Tide levels surged above past highs at six observation points in the Kinki and other regions, including Osaka and the city of Kobe where 2.33 meters was marked. The previous highest mark was 2.30 meters.
Storm surges are caused by multiple factors, including lower atmospheric pressure near the center of a typhoon that allows seawater to rise. According to experts, the sea level goes up 1 centimeter as the air pressure goes down 1 hectopascal. In addition, strong winds push seawater toward the coast and make it difficult for the water to recede. When the wind speed doubles, the height of the sea level rise is said to quadruple. Also, geographical conditions contribute to the creation of storm surges, and V-shaped bays such as Osaka Bay are prone to storm tides.
The city of Osaka marked high tide at 5:10 p.m. on Sept. 4. An official at the Osaka Regional Headquarters of the Japan Meteorological Agency explained that the high tide coupled with the advancement of Typhoon Jebi caused the historic storm surge.
(Japanese original by Shinpei Torii, Osaka Science & Environment News Department, and Kazuki Mogami, City News Department)