Strong wind and heavy rainfall anticipated across much of the country
Meteorological agency forecasts show that Typhoon Shanshan will make landfall in southern Japan on Tuesday, Aug. 27 local time.
As of 11 a.m. ET on Monday, Aug. 26, Typhoon Shanshan was south of Japan and had maximum sustained wind speeds of 75 mph (120 km/h). However, the storm is expected to intensify as it moves northwest then north before weakening just prior to landfall.
The Joint Typhoon Warning Center (JTWC) and Japan Meteorological Agency (JMA) estimate maximum sustained wind speeds of 86 to 92 mph (139 to 148 km/h) at landfall in the Kagoshima Prefecture on the southern tip of Japan’s Kyushu Island (Figure 1).
Pre-Landfall Proxy Events
Requires Asia Typhoon Model RQE License
Risk Quantification and Engineering (RQE®) and Navigate™ model users can download pre-landfall hazard-based proxy events from the Client Resource Center (CRC).
In addition to wind, forecasts call for heavy rain across the country as the system travels northeast through central Japan. This could lead to riverine and flash flooding as well as landslides in the more mountainous terrain of the island.
Historical Precedent for Typhoon Shanshan
Typhoon Shanshan’s forecasted track and intensity is similar to several notable typhoons and tropical storms that have affected Japan in recent history. Most recently, Typhoon Nanmadol brought Category-3 equivalent winds and torrential rains to southern Kyushu Island. According to PERILS, insured losses from Typhoon Nanmadol did not exceed $1 billion.
In 2005, Typhoon Nabi made landfall in southern Japan. Nabi crossed the islands of the Kagoshima Prefecture as a Category 4-equivalent typhoon before weakening and making a second landfall with maximum sustained winds around 90 mph (145 km/h).
Unlike large loss-causing events like Typhoon Hagibis in 2019 or Jebi in 2018, current Typhoon Shanshan forecasts do not show that the storm will bring catastrophic winds to major centers of economic development such as Tokyo or Osaka, which will limit the final insured impact.
Built to Last: Japanese Building Codes
The Building Standard Law of Japan of 2000 (BSLJ-2000) defines modern building code requirements for wind impacts. New construction in Japan must adhere to these regulations as a minimum, with some exceptions. For example, structures planned to be 60 meters or higher must adhere to a different standard that accounts for other forces that wind exerts on structures.
The BSLJ-2000 requires that all construction be built to withstand damage to frames and cladding at medium level winds (e.g., a return period recurrence interval of 50 years or 0.2% annual probability of occurring). Additionally, structures must not collapse in winds with a return period recurrence interval of 500 years (0.02% annual occurrence probability).
The basic wind speed (Figure 2) for which engineers design varies geographically across Japan. The design wind speed for no damage to the frame or cladding is equal to basic wind speed, and the design wind speed for no collapse is equal to 1.26 times the basic wind speed.
As of Monday, Aug. 26, multiple models indicate that Typhoon Shanshan will make landfall as a Category 1-equivalent typhoon with maximum sustained winds of 92 mph in the Kagoshima Prefecture, an area with very high 10-minute average design wind speeds.
The basic wind speed defined in the BSLJ-2000 increases to the northeast from the Shizuoka Prefecture towards Tokyo, where structures are more resistant to damage from strong winds. Additionally, Tokyo is home to larger structures that adhere to stricter building code requirements beyond what was outlined in BSLJ-2000.
The CoreLogic Hazard HQ Command Central™ team will monitor Typhoon Shanshan and its impacts in Japan. Additional analysis of the impacts in Japan will be provided after landfall.
Pre-Landfall Proxy Events
Requires Asia Typhoon Model RQE License
CONTACT: Please email [email protected] with questions regarding Typhoon Shanshan or any CoreLogic event response notifications. Visit www.hazardhq.com for updates and information on catastrophes across the globe.
©2024 CoreLogic, Inc. The CoreLogic statements and information in this blog post may not be reproduced or used in any form without express written permission. While all the CoreLogic statements and information are believed to be accurate, CoreLogic makes no representation or warranty as to the completeness or accuracy of the statements and information and assumes no responsibility whatsoever for the information and statements or any reliance thereon. CoreLogic® and Hazard HQ Command Central™ are the trademarks of CoreLogic, Inc. and/or its subsidiaries.
