Typhoon Nanmadol

Updated Similar Stochastic Events | Summary
Posting Date: September 22, 2022, 3:00:00 PM

After extensive review of wind observations, damage reports, and other relevant information, the Verisk ALERT team is providing a refinement of our selection of similar stochastic events from our release earlier this week.  These simulated events were selected primarily to capture wind impacts over Kyushu Island, where we anticipate most impacts from wind to have occurred.  They do not necessarily represent wind impacts over the island of Honshu, nor are they meant to explicitly represent impacts from storm surge, for which we do not expect significant insured losses for this event.  The path of Nanmadol took the worst winds in the right front quadrant of the storm east of the bay near Kagoshima, rather than directly over it, limiting the impacts.

ALERT™ subscribers can download refined similar stochastic event (SSE) IDs for Typhoon Nanmadol from the Downloads tab of this posting on the ALERT website. Compatible with Touchstone® and Touchstone Re™, the SSEs were selected based on Nanmadol’s key meteorological parameters and should be used only for exposures in Japan.   

Wind and Flood Observations

The highest winds observed from Nanmadol were over Yakushima Island, about 30 miles south of the landfall point near Kagoshima city – a sustained 10-minute wind of 82 mph (36 m/s) and a 3-second gust of 114 mph (51 m/s).  However, there were not widespread reports of especially high winds as the storm moved inland.  A station just southwest of Kagoshima city recorded a sustained 10-minute wind of 46 mph (21 m/s) but a 3-second gust of 97 mph (43 m/s), though this observation was taken at a height of 45 meters.

Significant rainfall was also measured across Kyushu Island and parts of Honshu.  Widespread reports of 10-15 inches (~250-375mm) with several locations reporting 25” (~600mm) or more across Kagoshima, Miyazaki, Kumamoto, and Oita prefectures.  Widespread observations of 10 inches or more were also reported across Yamaguchi, Ehime, and Kochi prefectures in southwestern Honshu.  Parts of the Mimi River in Miyazaki overflowed, flooding nearby fields and roads.

Commentary on Similar Stochastic Events

The similar stochastic event selection process for the Verisk Typhoon Model for Japan relies primarily on storm parameters that tend to drive wind losses, and it does not explicitly consider flood impacts or any estimated or modeled flood footprints.  These events were however selected to include some proportion of loss to come from flood, given the rainfall and other flooding observed from this event.  The Verisk ALERT team continues to study the impacts of precipitation flood from this event, and we will provide an update on this aspect of Nanmadol next week.

There was a significant divergence in the reported minimum central pressure at landfall between agencies.  The Japan Meteorological Agency reported 935 mb, while the Joint Typhoon Warning Center had estimates of 947 mb and 958 mb just before and after landfall, respectively.  In addition, the peripheral pressure – that is, the environmental surface pressure outside of the storm – was 7 mb less than the Verisk Typhoon Model for Japan’s default values, indicating a slightly higher modeled minimum central pressure to get the equivalent pressure deficit, which in turn is key to estimating winds.  The range of central pressure values for this final set of similar stochastic events reflects these sources of uncertainty. 

The modeled losses for these events also do not include the impacts of economic inflation that could lead to increased building costs.  Though the CPI is currently not as high in Japan as many other developed economies, rising energy costs and supply chain interruptions could potentially exacerbate losses.  These events also do not contain losses due to social inflation, landslides, losses to infrastructure, engineering risks, marine hull, marine cargo, business interruption, loss adjustment expense, or demand surge.  Clients may wish to adjust losses directly from the model to account for these non-modeled factors.

The Verisk ALERT team is continuing to study the flood impacts from Typhoon Nanmadol and will provide another update on any potential additional ALERTs on Monday, September 26^th.

Updated Similar Stochastic Events | Downloads
Posting Date: September 22, 2022, 3:00:00 PM

The information provided herein is strictly confidential and is solely for the use of AIR clients; disclosure to others is prohibited.

Similar Stochastic Event IDs

Note: These lists give event IDs taken from our stochastic catalog that have similar characteristics as the current event.

Product	File Type	Description	Download
TOUCHSTONE / Re	Excel (xls)	Selected set of stochastic events with Readme and Event Information
TOUCHSTONE / Re	CSV (csv)	Selected set of stochastic events formatted for import into Touchstone/Re