Typhoon Hagibis: Japan's costliest typhoon?
Typhoon Hagibis made landfall in Japan on 12 October 2019, causing widespread flooding and damage. On 14 October, JBA’s event response team produced an initial event commentary (see below on page) as well as an event footprint. This updated event report explores the typhoon in more depth.
The storm and widespread flooding
Typhoon Hagibis carried with it a large volume of warm moisture, resulting in unprecedented rainfall across a third of Japan (Figure 1). In some areas, it was reported that approximately 30-40% of annual rainfall fell within 24 to 48 hours (Yotsumoto, 2019).
Extensive residential areas were inundated in Nagano prefecture while houses in the city of Ichihara, Chiba prefecture, were damaged by strong typhoon winds (Nochi, 2019; Olano, 2019). Across Japan, 13,000 houses were inundated and 900 were completely or partially destroyed (Yotsumoto, 2019). Industrial sites located near the Chikuma River in Nagano prefecture and Koriyama city in Fukushima prefecture were also severely inundated (Insurance Business Magazine, 2019). The shinkansen (bullet train) maintenance yard in Nagano was flooded, with 10 trains and 120 carriages reported to be damaged by floodwater (Yotsumoto, 2019). Two major Japanese airlines, All Nippon Airways (ANA) and Japan Airlines (JAL) , cancelled a total of 558 and 540 flights respectively as services were disrupted at Tokyo airports on 13 and 14 October 2019 (Asquith, 2019).
Due to Typhoon Hagibis, 85 fatalities and 9 missing people were reported at the time of writing (NHK, 2019).
Hakone town in Kanagawa prefecture (a resort town approximately 90km south-west of Tokyo) was one neighbourhood that experienced severe flooding. Within 24 hours, Hakone received a total of 922.5mm of rainfall, which is the highest volume of rainfall ever recorded in Japan over a 24-hour period (Mori, 2019). It has an estimated return period of greater than 1,500 years based on JBA’s rainfall return period data.
Similar statistical analysis of NASA radar precipitation data to calculate a rainfall return period for Nagano prefecture and Koriyama city shows that both have an estimated return period of 50 years. The greater Tokyo region has an estimated return period of approximately 1,500 years or greater (Table 1).
Impacts for insurers
Insurance losses for Hagibis remain uncertain at the moment; however, severe damages were reported across 13 prefectures.
As a result, Typhoon Hagibis is likely to result in losses greater than USD $10 billion and the losses may slowly increase over the weeks to come, similar to Typhoon Jebi (Artemis BM, 2019). Insured losses due to Typhoon Jebi, which hit Osaka directly last year, have since passed the USD $10 billion mark. In early May 2019, it was reported that the industry loss caused by Jebi was approximately USD $13 billion and may even increase to USD $16 billion (Evans, 2019a and 2019b). One of the reasons for the high losses from Typhoon Jebi was the close proximity in time between Typhoon Jebi and Typhoon Trami (Evans, 2019a).
The total losses from Typhoon Hagibis and Faxai (which occurred earlier in September 2019) are likely to be comparable to these two large typhoon events which hit Japan in 2018, totalling USD $18 billion (Artemis BM, 2019).
Why did Hagibis cause severe damages?
According to reports, Hagibis has been one of the strongest tropical systems globally this summer. As the weather system crossed the warm waters near the Mariana Islands, to the south-east of Japan, the typhoon intensified rapidly, with the pressure at the centre of the typhoon decreasing from 992hPa to 915hPa within 24 hours (Mori, 2019). Based on historical track data, typhoons which passed through this warm water before reaching Japan are likely to result in damages with a greater severity, due to the warm water strengthening the typhoon and allowing it to carry more warm moisture towards Japan.
Additionally, there are no land masses nearby to dissipate the strength of the typhoon before reaching Japan.
The severity of Hagibis’ damage can also be understood in the context of the typhoon’s size – Typhoon Hagibis was a large typhoon, with a diameter of around 1,400km (Mori, 2019). This size meant that heavy rainfall had begun in several prefectures in Japan before Hagibis made landfall near Izu Peninsular. Hagibis then made slow progress, with a forward moving velocity of 30kph, meaning the typhoon lingered longer over the land mass and resulted in a high accumulation of rainfall in several regions (Mori, 2019).
The effects of Typhoon Hagibis may worsen as two more storm systems are likely to approach Japan in the coming days. First is Typhoon Neoguri, a former category 2 storm and now an extratropical cyclone as classified by the Japan Meteorological Agency. Neoguri may result in heavy rainfall near Ise and Mikawa bays, in previously-hit Hakone and Tokyo, and in China. Bualoi is the second to follow and is predicted to have a close encounter with south-east Japan. However, it is too early to understand the severity of rainfall and possible floods.
Historical typhoon events
Typhoon Hagibis may be on track to be one of the costliest typhoons affecting Japan. To date, the costliest typhoon in Japan was Typhoon Mireille, which made landfall in 1991 near Nagasaki in Kyushu Island (Figure 4), at the south of Japan with wind speeds of up to 185kph (115mph). The total damage was estimated to be USD $10 billion, with more than 30% of losses attributed to agricultural damage, especially in relation to the apple industry. In addition, 62 deaths were reported, with at least 170,000 houses damaged and 22,965 houses inundated (National Institute of Informatics, 2019). The total insurance payout from Typhoon Mireille was estimated to be USD $5.32 billion (Sonpo, 2019).
Ranked as the third deadliest natural disaster in Japan based on recorded data, Typhoon Vera, known as Typhoon Isewan in Japan, hit Honshu on 26 September 1959 with maximum sustained wind gusts of up to 222kph (138mph) and a central pressure of 920hPa. At the time, total damages were estimated to be USD $600 million (equivalent to USD $5.16 billion in 2018). A total of 4,697 deaths were reported with approximately 834,000 houses damaged or destroyed. All prefectures except Kyushu were affected by Typhoon Vera. (EM-DAT, 2019)
Future outlook
In the future, climate change is likely to result in an observable increase in the intensity of hurricanes and typhoons (Normille, 2019). In addition, several major cities in Japan, including Nagoya, Osaka and Tokyo are now located below sea level, causing them to be vulnerable to stronger storms and typhoons of higher intensities (Normille, 2019). To mitigate impacts from future storms, it will be crucial to invest in engineering methods and disaster management measures such as evacuation planning.
JBA Risk Management has nationwide return period flood maps and a flood model for Japan at 30m resolution. We have also produced an updated flood footprint for the typhoon, estimating extents and depths from river flooding.
Please get in touch for more information on how we can help you manage your risk.
