Assessment of the impacts of Super Typhoon Saola and the record-breaking rainstorm due to the remnant of Severe Typhoon Haikui on Hong Kong in September 2023

In early September 2023, Hong Kong was severely impacted by the ferocious strike of Super Typhoon Saola on 1–2 September and the phenomenal rainstorm on 7–8 September triggered by the remnant of TC Haikui. Given the rarity of these two successive extreme weather events which wreaked havoc in Hong Kong within 10 days, impact assessment on the damage and economic loss in Hong Kong due to these two extreme events was conducted. Utilizing available data from government reports, media, surveys, and insurance claims, the direct economic losses incurred by Super Typhoon Saola on 1–2 September and the record-breaking rainstorm on 7–8 September were estimated to be around HK$0.48 billion and HK$1.74 billion respectively. Moreover, the impacts of Saola and the record-breaking rainstorm in September 2023 are compared with other super typhoons and Black Rainstorm events in Hong Kong mainly in the last decade for reference. It is noted that, when compared with the Super Typhoons Hato and Mangkhut which also necessitated the issuance of Hurricane Signal No. 10 in Hong Kong respectively in 2017 and 2018, the overall impact of Saola in 2023 was less than those of Hato and Mangkhut. In terms of rainstorm events, the impact of the Black Rainstorm event on 7–8 September 2023 was significantly higher than those of the Black Rainstorm events in March 2014 and June 2020. The possible attributing factors related to the differences in the impact of these super typhoon and rainstorm events were also briefly discussed.