The first half of 2019 had been unusually quiet in the western North Pacific tropical cyclone basin. Following the dissipation of the strongest-ever February typhoon – Wutip, there were no subsequent typhoons until Francisco reached Category 1 strength on August 4. A few days later, Typhoon Lekima strengthened significantly on its approach towards the China coastline and then became the strongest landfalling storm of the year so far.
Lekima Enters the Record Books
Typhoon Lekima made landfall in Wenling City, Zhejiang Province (pop. ~1.3 million), at 1:45 a.m. local time on Saturday, August 10, with an intensity equivalent to a Category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale according to the China Meteorological Administration (CMA). With two-minute sustained winds of 116 miles per hour (187 kilometers per hour) and a central pressure at landfall of 930 millibars, Lekima became the third strongest tropical cyclone to impact eastern China after Saomai in 2006 and Wanda in 1956.
After landfall, Lekima tracked northwards close to Shanghai and made a second landfall in Shandong Province, where it dumped record breaking amounts of precipitation. Over the space of five days, rainfall accumulations reached 250 millimeters across central and western Shandong, and even topped 400 millimeters in places, as Lekima slowed while passing over the province. This heavy rainfall led to widespread flash and river flooding, with 92 rivers across eight provinces exceeding their flood warning levels. According to authorities, Lekima affected around 13 million people, damaged more than 132,000 homes, and destroyed 996,000 hectares of crops.
While Lekima may take its place in the record books, it is by no means a particularly unusual event for China. As mentioned, there have been stronger typhoons that have made landfall in Zhejiang Province, as well as storms that have brought similarly high rainfall totals. Lekima was spawned from an active monsoon extending quite far into the Pacific; a system that persisted over a number of weeks and generated other tropical cyclones including Francisco and Krosa. With the subtropical ridge located to the southeast of Japan, all three storms tracked in a northwest direction towards northern China, Japan and the Korean Peninsula, following a strong jet associated with the monsoon.
Indeed, over the period from 1946 to the end of 2018, a total of 18 typhoons of Category 2 strength or greater made landfall in China within 200 kilometers of the landfall location of Lekima. Many of these storms followed a very similar path to Lekima, approaching from the southeast before curving northwards after landfall.
The RMS® China Typhoon Model contains thousands of simulated typhoon tracks, including a range of stochastic events similar to Lekima in terms of landfall location and intensity, and storm tracks that extend into the northern provinces of China. Based on maximum sustained winds at landfall, RMS estimates the return period of a Category 3 or greater event (≥111 miles per hour winds) striking Zhejiang Province in excess of 17 years. According to the RMS model, the return period of an event of this magnitude or greater striking anywhere along the coastline of China is four years.
Flood Risk Dominates Losses
Early estimates indicate that the economic losses caused by Lekima will approach the total losses brought about by Typhoon Fitow in 2013. Insurance penetration in China remains low, so insured losses are likely to be a fraction of the total economic cost. Fitow followed a track slightly to the south of Lekima’s and was a weaker storm at landfall, but brought extreme precipitation to Zhejiang province leading to widespread flooding. Indeed, the majority of annual losses from tropical cyclone events in China can be attributed to flood as opposed to wind.
The building stock in Zhejiang is generally constructed to a high standard that offers resilience against strong typhoon winds. Following three storms in consecutive years (Rananim (2004), Khanun (2005), and Saomai (2006)), which predominantly destroyed buildings constructed in 1980s or earlier, government rebuilding efforts and subsequent development saw the implementation of improved and more stringent design standards to mitigate against future typhoon losses. However, it is difficult to account for flood in individual building design codes and flood mitigation projects are usually on a larger scale to protect wider areas, which means more exposure is impacted when flood defences are overwhelmed.
The terrain in Zhejiang Province where Lekima made landfall is undulating and mountainous, which acts to weaken the strength of tropical cyclones but also causes heavy orographic rainfall leading to flash flooding. Conversely, the majority of Shandong Province lies within the flat North China Plain and contains the lower reaches of the Yellow River, leading to a high risk of flooding from heavy rainfall and overflowing rivers. The fact that Lekima, a fast-moving storm at landfall, slowed as it crossed Shandong acted to increase the precipitation accumulations and scale of flooding that followed.
Economic Growth Increases Exposure
Lekima has become the latest damaging typhoon to impact China in recent years. An average of six tropical cyclones make landfall in China each year and the combination of rapid economic growth, expansion of cities, and increasing insurance penetration in China means the risk of large losses is increasing. RMS modeling solutions can help clients to understand their exposure and risk to catastrophic events in China, including tropical cyclones and earthquakes. The RMS China Typhoon Model contains a large stochastic event set to represent the full range of possible storms that could impact the country, and provide a realistic view of the risk.