The Impact of Typhoon Danas on the Typhoon Fitow Flood Event in East China

China experiences the most frequent tropical cyclone activity of any country on an annual basis – about ten such storms make landfall each year. Many of those are weak and make landfall in the southern part – impacting Guangdong or Hainan. Fewer but more intense storms can affect the more northern coastal provinces like Fujian and Zhejiang. In the 2013 season, seven storms made landfall in China; five of these were at minimum Category 1 strength (on the Saffir-Simpson scale). Precipitation-induced flooding is therefore a relatively important sub-peril.

In early October 2013, typhoon Fitow made landfall in Fujian Province with a central pressure of 975mb and maximum estimated wind speeds of 65 kts according to the Japan Meteorological Agency (JMA). Although it was a minimal typhoon by Saffir-Simpson standards, Fitow brought heavy precipitation with it that extended several hundred kilometers to the north. Yuyao in southern Zhejiang province received a record 770+ mm. The storm dissipated within 12 hours of landfall and the JMA stopped tracking it. Precipitation continued to fall over the same area – a heavily industrialized region surrounding and including Shanghai. Even as Fitow was dissipating, it was being absorbed by a weak synoptic trough that was moving slowly eastward. Close on its heels was another typhoon, Danas, that passed within several hundred kilometers of Shanghai to the east only 6-12 hours after Fitow dissipated. The interaction of typhoon Fitow, the approaching trough, and typhoon Danas likely contributed to the widespread 300+ mm of precipitation across the region. As a result, it is estimated that around 2.5 B RMB in insured losses are the result of flooding from typhoon Fitow, making Fitow one of China's greatest typhoon-related flood losses since typhoon Nina in 1975.

This presentation will illustrate and explain some of the specific meteorological interactions and processes responsible for the heavy precipitation. It will also investigate the frequency with which nearby typhoons supply moisture into those making landfall in China. This aspect of China's typhoon climatology has important implications and may contribute to improvements in catastrophe modeling as well as forecasting weather (storm) conditions for several days after landfall.