East Asia: Water surpluses to persist on middle & lower reaches of Yangtze

The Big Picture
The water anomaly index for the 12-month period ending March 2017 shows widespread moderate to exceptional water surpluses in the middle and lower reaches of the Yangtze River in China. Both deficits and surpluses are forecast in western regions of China including the Tibetan Plateau. Moderate deficits are forecast in eastern Mongolia and exceptional deficits in northeast Inner Mongolia. Deficits are forecast for Honshu, Japan.

Impacts
Flooding along the Yangzte River Valley in central and eastern China has killed 237 people and cost $22 billion in damages, making it the 2nd costliest weather disaster on record in China and the 5th costliest non-US weather disaster in history. Over 21,000 square miles of farmland have been inundated and 147,200 houses destroyed in the worst flooding since 1998.

The Xinhua Road Sports Centre Stadium along the Yangtze in Wuhan, Hubei province filled up like a soup bowl. In Huarong County, Hunan eight rock-laden trucks were deliberately crashed into the river in a harrowing attempt to fill a gap where the Hedu had breached its banks, flooding villages downstream and forcing the hasty evacuation of 10,000 people.

The city of Xinxiang along the Yellow River in Henan province recorded its heaviest rainfall since 1949 - 370mm. Shoes, handbags and other merchandise bobbed through the lower level of a flooded shopping mall.

Forecast Breakdown
Water surpluses are expected to persist in many provinces of China along the middle and lower reaches of the Yangtze River, as seen in the July through September map below, though surpluses will not be as severe or widespread as in previous months. Widespread mostly moderate deficits are expected in Mongolia which will persist through March. Deficits are also forecast in Honshu, Japan. Moderate to extreme deficits are forecast in southeastern Yunnan.

In November southeast China will begin to transition from surplus to moderate deficit which will gradually encompass much of the country. Deficits will emerge on the Korean Peninsula in October, persist through March, and be especially severe in South Korea in November. By November deficits in Japan will spread in Honshu, Shikoku, and Kyushu.

(It should be noted that forecast skill declines with longer lead times.)