A stalled out frontal boundary combined with abundant moisture will lead to widespread rain and thunderstorms from Indochina northeast through northern Vietnam, southeast China and Taiwan for much of the week ahead.
While much of this region has received only 60-90 percent of normal precipitation so far this year, the magnitude of rain expected over the next five to seven days will still result in an elevated flooding threat.
Despite the threat for flooding, the rain will be beneficial for most of Taiwan as rainfall shortages dating back to the start of 2014 have resulted in water rationing prior to last week's heavy rain from former Typhoon Noul.
Daily soaking rain and thunderstorms will elevate the threat for flooding as rainfall of 25-75 mm (1-3 inches) has already fallen across much of southeast China since the weekend. Yangjiang was hammered by thunderstorms three days in a row, totaling more than 375 mm (15 inches).
Additional rainfall of 50-100 mm (2-4 inches) will be common from Guizhou and Guangxi provinces eastward to Fujian province. Similar rainfall amounts are also expected across far northern Vietnam, Hong Kong and Taiwan this week.
The hardest hit locations could receive up to 300 mm (12 inches) of additional rainfall. The most likely areas to receive this rainfall are southern Jiangxi, Guangdong and southern Fujian provinces along with western and northern Taiwan.
Cities that are at high risk for flooding this week include: Guangzhou, Hong Kong, Quanzhou, Nanning and Taipei.
While daily rain and thunderstorms are expected in Guangzhou and Hong Kong this week, the heaviest rain will fall from Friday into the weekend.
In Quanzhou and Taipei, the heaviest rain is expected from Wednesday into Friday, though a shower or thunderstorm cannot be ruled out over the weekend.
The heavy rain will be enhanced by tropical moisture from the Bay of Bengal. A tropical disturbance will release pulses of moisture this week that will track from Myanmar into China and northern Vietnam. Hanoi will remain dry through Wednesday; however, rain and thunderstorms will drench the city from Thursday into the weekend.