by Brandon Miller
CNN International Senior Meteorologist
Metro Manila has received record amounts of rainfall since Monday, with over 530mm (20.8 in.) falling in 48 hours. This tops the average Manila would normally see in the entire month of August (486mm), which is traditionally their rainiest month. The rainfall totals have also surpassed those seen in September 2009 when Tropical Storm Ketsana (known locally in the Philippines as Ondoy) dealt Manila its worst flooding disaster in 40 years, leaving hundreds dead.
The intense rainfall is a result of a strong Southwest Monsoon being enhanced by the presence of Tropical Storm Haikui, which is located over 1,100 km (700 miles) to the north of the Philippines. The strong and moisture-laden circulation around the tropical storm is fueling the monsoon which is already in place over the northern Philippines. The mountainous terrain of Luzon further increases the rainfall, and makes for an area susceptible to flooding and mudslides.
Tropical Storm Haikui will be making landfall in eastern China’s Zhejiang Province Wednesday morning local time. The storm is the third tropical cyclone to make landfall on China’s east coast in the past 5 days, with Typhoon Damrey and Tropical Storm Saola hitting last Friday. The storm threatens to dump heavy rainfall in excess of 150mm (6 in.) on Shanghai, China’s most populated city.
The recent uptick in tropical activity brings the Western Pacific tropical cyclone season back up to average after a slow start. But several recent flash-flooding events from higher-than-normal seasonal rainfall in southern Japan, as well as North Korea, have left soils full of moisture and vulnerable to additional flooding if typhoons and tropical storms track their way. This is a very real threat as the Western Pacific tropical season runs year-round, but has a seasonal peak around September, mirroring the tropical Atlantic. We will likely see more flooding disasters around East Asia over the next couple of months as the tropics heat up and cyclones traverse these already hard-hit areas from the Philippines all the way to North Korea.