Early on August 25, an area of low pressure formed about 600 kilometres (370 mi) southeast of Hong Kong.

At the same time, a tropical upper tropospheric trough (TUTT) was located in the east of the system.

[2] On August 28, the JMA upgraded the system to a tropical storm, and it was named "Lionrock",[3] with winds up to 83 kilometres per hour (52 mph).

[5] Lionrock made landfall on the east coast of Guangdong Province, China, just north of the city of Shantou.

It then started to dissipate and weaken into a tropical storm and moved over Guangzhou, Guangdong's capital.

Analysis showed that the reason for the unusual movements were interaction between all three of the storms, including a Fujiwhara effect absorbing Namtheun.

A more intense amount of rain was recorded in the Hong Kong International Airport with a total of 139.5 millimetres (5.49 in).