Koni originated from a tropical depression situated within the monsoon trough to the east of the Philippines on July 15 . Tracking westward , intensification was slow and the system remained a tropical depression as it moved across the central Philippines on July 17 . Upon moving into the South China Sea , conditions allowed for quicker strengthening , and the cyclone reached tropical storm status on July 18 before reaching its peak intensity with maximum sustained winds of 110 km / h ( 70 mph ) , making it a severe tropical storm . However , atmospheric conditions began to deteriorate as Koni made landfall on Hainan on July 21 , weakening the system . The tropical storm continued to weaken as it moved over the Gulf of Tonkin prior to a final landfall near Hanoi , Vietnam the following day . Tracking inland , the combination of land interaction and wind shear caused Koni to dissipate over Laos on July 23 .