On September 17, a tropical depression formed from the remnants of Tropical Depression Marilyn east of Batanes. PAGASA later named the tropical cyclone as "Nimfa", Tropical Depression. Tropical Depression Nimfa was upgraded into a tropical storm. A tropical depression in the South China Sea merged with the circulation of Tapah on Thursday, September 19. Tapah still had a disorganized and mostly exposed center on September 19. Tapah later re-organized itself, and further intensified into a severe tropical storm.
Early morning on September 21, Tapah exited the Philippine Area of Responsibility and then the PAGASA gave its last advisory on it. It even intensified further as it passed the Ryukyu Islands. Tapah then intensified into a typhoon as per the JMA, Tapah weakened into a severe tropical storm, as its diameter explosively expanded. Tapah then rapidly weakened into an extratropical storm on 00:00 UTC of September 23.