[3][4] Multispectral animated satellite imagery revealed a partially exposed low-level center with deep convection to the southeastern quadrant of its disturbance.

[5] At 06:00 UTC on September 6, the United States Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert to the exposed system.

[9] It eventually entered the Philippine Area of Responsibility (PAR) with PAGASA assigning the name Inday.

[10] Deepest formative maintained with a ragged central dense overcast continued to obscure low-level circulation center.

[11] By 00:00 UTC on September 8, the JMA upgraded the system to a tropical storm, assigning it the name Muifa.

[12] Muifa's center was elongated due to a tropical upper tropospheric trough from the north on the system.

[16] At 21:00 UTC that day, the JTWC also upgraded Muifa to a Category 1-equivalent typhoon, approximately 388 nautical miles (720 km; 445 mi) south of Kadena Air Base.

[18] Muifa strengthened to Category 2-equivalent typhoon after deep convection becoming more symmetric in the 24 nautical miles (44 km; 28 mi) eye.

[20] Satellite imagery revealed a 20 nautical miles (37 km; 23 mi) round eye with core convection in the eyewall.

[26][27] Satellite imagery revealed a 30 nautical miles (56 km; 35 mi) ragged eye around a convective banding.

[45] Muifa caused much damage and heavy rainfall throughout Eastern China, most of it in towns close to the populous Yangtze River delta.