In the following days, Krosa rapidly intensified into a Category 4 super typhoon and reached peak intensity of 105 knots (194 km/h) (in 10-minute winds).

[2] In late September, a new system formed east of the Philippines, leading to a Tropical Cyclone Formation Alert by JTWC.

[3] PAGASA declared it a tropical depression and assigned a local name Ineng early on October 1, and the JMA[4] and JTWC[5] soon followed.

It was upgraded to a tropical storm early on October 2 by JMA, receiving the international name Krosa.

[5] As it intensified, it gained a wide, ragged eye and began to track to the west, becoming a typhoon by the JMA early on October 3.

[3] Fluctuations in intensity soon followed as Krosa approached Taiwan, as the JMA upgraded it to 105 knots (194 km/h) and the JTWC into a super typhoon early on October 5.

After landfall in Taiwan, Krosa quickly weakened into Category 1 typhoon as it approached China.

[6] An evacuation of 730,000 people from China's Zhejiang and Fujian provinces was ordered on the evening of October 6.