"Super typhoon Megi was threatening TW for over a week, without actually coming here. Went through northern PPE as cat 5, stalled on other side, then went up TW strait in weakened form and finally made a second landfall in China as cat 1-2.

In SC, the big rain came on the Sat night, Oct 16, just before it entered PPE. Torrential rain for 5-6 hours – about 200 ml.
Five days later, as the typhoon was stalled between PPE and China, Ilan was clobbered with 947 ml of rain in a day, 2500ml + over that five day period. This was caused by broken off blobs from the typhoon colliding with the north east monsoon resulting in torrential downpours. This is probably what they mean when they say autumn typhoons are the most dangerous.

Previously I had thought the dbjf to be a typhoon killer, due to the cross winds interfering with its structure, but it seems an interaction with the outer bands can also cause tremendous rainfall.

Not surprisingly, the Su-Ao to Hualien highway was a total disaster zone – two buses went over the edge and 450 people were stranded. So far 25 people are confirmed dead."

This current typhoon bears some similarities to Megi, a massive late season typhoon from 2010. The scary bit is that Usagi is a lot closer! On the positive side, it doesn't have that wicked poleward outflow that Megi had.
Megi

Usagi