I just checked the train situation
Sanyo Shinkansen (toward Osaka) *may* cancel runs later this afternoon/evening (further announcement will be made at 10 a.m. - 35 minutes from now).
JR Kyushu local trains appear to be unaffected as of now in Fukuoka, but both express and slow trains are cancelled if you are going to Nagasaki, Miyazaki, Oita, Kumamoto or Kagoshima.
Information is kept updated at https://trafficinfo.westjr.co.jp/sanyo.html
note this page only covers West JR section of the Shinkansen (Hakata - Shin-Osaka).
It looks like the typhoon won't affect the trains till evening hours, so you should leave early and be prepared for a packed train (everyone else is trying to get out of Kyushu before late!) if you have a non-reserved ticket.
@salixlucida thank you so much for your help! I’ll see about taking a train earlier to maybe be ahead of the rush. I haven’t reserved yet so I think it’s best I get to the station as soon as possible.
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