It looks like the winds in Kumamoto will be strongest at about 9 AM tomorrow. The graph shows the probability of winds over 50 knots. According to the page I found at the second address shown below, 50 knots is associated with the following kinds of impacts:
"Whole gale trees uprooted; considerable structural damage occurs"
http://www.jma.go.jp/en/typh/storm-349.html?t=1408
http://www.disastercenter.com/convert.htm