A wind coming from the west would take a radioactive plume towards the east! That means the Aleutians, Alaska, the USA.
Aren’t there really bad jet streams there that move in a northeasterly direction? At this time of year I remember how they would give us one heck of a tailwind going from Japan to the US West Coast.
I know ive took a nonstop flight from tokyo to new york if that helps hehe.