most often that yellow arrow "but kinda grey" area between 10 and 15kn if it is a nice steady 15 you should be fine. if it's holey or closer to the 10kn end of the spectrum it will take a bit more kite and board skill to keep it flying, let alone stay upwind. there are alot of guys who use 10s to do their DW runs in 15 kn and just under in WA.
i used to use my 9m in those winds and just unhook or DW, now i throw up a 12 and have a lot more fun.
are you in WA? plenty of wind coming in the next week once this trough f&*ks right off, enjoy when you get out there!