Well, having flown thru Chinese airspace many times, you do have to plan ahead with regards to WX/CBs enroute.
You ask for deviation, if not granted ask for alternative routing. Then you make a Pan call, then finally declare a Mayday as a last resort, and go around the Wx and/or hold present position if suitable. Usually you get the response clear to avoid. There are procedures for this if you do not get a response, radio busy, which is common at times in Chinese airspace. Follow them, but fly through CB's nah.
SyB
