I have been flying into HKG for nearly 3 decades with a well known HKG airline, which at least always carries an alternate. But all the close alternates can fill up with diverting traffic. Over the last few years the traffic has become crazy and the weather forecasting, never particularly good, has got to the point where I just don’t trust it at at all in the HKG summer.
Years ago an ‘old and bold’ told me, ‘If any one of HKG, Macao or Shenzhen have even a prob of thunderies, put the fuel on’. This advice has served me well.
Has not happened to me yet, but I have heard northbound aircraft, even some overflying HKG, being told to hold in Manila’s airspace as ‘Hong Kong will not accept them’ due traffic. Even enroute ‘large scale weather avoidance’ causes chaos in the FIR.
Couple years ago our bean counters cut back Contingency fuel to save $$$ (due to stupidly hedged fuel). A few diversions into Manila with several hundred punters eventually dissuaded them of that great money-saving idea.