Hi Sandy:
Welcome to HK Outdoors!
Lest no surf dudes drop by: found this page re Cheung Sha surfing:
http://www.wannasurf.com/spot/Asia/Hong_Kong/cheung_sha_beach_lantau/
Looks to me like southwest monsoons might be best (few n far between so far this summer), maybe also tropical storms to sw of us (care with these!), or even overland to west/northwest.
HK Obs site maybe worth checking, inc for 7-day forecast, mind you must take latter with pinch of salt: http://www.hko.gov.hk/contente.htm