How might Japan ambush Allied forces north of the Philippines?

How could Japan ambush Allied forces north of the Philippines if Hong Kong supported long-range reconnaissance?

The most likely method would be submarine ambushes along the Allied approach and supply routes.

Allied forces moving north of the Philippines could use Hong Kong for long-range reconnaissance and supply activity. The most likely Japanese response would be submarines. Boats waiting along the likely approach and supply routes could attack without requiring Japan to expose a major surface force. Reconnaissance and supply patterns would therefore shape the most promising submarine ambush areas.