You can
You can somewhat predict weatherhelm by comparing the kayaks center of effort with the boats center of lateral area. While doing this make sure that for center of effort, you’re including the paddler and anything else that might be on the deck.
If you don’t have the numbers, make a cardboard cut out of the profile of the kayak with paddler and junk on deck. Cut the cardboard at the waterline and balance each piece on a pin.
Generally, it’ll predict like this:
If the pin locations line up, there won’t be weatherhelm.
If CE is behind CLR, you weatherhelm.
If CE is ahead of CLR, you leecock.