3. On either side, you'll see a couple of what look like rubber sockets. These come into contact with the metal just above the tail light housings. They're threaded -- and therefore adjustable. Turning them clockwise should shorten them up -- allowing the trunk lid to close more firmly against the rubber seals.
4. Monitor the situation closely. In fact, the next time it rains while you're out -- pull into a covered area and pop the trunk with the remote while standing in back of it. Open the lid quickly -- and look at the seal around the perimeter of the trunk opening. Note any wet areas -- going so far as drawing a picture of the seal in case you have to go to the dealer -- and then check the trunk for moisture.
Try adjusting the trunk stops first. I'll bet you this will work -- as mine were all screwed up from the factory. Be sure to yank your trunk mat and everything in the spare tire well out and get it good and dry -- so you don't wind up with anything that could start to stink or rust.
That said, if you're indeed getting blow by over the top of seal toward the bottom of the backlight, the dealer's going to have to get involved. Probably the quickest and most effective way of fixing the problem would be to attach a piece of seal to the top of your trunk lid -- so you get two pieces of material compressed together.
NOTE: Be sure you don't make the stops too short -- otherwise, the bottom of the trunk lid will bang into the top of your bumper. Another problem is that the trunk lid might gently rest on it -- which will scratch the hell out of the bumper cover. Put a good coat of wax on this area first. When everything's perfect, the trunk should pop up a little when you hit the release, not leak, and close easily without slamming, etc.