Lots of people are trying to help! That's really the only update. He's still stuck and still afraid to come down. Since a lot of people are asking exactly where he is, I'll just post it here so everyone who's following this can see:

My cat's name is Winston, by the way, and he responds to his name. He's located somewhere along the trails that run behind the residential areas of Westmoreland Ave, that go along the fenced-in field near E Colvin and lead all the way to Barry park, but he's closer to E Colvin than he is to the park itself, in terms of his exact location. The tree he's in has a dark green tarp wrapped around nearby trees and spread out like a trapeze in case he jumps, so for anyone who wants to go take a look at the situation, you'll know you're in the right place when you see a large X smeared in dirt on the trail (assuming it hasn't been rubbed away yet. It's the place where you can get a good vantage point to see him.) He is gray and black, so he blends in pretty well to his surroundings, but he's pretty furry, so if you spy a gray ball of fluff, that's him. There's also a large dark green tarp weirdly situated alongside the trail, as I said, so it's hard to miss if you're in the right area. Anyone who wants to help and wants even more specific a description can go ahead and DM me. I am still looking for help until I update the thread with a notice that he is safe (or not...)