Hi,
This is an interesting team, but I'm sort of confused about your use of Infernape here. Every other Pokemon would be perfect for a rain team (100% accuracy Hurricanes and Thunders for DNite and Torn, Starmie's Water STAB boosted, ect.), but you've put Infernape, a Fire-type, here and it just seems out of place. Infernape is also a pretty niche Pokemon in general, and I don't think this team takes advantage of its strengths enough to justify it here. That being said, I would suggest using
Choice Specs Politoed over Infernape. The permanent rain Politoed summons is great for this for the aforementioned reasons, while Choice Specs gives Politoed a lot of extra power, which an offensive team like this really appreciates.
Now onto Jolteon. I understand why using a Choice Scarf on it seems appealing, since it outspeeds basically the entirety of OU, but I don't think it's such a great idea. The reason it that, although its very fast, it often lacks the power possessed by other revenge killers to get the job done. Because of that, I'd suggest
changing Choice Scarf on Jolteon to an Expert Belt. This makes Jolteon more of a wall-breaker, but doesn't lock it into an undesirable move like Choice Specs, or cause recoil from Volt Switching like Life Orb. With this change you lose your revenge-killer, which leads to my next change. Using a Hurricane set on Dragonite seems redundant when you already have the faster and stronger Tornadus to fill this role. To remove this redundancy and give you a new revenge-killer, I would
swap Dragonite for Choice Scarf Keldeo. Keldeo possesses a blazing 108 speed to take advantage of Choice Scarf, loves rain to boost its Water STAB, and also fills the missing spot of a Fighting-type on your team now that Infernape is gone. For these reasons, I think it would be a good fit.
Now for a few smaller changes. Since rain weakens Fire moves, you should probably
get rid of Heat Wave of Tornadus in favor of U-turn. U-turn eases prediction when trying to work around Tornadus' checks and counters, and can potentially gain you momentum throughout the match if you keep Stealth Rock off the field. Since Rain makes Thunder 100% accurate, you might want to consider using
Thunder on both Jolteon and Starmie. This is more personal preference than anything, since it will make you more vulnerable to opposing weather, but it's something to consider. Finally, if you replace Dragonite with Keldeo, just about all of your team members will be very fast, and therefore won't allow you to take advantage of the paralysis Ferrothorn spreads. Because of this,
Gyro Ball over Thunder Wave is an option. Gyro Ball will allow Ferrothorn to fare better against the Dragon-types you would want it to wall, since Power Whip is resisted by Dragon.
Hope this helps you improve the team! I'll post all of the sets of the Pokemon I changed out below.