This team I am presenting is a Gen 5 team and is designed as a Sunny Day team.
Ninetales @Leftovers
136 HP/252 SpA/120 Sp
Modest
Drought
Sunny Day
Solar Beam
Hypnosis
Flamethrower
Ninetales is the backbone of my setup obviously, like most in most Sunny Day teams. His role is to set up the weather conditions and neutralize any other weather. I set him up so he is able to sweep if necessary and can neutralize an opponent with Hypnosis. He’s not too bad defensively because I found that when I was testing out this team, he was able to be roughly 4HKO’d by a Politoed using Scald. I never use him as my lead though because I like to set up entry hazards initially, so he's usually swapped in with U-Turn Xatu or Volt Switch Forretress.
Charizard @Choice Specs
252 SpA/4 SpD/252 Sp
Timid
Solar Power
Fire Blast
Hidden Power Ice
Air Slash
Focus Blast
Charizard’s role is to be my primary sweeper and I optimized him to be able to OHKO most stuff with Fire Blast once the weather conditions are ideal. The most recurring problem I’ve had is when I am in the situation of having Forretress KO’d while Stealth Rock is on the field. He’s absolutely fucked if something like Rotom-Wash or Heatran gets on the field since both cant take his hits and the former also has STAB Thunderbolt to fuck Charizard’s shit up. Of all the pokemon on my team, Charizard is the one I am most seriously considering replacing.
Swampert @Leftovers
240 HP/216 Att/52 Sp
Relaxed
Torrent
Scald
Earthquake
Stealth Rock
Ice Beam
I initially put Swampert on my team to serve as a check for threats like Tyranitar and Metagross as well as to provide additional coverage but I found during battles in Pokemon Showdown that Swampert has another niche, and that’s to wall in Rain and Sand teams. Because of his type coverage, Swampert absolutely thrives in that environment and I can use him to take a hit before swapping him out for Ninetales. He is also my Stealth Rock user so he is also valuable for setting up entry hazards. In addition, Swampert can function ok even when Sunny Day is active since he has access to STAB Earthquake. I found that his most dangerous opponents are Breeloom and Conkledurr, since they can outspeed him and OHKO him with Drain Punch. In short, Swampert complements my team rather well due to his bulk and adaptability to other weather situations, as well as being my counter to Tyranitar, Metagross, and Heatran (who can wall my sweepers all day long btw).
Forretress @Shed Shell
252 HP/176 Def/80 SpD
IVs 0 Sp
Relaxed
Study
Volt Switch
Toxic Spikes
Spikes
Rapid Spin
Forretress’s primary role is to set up entry hazards and because of his defensive typing along with his bulk and Sturdy ability, he can do that job very well. Not only that, his job is to be my Rapid Spinner which is very valuable since I have Charizard on my team and without a Rapid Spinner, Charizard has to deal with Stealth Rock which severely cuts into his use. Volt Switch is there to help deal with flying and water types while also swapping out for Ninetales. He’s an excellent lead pokemon since he can just start setting up hazards immediately and run when the going gets tough. He does do really badly if a pokemon has Hidden Power Fire or any other powerful fire move on them (and because he ends up with 1 HP from taking it, that means he can’t Rapid Spin if I want to switch him back in at a later date).
Xatu @Light Clay
252 HP/104 Def/152 SpD
Impish
Magic Bounce
Reflect
Light Screen
U-Turn
Roost
Xatu’s role is pure support, so I chose the bread and butter Double Screens setup for Xatu. He’s also a good lead pokemon since he can start improving my team’s defense immediately and his access to U-Turn means I can also swap him in for Ninetales when needed. I also found Xatu makes good Pursuit bait and his defensive IVs plus Roost can make him perfect for baiting other stuff as well. He is fucked if something like Rotom-Wash gets onto the field though, but he could serve as a sacrifice instead of like, Charizard or something.
http://www.smogon.com/download/sprites/bw/3.png
Venusaur @Life Orb
4 HP/252 SpA/252 Sp
Modest
Chlorophyll
Growth
Solar Beam
Sleep Powder
Hidden Power Fire
Venusaur is another sweeper and my most reliable one. Chlorophyll combined with Growth and STAB Solar Beam means he can out speed and OHKO things very well. He also can take a few hits as well and he has Hidden Power Fire to deal with enemies that Solar Beam is ineffective against and to continue sweeping. Furthermore, Venusaur’s access to Sleep Powder means he can neutralize other threats while simultaneously allowing him to set up for a quick Growth use or two. Growth really does put Venusaur’s offense over the top. For example, in one battle, I managed to put a Crobat to sleep and with a quick Growth use, he was able to take away 98% of Crobat’s health with Solar Beam and this saved me from a loss (since Crobat woke up that turn and used Brave Bird, KOing both pokemon and ending the match in a draw). His grass type means he can also be a defensive counter for Rotom-Wash (although he’s inferior to Swampert for that job) and this combined with access to Sleep Powder means he can still be useable when it’s raining as well. Because of all this, Venusaur has excellent synergy with my team since he can be used in a variety of situations.
[u][SIZE=6][COLOR=Red]Threats[/COLOR][/SIZE][/u]
Heatran: With his Fire/Steel type, excellent defenses, and his access to Flash Fire, Heatran can completely shut down Ninetales and Venusaur and can decrease Charizard's effectiveness. While Swampert is a good counter for him, Swampert is still outspeeded by him and Heatran can wall the rest of my team all day long while tearing them a new one.
Tyranitar: Tyrnaitar's rock type and Sand Stream can vastly reduce the effectiveness of my team and stop my sweepers cold. Like with Heatran, Swampert is an excellent counter for him but Tyranitar can still outspeed Swampert with the right EVs and if Swampert is KO'd for some reason, then Tyranitar can destroy the rest of my team easily.
Rotom-Wash: While Solar Beam combined with Drought is often a OHKO on Rotom-Wash, the Electric-Water type can still ruin my day. For example, he is capable of OHKOing Charizard and Xatu with Thunder and he is also effective as a wall against Swampert since Swampert's offense against it is terrible. It's even worse in Rain Dance teams where it can sweep much of team with Hydro Pump.
There are other numerous threats to my team as well, but these three have stuck out like a sore thumb.
[u][COLOR=Red][SIZE=6]Final Thoughts[SIZE=2][COLOR=Black][/u]
This team seems pretty ok in terms of synergy and it does have some support. It does lack some of the sweeping power compared to other teams I've seen and it's easily stopped by things like Rain Dance teams. It might require tighter tactics and more practice (since I'm a newbie, that might be a big reason for problems I've had with this team) too, although it could use a swap in pokemon or items to be more effective. For example, I've considered swapping out Choice Specs for a Choice Scarf on Charizard so he can outspeed more enemies but he might lose some ability to OHKO stuff (though he can put enemies into the KO range for other pokemon).
[/COLOR][/SIZE][/SIZE][/COLOR]
Please tell me if it's a good team and if there's anything I can do to fix it or improve it, I'm happy to make changes.
EDIT: I have provided descriptions on the pokemon I have set up. Sorry about the bad post before.

Ninetales @Leftovers
136 HP/252 SpA/120 Sp
Modest
Drought
Sunny Day
Solar Beam
Hypnosis
Flamethrower
Ninetales is the backbone of my setup obviously, like most in most Sunny Day teams. His role is to set up the weather conditions and neutralize any other weather. I set him up so he is able to sweep if necessary and can neutralize an opponent with Hypnosis. He’s not too bad defensively because I found that when I was testing out this team, he was able to be roughly 4HKO’d by a Politoed using Scald. I never use him as my lead though because I like to set up entry hazards initially, so he's usually swapped in with U-Turn Xatu or Volt Switch Forretress.

Charizard @Choice Specs
252 SpA/4 SpD/252 Sp
Timid
Solar Power
Fire Blast
Hidden Power Ice
Air Slash
Focus Blast
Charizard’s role is to be my primary sweeper and I optimized him to be able to OHKO most stuff with Fire Blast once the weather conditions are ideal. The most recurring problem I’ve had is when I am in the situation of having Forretress KO’d while Stealth Rock is on the field. He’s absolutely fucked if something like Rotom-Wash or Heatran gets on the field since both cant take his hits and the former also has STAB Thunderbolt to fuck Charizard’s shit up. Of all the pokemon on my team, Charizard is the one I am most seriously considering replacing.

Swampert @Leftovers
240 HP/216 Att/52 Sp
Relaxed
Torrent
Scald
Earthquake
Stealth Rock
Ice Beam
I initially put Swampert on my team to serve as a check for threats like Tyranitar and Metagross as well as to provide additional coverage but I found during battles in Pokemon Showdown that Swampert has another niche, and that’s to wall in Rain and Sand teams. Because of his type coverage, Swampert absolutely thrives in that environment and I can use him to take a hit before swapping him out for Ninetales. He is also my Stealth Rock user so he is also valuable for setting up entry hazards. In addition, Swampert can function ok even when Sunny Day is active since he has access to STAB Earthquake. I found that his most dangerous opponents are Breeloom and Conkledurr, since they can outspeed him and OHKO him with Drain Punch. In short, Swampert complements my team rather well due to his bulk and adaptability to other weather situations, as well as being my counter to Tyranitar, Metagross, and Heatran (who can wall my sweepers all day long btw).

Forretress @Shed Shell
252 HP/176 Def/80 SpD
IVs 0 Sp
Relaxed
Study
Volt Switch
Toxic Spikes
Spikes
Rapid Spin
Forretress’s primary role is to set up entry hazards and because of his defensive typing along with his bulk and Sturdy ability, he can do that job very well. Not only that, his job is to be my Rapid Spinner which is very valuable since I have Charizard on my team and without a Rapid Spinner, Charizard has to deal with Stealth Rock which severely cuts into his use. Volt Switch is there to help deal with flying and water types while also swapping out for Ninetales. He’s an excellent lead pokemon since he can just start setting up hazards immediately and run when the going gets tough. He does do really badly if a pokemon has Hidden Power Fire or any other powerful fire move on them (and because he ends up with 1 HP from taking it, that means he can’t Rapid Spin if I want to switch him back in at a later date).

Xatu @Light Clay
252 HP/104 Def/152 SpD
Impish
Magic Bounce
Reflect
Light Screen
U-Turn
Roost
Xatu’s role is pure support, so I chose the bread and butter Double Screens setup for Xatu. He’s also a good lead pokemon since he can start improving my team’s defense immediately and his access to U-Turn means I can also swap him in for Ninetales when needed. I also found Xatu makes good Pursuit bait and his defensive IVs plus Roost can make him perfect for baiting other stuff as well. He is fucked if something like Rotom-Wash gets onto the field though, but he could serve as a sacrifice instead of like, Charizard or something.
http://www.smogon.com/download/sprites/bw/3.png
Venusaur @Life Orb
4 HP/252 SpA/252 Sp
Modest
Chlorophyll
Growth
Solar Beam
Sleep Powder
Hidden Power Fire
Venusaur is another sweeper and my most reliable one. Chlorophyll combined with Growth and STAB Solar Beam means he can out speed and OHKO things very well. He also can take a few hits as well and he has Hidden Power Fire to deal with enemies that Solar Beam is ineffective against and to continue sweeping. Furthermore, Venusaur’s access to Sleep Powder means he can neutralize other threats while simultaneously allowing him to set up for a quick Growth use or two. Growth really does put Venusaur’s offense over the top. For example, in one battle, I managed to put a Crobat to sleep and with a quick Growth use, he was able to take away 98% of Crobat’s health with Solar Beam and this saved me from a loss (since Crobat woke up that turn and used Brave Bird, KOing both pokemon and ending the match in a draw). His grass type means he can also be a defensive counter for Rotom-Wash (although he’s inferior to Swampert for that job) and this combined with access to Sleep Powder means he can still be useable when it’s raining as well. Because of all this, Venusaur has excellent synergy with my team since he can be used in a variety of situations.
[u][SIZE=6][COLOR=Red]Threats[/COLOR][/SIZE][/u]
Heatran: With his Fire/Steel type, excellent defenses, and his access to Flash Fire, Heatran can completely shut down Ninetales and Venusaur and can decrease Charizard's effectiveness. While Swampert is a good counter for him, Swampert is still outspeeded by him and Heatran can wall the rest of my team all day long while tearing them a new one.
Tyranitar: Tyrnaitar's rock type and Sand Stream can vastly reduce the effectiveness of my team and stop my sweepers cold. Like with Heatran, Swampert is an excellent counter for him but Tyranitar can still outspeed Swampert with the right EVs and if Swampert is KO'd for some reason, then Tyranitar can destroy the rest of my team easily.
Rotom-Wash: While Solar Beam combined with Drought is often a OHKO on Rotom-Wash, the Electric-Water type can still ruin my day. For example, he is capable of OHKOing Charizard and Xatu with Thunder and he is also effective as a wall against Swampert since Swampert's offense against it is terrible. It's even worse in Rain Dance teams where it can sweep much of team with Hydro Pump.
There are other numerous threats to my team as well, but these three have stuck out like a sore thumb.
[u][COLOR=Red][SIZE=6]Final Thoughts[SIZE=2][COLOR=Black][/u]
This team seems pretty ok in terms of synergy and it does have some support. It does lack some of the sweeping power compared to other teams I've seen and it's easily stopped by things like Rain Dance teams. It might require tighter tactics and more practice (since I'm a newbie, that might be a big reason for problems I've had with this team) too, although it could use a swap in pokemon or items to be more effective. For example, I've considered swapping out Choice Specs for a Choice Scarf on Charizard so he can outspeed more enemies but he might lose some ability to OHKO stuff (though he can put enemies into the KO range for other pokemon).
[/COLOR][/SIZE][/SIZE][/COLOR]
Please tell me if it's a good team and if there's anything I can do to fix it or improve it, I'm happy to make changes.
EDIT: I have provided descriptions on the pokemon I have set up. Sorry about the bad post before.