How do I convince my parents to let me travel out of state alone?

I'm 15 years old and I live in Missouri. A while ago, I met a friend on twitter, and he's 16 and lives in california. it's been months since we first met and he wants me to come stay with him for a while during the summer. I know and trust him, its like we've been friends forever. His dad already said it was okay if I came, its just my dad said no. my mom said yes though, so i need help convincing my dad/brother/sisters etc... His parents are willing to talk to mine, my parents just don't like the feeling of me going alone. Money is not an issue . Please help me :(