I can tell you from experience that you can lose a lot in a short period of time. But....no matter how much you lose it will not be enough. You will want more and you still will not be happy.
At least that is how I am. I wouldn't say go as you are now but I would say start now and know that the process does not happen in 30 days. You didn't put it on that fast and it will not come off that fast either.
Start hitting it hard, diet hard, cardio hard twice a day if you can, and know that when this reunion is over you are still going to do the same thing. This isn't about impressing anyone else this is about you. You have to want this because it is right and you want to be better than you are.
You have to burn for the end result (which you will never see) and you have to approach each session like it is the last time you will ever get to train hard again and give it everything you have.
You will have to fail to succeed, learn to grow, and tear yourself down again and again just to rebuild into something better than you are.
Ask yourself how much do I want this? How much am I willing to give and how much will I suffer to make this happen? Revel in the suffering, enjoy the journey, and embrace the pain. Because you will suffer, you will journey and you will hurt! If you don't you are just wasting your time.
Gig