HIIT question

Hi guys, I have a question. I can't lose the last few pounds of belly fat. So i'm starting HIIT. I weight train 2-3x a week after school. My diet is alright and this is How i will do my HIIT. 20 second sprint 50 second rest and go for about 6-8 intervals with a 5 minute warm up and 10 minute jog after. Now my question is how often should i do HIIT? And on the days i shouldn't, should i still do cardio? and for how long. I usually run 2-3 miles. And how long before I start to see the fat going away?
REPLY

You have a great little HIIT program there, although 60 seconds might be a better recovery time. Kudos for even trying the HIIT, most people have not figured out that long, slow cardio does not promote fat loss.
If you have the extra time to devote to working out, I would add resistance training, i.e. Bodyweight exercises instead of any more cardio. 

I generally advise my clients to work toward a 1 to 1 ratio (run 200 meters/walk 200 meters, run 20 seconds/walk 20 seconds). Even this should vary, however for best results. Try changing interval lengths and intensity every workout to prevent plateaus.
Personal Trainer Hollywood - Los Angeles

The best thing for stubborn fat would be to do HIIT first thing in the morning, followed immediately by 30 min or so of steady state cardio. 
Two resources you may want to check out on my website:
1. Lyle McDonald books: click it, then go to The Stubborn Fat Solution
2. My article on Yohimbine