after much experiment i have found that you need at least 1/2000 or above in order to freeze a jump in mid air. it would be better if its 1/4000 or 1/8000 bur there lies the problem once your shutter speed is so high your aperture would have to open up which means that the sharpness of your images won't be as good as when your aperture is at F8 or F11.
Adding flash into the equation you will need to place your flash quite close to your subject as you would need to use FP mode otherwise flash is useless. the best you can do is hope that the sun is on your back so that it will illuminate you subject properly.
the other thing is the models expression that one you will have to hope your luck is good enough
hope this is some good info for you all. please comment if you agree or not agree