The initial velocity of the ball is simply the velocity at which it's thrown upwards, which is 16 ft/sec.

However, the velocity of the ball will change over time due to gravity. It will slow down as it goes up, reach zero at its highest point, and then speed up as it falls back down.

If you want to know the velocity of the ball at a specific time after it's thrown, you would need to use the equations of motion and account for the acceleration due to gravity.