Heavy rain brought a premature end to the match with Sussex poised for a huge total at 203 for five from 17.4 overs as the Hampshire bowling took a battering. The second-placed hosts were saved from further punishment by the weather and, with the one point gained from an unexpected no-result, edged closer to joining Sussex in quarter-finals.
Hampshire captain Dimitri Mascarenhas chose to field first and must have wondered if he had guessed right under overcast skies as Sussex went on the attack from the first ball.
Chris Nash departed in the first over of the match from Liam Dawson, but that brought England wicketkeeper Prior and Luke Wright together in a breath-taking stand of 114 for the second wicket from only 51 balls.
Prior reached his half century off 23 balls as only left arm spinner Danny Briggs returned respectable figures.
Australian Glenn Maxwell broke the partnership when he had Wright caught on the midwicket boundary.
But Wright was upstaged by the aggressive Prior, who smashed 11 fours and three sixes before falling to another catch by Vince on the boundary.