They restricted the Outlaws to 149-9 in their 20 overs by collectively tight bowling led by a competition-best 4-29 from Oliver Hannon-Dalby.
It was a moderate target which Birmingham, their batting enhanced by the presence of Ian Bell, would have fancied, but the equation became harder following a rain break - when they were nought for one after four balls.
That left them facing a Duckworth/Lewis equation of 98 from 11 overs but they reached their target with four balls to spare after Bell laid the perfect platform with 38 from 24 balls and William Porterfield saw the job through with an unbeaten 37 from 23.
Put in, the Outlaws were given an explosive start by Rikki Wessels who hit three sixes and three fours in 39 from just 19 balls before skying Recordo Gordon to cover.
That early onslaught included a rare roughing-up for spinner Jeetan Patel who conceded 21 in his first over. But Wessels’ dismissal slowed things down and Patel’s other three overs cost only 14 while his young fellow spinner Josh Poysden also applied a brake.
Playing only his second senior T20 match, the 23-year-old conceded just six runs from his first two overs which also brought the wicket of Greg Smith, lbw.
James Taylor (23 from 26 balls) and Darren Sammy (23 from 18) tried to reinject momentum but the former was lbw, slogging at Rikki Clarke, and the latter was beautifully caught by Clarke at long on, the first of wickets with successive balls for the impressive Hannon-Dalby.
When Birmingham began their reply, their fans had high hopes of seeing another masterclass from Bell to follow his 90 at Durham last week. Varun Chopra edged Ben Hilfenhaus’s fourth ball to slip but Porterfield reached the middle just in time to be accompany the rest of the players straight back off, out of the downpour.
When play resumed, the required rate was nine per over but Bell hit three sixes and two fours in a spectacular cameo which was ended by a superb catch by Wessels at long on.
Porterfield stayed to time the chase perfectly though. Birmingham went into the last three overs needing only 20 and they eased home with four balls unused.