Ulster couldn't convert a 19-point half time lead into a victory as Cardiff produced a remarkable second-half turnaround at a raucous Arms Park in the United Rugby Championship.Jude Postlethwaite grabbed two tries and Cormac Izuchukwu another for Ulster, with Nathan Doak adding two conversions.It left the lethargic home side looking dead and buried at half-time but, after the interval, they emerged a totally different outfit to register 21 unanswered points.Iwan Stephens, Dafydd Hughes and Thomas Young scored their tries, with Callum Sheedy converting all three.It took Ulster 10 minutes to raise their first attack but they certainly made it count with a continuous battering of the opposition line.Cardiff hooker Evan Lloyd was yellow-carded for persistent team infringements before Izuchukwu capitalised by forcing his way over.Worse was to follow for the Welsh region when a strong run from Doak split the home defence to create a try for Postlethwaite before another flowing move culminated in the centre crossing for another.Lloyd eventually returned from the sin-bin after seeing his side concede 19 points in his absence before Ulster suffered a blow when their captain Iain Henderson departed with an injury.The only positive for Cardiff in a dismal first-half performance was the solidity of their scrum which won a couple of penalties but they still remained scoreless at the interval.Five minutes after the restart, the home side had their best chance for points when a neat break from Ben Thomas gave Mason Grady an opportunity.However, the wing fumbled before stumbling into touch with the line only metres away.Cardiff maintained their momentum and were aided by a yellow card for Ulster No 8 David McCann for a deliberate