Ulster suffered their second successive defeat in the competition as Glasgow's Dan Parks kicked five penalties and converted Thom Evans' try to move within five points of breaking the Magners League's 1,000-point barrier.

The Warriors showed the greater cohesion and commitment after half-time, with three pinpoint kicks from Parks soon erasing Ulster's 13-6 interval lead.

A try from Ireland prop Tom Court had nudged Ulster ten points clear, while Glasgow prop Jon Welsh was in the sin-bin for a scrummaging offence.

Welsh saw yellow for falling foul of referee James Jones' interpretation of the scrum, leaving Glasgow a man down with ten minutes to go in the first half.

Ulster seized their opportunity as Court piled over on a close range drive and Ian Humphreys converted for a 13-3 advantage.

But Parks reduced the arrears to six points for half-time and the Australian-born stand-off, who displayed his place-kicking brilliance in rainswept conditions, changed the complexion of the game in the third quarter.

Between the 42nd and 60th minutes, the man-of-the-match landed four successive penalties.

Parks was off target with another effort from wide out on the left, but Glasgow ended the match as a contest when replacement Chris Cusiter raided out to the right off a ruck in the Ulster 22 and passed for speedster Evans to notch his fourth try of the campaign.

Ulster were devoid of ideas as they tried to muster a comeback and missing the influence of the injured Rory Best, Stephen Ferris, Paddy Wallace and BJ Botha, there was no way back for Brian McLaughlin's men.

The Ulster crowd were subdued during the opening exchanges as their side took their time to adapt to the swirling wind and driving rain.

A scrum infringement with Court singled out allowed Parks punt a left-sided penalty kick through the posts for the lead score in the sixth minute. Flankers Kelly Brown and John Barclay were prominent in the loose as the Warriors took to their task.

Before Isaac Boss was penalised for not coming through the gate at a ruck, Thom Evans almost blitzed his way through for an early try.

He scampered into the Ulster 22 after an excellent break from Richie Vernon who dummied the Ulster defence before racing down the right touchline. It took a well-timed tackle from Simon Danielli to bring Evans, his Scottish international colleague, to ground.

Boss' infringement saw Parks lining up his second shot at the posts but his effort from the right was never on target.

Ulster's lineout malfunctioned throughout the game and Richie Gray put constant pressure on Andy Kyriacou's throw and the home jumpers.

However, the men in white did muster a couple of notable lineout mauls in the opening 40 minutes, the first of which led to Humphreys kicking them level with his first penalty - a fine kick from the right.

Humphreys failed to punish Welsh for a binding offence two minutes later, missing his kick from the left, but there were definite signs of improvement from Ulster. Errors were creeping into Glasgow's game, Parks enduring a couple of knock-ons as he defended high kicks.

Playing for the first time in a number of weeks, there was an understandable lack of fluency on both sides. Ulster, it seemed, were increasing the tempo and another good maul drive and half breack from Humphreys was finished off with a well-struck penalty from the number 10.

Humphreys were beginning to assert more control as, after Glasgow had botched some good field position, he used the wind to find a terrific touch on halfway.

There was more encouragement for Ulster when Glasgow prop Welsh was sin-binned for not scrummaging straight after earlier being warned.

However, Ulster suffered a significant blow soon after when a bruised shoulder ended Timoci Nagusa's night prematurely. He was replaced by Paul Marshall, who slotted in at scrum half, with Boss moving to full-back and Clinton Schifcofske repositioned to the wing.

Using their numerical advantage in the forwards, Ulster did some more damage with a maul that gained 15 metres for them.

Marshall was stopped short of the try-line by Glasgow debutant Alex Dunbar and after a couple of forward drives, Court picked off the base and with Willie Faloon and David Pollock providing support, the former shot putter drove over the line for a deserved try.

Humphreys added the extras, only for Parks to land a superb penalty kick in the dying embers of the half, firing over from outside the ten-metre line and into the wind.

Ulster made a poor start to the second half with stand-in captain Chris Henry being penalised for going off his feet at a ruck and Parks mopped up with a penalty from a central position.

A scrum infringement saw Parks close the gap to just a single point and Glasgow were ahead on 50 minutes as Parks and his forwards started to suck the life out of an increasingly flat Ulster outfit.

Ulster got back on the attack and some patient build-up from the forwards saw them get to within metres of the Glasgow try-line. The visitors' defence was rock solid and a thumping hit from Vernon on Marshall saw the attack peter out.

Some foul play from Ulster lock Dan Tuohy allowed Parks land his sixth penalty goal, moving Glasgow 18-13 ahead, before Parks was off target with a 45-metre effort following a stray boot from Marshall at a midfield ruck.

Glasgow had hardly threatened the Ulster whitewash all night, but from an up and under from Parks, Ulster were slow to get back and the Scottish side broke through for an opportunist try.

Humphreys failed to collect Parks' aerial bomb and Glasgow poured forward into the hosts' 22 with skipper Barclay snaffling possession.

A ruck was quickly set up and a clever change of direction from replacement scrum half Cusiter sent Thom Evans diving over in the right corner past covering defender Boss.

A top drawer conversion from the touchline from Parks added to Ulster's frustrations but the Irish side had the game in their grasp at 13-3 and Glasgow deserve credit for playing the conditions and working their way to a well-earned comeback win.