Finn Russell kicked Glasgow's points

In appalling conditions at Parc y Scarlets, Gregor Townsend's team celebrated their century with four points and also made it back-to-back victories in the middle of the pool stages for the first time in 15 seasons as they triumphed 9-6.

But they were forced to dig deep in the second half when they were reduced to 13 men for seven minutes after ex-Scarlets player Sean Lamont and back-row man Simone Favaro were both sent to the sin-bin by French official Pascal Gauzere in the space of three minutes.

Lamont got his marching orders for playing the ball on the floor after a tackle and then Favaro followed him into the bin for a late charge on Aled Thomas after he had kicked ahead.

The win means the reigning PRO12 champions are back in the hunt for a quarter-final place after losing their opening game at home against Northampton.

They now sit in third place in Pool Three, one point behind Saints, with a game in hand, and three behind Racing 92, who they still have to play home and away.

The torrential rain meant there was never any likelihood of a repeat of the try-fest at Scotstoun the previous weekend and the first half turned into a battle of the kickers.

Finn Russell hit the mark with two out of three of his penalty attempts, while Thomas was wide with his one shot.

The Scarlets lost Thomas to the sin-bin after 28 minutes for cynically knocking the ball out of the hands of his opposite number Russell in a tackle, but the home side only conceded three points while he was off the field.

The game was still finely balanced at the break with the visitors 6-0 to the good and Russell extended the lead to nine points with his third success five minutes after the restart.

Then came the yellow cards and Thomas got the Scarlets off the mark with a penalty shortly after Lamont went off and then added a second moments before Fusaro returned.

That left the home side with 13 minutes to try to find a way to win the game and add to their one point from three games.

Thomas had a 45-metre kick at goal six minutes from the end, but pushed his kick wide.

After the match, Glasgow Warriors head coach Gregor Townsend said: "The Scarlets had the edge at the scrum in the first 20 minutes, but we got better as the game wore on. Overall I thought our set-piece was very good, especially our line-out.

"But we know we have to be better in the scrum given the two teams we have left to play in the pool, Northampton Saints and Racing 92."

"I thought both yellow cards were a bit harsh, but discipline is something we need to work on.

"We've just had two matches in terrible conditions and we can't play the rugby we want to play."