Owen Williams gave the Scarlets an early lead, but tries from Tommy Bowe and Robbie Diack combined with Ruan Pienaar's reliable boot have left Ulster 18-3 up at half time.
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Two people have died after being involved in separate lightning strikes in Wales' Brecon Beacons today.
Any lingering showers will ease this evening, to leave a dry night with plenty of clear spells. Minimum temperature 11 deg C (52 deg F).
Blackwood mother Trudy Jones was on holiday when she was gunned down in the Tunisian beach massacre that claimed the lives of 30 Britons.