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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The tree was blown down in a gale in February after standing for more than 200 years.
Aberdaron recorded wind speeds of 70mph this morning. A warning is issued covering the whole of Wales.
Ospreys prop Nicky Smith is the only uncapped player named in the party.