Worcestershire paceman Charlie Morris claimed his second five wicket haul for the county as Somerset were dismissed for 250 on the opening day of the LV = County Championship clash at New Road.
Morris picked up the first four wickets in a superb opening spell of 11-2-34-4 after the visitors had been put into bat by Worcestershire skipper Daryl Mitchell.
He finished with overall figures of 5-71 from 24 overs.
Morris received excellent support from the returning Joe Leach who replaced the injured Gareth Andrew.
The all-rounder continued the consistent form of last season, troubling all the batsmen and finishing with 3-76 from 22 overs.
It was the 28th time in the last 29 Championship matches that the county have claimed maximum bowling points.
Morris and Leach were backed up by some excellent fielding behind the wicket with Ben Cox claiming five catches – four of them off the bowling of Morris.
Worcestershire closed the day on 35-2 from 18 overs after the dismissal of Richard Oliver and Tom Fell – century-makers against Sussex and Yorkshire respectively.
Mitchell finished unbeaten on 20 and Alex Gidman seven.
Morris dismissed Marcus Trescothick, Johann Myburgh, Tom Cooper and Jim Allenby in his first spell and received rapturous applause when he finally came out of the attack.
Trescothick had collected two boundaries in the opening over from Jack Shantry at the New Road End.
But after making 10 he gloved a lifting delivery from Morris through to Cox who held onto a good low catch. Tom Cooper hooked Morris for six and a straight drive for four off the same bowler raised the half century.
But without addition to the score, he pushed forward to Morris after making 11 and Cox held onto a good catch in front of first slip.
Morris then removed Cooper and Jim Allenby in successive overs.
Cooper (30) aimed an expansive drive at Morris and Cox claimed a third catch.
Then Allenby(7) pushed forward and Mitchell safely pouched a good low catch at second slip.
Morris had taken three wickets in 15 balls for 10 runs before finally taking a well earned breather and being replaced by Ross Whiteley.
Somerset reached 98-4 off 29 overs by lunch and either side of the interval James Hildreth and Alex Barrow added 61 in 23 overs.
But then the wickets started to tumble again.
Senanayake followed up his six wickets at Hove by accounting for Barrow (26) who pushed forward and nicked through to Mitchell at slip.
Then in the next over Hildreth (41) edged a delivery that left him from Leach and Cox collected his fourth victim of the innings at 134-6.
Peter Trego became Leach's second victim after making 14 when he tried to get out of the way of a short ball but the ball hit the bat and was pouched at second slip by Mitchell.
Somerset were then 169-7 but Lewis Gregory and Craig Overton lifted the total to 212-7 at tea.
Leach broke through again after the stand was worth 52 when Gregory (30) mistimed a drive to Senanayake at cover.
Morris completed his nap hand when Cox produced another good catch to his right from a nick by Overton on 41.
The innings ended when Abdur Rehman (13) turned Shantry to Fell at leg slip.
Worcestershire were left with a maximum of 19 overs to face and Mitchell needed treatment after being hit on the glove by Thomas.
Oliver was caught and bowled by Gregory following through for three and Fell (1) turned a lifting ball from Thomas to Trego at third slip.