But the boot of Dan Newton kept the away side in touch until the final quarter when scores from replacements Duncan Williams and Tommy O'Donnell sealed their first bonus-point victory of the season.
Munster Head coach Tony McGahan made five changes to his starting XV from the side that beat Glasgow last weekend as Mike Sherry came into the side in place of Damien Varley who has flown out to New Zealand as cover for the injured Jerry Flannery.
The Scarlets meanwhile had tripped up 11-13 at Connacht last Friday and have still not won a match in Ireland for over two years but they did make a bright start against the defending champions.
Newton's penalty put them ahead in the opening stages before Ian Keatley's reliable right foot brought the home side level and they were soon in the lead for good.
Less than a quarter of an hour was on the clock when a turnover on the halway line allowed Howlett to race clear in trademark fashion to touch down and put Munster 10-3 ahead.
Newton and Keatley then traded penalties before the home side really started to make their dominance count and after a spell of concerted pressure were awarded a penalty try as the Scarlets continually infringed at the scrum, Rob McCusker adjudged to be the guilty party.
That score put them 20-6 ahead but a long-range penalty from Welsh full-back Dale Ford on his debut before half-time and another Newton kick soon after brought the Scarlets right back into the game at 20-12.
But that was as good as it got for the Welshmen as Munster really turned the screw late-on to seal the points.
Keatley had already added his third penalty after anothe strong Munster scrum when replacement scrum-half Williams scampered clear after being fed by hooker Mike Sherry, Keatley for once missing with the extras.
And Munster flanker O'Donnell then crashed over in the closing stages to add a touch of gloss to the scoreline, securing Munster's first bonus point of the season in the process.
|Munster Rugby Score Card|
|Scarlets Score Card|