Yorkshire 167 for 4 (Kohler-Cadmore 68, Brooks 3-38) trail Somerset 424 (Abell 116, Gregory 77, Aldridge 41, Bess 4-68) by 257 runs
Facing his former club, the veteran seamer turned back the years with 3 for 38 from ten overs to help restrict them to 167 for 4 in their first innings, 257 runs behind.
The hosts began the day poorly when Abell, having added only two to his score, fell to the second new ball, lbw to a delivery from Waite that thumped into his back pad.
Floodlights were on under grey skies as Gregory and Aldridge progressed the innings to 298 for 6 before rain caused a 45 minute delay, with 11 overs overs lost. By lunch, the pair had added a further 26.
Gregory reached his half-century with an edged four to third man off Jordan Thompson, having faced 87 balls and hit seven fours.
Aldridge grew in confidence from a sketchy start and brought up 350 with an elegant back-foot boundary off Thompson.
Gregory smacked Bess for a straight six, but perished trying to repeat the shot, caught at long-on by Adam Lyth with the total on 376.
Somerset had settled for four batting points. But Jack Leach dispatched Bess over long-off for six and cleared the ropes again with a reverse sweep off Jack Shutt, who gained revenge by having the England spinner stumped for 16.
Brooks was caught behind to give Bess his fourth wicket before Marchant de Lange took six and four off successive balls from Shannon Gabriel.
Aldridge was last man out, bowled attempting a big hit off Gabriel, having boosted his reputation with a composed contribution.
Adam Lyth began Yorkshire’s reply with two quick boundaries. But, on 13, he drove at Brooks and was picked up at gully by a tumbling Abell.
Brooks almost had a second wicket with the total on 36, just failing to hold a low caught and bowled chance, offered by George Hill on 12.
Hill didn’t profit for long, advancing to Leach in only his second over and miscuing a running catch to Matt Renshaw at mid-off to make it 55 for two.
Kohler-Cadmore had already hit Leach for a straight six and repeated the dose as he and Brook built a half-century stand, off 92 balls.
Tall seamer Aldridge produced a tight six-over spell from the Marcus Trescothick Pavilion End. But Brook pulled his replacement, de Lange, over the short leg side boundary as the South African went for 23 from three overs.
Leach switched to the same end, only to be dispatched for another six by Kohler-Cadmore. The Yorkshire pair looked in complete control when Brook clipped Brooks off his toes to mid-wicket where Aldridge took a diving catch.
The next ball saw Matthew Revis fall lbw on the back foot and suddenly Yorkshire were 129 for 4, with Brooks rampant.
Kohler-Cadmore went to fifty off 86 balls, with four fours and four sixes, showing a relish for his future environment. But when bad light ended play two overs early, he faced more important work in the morning.