Celtic, playing in front of a full house at Celtic Park for the first time since March 2020, held a healthy lead from the first leg and had little trouble seeing the job through.
Scotland international Turnbull opened the scoring in Glasgow with 25 minutes played and doubled his tally 10 minutes into the second period with a fine finish.
James Forrest tapped in a third to make it 3-0 on the day to Celtic, who will now face AZ over two legs for a place in the group stage of the competition.
Ange Postecoglou's side was on top from the off and thought they had taken the lead inside 14 minutes, only for Kyogo Furuhashi to be flagged for a marginal offside call.
The home side's pressure told soon after when Greg Taylor played in Turnbull and the midfielder poked the ball past Jan Hanus with the outside of his boot.
Despite a drop off in tempo, Celtic remained in complete control and went further in front thanks to Turnbull's shot from outside the box that Hanus could not get down to.
Joe Hart twice made saves as Jablonec finally gave the home keeper something to do, but the final goal of the one-sided tie went Celtic's way.
Forrest was on hand to slide in and convert after Odsonne Edouard, brought on as a second-half substitute for the third game running, had a shot well saved.