Tiling curves

Hi,

Plumber recently fitted a basin for me. Unfortuantely the top surface of the basin has a slight curve rather than a straight edge. this means I can't just start the tiling directly above and drop a silcone bead on it as I have done in the past on other basins. I know the better way maybe to simply unscrew the basin from wall put some tiles up and then place the basin back over them but... I was wondering whther there are anyway I could use a tool to cut a curve in the tiles. I can work out the line of the curve by simply loosing the basin from the wall and tracing the curve onto a piece of paper

any ideas

there are tools out there. you can use tile nippers to cut the shape in the tile or a wet cutter.the tile nippers are the cheaper option to buy though