No. The planks will move too much between seasons. A plank floor requires a minimum of 1/2" plywood on top of it, then either a membrane (thinner) or cbu (1/4" is fine), then the tile. The only other alternative is to remove the planks and put down a layer of 3/4" ply. Also, check the overall deflection of the joists to see if they are strong enough for a tile install. A good place to do that is at www.johnbridge.com. Use the "Deflecto" tool in the blue bar of the forum.