A catheter carries a position sensor in a distal, on-axis position in an irrigated ablation tip electrode. The tip electrode has a shell wall that defines a cavity through which fluid flows and exits via fluid ports formed in the shell wall. The cavity is sealed by an internal member extends into the cavity with a baffle portion and a distal portion. The distal portion safely houses the position sensor and the baffle portion diffuses and disperses fluid entering the tip electrode for a more uniform flow through the cavity. The distal portion is configured to provide an annular region that runs along the length of the tip electrode to better feed fluid to the more distal fluid ports on the tip electrode for more uniform cooling at all locations on the tip electrode.