A319
Air Traffic Control Fully Certified
ATC Issue All Types
Air Traffic Control Issued New Clearance
Staffing; Human Factors
While working LC3/4 combined at LC4; I had two CRJ's land Runway XXR and exit at Taxiway XX. An A319 then landed Runway XXR and was rolling out towards the second high speed exit; Taxiway XY. I informed the A319 that company traffic was on short final. I then attempted to stop the second CRJ short of Taxiway DY so that the A319 could exit the runway unimpeded. While talking to the CRJ; I realized that the A319 was not going to be off the runway in time and sent the A320 around. At the time I sent the A320 around; the aircraft was crossing the runway threshold. I then gave the A320 runway heading; a climb to 9 thousand; and handed him off the appropriate departure sector. In the future; I will give priority to the possible go-around situations and initiate the missed approach much sooner (before the landing threshold; when it is obvious that the operation will not work). It is also critical to 'paint a picture for each aircraft involved.' Advising the preceding aircraft to plan the first high speed exit and minimal time on the runway for traffic close in trail; and ensuring that the trail aircraft knows of the distance between the preceding aircraft and any speed overtakes.
Two sick leave hits for staffing; leaving only 7 CPCs for the shift. Normal would be 10; and won't approve leave below this. However; in the event of sick leave; OT will not be called and supervisors who are not proficient during normal traffic are forced to work. This was the case here. A Supervisor working due to staffing; no OT was attempted. Due to lack of proficiency; an A320 was sent around very late after crossing landing threshold with another aircraft on the runway. This was during normal arrival rush. If 10 is what we need for staffing; we should be calling fully proficient OT CPC's to replace them; and not try to save the budget by staffing with supervisors who do not work busy traffic.
Tower Controller described a very late go-around instruction noting his/her lack of timely instructions.