B737 Undifferentiated or Other Model
Air Traffic Control Fully Certified
Other / Unknown
ATC Issue All Types; Conflict Ground Conflict; Less Severe
Air Traffic Control Issued New Clearance
ATC Equipment / Nav Facility / Buildings; Procedure
I was working Local Controland had circling approaches to Runway's 22.  Aircraft X was issued line-up-and-wait. Previous departure delayed take off roll.  Aircraft X then delayed entry onto Runway 22L and was told to expect an immediate take off clearance.  Aircraft X was issued an immediate take off clearance.  Aircraft X delayed take off roll.  Aircraft Y turned tight base to final.  ASDE Alert went off while Aircraft Y was on still on base.  Aircraft Y was issued go around.  Recommendation; ASDE determined go-around while Aircraft Y was on base and not on final.
MDW Controller described a mandatory ASDE Alert go around; the reporter noting the alarm activated when the subject traffic was still on base and the departure was rolling.