ATL LCL CTLR EXPRESSED CONCERN REGARDING LACK OF SUBSEQUENT AURAL ALARM ON LLWAS EQUIP AFTER INITIAL WINDSHEAR NOTIFICATION.

Narrative

ACR X ACFT CHKED ON FREQ AT THE OM (5 MI FINAL) FOR RWY 27L (ARR RWY) AT ATL. LLWAS ALERT AURAL ALARM SOUNDED AND I INFORMED THE PLT OF RWY 28 WINDSHEAR ALERT; 20 KT LOSS; 1 MI DEP. ACFT CONTINUED APCH. ABOUT 2 MI FINAL; I NOTICED THAT LLWAS DISPLAY WAS NOW SHOWING RWY 28 MICROBURST ALERT; 48 KT LOSS; 1 MI DEP; HOWEVER; THERE WAS NO AURAL ALARM ASSOCIATED WITH THE UPDATE OF THE LLWAS DISPLAY. PLT WAS ADVISED OF MICROBURST ACTIVITY AND ACFT LANDED NORMALLY. FOR YRS WE HAVE COMPLAINED ABOUT LLWAS NOT PRODUCING A SUBSEQUENT AURAL ALARM WHEN CONDITIONS DETERIORATE FROM THE INITIAL ALARM. IF I HAD NOT VISUALLY NOTICED THE MICROBURST ALERT AND THE ACFT HAD EXECUTED A MISSED APCH; THEY WOULD HAVE UNKNOWINGLY FLOWN DIRECTLY INTO THE PATH OF THE MICROBURST ACTIVITY. THE LCL CTLR FOR RWY 27R (DEP RWY) WAS UNAWARE OF THE MICROBURST ALERT UNTIL I POINTED IT OUT. HE TOOK EVASIVE ACTION AND VECTORED A ROTATING ACR Y AWAY FROM THE MICROBURST. THE LLWAS AURAL ALARM PARAMETERS MUST BE ADJUSTED SO CTLRS ARE ALERTED TO CHANGES IN WINDSHEAR CONDITIONS.