RPTR STATES THE ASOS IS UNRELIABLE. CTLR HAD TO AUGMENT WX RPTS WITH VISIBILITY CHANGES AND TSTM ACTIVITY. RPTR CLAIMS ASOS GENERATED SPECIAL OBSERVATIONS WITH NON- REPRESENTATIVE WX ELEMENTS.

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ASOS EQUIP CONTINUES TO PROVE UNRELIABLE. ON JUN/MON/96 AT XA50 LCL AT COS ATCT WX DETERIORATED WITH TYPICAL CONVECTIVE ACTIVITY. TSTMS WERE OBSERVED AND MANUALLY ENTERED INTO ASOS SINCE THE SYS CANNOT DETECT THIS GREATEST HAZARD TO AVIATION SAFETY. AT XA47 LCL ASOS XMITTED A SPECIAL OBSERVATION SHOWING VISIBILITY 1 1/2 TR+. ACTUAL VISIBILITY WAS MUCH HIGHER SO THE SYS WAS AUGMENTED TO SHOW 5 MI. THE XA55 LCL WX OBSERVATION WAS XMITTED WITH A VISIBILITY OF 5 MI BUT AT XA57 LCL ASOS GENERATED AND XMITTED ANOTHER SPECIAL WITH VISIBILITY 2TR. THIS OCCURRED WHILE THE CTLR WAS ATTEMPTING TO MAKE A NEW ATIS BROADCAST; CTL TFC AND ENSURE THAT PLTS RECEIVED CURRENT WX INFO. ASOS VISIBILITY WAS AGAIN AUGMENTED TO 5 MI AND A SPECIAL OBSERVATION WAS XMITTED AT XB01 LCL SHOWING VISIBILITY AT 5 MI. FOR THE NEXT 45 MINS ASOS CONTINUED TO GENERATE SPECIAL OBSERVATIONS WITH NON-REPRESENTATIVE WX ELEMENTS CAUSING DISTR AND INCREASED WORKLOAD FOR THE TWR CTLRS. WHEN CONVECTIVE WX IS PRESENT IT IS DIFFICULT ENOUGH TO PROVIDE ATC SVCS AND WX INFO TO THE USERS WITHOUT THE ADDED DISTRS OF MAKING CORRECTIONS TO A SYS THAT CANNOT DO WHAT IT WAS SUPPOSEDLY DESIGNED TO DO. ASOS IN NO WAY ELIMINATES THE NEED FOR TRAINED WX OBSERVERS. PROBS WITH ASOS ARE FREQUENT AND CONTINUING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THE ASOS IS BASICALLY DOING WHAT IT IS DESIGNED TO DO. RPTR INDICATED THAT WHEN ANY OF THE ASOS SENSOR VALUES ARE OVERRIDDEN; THE PARTICULAR SENSOR REVERTS TO MANUAL OPS UNTIL THE NEXT SCHEDULED ASOS WX OBSERVATION. RPTR INDICATED THAT IF THERE IS AN INACCURATE READING OF ONE OF THE ELEMENTS; IT IS AT THIS TIME THE CTLR WILL AUGMENT THE RPT AND OVERRIDE THE SPECIFIC ELEMENT(S). RPTR STATED THE ASOS SYS CANNOT DETECT TYPES OF CLOUD ACTIVITY WHICH THEN HAS TO BE INPUT INTO THE SYS BY THE CTLR. THE RPTR SAID THAT IT IS THE RESPONSIBILITY OF THE FD/CD POS TO HANDLE THE ASOS CHANGES BUT IF THE POS GETS BUSY; THE OTHER CTLRS WILL MAKE THE WX CHANGES. RPTR IMPLIED THAT THE SOFTWARE FOR THE VISIBILITY ELEMENT SHOULD BE CHANGED IN ORDER TO PROVIDE MORE ACCURATE READINGS. RPTR STATED THE WORKLOAD/DISTR OF THE ASOS VARIES WITH THE WX AND THE TIME OF DAY/TFC VOLUME.