Automated surface observation system (ASOS) erroneous WX reporting. Equipment problem.

Attributes
ACN	226504
Time
Date	199211
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ama
State Reference	TX
Environment
Light	Daylight
Person 1
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
ASRS Report	226504
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
ASRS Report	226551
Events
Anomaly	other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Air Traffic Incident	other
Situations
Airport	other physical facility

Narrative:

On nov/xx/92 there was drizzle in the amarillo area and the ASOS was unable to decide whether it was rain or snow and substituted the letter 'P', for precipitation, on the observation. We had to put precipitation on the ATIS and when pilots asked us what type, we were unable to answer. Officially we had precipitation at the airport, we didn't know what type. Supplemental information from acn 226551: it was counted during 1 hour that the ASOS reported 9 different observations. Many were ceiling changes from broken to scattered and back when there was no apparent change in WX and the others were for visibility. It wants to disagree between what the tower says is visibility and what it is reporting. It is wholly unreasonable to ask a controller to put on 9 ATIS's in 1 hour and still keep up with safe traffic flow. Supplemental information from acn 226558: ASOS reported measured ceiling 300 variable, but on the cvd, which is what the controller uses, it did not tell you what it was variable from.

Original NASA ASRS Text

Title: AUTOMATED SURFACE OBSERVATION SYS (ASOS) ERRONEOUS WX RPTING. EQUIP PROB.

Narrative: ON NOV/XX/92 THERE WAS DRIZZLE IN THE AMARILLO AREA AND THE ASOS WAS UNABLE TO DECIDE WHETHER IT WAS RAIN OR SNOW AND SUBSTITUTED THE LETTER 'P', FOR PRECIPITATION, ON THE OBSERVATION. WE HAD TO PUT PRECIPITATION ON THE ATIS AND WHEN PLTS ASKED US WHAT TYPE, WE WERE UNABLE TO ANSWER. OFFICIALLY WE HAD PRECIPITATION AT THE ARPT, WE DIDN'T KNOW WHAT TYPE. SUPPLEMENTAL INFO FROM ACN 226551: IT WAS COUNTED DURING 1 HR THAT THE ASOS RPTED 9 DIFFERENT OBSERVATIONS. MANY WERE CEILING CHANGES FROM BROKEN TO SCATTERED AND BACK WHEN THERE WAS NO APPARENT CHANGE IN WX AND THE OTHERS WERE FOR VISIBILITY. IT WANTS TO DISAGREE BTWN WHAT THE TWR SAYS IS VISIBILITY AND WHAT IT IS RPTING. IT IS WHOLLY UNREASONABLE TO ASK A CTLR TO PUT ON 9 ATIS'S IN 1 HR AND STILL KEEP UP WITH SAFE TFC FLOW. SUPPLEMENTAL INFO FROM ACN 226558: ASOS RPTED MEASURED CEILING 300 VARIABLE, BUT ON THE CVD, WHICH IS WHAT THE CTLR USES, IT DID NOT TELL YOU WHAT IT WAS VARIABLE FROM.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.