Narrative:

ASOS installed at the fsm airport and commissioned on aug/mon/94. On aug/wed/94 ASOS reporting visibility as 2 1/2 mi, but tower visibility 4 mi. According to regulations when visibility is 4 mi or less, tower visibility is the official visibility for the airport. With the ASOS reporting visibility (different from tower visibility) it automatically reports the ASOS visibility and that becomes official which is contrary to the regulations. In this case, ASOS visibility made the class D surface area IFR when in actuality it was VFR. By making the class D surface area IFR flying is restr. No provision was made in the ASOS system to report tower visibility other than in remarks or if the tower visibility is less. Since tower visibility is the official visibility for the airport when the visibility is 4 mi or less, the process of reporting and disseminating the visibility through the ASOS needs to be changed. Callback conversation with reporter revealed the following information: tower supervisor said generally the ASOS works good. During rapidly changing WX conditions, it will not update itself fast enough. Incorrect visibility is being reported. NWS personnel will not augment the system and make the update.

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Original NASA ASRS Text

Title: WX RPTING EQUIP PROB AUTOMATED SURFACE OBSERVATION SYS UNABLE TO UPDATE CORRECT WX DURING RAPIDLY CHANGING WX CONDITIONS.

Narrative: ASOS INSTALLED AT THE FSM ARPT AND COMMISSIONED ON AUG/MON/94. ON AUG/WED/94 ASOS RPTING VISIBILITY AS 2 1/2 MI, BUT TWR VISIBILITY 4 MI. ACCORDING TO REGS WHEN VISIBILITY IS 4 MI OR LESS, TWR VISIBILITY IS THE OFFICIAL VISIBILITY FOR THE ARPT. WITH THE ASOS RPTING VISIBILITY (DIFFERENT FROM TWR VISIBILITY) IT AUTOMATICALLY RPTS THE ASOS VISIBILITY AND THAT BECOMES OFFICIAL WHICH IS CONTRARY TO THE REGS. IN THIS CASE, ASOS VISIBILITY MADE THE CLASS D SURFACE AREA IFR WHEN IN ACTUALITY IT WAS VFR. BY MAKING THE CLASS D SURFACE AREA IFR FLYING IS RESTR. NO PROVISION WAS MADE IN THE ASOS SYS TO RPT TWR VISIBILITY OTHER THAN IN REMARKS OR IF THE TWR VISIBILITY IS LESS. SINCE TWR VISIBILITY IS THE OFFICIAL VISIBILITY FOR THE ARPT WHEN THE VISIBILITY IS 4 MI OR LESS, THE PROCESS OF RPTING AND DISSEMINATING THE VISIBILITY THROUGH THE ASOS NEEDS TO BE CHANGED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: TWR SUPVR SAID GENERALLY THE ASOS WORKS GOOD. DURING RAPIDLY CHANGING WX CONDITIONS, IT WILL NOT UPDATE ITSELF FAST ENOUGH. INCORRECT VISIBILITY IS BEING RPTED. NWS PERSONNEL WILL NOT AUGMENT THE SYS AND MAKE THE UPDATE.

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.