RPT ON WX FACTORS; IE; OBTAINING CORRECT ARPT TEMP FOR ACFT PERFORMANCE TKOF CHARTS.

Narrative

WE WERE TO DEPART RENO AT MAX ALLOWABLE WT AND DISCOVERED A SUBSTANTIAL TEMP DIFFERENCE BTWN OUR COMPANY GENERATED WT AND BAL TEMP AND THE RPTED TEMP AT THE ARPT. APPARENTLY THE NATIONAL METEOROLOGICAL SVC TEMP CAN BE SEVERAL (8 DEGS IN THIS CASE) DEGS OFF THE ARPT TEMP. IN HIGH ALT; HIGH TEMP ARPTS; THIS DIFFERENCE CAN EASILY CAUSE ACFT TO BE OPERATING OUTSIDE MAX PERFORMANCE PARAMETERS. THIS DIFFERENCE IN WX INFO SOURCES MAY BE QUITE COMMON AND SHOULD BE INVESTIGATED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE ATIS TEMP AT RNO IS OBTAINED FROM THE NATIONAL WX BUREAU SVC (NWBS) WHICH IS DERIVED FROM THE RPT FROM THE LCL WX BUREAU. THAT OFFICE IS A 'CONSIDERABLE' DISTANCE FROM THE ARPT AND IS NOT REALISTIC. RPTR'S MAIN COMPLAINT WAS THE UNEXPECTED DIFFERENCE BTWN THE TWR TEMP AND THE ATIS TEMP. THE ATIS TEMP WAS USED FOR PLANNING PURPOSES. THE TWR TEMP 'DEPICTING REALISM' AND BEING DIFFERENT; ALTERED THEIR FINAL PLANNING FOR TKOF DATA INPUTS AND DIFFERED BY A CONSIDERABLE AMOUNT. THE A-320'S PWR TO WT RATIO IS MORE TEMP CRITICAL; WITH THE ABORT PROCS BEING MORE AFFECTED BY THESE VARIABLE TEMPS THAN OTHER ACFT. RPTR'S COMPANY AND ALPA WERE ADVISED OF THIS SIT. RPTR QUESTIONS THE NUMBER OF STATIONS IN THE COUNTRY THAT HAVE WX BUREAU RPTING STATIONS LOCATED AWAY FROM THE 'REAL' ENVIRONMENT OF THE ARPT AS IN RNO.