Narrative:

We were to depart reno at maximum allowable weight and discovered a substantial temperature difference between our company generated weight and balance temperature and the reported temperature at the airport. Apparently the national meteorological service temperature can be several (8 degrees in this case) degrees off the airport temperature. In high altitude, high temperature airports, this difference can easily cause aircraft to be operating outside maximum performance parameters. This difference in WX information sources may be quite common and should be investigated. Callback conversation with reporter revealed the following information: the ATIS temperature at rno is obtained from the national WX bureau service (nwbs) which is derived from the report from the local WX bureau. That office is a 'considerable' distance from the airport and is not realistic. Reporter's main complaint was the unexpected difference between the tower temperature and the ATIS temperature. The ATIS temperature was used for planning purposes. The tower temperature 'depicting realism' and being different, altered their final planning for takeoff data inputs and differed by a considerable amount. The A-320's power to weight ratio is more temperature critical, with the abort procedures being more affected by these variable temperatures than other aircraft. Reporter's company and alpa were advised of this situation. Reporter questions the number of stations in the country that have WX bureau reporting stations located away from the 'real' environment of the airport as in rno.

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Original NASA ASRS Text

Title: 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.

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.