Using METAR Weather Reports of Wind and Gust Observations to Infer Near Surface Atmospheric Turbulence in the Graphical Turbulence Guidance Nowcast (GTGN)

The Graphical Turbulence Guidance Nowcast (GTGN) product aims to provide a gridded picture of the current turbulent conditions over the Continental US by seamlessly combining short-term turbulence forecasts with currently available turbulence observations updated at 15 minute intervals. The observations used consist primarily of turbulence pilot reports (PIREPs) and in situ reports of Eddy Dissipation Rate (EDR). PIREPs provide general aircraft position information and a pilots' assessment of the level of turbulence intensity they experience flying a specific airframe, classified into 9 severity categories ranging from null to extreme. In situ EDR reports are more routine turbulence measurements that estimate the atmospheric quantity EDR during every minute of flight. These EDR values are then reported along with aircraft position information from the aircraft's avionics system. These observations of turbulence however, especially at near surface altitudes, are sparse and generally only located around airports. In order to supplement the PIREP and EDR data at low levels, a study was conducted to compare low level wind and gust information from METAR weather reports to nearby in situ EDR and PIREP turbulence intensity. As expected, this analysis showed a correlation between increased winds and elevated turbulence. This paper will describe the analysis as well as the results and discuss how this information is used in GTGN.