Clear-air turbulence nowcasting and forecasting using in-situ turbulence measurements

The Graphical Turbulence Guidance (GTG) system for clear-air turbulence (CAT) nowcasting and forecasting, developed by the Research Applications Lab at the National Center for Atmospheric Research Research (NCAR/RAL) and the Forecast Systems Laboratory at the National Oceanic and Atmospheric Administration (NOAA/FSL) under sponsorship from the Federal Aviation Administration's Aviation Weather Research Program (AWRP), is currently in operational use at the Aviation Weather Center. The operational version of GTG uses output from numerical weather prediction model forecasts to derive a number of turbulence diagnostics. The diagnostics are combined as a weighted sum with the weights determined by diagnostics' agreements with the most recent available turbulence observations, pilot reports (PIREPs). Until recently, PIREPs were the only available turbulence observations; now, in-situ turbulence measurements of the eddy dissipation rate (EDR) are taken every minute in flight from some United Airlines aircraft, with other airlines slated to follow. The Turbulence Product Development Team at NCAR/RAL is developing a new version of GTG that uses this in-situ data along with PIREPs as the turbulence observation data sources. Initial results demonstrating GTG forecast skill improvements with the inclusion of in-situ data are presented.