Using the Advanced Research Version of the Weather Research and Forecasting Model (WRF-ARW) to Forecast Turbulence at Small Scales

Abstract : The U.S. Army Research Laboratory (ARL) has an interest in high spatial and temporal resolution weather output with an emphasis on products that assist warfighter decision aids and applications in battlefield environments. This model study was done in support of the short-range Army tactical analysis/nowcasting system called the Weather Running Estimate-Nowcast (WRE-N) as well as for longer-range forecasting support. The model utilized to investigate fine-scale weather processes, the Advanced Research version of the Weather Research and Forecasting model (WRF-ARW), was run with a triple nest of 18-, 6-, and 2-km grids over a 24-h period. One of the long-term intriguing model areas of study is clear-air turbulence due to the effects of turbulence on Army Aviation aircraft and onboard sensors. This study investigates the WRF-ARW output over northeastern New Jersey during the winter season of 2006-2007. Using a combination of the Panofsky Index (PI) in the boundary layer and the Turbulence Index (TI) above the boundary layer, a small sample of 75 pilots reports was compared to "YES/NO" turbulence forecasts over the 24-h forecast period. Results were very encouraging using both the 18- and 2-km output, with a possibility of detection over 0.70, although the testing was biased to days with a high probability of turbulence.