Spatial Patterns of Turbulence Near Thunderstorms

Severe turbulence encounters can result in serious injuries and millions of dollars of operational costs to airlines. While storms themselves are highly turbulent, they can also modify their environment in ways that lead to turbulence far from the storm. Using relatively limited datasets, past studies have indicated that severe turbulence can extend beyond the current federal guidelines for avoidance (20 mi/~32 km), but many questions remain. For example, 1) What is the spatial distribution of convection induced turbulence relative to individual storms? 2) What factors influence the spatial distribution of CIT? Now, extensive archives of operational radar data and automated eddy dissipation rate (EDR) reports from commercial aircraft present an opportunity for detailed analysis. To address the above questions, we objectively identify thunderstorms in the GridRad hourly archive and compare them to automated turbulence reports over a period of 9 years (2009-2017). We find that 32 km from 10-dBZ echoes at flight altitude, the risk of MoG turbulence is nearly 5 times the background occurrence, and that elevated risk extends beyond 100 km. At 2 km above echo tops, the risk of MoG turbulence exceeds 20 times the background risk. This decreases exponentially but remains elevated at all separation distances. Risks increase with storm intensity. Finally, when we use ERA5 reanalysis to assess environmental factors, we find increased risk with stronger mean wind and wind shear, with slightly higher risk downstream and to the left of the wind/shear vector. Preliminary results exploring sensitivity to season, region, and storm characteristics may also be shared.