An investigation of a commercial aircraft encounter with severe clear-air turbulence over western Greenland

The environmental flow was dominated by an extratropical cyclone to the southeast of the Greenland tip, resulting in easterly flow at all levels. The results of the analyses indicate that the CAT encounter was related to mountain-wave breaking on the western lee (downslope) of the Greenland plateau.

The simulations were not of especially high resolution (5-km horizontal grid spacing) by today's standards, yet the simulation results do produce large-amplitude lee waves and overturning in good agreement with the encounter location as indicated by the DFDR. The success of this and other simulations in reproducing mountain-wave turbulence (MWT) events suggests that operational implementation of high-resolution nonhydrostatic simulation models, possibly an ensemble of models, over MWT-prone areas could produce more reliable forecasts of MWT than are currently available using gravity-wave-drag or MWT-postprocessing algorithms derived from global weather prediction models of relatively coarse scale.