Analysis of model output at 1-min temporal resolution revealed the development of a
mountain wave and downslope flow, followed by the appearance of a rotor beginning at 0923 UTC.
During the piteraqs, the
mountain wave becomes so steep that it breaks, like a big wave of water that collapses and crashes onto the shore.
After analyzing the D03 output of WRF, we concluded that the severe icing of the C-212-200 aircraft was caused by
mountain waves. The aircraft first crossed the second (southernmost)
mountain wave, experiencing light to moderate icing since the updraft there was less intense, and there was less LWC.
10, cyclonic flow associated with a low pressure system produces easterly winds at the surface over southern Greenland, generating a vertically propagating large-amplitude
mountain wave, and a subsequent breakdown at the critical level at which there is a reversal of the background with height, from easterly to westerly.
Pilots need to be aware that
mountain wave turbulence produces the most violent type of turbulence outside of thunderstorms.
The FAA's FAASTeam, quoting the Colorado Pilot's Association--who should know--offers these tips for dealing with
mountain waves:
Furthermore, because real-time forecasts suggested conditions favorable for strong
mountain wave generation and deep upward propagation, an enhanced number of launches were performed.
In winter and early spring with strong westerly winds,
mountain waves are an issue at 8000 and sometimes even 10,000 ft.
We covered
mountain wave turbulence in December, 2012, so here we'll just cover the basics.
None of the weather information obtained specifically mentioned the possibility of
mountain wave activity over the mountainous terrain.
The crash was ultimately linked to rudder design defects, but the final NTSB report contained many pages describing the high winds and
mountain wave conditions that day, requiring the large control inputs needed to manage the flight path.
The model supported light-to-moderate clear air turbulence from 6400 feet msl through 8000 feet, and
mountain wave development from 10,000 to 12,000 feet msl.
