General Information

Amplitudes of 1-15 hPa/MB and Wavelengths of 50-500 KM (Uccellini and Koch, 1987) Periods of 1-4 HR

Most likely energy source mechanisms are latent heat release in deep convection and shear instability in which waves can extract energy from the Jet Stream when vertical wind shear is sufficiently strong to reduce the Richardson number below 0.25. Alternatively wave energy loss can be prevented by an efficient wave duct, which appears to be the most prevalent of the three mechanisms described. 

Strongest upward motions with Gravity Waves occur just following the surface pressure trough and lead to maximum precipitation rates just ahead of the ridge.

Gravity waves typically form within or near the back edge of a precipitation shield.

Recent studies indicate that Gravity Waves may occur as frequently as 34% of the time in the Central US during the Winter months.

Current poor understanding of gravity waves and acknowledged skepticism of their existence stems from the fact that it is both difficult and tedious to conduct a study of even a single event. In addition forecasters have often been mislead by the existence of large scale gravity waves in 2 noteworthy events.

 This is changing due to an increase in the spatial and temporal resolution of meteorological data Barnes et al 1996 has shown that the 29 KM Meso-Eta produces coherent gravity waves with wavelengths under 300 KM and that these waves can dominate the QG field.