A Case Study of a Large-amplitude Mesoscale Inertia–Gravity Wave over the Southeast US

Previous research has shown that the passage of large-amplitude mesoscale inertia–gravity waves (IGWs) can exert significant impacts on sensible weather and be associated with severe turbulence. Examples of sensible weather effects associated with IGW passages include the abrupt cessation of precipitation, large variations in sea level pressure (SLP), and significant wind shifts accompanied by damaging wind gusts, the latter of which can pose a major threat to aviation. The purpose of this analysis is to provide an overview of the environment that favors large-amplitude IGW genesis, organization, and maintenance, and show the results of an analysis of a large-amplitude IGW event that occurred on 7 March 2008 over the inland Southeast US. Surface observations, operational Doppler radar data, and satellite imagery all displayed the signatures of large-amplitude IGW activity in the Southeast on 7 March 2008. IGW passage was accompanied by maximum crest-to-trough surface pressure falls of 10 hPa (30 min)-1, vector wind shift of 20 m s-1, a sharp back edge to the precipitation shield in radar imagery, and cloud desiccation in satellite imagery. The observed IGW activity appeared to originate in northeastern Mexico near the Rio Grande Valley in association with appreciable upper-level geostrophic imbalance, ample mountain wave activity, and low-level frontogenesis. As the IGW amplified and propagated northeastward at an estimated 26 m s-1, the wave front developed a sawtooth pattern, possibly indicative of spatially variable ducting ability, and peaked in amplitude over parts of Mississippi, Alabama, and Tennessee. Though IGW genesis evidently occurred devoid of convection, greatest amplification occurred at the onset of interaction between the IGW and a broad region of elevated convective and stratiform precipitation, and on the cold side of a surface front that provided a low-level stable layer, which was further enhanced by low-level melting and evaporation.