Investigating Cyclogenesis and the Genesis of Large Amplitude Mesoscale Gravity Waves

Understanding the multiscale interactions between the extra tropical cyclones (ETC) and mesoscale scale gravity waves (MGW) is not only intriguing but also requires in-depth investigation as it can impact the operational forecast of precipitation and high winds. Forecasters often do not have sufficient information to accurately forecast the MGW modes in real time. The compelling problem arises since synoptic patterns and precursors associated with rapid ETC genesis are similar with or without the MGW modes. While previous studies have provided insights as to how convection is modified by MGWs, studies documenting the processes through which convection modifies MGWs pinpointing the MGW generation and amplification mechanisms, are limited owing to the 1) lack of relevant observations, and the 2) complexity of the nonlinear processes. Consequently, the problem of MGW emission and maintenance during rapid ETC genesis has not been unambiguously solved. Its broader implications are significant because the MGWs can favor the initiation or possibly be maintained synergistically with the existing meso--scale convection. Therefore, sensible weather impacts are substantial as large amplitude MGWs can produce strong winds, heavy precipitation, and mesoscale weather variability which confounds both operational forecasters and numerical modelers. The present study attempts to fill this gap by performing a detailed analysis employing meso-γ scale resolution within a numerical simulation integrated over the 16-hour lifetime of the well-observed gravity-wave event of 7 March 2008. This event featuring two large amplitude MGWs impacted the sensible weather over a region in excess of 1500 km including the Southern Plains, Gulf of Mexico Coast, and Mississippi River Valley of the United States (Ruppert and Bosart 2008). Using the diagnostic methods of the flow imbalance, including cross-stream Lagrangian Rossby number, the residual in the nonlinear balance equation, and the Ertel PV equation-derived unbalanced geopotential-height field we aim to understand the genesis, amplification, and maintenance of MGWs of depression and elevation and determine if and how convection, enhanced the surface pressure falls (rises) when MGW are generated.