Conditioning of the inflow environment by organized convection: An investigation based on BAMEX data

Numerical simulations of squall lines have shown that the near-field inflow environment is more favorable for the propagation of convection, both continuous and discrete, then the far-field environment. Theoretical, simple models and idealized models have provided an explanation and a mechanism, showing the importance of gravity waves generated in response to persistent heating and cooling in the squall line in environmental conditioning. In model storms, the near-field is often seen to possess a tongue of air that is cooler and more moist than in the far-field. This moist tongue conditions the inflow environment for convection by bringing air closer to saturation and destabilizing it and is a consequence of long period convection-associated gravity wave activity. Due to the difficulty of finding wave signals in data with poor spatial or temporal coverage, however, verification of this mechanism in observations has proven somewhat elusive.  

The BAMEX project has provided relatively concentrated data coverage of the inflow environment. Observational data (especially dropsondes) from the BAMEX project are used to investigate the signal of environmental conditioning ahead of squall lines.  The cool and moist tongue signature, manifested by higher midtropospheric humidity closer to the line than farther away, is detected at various distances ahead of the main squall line. Modeling studies have shown that in addition to the moist tongue, trapping of higher frequency waves is also important for convective propagation. The feasibility of observing these higher frequency waves will be discussed.