The rear inflow current is a ubiquitous feature of squall line storms. The descent of this current as it approaches the convective region from behind brings strong, possibly damaging winds to the surface. The origin and/or organizational role of this airflow feature has been examined from somewhat different viewpoints in Weisman (1992, 1993) and Pandya and Durran (1996), for example. The former extended Rotunno et al.?s (1988) theory to incorporate the current?s vorticity contribution while the latter study interpreted rear inflow formation as a response to convective heating patterns.

This study revisits the mechanisms for rear inflow generation, with the intent of unifying the two viewpoints referenced above. A traditional cloud-resolving model and also a simplified convection model, along with its adjoint, are used to elucidate the factors which control where, when and why the rear inflow descends. The direct and indirect impact of the rear inflow on the strength of the overall storm circulation will be demonstrated. The strength of the resulting surface winds will also be addressed.

References: Pandya , R. E., and D. R. Durran , 1996: The influence of convectively generated thermal forcing on the mesoscale circulation around squall lines. J. Atmos. Sci., 53, 2924-2951.

Rotunno, R., J. B. Klemp, and M. L. Weisman, 1988: A theory for strong, long-lived squall lines. J. Atmos. Sci., 45, 463-485.

Weisman, M.L., 1992 :The role of convectively generated rear-inflow jets in the evolution of long-lived mesoconvective systems. J. Atmos. Sci ., 49, 1826-1847.

Weisman, M.L., 1993 :The genesis of severe, long-lived bow echoes. J. Atmos. Sci ., 50, 645-670