Frontal focusing of a flooding rainstorm

A heavy rainstorm over Kentucky, producing extensive flooding, was concentr ated in a narrow band oriented nearly zonally just south of the Ohio River. Analysis of routine surface observations showed that an intense quasi-stat ionary surface front formed during the 24-h period of heaviest rainfall. Th is front was parallel to the rainband and was some distance to the south of it. Horizontal temperature gradients reached more than 20 degreesF over 11 0 km. Analysis of sea level pressure showed that geostrophic deformation wa s present in a small region ahead of each of two small centers of low press ure that migrated eastward along the front. Vertical cross sections normal to the front showed that conditional upright and symmetric stabilities were small or negative in the frontal updraft. It was inferred from this that t he frontal updraft was unusually intense and narrow, qualitatively consiste nt with the intensity of the rainband.