A wintertime gulf coast squall line observed by EDOP airborne Doppler radar

An extensive wintertime squall line on 13 January 1995 occurring along the U.S. Gulf of Mexico coastline is examined using airborne radar observations combined with conventional data analysis. Flight tracks with the ER-2 Dopp ler radar (EDOP) mounted on the high-altitude (20 km) ER-2 aircraft provide d a unique view of the vertical structure of this line. In this paper, the authors document the squall line structure, and compare and contrast this s tructure with Ether published cases. The squall line had several prominent features that differ from previous st udies: 1) the stratiform region was wide in comparison to more typical syst ems that are 50-100 km wide; 2) the trailing stratiform region consisted of two to three separate embedded trailing bands rather than one continuous b and; 3) vertical motions in the trailing stratiform region were nearly twic e as strong as previously reported values, with mean values approaching 1 m s(-1) between 7- and 9-km altitude, and larger values (1.5 m s(-1)) in the embedded bands; 4) reflectivities were large with mean stratiform values o f about 38 dBZ, and maximum convective values of about 55 dBZ; 5) the squal l line rear inflow descended to the surface well behind the leading edge (s imilar to 200 km); 6) the convective and squall line inflow region exhibite d unique microphysics with small graupel or hail falling out of the tilted squall line updraft, and a wavy, elevated melting region associated with th e inflow; and 7) the squall-scale transverse circulation was directly coupl ed with a jet streak thermally direct circulation, and the ascending branch of this direct circulation may have enhanced production of widespread stra tiform rainfall. A conceptual model is presented highlighting the features of this squall line and the coupling of the squall line to the larger-scale flow.