OBSERVATIONS OF THE FINESCALE STRUCTURE OF A DRYLINE DURING VORTEX-95

The three-dimensional finescale structure of a dryline observed over t he Texas panhandle during the Verification of the Origins in Tornadoes Experiment (VORTEX) on 6 May 1995 is presented. High-resolution obser vations documenting dryline evolution were collected from midafternoon while it moved slowly eastward until late afternoon as it retrogresse d back to the west. Dryline variability in the horizontal along-line d irection was revealed by airborne Doppler radar observations from the National Center for Atmospheric Research Electra Doppler radar and gro und-based measurements from the nearby WSR-88D at Amarillo, Texas. Thi s variability was created as the dryline interacted with horizontal co nvective roils forming west of the dryline. The rolls intersected the dryline at periodic locations creating radar reflectivity and vertical velocity maxima. More importantly, clouds initiated at these intersec tion points. Additional dryline variability was generated through the interaction of the low-level flow with the local topography. The kinem atic and thermodynamic characteristics of the leading edge of the dryl ine circulation closely resembles those of laboratory and atmospheric density currents such as the sea breeze. A comparison between the obse rved and calculated dryline propagation speeds suggests that the Row-f orce balance between the cross-frontal acceleration and the density gr adient, which exists for density currents, occurs only on the horizont al scale of the leading edge (2-5 km) of the dryline circulation.