STRUCTURE OF AN ATMOSPHERIC UNDULAR BORE GENERATED FROM COLLIDING BOUNDARIES DURING CAPE

A case study of a sea-breeze front originating from the east coast of Florida colliding with a gust front moving toward the southeast is pre sented. Single- and multi-Doppler radar analyses combined with serial balloon ascents suggest mat the denser sea-breeze flow undercut the co ld pool behind the gust front and may have generated a westward-propag ating undular bore. In addition, another undular bore was generated by the collision and propagated eastward through the CaPE network. The l atter bore propagated upstream, against the southeasterly flow behind the sea-breeze front and was apparent as a narrow band, 5-6 km wide, o f near-zero radial velocities embedded within an overall Row that was positive as seen by the CP-4 Doppler radar. As the eastern bore propag ated through the dual-Doppler lobe defined by the NCAR CP-3 and CP-4 r adars, a detailed and unique wind synthesis revealed its three-dimensi onal kinematic structure. Significant along-bore variability was shown in the convergence and vertical velocity fields. Vertical cross secti ons of the synthesized wind were similar to past studies of wavelike p henomena embedded within an ambient dow. A sounding was launched withi n the leading edge of the undular bore as it passed over a CLASS site. The thermodynamic profile revealed a change from a frontal stable lay er to a well-mixed zone indicative of forced uplift: of surface air pa rcels within the cold air behind the sea-breeze front. Theoretical cal culations of the propagation speed and wavelength of an undular bore c losely matched the observations.