Single Doppler radar observations of an intense bowing phase of a cold season bow echo in a high shear, low CAPE environment

This paper meticulously examines the kinematic structure and evolution of an intense bowing phase of a cold-season bow echo that occurred on 9 March 2006. As the apex of the bow passed 40 km south of the Columbus, MD WSR-88D (KGWX), detailed observations were acquired. The internal flow of the bow echo is derived from both single-Doppler and Synthetic Dual-Doppler (SDD) analyses of the convective region. Because the bow echo moved rapidly (21 ms^-1) and maintained a steady circulation over 20-30 minute periods, the reliability of sequential SDD analyses is considered to be excellent. In addition, the bow echo was highly two-dimensional with very little cellular structure along the leading convective line. Comparison of single-Doppler wind syntheses in the vertical plane normal to the bow echo agree very well with the airflow derived from the 3-D SSD analyses. The Doppler analyses identify a number of interesting attributes of this system during its bowing phase at very high spatial resolution, such as:

• Updraft magnitudes of about 20-25 ms^-1, peaking near the 3.5 km AGL level;

• Downdraft located upshear of the updrafts, with magnitudes of about 6 ms^-1, peaking near 3 km AGL;

• A rear inflow jet that appears to provide a partial feed to the convective downdraft region;

• A low-level jet (LLJ) peaking at 45 ms^-1 (near 4.0 km AGL) ahead of the bow echo;

• A prominent leading rotor circulation, marked by a persistent deep downdraft of 2-4 ms^-1 magnitude, located 13 km ahead of the convective line;

• Enhanced cyclonic vorticity at the northern edge of the apex;

• The slantwise descent of the downdraft, and the cellular structure of updrafts at the leading edge.

Trajectory analyses and thermodynamic retrievals are also presented to show the origins of downdraft air parcels within the convective region, and define the dynamics of the updraft and downdraft circulations.