Analysis of a cold-season bow echo: kinematic and precipitation structure during the late mature phase

On 9 March 2006, a severe cold season squall line formed over Louisiana and intensified near the Mississsippi (MS) – Alabama (AL) border, where it assumed a bow echo configuration and produced a long swath of damaging winds from eastern MS to northern AL. This paper investigates the late mature stages of this bow echo over northern Alabama, using Doppler radar data from the UAH (C-band dual polarization) Advanced Radar for Meteorological and Operational Research (ARMOR), combined with the Hytop WSR-88D radar (KHTX), located 65 km ENE of the ARMOR. As the bow echo approached the Huntsville region, a break in the squall line occurred in the vicinity of the apex that formed over eastern MS, dividing it into distinct northern and southern segments. As the squall line moved on, the different segments developed distinct kinematic features and, therefore, behaved in different ways.

The evolution of this break is examined with single-Doppler data. Data collection begins at 22:40Z from ARMOR as the storm is approaching (west – southwest of) the Huntsville region. Dual Doppler analyses using ARMOR and KHTX are performed on the squall line after the break from 23:30Z to 00:18Z. These analyses reveal the different kinematic features between the northern and southern segments. Single Doppler analyses applying the synthetic dual Doppler technique to the KHTX data are then applied to examine the late mature phase of the squall line after 00:18Z, and compare the kinematic features to those analyzed over eastern MS two hours earlier. ARMOR is a dual-polarization radar, therefore analysis is also done on precipitation characteristics. These characteristics shed insight on the dynamic processes occurring in both the convective and stratiform regions of the system. Throughout the analysis process, special attention is given to the kinematics, characteristics and structure of the break.