Synoptic and Mesoscale Severe Weather. A Two Day Case Study of a Derecho and Local Hailstorms.
AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH
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A case study was conducted on the evolution and damage path of the 4 June 1 993 derecho and several severe hailstorms in central North Carolina that occurred the next day. Both events produced significant damage. Wind damage from the derecho totaled over 60 million dollars in Virginia alone. The following day hailstones greater than three inches fell on China Grove North Carolina causing at least three million dollars in damage there and six hundred thousand dollars elsewhere in North Carolina. The synoptic environment over the initiation area of the 4 June 1993 derecho compares favorably to those already documented for warm season derechos. The convective system resembled a warm season progressive derecho. The bow echo squall line associated with the storm developed many signature features such as weak echo channels and bookend vortices. Several other cells developed between the derecho and the leading convective cell. Severe hail storms developed in central North Carolina on 5 June 1993 and seemed to have originated near an intense thermal boundary that was the remains of the derecho outflow boundary. This thermal boundary extended from the foothills to off the North Carolina coast. The pressure field apparently responds to the thermal forcing with roughing in and around the thermal boundary throughout the evening and early morning. A persistent convergence zone aligned with the trough. This combination of thermal boundary, convergence boundary and pressure trough are referred to as the sandhills boundary. A slow moving cold front approaching the Appalachian mountains seemed to affect both the wind and pressure fields. With diurnal destabilization the interaction of the lee side trough and the increased convergence with the sandhills boundary initiated the convection which led to the large hail event.