Explosive East Coast Cyclogenesis over the West-Central North Atlantic Ocean: A Composite Study Derived from ECMWF Operational Analyses

Abstract

This paper describes the observational aspects of explosive East Coast cyclogenesis using composites constructed from the daily global analyses generated and archived by the European Center for Medium Range Weather Forecasts (ECMWF). An explosively deepening storm or bomb is defined following Sanders and Gyakum as an extratropical cyclone whose mean sea level pressure falls at least 1 mb per hour for 24 hours. The ECMWF datasets are used to examine the three-dimensional kinematic and thermodynamic structure of bombs over the entire depth of the troposphere. The evolution and structure of the composite bomb is diagnosed using a moving coordinate system consisting of a box with dimensions of 35°?35° of latitude-longitude. The results reveal that explosive cyclogenesis is a baroclinic phenomenon in which the rapid development in the presence of strong upper tropospheric forcing is most likely enhanced by a highly destabilized lower troposphere. Additionally, the composite analyses of the bomb show a considerable amount of detail considering the horizontal and vertical resolution of the ECMWF data.