An investigation of the ERICA IOP-5A cyclone

Abstract

A synoptic investigation was conducted of the rapid coastal cyclogenesis event that occurred during Intensive Observation Period (IOP) 5A of the Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA). Navy Operational Regional Analysis and Prediction System (NORAPS) objective analyses, utilizing operationally available and some special ERICA data, were examined in order to study the environment in which rapid development took place and to determine key synoptic and subsynoptic features important in the evolution of this storm. Additionally, the ability of NORAPS to accurately simulate the rapid cyclogenesis was investigated. Several processes contributed to the storm's intense development including strong low tropospheric temperature advection and upper-level cyclonic vorticity advection and divergence associated with a mobile trough and jet streak. NORAPS forecasts initialized 12 h prior to the explosive deepening phase of the IOP 5A cyclone provided a reasonably accurate simulation of the event. However, subjective hand analysis of hourly data for the period surrounding the onset of rapid deepening revealed the presence of a mesoscale coastal cyclone. The development of this separate cyclone was not resolved by the model, resulting in a forecast track north of the actual storm's path.