The effect of latent heat release on the ERICA IOP-5 cyclone

Abstract

The effect of latent heat release on the development of a rapid deepening extratropical cyclone that occurred during Intensive Observation Period (IOP) 5 (18-20 January 1989) of the Experiment on Rapidly Deepening Cyclones over the Atlantic (ERICA) is examined usinf a diagnostic height tendency equation. Data consist of Nested Grid Model (NGM) forecasts executed with and without latent heating feedback. Withholding latent heat significantly decreased the intensity of not only the surface cyclone, but its associated 500 mb trough/ridge system as well. Propagation speed differed only slightly between the two forecasts, allowing the differences in intensification to be explored through height tendency differences between the two forecasts. Model results show that at 500 mb, latent heat release affects the height tendencies primarily, through indirect means, chiefly by enhancing vorticity advection. Differential thermal advection and vertical advection of static stability tended to offset each other, as did vertical advection of vorticity and tilting effects. A height anomaly due to latent heat release was located downstream of the 500 mb trough and served as a focus for forcing differences associated with latent heating.