A Climatology of Extratropically Transitioning Atlantic Tropical Cyclones and Associated Case StudiesEPA Grant Number: U915368
Title: A Climatology of Extratropically Transitioning Atlantic Tropical Cyclones and Associated Case Studies
Investigators: Hart, Robert E.
Institution: Pennsylvania State University
EPA Project Officer: Michaud, Jayne
Project Period: August 1, 1998 through July 1, 2001
Project Amount: $85,635
RFA: STAR Graduate Fellowships (1998) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Air Quality and Air Toxics , Fellowship - Atmospheric Sciences
The objective of this research project is to conduct the first climatology study of Atlantic tropical cyclones that undergo a transition to the extratropical stage at higher latitudes (i.e., extratropical transition). The climatology results will be used as the basis for several case studies and future numerical simulations.
The climatology of extratropical transition was developed using numerous data sets, including the National Hurricane Center's (NHC) Best Track historical data, the European Center for Medium Range Weather Forecasting’s and the National Center for Atmospheric Research's reanalyses (model- and satellite-enhanced gridded analyses), and sea-surface temperature data that are derived weekly. Using these data sets, the occurrences, intensity changes, and structural changes were examined for 54 transitioning storms between 1979 and 1993. Once the spatial, temporal, and structural climatology was complete, we began to examine objective measures to define transition. Currently, transition is subjectively defined by the NHC using satellite images and underlying ocean temperature. As a result, the point of transition often is questionable. This research project examines objective methods to determine the point of transition and, more generally, methods to define the full lifecycle of the cyclone—from purely tropical to hybrid to transitioning to purely extratropical. The case studies will be completed in the next 6 months, and high-resolution numerical simulations will be performed on certain cases. Only through such high-resolution simulations can the details of transition be determined. The current observational data sets are too coarse to extract the necessary mesoscale detail of transition.