Investigation of Tropical Cyclone Forecasts in the Basin-Scale HWRF Ensemble System

Tropical Cyclone (TC) track and intensity forecasts have steadily improved for the operational Hurricane Weather Research and Forecasting model (HWRF) under the Hurricane Forecast Improvement Program (HFIP). In an effort to further improve multi-scale interactions and the consequent forecasts, HFIP supported HRD/AOML, along with its partners at NCEP/EMC and the Developmental Testbed Center (DTC), to create a basin-scale configuration of HWRF (HWRF-B), which features multiple sets of multi-level moving nests and a large, static outer domain that encompasses both the Atlantic and East Pacific basins. More recently, an HWRF-B ensemble system was created and is employed here to investigate the relationship between environmental steering flow and TC vortex depth. Since the environmental steering flow may vary for different atmospheric layers, a TC with a shallow vortex and one with a deep vortex could have unique track forecasts. In particular, HWRF-B ensemble forecasts for Major Hurricane Joaquin (2015) and Tropical Storm Erika (2015) are compared with the operational HWRF ensemble system, the Global Ensemble Forecast System (GEFS), and observations to investigate the relationship between the large-scale environment and TC vortex.