10.8 Diagnosing Forecast Errors in Tropical Cyclone Motion in AHW

Galarneau, Thomas and Christopher Davis, National Center for Atmospheric Research

This presentation reports on the development of a diagnostic approach that can be used to examine the sources of numerical model forecast error that contribute to degraded tropical cyclone (TC) motion forecasts. Results from an analysis of 24-h forecasts from the 2011 and 2012 versions of the Advanced Hurricane Weather Research and Forecasting model for TCs Earl (2010) and Fiona (2010) show that forecast motion errors are dominated by errors in the environment wind field. Contributions from errors in the vertical depth of the vortex and near-vortex asymmetries are occasionally large and are interpreted using “vorticity thinking.” The utility of this new diagnostic equation is that it can be used to assess TC motion forecasts from any numerical modeling system.