A Gridded TCM to Support Forecast Operations at National Centers and Weather Forecast Offices (WFOs)

A new gridded representation of the Tropical Cyclone forecast advisory Message (TCM), generated by the GWAVA (gradient wind asymmetric vortex algorithm; Mattocks and Forbes, 2008) parametric wind model, is being implemented experimentally during the 2018 tropical season across the Atlantic basin at the National Hurricane Center (NHC). It is accessible to WFOs and National Centers for evaluation. It provides WFO and National Center forecasters with a two dimensional version of NHC’s official forecasts that they can use to develop their tropical cyclone wind field forecasts. A description of the algorithm, along with additional development efforts currently underway (expanding the domain for the Atlantic and Pacific basins, terrain processing of the inland friction algorithm for Northern Maine, Mexico, the Caribbean and the Pacific, and elevation adjustments), will be presented. The gridded TCM wind output correlated well with in situ observations at coastal and inland sites during 2017 validation testing. These results will be presented along with additional ones based on 2018 cases. A blending tool that allows forecasters to incorporate the gridded TCM into their Wind forecast grids has been provided. A description and illustration of how the tool works will also be presented.

Congruent with the Hurricane Specialists’ OFCL forecast track parameters, these tropical cyclone depictions of the surface wind forcing will be used to drive the Nearshore Wave Prediction System (NWPS; Van der Westhuysen, A. J. et al., 2013, 2014) at coastal WFOs and the Regional Wave Prediction System (RWPS; Padilla-Hernandez et al., 2017) at National Centers during tropical cyclone events. Envisioned as a replacement for the current labor-intensive methodology used in AWIPS, the gridded TCM significantly streamlines tropical cyclone wind forecasts preparation at National Centers and WFOs while keeping them consistent with official forecasts.