Improved Intensity Prediction in COAMPS-TC

The Coupled Ocean/Atmosphere Mesoscale Prediction System for Tropical Cyclones (COAMPS-TC^®) has been developed for forecasting tropical cyclone track, structure, and intensity over the past several years and transitioned to Navy operations at the Fleet Numerical Meteorology and Oceanography Center in 2013. Here we highlight the latest advancements to the COAMPS-TC system in 2016 and 2017 including: i) increased horizontal resolution (from 5 km to 4 km in 2017), ii) improved vortex initialization, iii) new tropical cyclone boundary layer and surface drag parameterizations, and iv) inclusion of more complete air-sea coupling. The COAMPS-TC system has been run operationally worldwide at a horizontal resolution of 4 km in 2017 using the NAVGEM global model for initial and lateral boundary conditions (denoted as COTC forecasts), and in real time using the GFS global model initial and boundary conditions (denoted as CTCX forecasts).

The development of the COAMPS-TC system has been carried out in conjunction with several recent multi-agency programs and efforts that we will report on including: i) the Hurricane Forecast Improvement Project (HFIP), which has focused on a multi-agency ensemble capability in the W. Atlantic, E. Pacific, and W. Pacific basins, and ii) the recent NASA HS3 and ONR Tropical Cyclone Intensity (TCI) field programs. An evaluation of a large sample of operational COAMPS-TC forecasts for 2015-2017 in the Atlantic, E. Pacific and W. Pacific basins reveals much improved COAMPS-TC track, structure, and in particular intensity predictions, which are on par or in some aspects superior to any of the other operational dynamical forecast models. We will also highlight results from the 2017 season including for the high-impact events of Hurricanes Harvey and Irma. COAMPS-TC provided excellent forecast guidance for the track, intensity, and precipitation associated with Harvey, and provided skillful guidance for Irma’s intensity.

Results for a high-resolution (4 km) COAMPS-TC ensemble with 11 members that was run over the W. Atlantic and E. Pacific basins will be discussed. The COAMPS-TC ensemble was performed in collaboration with the HFIP program, which includes a 20 member high-resolution HWRF ensemble. The results show considerable promise for probabilistic intensity and track prediction using a multi-agency, multi-model tropical cyclone ensemble approach.