Coupled COAMPS-TC Real-Time Forecasts for the ITOP Experiment

Real-time forecasts using the fully Coupled Ocean/Atmosphere Mesoscale Prediction System – Tropical Cyclone (COAMPS®-TC) were conducted over the Western Pacific in support of the Office of Naval Research (ONR)'s field experiment Impact of Typhoon on the Ocean in the Pacific (ITOP) in the summer of 2010. The coupled COAMPS-TC, developed by the Naval Research Laboratory (NRL), coupled COAMPS with the NRL Coastal Ocean Model (NCOM) using the Earth System Modeling Framework (ESMF). The real-time coupled forecasts were run on the Mercator map projection with the triply nested COAMPS domains at 45-km, 15-km, 5-km horizontal grid resolution and the two inner domains moving along with TCs. The NCOM domain is fixed at 10-km resolution. A dynamic web site (http://www.nrlmry.navy.mil/coamps-web/web/cpltc) was built to post the coupled forecasts online in real-time and used to provide guidance for the deployment of AXBT and dropsondes deployed from Air Force C-130, to schedule research ship routing to distribute drifters, and to provide drifter motion track forecasts to help to retrieve them after storms. The real-time coupled forecasts captured well the tracks and intensity changes during ITOP for typhoons Fanapi and Malakas. For example, the track forecast errors for the first 96 h is below 100 nm and intensity errors are below 15 kt for the coupled model, compared favorably with the best tracks than the uncoupled real-time forecasts. The observational data collected during ITOP field experiment were used to verify the model forecasts in both the atmosphere and ocean. We will present some case studies of ocean and typhoon interactions, and the evaluation of the performance of the coupled real-time forecasts for ITOP.