Ocean Model Impact Study for Improvement of Tropical Cyclone (TC) Forecasting

As seen in the 2017 Atlantic hurricane season, the ocean was a dominant source of thermal energy for TCs that rapidly intensified to major hurricanes over warm oceans under favorable atmospheric conditions. In this broad context, accurate ocean coupling is essential for TC prediction models to forecast the evolving intensity fluctuations. Because ocean coupling was not accurately represented in previous-generation fully-coupled prediction models, they often produced forecasts with equal or reduced skill compared to simpler or uncoupled models. These results produced skepticism in the operational forecasting community concerning the need to include state-of-the-art coupling to a three-dimensional ocean model in operational prediction systems to forecast the intensity. Notwithstanding, the present generation of coupled prediction systems, along with next-generation systems under development, all contain major improvements to the atmospheric model, surface flux parameterizations, ocean model physics, and parameterizations of both atmospheric and oceanic planetary boundary layer dynamics. These improvements along with more accurate initialization procedures using analyses produced by data assimilation, require a more comprehensive approach to resolving the complexities of ocean coupling and TC intensity evolution. Central to this revisit, there is a need to acquire 3D ocean profiles to assess the fidelity of the ocean model in this coupled approach for operations.

The Ocean Model Impact Tiger Team (OMITT) formed in December 2014 as part of the NOAA Hurricane Forecast Improvement Project (HFIP) serves to investigate the need of ocean coupling, focusing primarily on numerical guidance models, and to demonstrate the degree of ocean model complexity required for ocean coupling to optimize TC intensity forecasts. Teams of research and operational scientists from various institutions continue to coordinate efforts in pursuit of this important goal. In this presentation, we describe key findings and accomplishments, and summarize our ongoing efforts and future plans from the perspectives of experimental field campaigns and numerical model experiments.