Improving NOAA’s HWRF Prediction System through New Advancements in the Ocean Model Component and Air-Sea-Wave Coupling

Investigators:
Biju Thomas,
Isaac Ginis

This is project is funded by NOAA HFIP Program

In collaboration with:

This project primarily addresses HFIP priority I.B.2 by making advancements in hurricane NWP, including development of new and enhanced techniques suitable for high resolution model physics of air-sea interaction to improve HWRF forecast skill. Specifically, the proposed HWRF advancements include a major operational upgrade to the ocean model component and the operational implementation of three-way air-sea-wave coupling that can accurately capture the physics at the air-sea interface. All such operational upgrades will be implemented in a way that ensures ESMF-compliance as HWRF eventually transitions from its current WRF-NMM architecture to the new NEMS-based NMM-B architecture, thereby addressing HFIP priority I.B.3. In addition, this project addresses HFIP priority I.B.5 through development of advanced real-time ocean model diagnostic techniques to support model improvements in the identification and analyses of oceanic sources of HWRF model errors. Finally, this project addresses HFIP priority I.B.6 by making advancements in the development of a high-resolution single model ensemble to improve intensity guidance through the addition of new HWRF ensemble members that each has a different ocean initial condition.

FIG. 1. Surface wind (left) and significant wave height (right) at 90 hours into the coupled HWRF/WAVEWATCH III/POM-TC simulation of Hurricane Sandy. Initial time: 18 UTC 22 October 2012. Black dots indicate the locations of the wave spectra shown in Fig. 2.

The scope of this project has the following seven objectives

  1. evaluation of HWRF/MPIPOM-TC and HWRF/POM-TC coupled model forecasts;
  2. evaluation of alternative MPIPOM-TC initial conditions for operational HWRF implementation and/or HWRF ensemble development;
  3. upgrade of the three-way coupled HWRF/WAVEWATCH III/(MPI)POM-TC system;
  4. upgrade of MPIPOM-TC physics and air-sea-wave coupling;
  5. development of real-time ocean diagnostics for the operational HWRF system;
  6. ESMF-compliance for the Nonhydrostatic Multiscale Model on a B-grid (NMM-B);
  7. continued support of EMC and the DTC’s community-based HWRF system.

In the HWRF/WAVEWATCH III/(MPI)POM-TC coupled framework, which is based on a comprehensive, physics-based treatment of the wind-wave-current interaction, the bottom boundary condition of the atmospheric model incorporates sea-state dependent air-sea fluxes of momentum, heat, and humidity, and it includes the effect of sea-spray. The wave model is forced by the sea-state dependent wind stress and includes the ocean surface current effect. The ocean model is forced by the sea-state dependent wind stress and includes the ocean surface wave effects (i.e. Coriolis-Stokes effect, wave growth/decay effect, and Langmuir turbulence effect).

Figure 1 shows the surface wind and significant wave height in a coupled HWRF/WAVEWATCH III/POM-TC simulation of Hurricane Sandy (2012), and Fig. 2 shows the wave spectra simulated at the four locations indicated in Fig. 1.

FIG. 2. Simulated two-dimensional wave height spectra at 90 hours in the coupled HWRF/WAVEWATCH III/POM-TC simulation of Hurricane Sandy at the four locations shown in Fig. 8. Initial time: 18 UTC 22 October 2012.