NCEP/EMC HWRF Genesis for Atlantic Basin

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The HWRF group at EMC works in conjunction with members of the Global, Mesoscale, and Marine branches to continually make improvements to the Hurricane Weather Research and Forecast (HWRF) modeling system for each hurricane season. Extensive testing and evaluation is completed for each new model configuration before these changes are incorporated into the operational model. Collaboration from organizations like GFDL, DTC, NHC, and HRD is also essential to the hurricane team's progress.

The atmosphere-ocean coupled Hurricane Weather Research and Forecast (HWRF) modeling system runs in the NCEP production suite on the NOAA Central Computer System. This system is developed and supported by the Environmental Modeling Center (EMC) and operated by NCEP Central Operations (NCO) since 2007. HWRF consists of multiple movable two-way interactive nested grids that follow the projected path of the storm. Atmospheric component of the HWRF model was coupled to the Princeton Ocean Model (POM) developed by GFDL/URI using a sophisticated coupler developed at NCEP for providing accurate representation of air-sea interactions. An advanced vortex initialization scheme and NCEP GSI based HWRF Data Assimilation System (HDAS) provide means to represent the initial location, intensity, size and structure of the inner core of a hurricane and it’s large-scale environment. The NCEP Global Forecast System (GFS) analysis and forecasts provide initial and boundary conditions for the HWRF model. POM uses a feature based initialization procedure for representing oceanic features such as the loop current, warm/cold core rings and the cold wake generated by the storm.

HWRF team at EMC has also been providing experimental real-time forecast guidance for all tropical cyclone basins in the world (including Western North Pacific, Southern Pacific, North Indian and South Indian Ocean regions) to the Joint Typhoon Warning Center (JTWC) and National Weather Service (NWS) Pacific Region (PR) with support from NOAA’s Hurricane Forecast Improvement Project (HFIP) and using HFIP Research&Development computational resources on Jet supercomputers. Based on the demonstration of superior performance from HWRF compared to other regional models, JTWC has included HWRF model guidance in their operational consensus forecasts.

The objective of the HWRF team is to implement planned scientific and product enhancements to the operational HWRF annually, with an aim towards improved forecast performance using state-of-the-art numerical techniques. The HWRF project is an NCEP Annual Operating Plan (AOP) milestone which maps to NCEP’s strategic goal to produce and deliver the best products and services, and prepare for a Weather Ready Nation.

Highlights for HWRF's FY2016 implementation:

  1. HWRF Infrastructure/Domain Size Upgrades : The NMM core of the operational HWRF model will be upgraded to latest community version referred to as V3.7.1a. With the availability of additional computational resources on WCOSS Cray, the nested domain sizes will increase, d02 from (12°x12°) to (25°x25°), and d03 from (6.5°x7.0°) to (8.3°x8.3°). This allows the new system to provide improved storm structure forecasts and detailed smaller scale storm features. Also, HWRF will include one way coupling to wave model for AL/EP storms which would allow us to replace the Hurricane Wave model in FY17.
  2. HWRF Physics Upgrades : HWRF physics will undergo major upgrades which include a) implementation of new GFS PBL (2015 version; b) upgrade to new scale-aware SAS convection scheme for all domains; c) updated momentum and enthalpy exchange coefficients(Cd/Ch); and d) improved vertical wind profile in the surface and boundary layer. These upgraded surface and PBL schemes provide more realistic vertical wind profiles compared to the observations. These physics upgrades included in this version also help lay a solid foundation for future physics improvement of the system.
  3. HWRF Initialization Upgrades : For the first time, the system will use ROTFS data to initialize POM model for EPAC storms to have more realistic oceanic ICs and improved RI forecasts this coming season. Further, ocean coupling will be activated for all Northern Hemisphere Basins including CPAC, WPAC and NIO for enhanced forecast skill.
  4. HWRF Data Assimilation System (HDAS) Upgrades : DA changes include upgrades to GSI, assimilation of more satellite observation data in GSI (CrIS, SSMI/S, METOP-B changes) and deploying data assimilation for all storms in the East Pacific Basin along with the Atlantic Basin. These DA upgrades in the system provide for well-balanced initial conditions, eliminating initial shocks noted in previous version.
  5. HWRF Post-Processing and Product Upgrades : HWRF post processing upgrades will include changing the file naming convention in the 2015 version of HWRF to include domain and resolution information in the file name for the 2016 version. Additional simulated synthetic imagery from different satellite sensors will be included in the output files in order to provide global coverage for all oceanic basins, including:
    • GOES-13 for North Atlantic;
    • GOES-15 for East, Central Pacific;
    • SEVERI for South, East Atlantic, and Indian Ocean;
    • HIMIWARI (MTSAT-2 in 2015 version) for West, Central Pacific;
    • DMSP/F17 SSMI/S for all basins;
    • InSat-3D/Kalpana for Indian Ocean.
  6. HWRF Script Enhancements and Procedural Upgrades : For the first-time and with active help from NCO, operational HWRF in 2016 will use dev-ecflow for accelerated transition to operations. Success in this approach will provide guidelines for this to be adopted as a standard transition procedure for all future upgrades of HWRF and other operational systems.