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Bridges to Operations: HWRF Operational Implementation and Public Release

Winter 2016

With the conclusion of the 2015 hurricane season, assessments of model performance indicate that the upgraded 2015 Hurricane WRF (HWRF) model provided superior forecast guidance to the National Hurricane Center (NHC), with marked improvements over the previous HWRF system.

The unified HWRF system, for which the DTC provides the operational codes to the research community, is a cornerstone of HWRF’s success.

The community HWRF modeling system was upgraded to version 3.7a on August 31, 2015.  This release includes all components

of the HWRF system, including: scripts, data preprocessing, vortex initialization, data assimilation, atmospheric and ocean models, coupler, postprocessor, and vortex tracker (see Figure on the left).  Additionally, the capability to perform idealized tropical cyclone simulations is included (Figure in upper right). The HWRF community modeling system currently has over 1100 registered users.  The DTC provides resources for these users through updates to the user webpage, online practice exercises, datasets, and extensive documentation consistent with the latest release code.  With the HWRF v3.7a release, the HWRF helpdesk was migrated to a new tracking system (hwrf-help@ucar.edu), providing support for all aspects of the code.  Information about obtaining the codes, datasets, documentations, and tutorials can be found at the DTC HWRF user webpage: http://www.dtcenter.org/HurrWRF/users.

The HWRF v3.7a public release is compatible with the NCEP 2015 operational implementation of HWRF.  The HWRF model consists of a parent domain and two storm following two-way interactive nest domains.  Starting with the 2015 operational season, the default HWRF horizontal resolution increased to 18/6/2 km (from 27/9/3 km), and NCEP expanded high-resolution deterministic tropical cyclone forecast numerical guidance to all global oceanic basins for operations.  NCEP is running HWRF configurations with reduced complexity for global basins other than the Atlantic and Eastern North Pacific basins operationally.  However, the HWRF public release includes flexibility and alternate configuration options, such as running with full complexity including atmosphere-ocean coupled mode with data assimilation for all oceanic basins.  Additionally, the HWRF v3.7a maintains backwards compatibility to run the 27/9/3 km resolution.  One unsupported capability of the HWRF system is the use of an HWRF ensemble.

Improvements to the HWRF physics for the 2015 operational HWRF system demonstrate successful R2O transitions facilitated by the DTC.  The DTC acts as a conduit for code management and R2O by maintaining the integrity of the unified HWRF code and assisting developers with transitioning their innovations into the operational code.  Specifically, the DTC successfully facilitated R2O transitions for upgrades to radiation parameterization and PBL improvements that were implemented for the 2015 operational HWRF system.

Contributed by Kathryn Newman.