Transitions Newsletter Header

Bridges to Operations: The 2016 Hurricane WRF System

Winter 2017

The community Hurricane Weather Research and Forecasting (HWRF) modeling system was upgraded to version 3.8a on November 21, 2016.  This release includes all components of the HWRF system: scripts, data preprocessing, vortex initialization, data assimilation, atmospheric and ocean models, coupler, postprocessor, and vortex tracker.  In addition to default operational features, the release includes capabilities to perform idealized tropical cyclone simulations run with alternate physics, and backwards compatibility for inner nest grid sizes.

The HWRF community modeling system currently has over 1300 registered users.  The public release includes updates to the user webpage, online practice exercises, datasets, and extensive documentation.  The release code is fully supported, with community support provided via the HWRF helpdesk,

Information about obtaining the codes, datasets, documentation and tutorials can be found at

Soil moisture sensitivity plots illustrating the new idealized capability. As soil moisture increases from left to right, the storm intensity increases (contoured values). Courtesy of Subramanian, 2016.

The NCEP 2016 operational implementation of HWRF and the HWRF v3.8a community release are compatible systems.  Starting in 2016, the default configuration runs with ocean coupling for all northern hemisphere oceanic basins, and uses Real-Time Ocean Forecast System (RTOFS) data for ocean initialization in the Eastern North Pacific Basin.  Two specific capabilities, a 40-member HWRF ensemble for the assimilation of Tail Doppler Radar (TDR) data that NCEP began running in 2015, and the addition of one-way wave coupling using WAVEWATCH III in 2016, are not currently supported to the general community.

  • Other notable upgrades in HWRF version 3.8a include:
  • Code upgrades including, WRF v3.8, GSI v3.5, and UPP v3.1.
  • Inner domain (d02, d03) sizes increased to 25ºx25º and 8.3ºx8.3º, respectively.
  • Reduced time step from 38 4/7 s to 30 s.
  • Data assimilation enabled by default for both Atlantic and Eastern North Pacific Basins.
  • Improved physics for all scales:
    • Cumulus parameterization updates, including enabling by default for all 3 domains and a new Scale Aware Simplified Arakawa Shubert (SAS) scheme.
    • New GFS Hybrid-Eddy Diffusivity Mass Flux PBL scheme.
    • Updated momentum and enthalpy exchange coefficients (Cd/Ch).
    • Enhanced Idealized capability with landfall.
  • Enhanced products including simulated brightness temperatures for new satellite sensors in all basins.

DTC visitor contributes enhanced idealized capability

As noted in the HWRFv3.8a updates, an enhanced idealized capability to include simulated landfall using the GFDL slab land surface physics scheme is included in the v3.8a release. This capability was contributed through a successful DTC visitor project by Subashini Subramanian (Purdue University), “Developing Landfall Capability in Idealized HWRF for Assessing the Impact of Land Surface on Tropical Cyclone Evolution”.  The new feature introduces a namelist switch for allowing the landfalling capability, which specifies the type of land surface and an initial land-surface temperature to be used over land.  The default configuration introduces a homogeneous land surface that can be modified to account for heterogeneity. Additionally, the direction of land motion is a user-defined option. Work is underway to extend this capability to include other land-surface physics options.