Highlights for HMON's FY2020 Upgrades:

1. System & Resolution Enhancements:
   
   • Upgrade/enhance dynamic core NMMB
   • Increase number of vertical levels of the atmospheric model from 51 to 71
2. Physics Advancements:
   
   • Bug fix for cloud water tendencies, ice/rain fractions
   • Use original IGBP roughness length
   • Turn on GWD for the outermost domain
3. Coupling Upgrades:
   
   • Upgrade to the latest version of HYCOM
   • Momentum adjustment from 0.7 to 1.0
   • New version of mixed layer
   • Additional Cd formula based on CORE v3
   • Newtonian relaxation employed in an implicit time step

Highlights for HMON's FY2018 Upgrades:

1. System & Resolution Enhancements:
   
   • Upgrade to the latest NMMB dynamic core with bug fixes
   • Increase vertical levels from 42 to 51
   • NMMB dynamic core optimizatio
   • Change diffusion parameterizations
2. Physics Advancements:
   
   • Use scale-aware SAS scheme
   • Update momentum and enthalpy exchange coefficients (Cd/Ch)
   • Use GFS-EDMF PBL scheme
3. Vortex Initialization/Data Assimilation Improvements:
   
   • Update composite vortex
   • Change co-ordinates for vortex initialization
4. Coupling Upgrades:
   
   • Unified HMON/HWRF coupler
   • Add HYCOM coupling in NATL basin

Highlights for HMON's FY2017 implementation:

HMON v1.0.0, is the first version for the new Hurricanes in a Multi-scale Ocean-coupled Non-hydrostatic (HMON) Model system. The release has been fully tested and compared with the discontinued Geophysical Fluid Dynamics Laboratory (GFDL) Hurricane Model (GHM) results. It has shown significant skill improvements in term of storm track and intensity forecasts in Northern Atlantic (NATL) Basin, Eastern Pacific Basin (EPAC) and the Central Pacific (CPAC) Basin. HMON also provides a first step for NCEPs Environmental Modeling Centers (EMC) efforts towards unification of operational models within the NOAA Environmental Modeling System (NEMS) framework.

The scientific and technique details are as follows:

• The dynamical core is a Non-hydrostatic Multi-scale Model on a B grid (NMMB)
• There are 43 vertical levels, where the model top is at 50 hPa
• Includes vortex relocation, but has no data assimilation
• Two-way Coupling is with Ocean Model (HYCOM) for EPAC and CPAC basins; uncoupled for NATL basin
• The HMON system will provide improved track forecasts in NATL, EPAC and CPAC basins. It will also provide improved intensity forecasts for NATL, EPAC and CPAC basins. The coupled HMON system will provide additional ocean products when compared with GHM

This model is considered the replacement for the GHM (Geophysical Fluid Dynamics Laboratory (GFDL) Hurricane Model). Due to differences in underlying physics, two variables present in the GHM grib output will not be produced by HMON, and some others are being replaced by similar but not identical output. These differences are detailed in the Model Output section. For more information on the removal of the GFDL model, please see the following notices:
https://www.nws.noaa.gov/os/notification/pns17-07gfdl.htm
https://www.nws.noaa.gov/os/notification/scn17-45discontinue_gdflaaa.htm

The 2017 HMON system has been fully tested and compared with the forecast results with 2016 operational GHM. It has shown significant skill improvement in intensity and track forecasts in NATL, EPAC and CPAC basins. A PowerPoint presentation explaining the new HMON model and comparing its results to GHM can be found here.