Hurricane Analysis and Forecast System

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HAFSv2 FY2024 Operational Implementation: 07/16/2024

  1. Infrastructure and workflow enhancements:
    • Use the HAFS production/hafs.v2 branch with all HAFS submodules/subcomponents (including UFS_UTILS, GSI, ufs-weather-model, UPP, GFDL vortex tracker, etc.) being synced with their latest authoritative repositories/branches as of 02/05/2024.
    • Higher resolution moving-nesting (5.4-1.8 km, instead of 6-2 km) configuration with slightly adjusted parent domain coverage. (HFSA only)
    • Adjusted maximum terrain slope (max_slope=0.12 instead of 0.15) and internal tracker interval (6 mins instead of 3 mins).
    • Turn on FV3ATM restart file quilting through the write grid component.
    • Enable using parallel NetCDF for FV3ATM history output.
  2. Vortex initialization and data assimilation improvements:
    • Newly developed cloud variable and vertical velocity vortex relocation and warm-cycling capability. (HFSA only)
    • Updated HFSA-based (instead of HWRF-based) composite vortex for vortex intensity modification/adjustment. (HFSA only)
    • Reduce the warm-cycling vmax threshold from 50 kt to 40 kt (for NHC basins) and always turn on storm intensity modification. (HFSA only)
    • Enable using Scale-Dependent Localization (SDL) for innercore DA.
    • Assimilate high-resolution GOES-R mesoscale floater AMVs.
    • Refined DA for the GPS RO (Radio Occultation) data.
  3. Physics and dynamics advancements:
    • Upgraded Thompson MP with some bug fixes related to threshold in creating the ice table, rain creation due to graupel and rain collisions, and the logic of snow and graupel melting and sublimation.
    • Updated GFS TKE-based EDMF PBL scheme and SA-SAS CP scheme with vertical wind shear impacts being considered.
    • Updated CO2 fix files for 2024.
    • Switch to use the latest Thompson MP for NATL with dt_inner=45s and sedi_semi=.true. for HFSA. Meanwhile, keep using GFDL MPv1 for HFSA EPAC/CPAC and JTWC. (HFSA only)
    • Change the radiation calling time step from 720s to 900s. (HFSA only)
    • Turning on the prognostic sigma closure for EPAC/CPAC/JTWC storms.
    • Fine-tune the convection detrainment rate with c1_deep/c1_shal of 1.e-4 for JTWC storms. (HFSA only)
    • Reduce the model time step from 90s to 72s, and radiation calling time step from 1800s to 720s. (HFSB only)
    • Use the horizontal advection scheme options of hord_mt/vt/tm/dp/tr=1/1/1/1/-5 with fine-tuned lim_fac values (3.1 for HFSA NATL, 2.9 for HFSA EPAC, 2.5 for HAFS JTWC basins and 2.8 for HFSB, respectively).
  4. Air-sea interaction and coupling upgrades:
    • Established and transitioned to use MOM6 ocean coupling: (HFSA only)
      • Innovated and unified UFS regional coupling through CMEPS with inline-CDEPS for MOM6 ocean coupling.
      • Use time-varying GFS-forecasted SST (every 3-h) in non-overlapped atmospheric domain area.
      • Take into account sea surface current (SSC) in atmosphere-ocean coupling when estimating air-sea fluxes.
      • MOM6 utilizes 55 vertical levels and uses the KPP mixed layer scheme.
    • Speed up the coupling variable downscaling from FV3ATM parent domain to its moving nest.
  5. Post-processing and products updates:
    • Latest UPP and upgraded GFDL vortex tracker.
    • MOM6 ocean output/product. (HFSA only)
    • Produce a separate subset of grib2 files requested by NHC.

HAFSv1 FY2023 Operational Implementation: 06/27/2023

  1. Highlights of HAFS Initial Operational Capability (IOC) implementation:
    • Two HAFS configurations including HAFS-A (HFSA) and HAFS-B (HFSB) to succeed the two legacy regional HWRF and HMON hurricane forecast systems, respectively.
    • First ufs-weather-model based regional hurricane forecast system (UFS hurricane application), with Shared subcomponents (ufs-weather-model, UFS_UTILS, GSI, UPP, etc.) and infrastructure (CMEPS, CCPP, etc.) with other UFS applications.
    • First UFS application with high resolution storm-following moving-nesting capability using the regional Extended Schmidt Gnomonic (ESG) grid.
    • Advanced and diversified CCPP-based physics suites for (HFSA and HFSB, respectively) with optimized physics schemes for high resolution hurricane forecasting.
    • Modernized vortex initialization (VI) together with high-resolution inner-core DA with 3-hourly FGAT, and 4DEnVar with GDAS ensembles. Meanwhile, for the first time, use full DA increments in the storm inner-core region in a NCEP operational regional hurricane forecast system.
    • ESMF/CMEPS based HYCOM ocean coupling for all global TC basins with extended ocean domains.
    • Unified hurricane application workflow to support both research and development Rocoto workflow and operational Ecflow workflow.
  2. Infrastructure and workflow:
    • Use the HAFS production/hafs.v1 branch with the latest submodules/subcomponents including ufs_utils, GSI, ufs-weather-model, UPP (as of 01/17/2023)
    • Storm-centric regional Extended Schmidt Gnomonic (ESG) grid based storm-following moving-nest configuration:
      • HFSA: 6-km parent domain (1320x1200, ~78x75 degree) with a 2-km moving nest (600x600, ~12x12 degree)
      • HFSB: 6-km parent domain (1200x1200, ~75x75 degree) with a 2-km moving nest (600x600, ~12x12 degree)
    • Increased model vertical levels (L81) with a higher model top (2 hPa).
    • Model physics time step of 90s (dt_atmos):
      • HFSA: k/n_split of 2/4 for parent and k/n_split of 4/10 for nest
      • HFSB: k/n_split of 2/4 for parent and k/n_split of 4/9 for nest
    • Atmospheric initial condition and 3-hourly lateral boundary conditions from GFSv16, LBC blending with nrows_blend of 20.
    • Using VIIRS vegetation type.
  3. Vortex initialization and data assimilation:
    • Modernized vortex initialization (VI) including vortex relocation (VR) and automatically determined vortex modification (VM) based on intensity difference.
      • HFSA: warm-cycling intensity threshold of 50 kt
      • HFSB: warm-cycling intensity threshold of 40 kt
    • High-resolution inner-core DA with 3-hourly FGAT, and 4DEnVar with 3-hourly 80 member GDAS ensembles.
    • For the first time, use full DA increments in the storm inner-core region in a NCEP operational regional hurricane forecast system.
    • Updated adaptive observation error coefficients for flight recon data.
    • Assimilate all the observation types ingested by HWRF and GFS/GDAS.
    • Newly developed flexible HAFS DA tool for domain and storm merge to support HAFS VI and DA needs.
  4. Dynamics:
    • hord_mt/vt/tm/dp/tr=6/6/6/6/-5
    • kord_mt/wz/tr/tm=11/11/11/-11
    • Damping related options:
      • tau=5, n_sponge = 24
      • rf_cutoff = 50.e2, sg_cutoff = -1.
      • d2_bg_k1=0.20, d2_bg_k2 = 0.15
      • vtdm4 = 0.04, delt_max=0.008
    • full_zs_filter=.true., and max_slope=0.15 for both parent and nest.
  5. Physics:
    • HFSA: GFDL MP, RRTMG radiation (720s time step), modified TKE-EDMF GFS PBL (sfc_rlm=1, d02 elmx/rlmx=250), upgraded sa-SAS CP (clam_deep=0.15), Noah LSM, GFS SFC with HWRF exchange coefficients, unified UGWPv1.
    • HFSB: Thompson MP, RRTMG radiation (1800s time step), modified TKE-EDMF GFS PBL (tc_pbl=1, d02 elmx/rlmx=75), upgraded sa-SAS CP, Noah LSM, GFS SFC with HWRF exchange coefficients, unified UGWPv1.
  6. Air-sea interaction and coupling:
    • ESMF/CMEPS based HYCOM ocean coupling with extended HYCOM ocean domains with 1/12-degree grid spacing and L41 vertical levels. Ocean IC from RTOFSv2 with persistent oceanic LBC. Atmospheric forcing from GFSv16 grib2 files for non-overlapping area.
    • One-way WW3 wave coupling for NHC/CPHC basins (NATL, EPAC, CPAC) for HFSA, while no wave coupling for HFSB.
  7. Post-processing and products:
    • Latest UPP.
    • Upgraded GFDL vortex tracker.