Numerical Forecast Systems
Highlights for HWRF's 2013 implementation include the following:1. HWRF Infrastructure/Resolution Upgrades: The NMM core of the operational HWRF model will be upgraded to latest community version currently referred to as V3.5a. Due to computational constraints, FY12 HWRF was run with a smaller domain large physics time steps (180 sec. for 3km domain). Proposed FY13 HWRF will have 20% bigger 3km domain and will include higher frequency of physics calls (every 30 sec.). In addition, nest-parent interpolations have been re-designed for improved treatment of nest boundaries and to allow advection of several microphysical variables across the domains. Another resolution related upgrade is to interpolate GDAS/GFS spectral files to 0.25 degree resolution (instead of 0.5 degree) in hwrf_prep_hybrid to get maximum benefit from global analysis and forecasts for HWRF initial and boundary conditions.
2. HWRF New Nest Motion Algorithm: The current mass centroid based nest motion algorithm will be replaced with a new storm tracking algorithm using Tim Marchok’s NCEP tracker functionalities. This will eliminate several problems identified with the centroid method, is more efficient in identifying and tracking the tropical systems more accurately, resulting in improved track and intensity forecasts.
3. HWRF Physics Upgrades: HWRF physics upgrades consist of modifications to the GFS PBL based on variable Richardson number following Vickery and Mahrt (2003) for improved PBL structure in hurricanes as well as over land.
4. HWRF Initialization Upgrades: Vortex initialization is modified with further improvements to the storm size correction and resizing the filter domain. For storms weaker than 16m/s, we eliminate the need for bogus by directly using the GFS vortex.
5. HWRF Data Assimilation Upgrades: A major upgrade for 2013 implementation is the 80-member global ensembles based one-way hybrid EnKF-3DVAR data assimilation system for HWRF. 75% weight is given the the ensemble covariances and 25% for the static covariances. First guess fields for the analysis are taken from GDAS forecasts and all conventional datasets are assimilated, with provisions to assimilate real-time inner-core TDR/ FL/SFMR/Dropsonde recon datasets.
6. HWRF Ocean Upgrades: Current operational procedure of 25% truncation for heat, radiation and momentum fluxes is removed in as it is found no longer needed due to improved physics in HWRF. Upgrades to multi-processor MPI-POM with single trans-Atlantic domain and 3D ocean for Eastern Pacific basin were withdrawn from 2013 implementation plans due to lack of sufficient T&E and potential increase in resources required for operational implementation on CCS. On WCOSS, this should not be a problem.
7. HWRF Post-Processing and Product Upgrades: HWRF post processing upgrades include bug fixes for simulated synthetic imagery to reduce domain discontinuities. Apart from very high-temporal resolution track and intensity forecast data at 5-sec. interval (HTCF), ATCF style output at every 9-minute interval will be added to the suite of products.
8. HWRF Script Enhancements and Procedural Upgrades: Operational HWRF scripts have been modified to accommodate changes due to one-way hybrid GSI, optimum utilization of CCS resources, and cross-platform compatibility required for transitioning to WCOSS in the middle of the season. Operational HWRF will remain in the vertical structure and will be known as hwrf.v7.0.0 on CCS and hwrf.v7.1.0 on WCOSS.