Numerical Forecast Systems
HURRICANE MODELING AT EMC
The HWRF group at EMC works in conjunction with members of the Global, Mesoscale, and Marine brances to continually make improvements to the Hurricane Weather Research and Forecast System (HWRF) model for each hurricane season.
Extensive testing and evaluation is completed for each new model configuration before these changes are incorporated into the operational model. Collaboration from organizations like GFDL, DTC, NHC, and HRD is also essential to the hurricane team's progress.
IMPLEMENTATION INFORMATION
Focal points for HWRF's 2012 implementation include the following:
1. HWRF RESOLUTION UPGRADE: For the first time in history, NCEP will be implementing a very high resolution hurricane model developed in joint collaboration with AOML/HRD. This is a resulted of a carefully drafted and executed R2O plan supported by NOAA Hurricane Forecast Improvement Project (HFIP).2. HWRF FRAMEWORK UPGRADES: from V3.2 to latest community version WRF NMM V3.4a: The NMM core of the operational HWRF model will be upgraded to latest community version currently referred to as V3.4a.
3. HWRF CODE OPTIMIZATION: The HWRF team members at EMC have put substantial efforts to accomplish higher order code optimization, improved utilization of MPI functionality, design and use of I/O servers and many other code efficiency related changes in order to fit the operational HWRF run within the allocated time and resources. It is expected that the operational HWRF forecasts will be made available to the National Hurricane Center (NHC) within 80 minutes from the start of integration (about 20 minutes more than the current operational HWRF run time at 9 km resolution), with one additional compute node required per forecast (four nodes, 246 CPUs).
4. HWRF NEW NEST MOTION ALGORITHM: The current nest motion algorithm based on dynamic pressure will be replaced with a new centroid based algorithm essential for high-resolution grids. The new algorithm is more efficient in identifying and tracking the tropical systems more accurately, resulting in improved track and intensity forecasts.
5. HWRF PHYSICS UPGRADES: HWRF physics upgrades consist of modifications to the GFS PBL based on observational findings, improved GFDL surface physics, GFS SAS convection and Ferrier Microphysics parameterization schemes, and implementation of new GFS Shallow Convection parameterization. The cloud-permitting 3km nest is configured to explicitly resolve convection in the inner core of the hurricane. These upgrades are consistent with higher resolution grids, and have shown significant improvements in the hurricane track and intensity forecasts in our retrospective tests for two seasons (2010-2011) in both Atlantic and Eastern Pacific basins.
6. HWRF INITIALIZATION UPGRADES: Vortex initialization is re-designed for 3 km resolution, with improved interpolation algorithms and storm size and intensity correction procedures. In addition, different composite storms are designed for application in storms designated as deep and medium respectively. Data assimilation through HWRF GSI is now included for all storms (current operational HWRF GSI is used only for deep storms). Although no inner-core observations are assimilated, HWRF uses GSI to assimilate prepbufr data in the tropical storm environment. Keeping with the upgrades of NCEP GSI, HWRF GSI will be upgraded to community version V3.5.
7. HWRF OCEAN UPGRADES: Efforts are under way to couple the Eastern Pacific basin to 1-D POM for improved intensity forecasts in that basin.
8. HWRF POST-PROCESSING AND PRODUCT UPGRADES: HWRF post-processor based on NCEP Unified Post Processor is upgraded to generate simulated synthetic microwave imagery from SSM/I sensors. A new very high-temporal resolution (every time step) track and intensity forecast data at 5-sec. interval will be provided at the request of NHC.
9. HWRF Tracker Upgrades: HWRF tracker based on NCEP tracker is modified to account for tracking tropical systems at very high resolution (3 km). This will become a part of the unified NCEP tracker being considered for implementation for all NCEP models and ensembles.
10. HWRF SCRIPTS ENHANCEMENTS AND PROCEDURAL UPGRADES: Operational HWRF scripts have been modified to accommodate triple nesting capability, higher-order optimization, configuration of I/O servers and various namelist options suitable for high resolution. These upgrades will also include changes to WPS (pre-processing), UPP (post-processing), POM upgrades and initialization upgrades. A few procedural changes will be required to run the HWRF tracker along with the post-processing to provide forecast output on time. These changes are expected to increase the efficiency and optimum utilization of CCS resources for high-resolution HWRF model runs.