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Hurricane Model Transitions to Operations at NCEP/EMC

A Joint Hurricane Testbed (JHT) Program

Robert E. Tuleya, S. Gopalkrishnan, Vijay Tallapragada, Young Kwon, and Naomi Surgi (EMC/NCEP) Robert.Tuleya@noaa.gov

The emphasis for this 2005-2007 JHT project has concentrated on HWRF development. Continued progress has been made in the development of HWRF into an operational hurricane forecast system. This development is designed to take into account the strengths of the WRF software system, the use of the well tested NMM dynamic core, and the physics packages of the GFDL highly successful forecast system. The HWRF forecast system has progressed from a uniform-mesh WRF proto-type system installed and run at NCEP for the 2004 season to a moving nested HWRF automated system run for numerous cases for the 2005 season. For the 2006 season numerous cases were run with a two-way nested moving system. The system has proven quite robust with few failures. During this past six months, further refinements were made to the system. The physics packages were also brought in line with the GFDL model with changes to the momentum mixing in the cumulus parameterization and the inclusion of a refined surface roughness and flux parameterization. With the inclusion of the Ferrier cloud microphysics package into the 2006 GFDL operational system, the physics packages of the HWRF and the GFDL model are nearly identical. The physics packages and model systems of both the GFDL and HWRF will be presented and compared.

As mentioned, the design of the hurricane forecast system has progressed with new components added for both physical integrity and operational expediency. Options are available to run a forecast analysis cycle in a NOAA hurricane model system for the first time. An ocean initialization and coupled atmospheric-ocean model has recently been integrated into the HWRF hurricane system. The HWRF post- processing steps have been upgraded to include superior storm tracking and verification techniques as well as the availability of synoptic fields. For computational and operational expediency, the HWRF system now has the capability to process binary files and use input data on native operational model grids. Another major task of this project has been checking and tuning of the physics packages to attain high forecast skill. It has long been known that physics packages are key to successful forecasts in the tropics, especially that of hurricanes. Considerable time has been spent in testing and incorporating physics packages comparable to the GFDL forecast system which has been undergoing considerable changes over the last few years. The HWRF model sensitivity to various flavors of physic packages such as momentum mixing, surface flux and radiation parameterizations will be shown.

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