WFR/ARW real-time forecast with 12/4/1.33 km nested grids initialized at 00 UTC on 29 August 2006 depicting the simulated radar reflectivity for hurricane Ernesto within the 1.33 km and 4 km (horizontal grid size) moving nested grids embedded in the 12 km outer domain at 30 h (red domains), 56 h (green domains), and 75 h (blue domains); the dark brown dashed line reflects the forecast track with circles marking its location at 12 h intervals. These forecasts confirm that the WRF/ARW predictions for hurricane track and intensity are as or more accurate than those from current operational forecast models. The vortex-following moving nested grids allow very high resolution forecasts to be produced with great savings in computed time due to the reduced sizes needed for the moving nested grids.
Priority 3: Improving Prediction of Weather, Climate, and Other Atmospheric Phenomena
The WRF-ARW Effort
Background
The Weather Research and Forecasting (WRF) model effort has aimed to develop a next-generation mesoscale forecast model and data assimilation system that will advance the understanding and prediction of mesoscale weather and accelerate the transfer of research progress into operations. WRF has been developed as a collaboration among the Mesoscale and Microscale Meteorology (MMM) Division of NCAR, NOAA's National Centers for Environmental Prediction (NCEP) and Earth System Research Laboratory (ESRL), the Department of Defense's Air Force Weather Agency (AFWA) and Naval Research Laboratory (NRL), the Center for the Analysis and Prediction of Storms (CAPS) at the University of Oklahoma, and the Federal Aviation Administration (FAA), with the participation of numerous university scientists.
Progress
This year NCAR scientists continued to develop the Advanced Research WRF (ARW) and to support its widespread use as a community model. The ARW represents the primary modeling system used for the NCAR priority of investigating the dynamics and predictability of weather systems on time scales of 0 - 48 h. Advancing the NCAR Strategic Plan, the ARW effort addresses NCAR's goal of improving understanding of the atmosphere, the Earth system, and the Sun. Within that goal, the ARW effort serves the priorities of exploring atmospheric processes, improving prediction of weather, and developing community models.
The WRF activities over the past year have been in development, community support, and model applications. Developments include:
- Updates to physics (e.g., microphysics and land surface packages) as well as new capabilities, such as the new WRF Preprocessing System (WPS).
- Advances in both analysis and observation nudging techniques (in collaboration with Penn State and NCAR/RAL) for model initialization.
- Software architecture developments including refining moving nested grid techniques and using them in hurricane forecasts (see accompanying figure), enhancing parallel performance, and a project to port WRF to the Microsoft Windows operating system.
- Integrating WRF into the Earth System Modeling Framework (ESMF)
- Continuing research in a global implementation
Through the year NCAR has provided vital community service and leadership through its support of the system. The number of registered users of the ARW now stands at over 4,200. Over half of these are from outside of the U.S., with the total distributed over 78 countries.
In June 2006, NCAR organized the 7th Annual WRF Users' Workshop. NCAR also conducted three ARW user tutorials (including one in India) and convened international WRF workshops in Korea, Taiwan, and China.
In notable applications, the ARW began to be used in the Antarctic Mesoscale Prediction System (AMPS) that provides experimental, real-time NWP support for the United States Antarctic Program and serves international science across Antarctica. In addition, the ARW was applied in real-time, convection-permitting forecasts of landfalling hurricanes and in support of the MIRAGE (Megacities Impact of Regional and Global Environment) field campaign and FAA forecast demonstration experiments. The figure below illustrates forecasts of Hurricane Ernesto (August 2006). These simulations employed the highest-resolution, real-time hurricane forecast grid run anywhere (1.33 km).
Plans
In the coming year, NCAR will continue to support the ARW to the international community, including new code releases and the organization of workshops and tutorials. Comprehensive analyses of past real-time convection-resolving forecasts will also continue in order to better understand and to improve ARW performance. NCAR will further evaluate approaches to an optimal numerical framework for a global version of WRF for use in a future “global cloud model“ application.
Activities conducted under this effort have received support from NSF, NSF's Office of Polar Programs, NSF's UCAR and Lower Atmospheric Facilities Oversight Section, the Air Force Weather Agency, the Korean Meteorological Agency, the National Aeronautics and Space Administration, and the Federal Aviation Administration.
For further detail, please read the full project report linked below.