Pacific Northwest Mesoscale Model Weather Forecasts: Information

For a description of the MM5-NAM forecasts click here

For a description of our older, experimental WRF forecasts click here

For a description of our older, real-time MM5 forecasts click here

General Information: The Department of Atmospheric Sciences at the University of Washington is now running the Advanced Research WRF (WRF-ARW) core of the Weather Research and Forecasting Model (WRF) version 3.0.1.1 (WRF-ARW v3.0.1.1). Forecasts are run twice a day in order to produce high resolution meteorological guidance for the Pacific Northwest. This effort, supported by a consortium of local, state, and federal agencies, has several goals:

• To provide high resolution meteorological fields for air quality applications, weather forecasting, and other needs.
• To test the viability of local numerical weather forecasting completed on relatively low-cost workstations.
• To provide a large number of mesoscale model forecasts to determine model strengths, weaknesses, and biases.
• To improve mesoscale model physics and data assimilation approaches.
• To test the potential of directly coupling an atmospheric forecast model to air quality and hydrological numerical models.

Change Log: For the latest information on our setup, please consult the Change Log for Pacific Northwest WRF/MM5 Numerical Forecasts

Model Configuration: The WRF numerical forecasts currently feature an outer grid of 36 km horizontal resolution that covers much of western North America and the northeastern Pacific; a nested grid of 12 km resolution that covers Washington, Oregon, Idaho, Utah, much of Montana and Nevada, southern British Columbia, and northern California, Nevada; and an inner 4 km resolution grid encompassing all of Washington, Oregon, and Idaho plus the western third of Montana and the extreme northern sections of California, Nevada, and Utah, and the western third of Wyoming. The regions covered by each domain, showing topography and land use categories are shown in these plots:

New version Compatible with WRF		Old version from TERRAIN
Terrain	Land Use	Terrain	Land Use
36-km terrain	36-km land use	36-km terrain	36-km land use
12 km terrain	12 km land use	12 km terrain	12 km land use
4 km terrain	4 km land use	4 km terrain	4 km land use

A land use category color key is included in the links above, you may view it alone here.

A detailed description of the domain boundaries can be found in the actual geogrid.exe namelist.wps file or in the MM5 terrain.deck. Detailed land use information for each domain was derived from the 1-km USGS digital database, with some subjective modification using other data sources.

The model utilizes 38 vertical full-sigma levels see below, and is run in non-hydrostatic mode in order to limit pressure gradient force errors over the complex terrain. An upper-radiative boundary condition is used to allow gravity waves to radiate through the model top without being reflected. The following table describes the phyics options we are currently using:

Phyics and Other Options:

Physics	Comments
Radiation	Until 2009012200, both CAM longwave and shortwave radiation options used with default values. From 2009012212 onward, Dudhia shortwave and RRTM longwave radiation schemes used.
Thompson Microphysics	Includes graupel.
Kain-Fritsch Cumulus	Continuing what we began on 5 August 2004 (MM5 then) of using this on all domains.
YSU PBL	Yonsei University scheme (new MRF). Non-local-K scheme with explicit entrainment layer and parabolic K profile in unstable mixed layer. NOTE: the module_bl_ysu.F from version 3.0 of the WRF was backported into the version 2.2.1 WRF that was run up to and including the 2009010900 case.
Noah Land Surface Model	Four layers with soil temperature and moisture, fractional snow cover, and frozen soil physics.

Here are the exact namelist.input files that are used to run the model: 36/12 km namelist.input and 4 km namelist.input (these two links are updated with each model run.). For more information on any of these options, see the WRF model chapter of the WRF User's Guide.

1. MM5-NAM: 4-processor Intex Xeon Linux box.
2. WRF-GFS: Eight 8-processor Intel Xeon cluster running Debian Linux (Note, 6 of the 8 processors are used, since very little is gained by running with all 8. Keeping 2 available on each machine also allows for short research runs or make-up runs to be run concurrently with the real-time run with a small impact on that run).