The WRF Modeling System

The Weather Research and Forecasting (WRF) model activities in FY2015 included: providing user support for the core WRF model and related systems, WRFDA and WRF/DART; delivering WRF tutorials; hosting the annual WRF Users’ Workshop; oversight of the WRF repository and WRF Developers’ Committee; testing and incorporation of community-contributed code; and oversight of WRF releases and the WRF Release Committee. MMM personnel conducted WRF-based research, supported field campaigns with real-time WRF forecasts, and undertook basic research and development in numerical modeling and data assimilation. MMM’s weather research and its model development are fundamental to the vitality of the WRF system.

WRF continued to see strong user growth, and new registrations have averaged over 3,000 per year for the past five years.  The cumulative number of registered users of WRF is currently over 32,200, with 162 countries represented. The number of subscribers on the WRF e-mail list is over 8,200, and e-mail inquiries to wrfhelp (the WRF user assistance service) average about 350/month. As illustrated in figure 1 below, there has been a significant increase in the number of WRF-related published articles over the past thirteen years.

WRF Publications Graph
Figure 1: Solid line depicts the number of WRF-related published articles per year and the dotted line depicts the cumulative total. The red segments are the projection by year-end for 2015 based on data through mid-November.

In FY2015 MMM continued to support WRF to the community and released WRF Version 3.7 in April 2015 which included both the WRFDA (see below) and WRF-Chem systems. WRF V3.7 offered a number of enhancements, such as new physical process schemes and software improvements, reflecting contributions from throughout the WRF community. Features of the release included the following.

  • Cumulus schemes: New Teidke, new scale-aware Kain-Fritsch, new Wilson YSU shallow convection
  • WRF-Hydro V3.0: Hydrological model coupled to WRF
  • Microphysics schemes: New NSSL 2-moment scheme, updated Milbrandt, updated Thompson, WSM and WDM interaction with radiation scheme
  • LSM: Improvements to Noah-MP, updated RUC LSM
  • PBL: Scale-aware YSU scheme
  • WRFDA: Overhaul of radar DA capability
  • Software and infrastructure: Vertical nesting capability, Enhanced CF (Climate and Forecast) compliance.

In August MMM issued WRF minor release V3.7.1, a bugfix release.

WRFDA V3.7 was also released in April 2015.  Its new features included a new background error option (CV7) and new options for assimilating radar reflectivity data. WRFPLUS, the WRF adjoint and tangent linear model, was updated to V3.7 to be consistent with WRF V3.7. In addition, a new microphysics option was added to WRFPLUS, a modified Kessler scheme. WRFDA was also modified to be able to use WRF files with the "lat-lon" (cylindrical equidistant) map projection.

In this reporting period. MMM and IMAGe scientists implemented a real-time ensemble Kalman filter and ensemble prediction system. The system, which is based on WRF and DART, has been running 15-km cycled data assimilation and 3-km, 10-member ensemble forecasts continuously since March 2015. Forecast fields and derived products can be viewed at, and these were used as part of the 2015 Hazardous Weather Testbed Spring Forecast Experiment for the National Weather Service. An example is shown in figure 2 below.

USA Map WRF 24-h forecast probablity
Figure 2: 24-h forecast of probability of updraft helicity exceeding 75 m2/s2 for 17 Aug 2015, overlaid with boxes indicating NWS severe-weather warnings for the same date.