On 31 July 2018, the NSSL-WRF website will be upgraded and moved to The new page will also display 0000 UTC initializations of NSSL-FV3 and HRRRv3 and include a link for model verification. Until then, this page will remain and we encourage users to check out the new page and provide feedback at:

Click for more info

Thank you for your support of the NSSL-WRF. On 31 July 2018, this page ( and the older version of this page ( will be replaced by the web domain

The following provides some background behind these changes. As part of a project funded by NOAA's Office of Weather and Air Quality, NSSL is performing real-time, convection-allowing forecasts out to 60 hours from the Finite Volume Cubed Sphere Model (FV3), which has been selected as the Next Generation Global Prediction System for the NWS. The goal of this project is to assess the performance and accelerate the development of FV3 at convection-allowing scales. Additionally, NSSL is continuing to provide forecasts from an experimental configuration of the Weather Research and Forecasting Model (WRF), known as the NSSL-WRF, to provide support to the Storm Prediction Center and other users, and provide a framework to test and develop new forecasting tools and diagnostics.

In order to simplify the dissemination and visualization of both sets of forecasts, these forecasts will be displayed using a single web page. Because the existing web domain,, no longer makes sense since we'll be displaying FV3 in addition to WRF, a more general domain name that encompasses both forecast models is needed. The web domain serves this purpose (“cams” stands for “convection-allowing models”). Note, the new webpage will display the CONUS domain along with the option to display nine sector zooms, similar to the HREFv2 viewer at The WFO-level zooms will no longer be available. If you have questions, comments, or suggestions regarding this change please contact Adam Clark (

About the NSSL Realtime WRF Forecasts

The National Severe Storms Laboratory (NSSL) and Storm Prediction Center (SPC) first began exploring the use of 4-km grid-spacing convection-allowing Weather Research and Forecasting (WRF) model simulations as potential forecasting tools during the 2004 and 2005 NOAA/Hazardous Weather Testbed Spring Forecasting Experiments (Kain et al. 2006). The results from these tests were extremely positive with forecasters particularly impressed by the ability of the WRF simulations to depict realistic convective-scale storm structures associated with phenomenon like mesoscale convective systems and discrete supercells. These successful tests along with other experiments using convection-allowing WRF simulations conducted by NCAR (Done et al. 2004) motivated NSSL scientists to establish a more permanent experimental modeling framework to provide storm-scale guidance to SPC forecasters and serve as a testing ground for the development of storm-scale model diagnostics (e.g., Kain et al. 2010). Collaborations with scientists at NASA-SPoRT provided the necessary computing resources for daily forecasts beginning in 2006 and this real-time modeling framework became known as the NSSL-WRF.

The NSSL-WRF uses 4-km grid-spacing and is run twice daily at 0000 and 1200 UTC with forecasts to 36 h over a full CONUS domain integrated using NOAA’s high performance computing resources. The configuration has remained relatively constant with only two sets of updates as of this writing. In June 2009, the model domain was expanded and the WRF model version was updated from 2.2 to 3.1.1, and in April 2013 the WRF model version was updated to 3.4.1. Physics parameterizations include the MYJ boundary layer scheme and WRF single-moment six-class microphysics scheme. Despite recent works that illustrate advantages to using double-moment microphysics in high-resolution supercell analyses (e.g., Jung et al. 2012) and idealized simulations of squall lines (Bryan and Morrison 2012), research analyzing various WRF model configurations using single and double moment microphysics scheme as part of recent NOAA/Hazardous Weather Testbed Spring Forecasting Experiments has yet to find a quantifiable objective or subjective improvement using double moment schemes over the 15 to 30 h forecast period in which the NSSL-WRF forecasts are most heavily utilized (Clark et al. 2012, 2014). Thus, because of its relative simplicity, computational efficiency, and familiarity with SPC forecasters and other users, NSSL-WRF continues to use WSM6.

Deterministic NSSL-WRF Configuration

Daily, real-time runs of the Weather Research and Forecasting (WRF) model are generated using 256 processors on the Jet HPC cluster (Raytheon/Aspen Systems) in Boulder, CO. The current configuration includes:

  • WRF version 3.4.1
  • MYJ BL/turbulence parameterization
  • WSM6 microphysics
  • RRTM longwave radiation
  • Dudhia shortwave radiation
  • Noah land-surface model
  • Positive definite advection of moisture
  • 4 km grid length (1200x800)
  • 35 vertical levels
  • Time step 24s

Initial and boundary conditions are obtained from interpolation of the routinely available 40km NAM Model fields obtained from EMC/NCEP, using the WRF Preprocessing System (WPS). Initialization time is 00 UTC and 12 UTC and forecast length is 36 h.

Ensemble NSSL-WRF Configuration

In early 2014, NSSL requested and was granted an increase in computing allocation on the Jet HPC cluster (Raytheon/Aspen Systems) in Boulder, CO. The increased allocation is being used to run a nine-member NSSL-WRF Ensemble. Currently, the 9 members are comprised of the regular NSSL-WRF, which uses the 0000 UTC initialized NAM for ICs and LBCs, one member that uses the 0000 UTC initialized GFS for ICs and LBCs, and 7 members that use different members of NCEP's 2100 UTC initialized SREF system for ICs and LBCs. The SREF-initialized members are initialized at 0000 UTC using 3-h SREF forecasts (valid at 0000 UTC), and LBCs for the SREF-initialized members come from the corresponding SREF member used for the ICs. The SREF system ICs/LBCs include 3 WRF-ARW members (the control member and two perturbed members), 2 NMM members (the control and one perturbed member), and 3 NMMB members (the control and two perturbed members). The domain and physics parameterizations for each NSSL-WRF ensemble member are identical to the regular NSSL-WRF. Although the unvaried physics will have lower spread than a varied physics ensemble, forecasters are much more familiar with the behavior of the NSSL-WRF physics, and this will allow a clear diagnosis of the contribution of ensemble variance from the ICs/LBCs. Note, the current ensemble configuration is preliminary and will be changed based on subsequent objective and subjective evaluations and the development of new ensemble data assimilation approaches at NSSL. However, the configuration of the regular NSSL-WRF run will not change.

For more info on these experimental high resolution model forecasts, email Adam Clark at

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