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NOAA Rapid Refresh Forecast System (RRFS) Ensemble [Prototype]

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The Rapid Refresh Forecast System (RRFS) is the National Oceanic and Atmospheric Administration’s (NOAA) next generation convection-allowing, rapidly-updated ensemble prediction system, currently scheduled for operational implementation in late 2023. The operational configuration will feature a 3 km grid covering North America and include forecasts every hour out to 18 hours, with extensions to 60 hours four times per day at 00, 06, 12, and 18 UTC. Each forecast is planned to be composed of 9-10 members. The RRFS will provide guidance to support forecast interests including, but not limited to, aviation, severe convective weather, renewable energy, heavy precipitation, and winter weather on timescales where rapidly-updated guidance is particularly useful.

The RRFS is underpinned by the Unified Forecast System (UFS), a community-based Earth modeling initiative, and benefits from collaborative development efforts across NOAA, academia, and research institutions.

The S3 Bucket will provide datasets from three of the 2021 NOAA Testbed Experiments. During each of these experiments, a prototype version of RRFS under development will be run. The following is a high-level overview of the date ranges of each of the Testbed Experiments along with a broad overview of the planned configuration(s). Links are provided in the Documentation section for the detailed finalized configurations.

2021 Hazardous Weather Testbed Spring Forecast Experiment, May 3 through June 4 9-member multi-physics ensemble with stochastic perturbations run once per day at 3 km grid spacing covering North America out to 60 hours. Initial conditions and lateral boundary conditions are taken from the GFS and GEFS. 2021 Hydrometeorological Testbed Annual Flash Flood and Intense Rainfall Experiment (FFaIR), June 21 through July 23, excluding the week of July 4 9-member multi-physics ensemble with stochastic perturbations run once per day at 3 km grid spacing covering North America out to 60 hours. Initial conditions and lateral boundary conditions are taken from the GFS and GEFS. 2021-2022 Hydrometeorological Testbed Winter Weather Experiment, mid November through mid-March Planned -- RRFS data assimilation system updating hourly at 3 km grid spacing covering North America. Details are still TBD.

For each cycle, the dataset is organized by cycle day, time of day, and member. For example, rrfs.20210504/00/mem01/ contains the forecast from ensemble member 1 initialized at 00 UTC on 04 May 2021. Users will find two types of output in GRIB2 format. The first is:


Meaning that this is RRFS ensemble member 1 initialized at 00 UTC, covers the North American domain, and is the post-processed gridded data at hour 24. This output is on a rotated latitude-longitude domain at 3 km grid spacing. These are large files and users may wish to subset or re-project the grid after downloading. We recommend using the WGRIB2 application for such purposes.

The second output file in grib2 format is as follows:


These grids have been subset from the much larger North American domain to a CONUS domain on a Lambert Conic Conformal projection and also contain significantly fewer fields, resulting in smaller files. The project team produces these files to facilitate participation in various NOAA Testbed Experiments, such as the Hazardous Weather Testbed.

Graphics for select runs are also included in a plots/ directory under each experiment day for quick, yet simple visualization.

This work is supported by the Unified Forecast System Research to Operation (UFS R2O) Project which is jointly funded by NOAA’s Office of Science and Technology Integration (OSTI) of National Weather Service (NWS) and Weather Program Office (WPO), [Joint Technology Transfer Initiative (JTTI)] of the Office of Oceanic and Atmospheric Research (OAR).

DISCLAIMER The output provided here is experimental and is subject to change, outages, and gaps. Please contact the data managers for additional information or questions.

Update Frequency



Open Data. There are no restrictions on the use of this data.


Managed By

See all datasets managed by NOAA.


For any questions regarding data delivery or any general questions regarding the NOAA Open Data Dissemination (NODD) Program, email the NODD Team at
We also seek to identify case studies on how NOAA data is being used and will be featuring those stories in joint publications and in upcoming events. If you are interested in seeing your story highlighted, please share it with the NODD team by emailing

How to Cite

NOAA Rapid Refresh Forecast System (RRFS) Ensemble [Prototype] was accessed on DATE from

Usage Examples


Resources on AWS

  • Description
    Rapid Refresh Forecast System (RRFS) Data
    Resource type
    S3 Bucket
    Amazon Resource Name (ARN)
    AWS Region
    AWS CLI Access (No AWS account required)
    aws s3 ls --no-sign-request s3://noaa-rrfs-pds/
    Browse Bucket
  • Description
    New data notifications for RRFS, only Lambda and SQS protocols allowed
    Resource type
    SNS Topic
    Amazon Resource Name (ARN)
    AWS Region

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