The Rapid Update Cycle (RUC)

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1 hr precipitation / MSLP / Thickness

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Aviation Flight Rules

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2m Potential Temperature / 10m Winds

    Modified 1 May 2012: The RUC was a NOAA/ NCEP operational weather prediction system running every hour out to at least 18h comprised primarily of
    • A numerical forecast model (using isentropic-sigma hybrid vertical coordinate) and
    • An analysis/assimilation system to initialize that model.
  • Developed to serve users needing frequently updated short-range weather forecasts, including those in the US aviation community and US severe weather forecasting community.
  • The Rapid Refresh (RAP) is the next-generation version of the 1-h cycle system, and replaced the operational RUC at NCEP at 12z on 1 May 2012.

News items

  • 8 May 2012 - An experimental version of the RUC continues to run at ESRL for an undetermined period of time for baseline comparisons with the RAP (continued into 2016). 1 May 2012 RAP operational implementation at NCEP occurred at 12z on 1 May 2012 as planned. The last NCEP RUC run was 11z today.
  • 2 March 2010 - RUC upgrade (although not completely installed until 20 April 2010. Explanation ): Extension of RUC to 18h every hour, modification to hybrid coordinate, addition of Canadian aircraft observations. More info available at
  • 4 Dec 2009 Problem with radar reflectivity ingest into NCEP-operational RUC starting early August, script updated to changed directory Tues 1 Dec.
  • 12 Nov 2009 Rapid Refresh/RUC review presentation - latest news - PDF
  • 14 Oct 2009 TAMDAR moisture observations restored to RUC (and NAM) for NCEP runs today after 50-day absence due to upstream metadata change. TAMDAR moisture observations have been available all along for all ESRL/GSD RUC runs.
  • 31 Mar 2009. NCEP implementation at 12z with improved snow cover and improved cloud analysis, see Info PDF here. -
  • 16 Dec 2008. TAMDAR data added to operational RUC at NCEP
  • 17 Nov 2008. RUC upgrade implementation at NCEP Assimilation of radar reflectivity added, longwave radiation changed to RRTM scheme, convection (Grell-Devenyi) changes. Extended RUC upgrade ppt here for pre-implementation briefing
  • 8 Jan 2008. RUC crisis change for improved cloud/vis assimilation, wind gust, precip type. , PDF
  • 11 Dec 2007. RUC/RR summary Powerpoint/pdf presented at NCEP Production Suite Review meeting.
  • 4 Dec 2007. 13km/hourly RUC grids became available via NOAAPort and Family of Services.
  • Reflectivity real-time products available for devRUC13 and backup RUC13 uns since April 2007.
  • 4 April 07 - 3-d radar reflectivity data assimilated hourly in experimental devRUC13 since Feb07 and now in backup RUC13 as now. An example of the effect of radar reflectivity assimilation in available here
  • 28 June 2005 -- 13km RUC operational implementation at NCEP --
    -- Higher resolution, additional observation types assimilated (GPS PW, METAR cloud/vis, RASS, improved use of GOES cloud-top), improved moisture analysis, improved cloud/precip physics.
  • RUC journal articles available in Feb 2004 Monthly Weather Review.
    Mesoscale Weather Prediction with the RUC Hybrid Isentropic Terrain-Following Coordinate Model. pages 473-494. [GSD PDF version]
    An Hourly Assimilation-Forecast Cycle: The RUC. pages 495-518. [GSD PDF version]

    The key features of the RUC include:

  • high-frequency (every 1h) short-range weather model forecasts (out to 12+ h) in support of aviation and other mesoscale weather forecast users
  • high-frequency (every 1h) 3-d objective analyses over much of North America, including the contiguous United States and adjacent areas of Canada and Mexico, assimilating the following types of observations:
    • Commercial aircraft, including regional aircraft data with moisture (TAMDAR)
    • Radar reflectivity (3-d)
    • Profiler related
      • Wind profilers (404 and boundary-layer 915 MHz)
      • VAD (velocity-azimuth display) winds from NWS WSR-88D radars
      • RASS (Radio Acoustic Sounding System)
    • Rawinsondes and special dropwinsondes
    • Surface
      • Surface reporting stations and buoys (including cloud, visibility, current weather)
      • Mesonet
    • Satellite
      • GPS total precipitable water estimates
      • GOES cloud-top data (pressure and temperature)
      • GOES total precipitable water estimates
      • SSM/I total precipitable water estimates
      • GOES high-density visible and IR cloud drift winds
    • Experimental
      • Lightning - experimental
      • NASA Langley cloud products including water/ice path
  • a hybrid isentropic-sigma vertical coordinate.

Other RUC Information, Real-Time and Archived Data

Archived RUC gridded data available from:

Information on gridded data

Model fixed fields - topography, etc.