Skip Navigation Links
NOAA logo - Click to go to the NOAA homepage National Weather Service NWS logo - Click to go to the NWS homepage
EMC Logo
Navigation Bar Left Cap Home News Organization
Navigation Bar End Cap

         MISSION / VISION    |    About EMC

Mesoscale Branch Web Page Reference List

Mesoscale Branch Web Page Reference List

Table of Contents

Please note : Most of the NCEP real-time model web pages listed below are generated on the NCEP development computer, and therefore will not be updated when this computer is down. The web graphics for the NAM 12-km parent, GFS, GEFS, Alaska/CONUS NAM nests, SREF, HiRes Window runs, RTMA, RAP, and HRRR on the NCEP Model Analysis and Guidance (MAG) site are operational, created in near real-time, and subject to 24/7 monitoring by NCEP Central Operations. If you have any questions please email Eric Rogers at


Web Page Models Displayed Forecast Length Forecast frequency Animation? Archive of past forecasts?
NAM FORECAST METEOGRAMS NAM 84-h ; displays last two NAM runs for 1300+ stations, use NAM model grid point nearest to station 1 hour Not applicable No
NAM FORECAST PRECIPITATION TYPE METEOGRAMS AND REGIONAL PLOTS NAM 84-h (00Z/12Z runs only); data for 1300+ stations, use NAM model grid point nearest to station 1 hour Yes, for regional hourly plots of precipitation type No
RAP FORECAST METEOGRAMS RAP 18-h; displays latest RAP 3-h cycle, data for 500+ stations, use model grid point nearest to station 1 hour Not applicable No
NCEP North American Mesoscale (NAM-12) Model : NCEP Model Analysis and Guidance (MAG) page

NCEP North American Mesoscale (NAM-12) Model : Enhanced CONUS/North America/Hawaii Graphics (EMC page)

NAM 84-h 3 hours Yes 7 days on EMC page, 1 day on NCEP MAG page
NAM Nest runs (parent = Ops NAM 12 km run), EMC web pages
  1. 6 km Alaska
  2. 6 km Alaska (1-36 h hourly graphics)
  3. 4 km CONUS
  4. 4 km CONUS (1-36 h hourly graphics)
  5. 3 km Hawaii
  6. 3 km Puerto Rico

Ops NAM 12km run, NAM nests 60-h 3 hour (1-h for NAM Alaska and CONUS nest hourly web page) Yes 7 days
NAM Nest runs on NCEP Model Analysis and Guidance Page (Model Type = "NAM-HIRES")
  1. 6 km Alaska nest or 4 km CONUS nest

  • Model Area = ALASKA for 6 km Alaska nest
  • Model Area = NAMER for 4 km CONUS nest
  • 60-h 3 hour Yes 1 day
    NAM CONUS Nest runs ("quick look" web page)
    1. 4 km CONUS

    NAM CONUS nest 60-h 3 hour Yes Last 4 cycles
    NAM Fire Weather Nest 1.333 km (CONUS) or 1.5 km (Alaska) NAM Fire weather nest 36-h 1 hour Yes 7 days
    NCEP Model Graphics NAM, GFS, NAM or GFS parallel (if running) 84-h 6 hours Yes 7 days
    NCEP Operational NAM-12 : Convective Forecasting Page for 00Z/12Z cycles NAM 84-h 3 hours Yes No
    NCEP HiResWindow Forecast Page - EMC Web pages
  • CONUS NMMB and ARW (00Z,12Z) vs ops NAM CONUS nest
  • Hawaii NMMB and ARW (00Z/12Z) vs ops NAM Hawaii nest
  • Guam NMMB and ARW (00Z/12Z)
  • Puerto Rico NMMB and ARW (06Z/18Z) vs ops NAM Puerto Rico nest
  • Alaska NMMB and ARW (06z/18Z) vs ops NAM
  • 48-h 3 hours Yes No
    NCEP HiResWindow Forecasts on NCEP Model Analysis and Guidance Page
  • Model Area = CONUS, HAWAII, ALASKA, GUAM, or PR (Puerto Rico)
  • Model Type = HRW-NMM or HWR-ARW for CONUS, HAWAII, GUAM
  • Model Type = HRW-NMM-AK or HWR-ARW-AK for ALASKA
  • Model Type = HRW-NMM-PR or HWR-ARW-PR for Puerto Rico
  • 48-h 1 hour Yes 1 day
    NCEP Operational NAM, GFS, Parallel NAM/GFS - Forecast Trends over North America NAM, GFS, NAM/GFS parallel (if running) 84-h (00Z/12Z cycles only) 12 hours No 2.5 days
    NCEP Operational NAM Forecast Trends over CONUS, North America Operational NAM-12 km parent domain 84-h (00Z/12Z cycles only) 12 hours No 2.5 days
    NAM Nest runs (parent = Ops NAM 12km run) : Forecast Trends
    1. 6 km Alaska
    2. 4 km CONUS
    Ops NAM, NAM Nest runs 60-h 12 hours No 2.5 days
    NCEP Short-range Ensemble Forecast (SREF) System : NCEP Model Analysis and Guidance page

    NCEP Short-range Ensemble Forecast (SREF) System (EMC page)

    21 member SREF ensemble (WRF-NMM, WRF-ARW, NEMS-NMMB, 7 members each) 87-h 3 hours Yes 3 days
    NCEP Rapid Refresh (RAP) - NCEP Model Analysis and Guidance Page RAP version of WRF-ARW 18-h 1 hour Yes about 1 day
    NCEP 3 km High-Resolution Rapid Refresh (HRRR) - NCEP Model Analysis and Guidance Page

    NCEP 3 km High-Resolution Rapid Refresh (HRRR) - GSD/ESRL Page

    HRRR version of WRF-ARW 15-h 1 hour or 15 minutes Yes about 1 day
    NCEP Downscaled GFS by NAM Extension (DGEX) DGEX (CONUS at 06/18Z, Alaska at 00/12Z), GFS 84-192 h 6 hours Yes No
    NCEP Real-Time Mesoscale Analysis (RTMA) (NCEP page, click on "Observations and Analyses")
    Hourly Operational RTMA Not applicable 1 day
    NCEP Real-Time Mesoscale Analysis (RTMA) (EMC site)
    Hourly Operational RTMA Not applicable 1 day
    NCEP CMAQ Ozone and Particulate Matter Forecast Page Operational and Developmental Air Quality Forecasts and Verification

    Back to Table of Contents


    Web Page Models Displayed Forecast Length Forecast frequency Animation? Archive of past forecasts?
    4 km WRF-NMM Parallel - 00z cycle

    4 km WRF-NMM Parallel - 12z cycle

    WRF-NMM (CONUS domain), WRFV3.1+ code with old passive substance advection 36-h 1 hour Yes 1 day

    Back to Table of Contents


    Web Page Description Models Displayed Retention Period
    Daily Precipitation Verification Plots This site is an archive of model forecast precipitation vs. 24-h (12Z-12Z) observed precipitation analysis NAM (12 km parent and nests), RAP, HRRR, GFS, International Models (CMC (regional and global), UK Met, ECMWF, JMA, DWD, Meteo France), HiResWindow runs, SREF mean, NAM/GFS parallels, DGEX, HPC QPF forecast December 2001 - present
    NCEP/EMC Precipitation Skill Scores for Operational Models Monthly equitable threat and bias scores for 24-h forecast precipitation versus observed precipitation NAM, GFS, HiResWindow runs, various international regional and global models 1995 - present
    NAM/GFS Forecast 500 Mb Height Differences This page shows the forecast height difference at 500 mb for the NCEP NAM and GFS, compared to the NCEP Final (GDAS) analysis. NAM, GFS 3-4 months
    INTERACTIVE NCEP MODEL VERIFICATION WEB PAGE (at ESRL) Interactive web page tool for display of NCEP model verifications NAM, GFS, RAP January 2006 - present
    INTERACTIVE NCEP MODEL VERIFICATION WEB PAGE (NCEP EXPERIMENTAL PAGE, INTERNAL USE ONLY) Interactive web page tool for display of NCEP model verifications NAM, GFS, RAP January 2006 - present
    EMC MODEL FORECAST VERIFICATION STATS (Static Display) Verification (bias and RMS errors) of 06-84 h forecasts of 500 mb Height, 700 mb RH and Temp, 850 mb Temp, 300 mb Temp, and 250 MB Vector Wind vs. rawinsondes over the CONUS and Alaska; 2-m temps / 10-m winds vs. surface observations NAM, GFS, RAP Past 30 days vs rawinsondes, past 8 days vs surface data
    EMC MODEL FORECAST VERIFICATION STATS : 00z/12z NAM/GFS vs 06z/18z NAM/GFS Verification (bias and RMS errors) of NAM/GFS forecasts of 500 mb Height, 700 mb RH and Temp, 850 mb Temp, 300 mb Temp, and 250 MB Vector Wind vs. rawinsondes over the CONUS, comparing the "ontime" (00z/12z) NAM/GFS runs versus the "offtime" (06z/18z) NAM/GFS runs NAM, GFS Past 21 days
    NCEP/EMC Operational Model Cyclone Tracking Page This page shows the various model forecast tracks for tropical and extratropical cyclones NAM, GFS, GEFS, SREF, UKMET, NOGAPS, CMC Several months
    NAM-12 versus GFS 00-h analysis comparison page Comparison of NAM-12 vs GFS 00-h analysis to observations, with full fields (height/wind, temperature, specific humidity, total column precipitable water) and analysis/observation increments NAM, GFS analyses 7 days
    Operational NDAS, NAM analysis page Comparison of Operational NDAS, NAM analysis to observations (all 4 NDAS analyses per cycle), with full fields (height/wind, temperature, specific humidity, total column precipitable water) and analysis/observation increments Operational NDAS, NAM analyses 7 days
    Operational NDAS Satellite Radiance Assimilatiom Monitoring Page Plots of monitoring statistics for satellite radiance data (brightness temperature) assimilated in the NDAS GSI analysis
    1. Number of observations passing quality control check (last 4 NDAS cycles)
    2. Total Bias correction (last cycle, 1-day average, 7-day average)
    3. Guess (w/bias correction) - observation (1-day and 7-day average and standard deviation)
    4. Contribution to the penalty function (last cycle, 1-day average, 7-day average)
    EMC MODEL FORECAST VERIFICATION STATS - HI-RES WINDOW RUNS Verification (bias and RMS errors) of 06-48 h forecasts of 500 mb Height, 700 mb RH, 850, 700, 500, and 300 mb Temp, 250 MB Vector Wind vs. rawinsondes over each HIRESW domain; 2-m temps / 10-m winds vs. surface observations Operational HIRESW runs (NEMS-NMMB and WRF-ARW), Ops NAM (12 km parent and nests) Past 21 days vs raobs, past 10 days vs surface data
    Near-Surface Forecast Verification Statistics for operational NCEP models
  • Monthly (diurnal) composite of 00-hr to 84-hr forecast from the NAM and GFS models verified against observations averaged by region and composited on a monthly basis for 00z and 12z cycles.
  • Annual time series of the bias in the 84-hr forecast (end point) from the NAM model verified against observations averaged by region for the given year
  • NAM, GFS April 1998 - present
    Operational 12-km NDAS Surface Parameters 2-d graphics (animated) of NDAS surface fields (e.g., 12-h precip, soil temperature/moisture) over the CONUS/North America 12 km Operational NDAS 120 hours
    NDAS/NAM Surface Radiation Budget Verification This page shows the Operational and Parallel (if running) NDAS/NAM forecasts of surface radiation fields (downward short-wave and long-wave fluxes, skin temperature) at the seven SURFRAD sites in the CONUS Operational and parallel NAM runs 1-2 years
    NCEP NAM-12 SST analysis 2-d graphics (regional plots) of the most current SST analysis used by NAM model NAM 7 days
    NCEP NAM-12 Snow/Sea Ice analysis Plots of the most current Snow/Sea Ice analysis from NESDIS, USAF, and the analysis used as initial conditions in the NAM model NAM 7 days
    NCEP Observation Monitoring Web Page (EMC Internal Use Only) This page provides various diagnostic print messages on observation types and data counts used by NCEP operational models

    Back to Table of Contents


    Web Page Description Models Displayed Retention Period
    Daily Precipitation Verification Plots This site is an archive of model forecast precipitation vs. 24-h (12Z-12Z) observed precipitation analysis NAM, GFS, GFSX, CMC, CMC Global, UK Met, ECMWF, JMA, DWD, Meteo France, HiResWindow runs, various NAM parallels, DGEX December 2001 - present

    Back to Table of Contents


    Additional NCEP Model Change logs:

    1. Old Eta/EDAS production change log (Up to March 2004)
    2. RAP/HRRR Web page at ESRL, with list of RUC/RAP implementations at NCEP
    3. NCEP Air Quality Model Change Log

    Date (link goes to on-line documentation) Contents/major changes
    30 September 2014
  • Initial implementation of the hourly 3-km High-Resolution Rapid Refresh (HRRR) at NCEP
  • 12 August 2014
  • Changes to the North American Mesoscale (NAM) modeling system:
    1. Model Changes:
      1. Replace legacy GDFL radiation with RRTM
      2. Modified Gravity Wave Drag/Mountain Blocking; more responsive to subgrid-scale terrain variability
      3. New version of Betts-Miller-Janjic convection : moisture convective profiles; convection triggers less
      4. Ferrier-Aligo microphysics (see linked presentation for details)
      5. Modified treatment of snow cover/depth : Use forecast rime factor from microphysics in land-surface model
      6. Reduce roughness length for 5 vegetation types
        1. Evergreen Needleleaf Forest
        2. Deciduous Broadleaf Forest
        3. Mixed Forests
        4. Croplands
        5. Cropland/natural vegetation mosaic
      7. Model changes specifically targeting improving convective storm structure:
        1. All nests except Alaska will run with explicit convection
        2. Ferrier-Aligo microphysics (see linked presentation for details)
        3. Removed 4x increase in diffusion of specific humidity and cloud water mixing ratio
        4. Reduced 2nd order diffusion in nests
        5. Turn on separate microphysics species advection for all nests except Alaska
    2. Analysis/NDAS Changes
      1. Hybrid variational ensemble analysis
      2. New satellite bias correction scheme
      3. Variational quality control
      4. Raob level enhancement
      5. Begin use of mesonet wind reject list from RTMA
      6. Use new RTMA reject lists with most NWS Western Region stations removed
      7. Use GFS ozone analysis in radiance assimilation
      8. Diabatic digital filter initialization (12-km NDAS only)
      9. Resume calculation of NDAS long-term precipitation budget adjustment (used to bias correct Stage II/IV precip analyses using CCPA
      10. New observation types:
        1. GPS bending angle data replaces refractivity
        2. GOES-15 radiances
        3. New VAD winds (higher vertical resolution, produced at NCEP with radial wind QC)
        4. Meteosat-10 wind subtypes w/different data thinning
    3. Changes to NAM Downscaled Grids
      1. 5 km CONUS / 6 km Alaska DNG grids extended to 192-h via DGEX
      2. Added Haines Index for fire weather
      3. Improved 10-m wind treatment; use mass-consistent wind field, based on velocity potential, incorporating local terrain effects
    4. Other Changes:
      1. Discontinue use of AFWA snow depth product; NDAS snow depth will be continuously cycled, once per day (start of 06z NDAS) snow will be removed at any grid point that is snow-free in the IMS snow cover analysis. Points that are snow-covered in the IMS product that are snow-free in the NDAS will have a minimum snow depth assigned of 5 cm
      2. Over the Great Lakes, replaced the GLERL water temperatures with those from the RTG_SST_HR analysis (SST product used over the rest of the NAM domain)
  • 11 June 2014
  • Changes to the High-Resolution Window (HiResW) modeling system:
    1. Replace WRF-NMM with NEMS-NMMB (~ August 2013 version with updates)
    2. New version (WRFv3.5) of the WRF-ARW model
    3. East and West CONUS domains replaced by a single full CONUS domain run at 00z and 12z
    4. Alaska domain now run at both 06z and 18z
    5. Resolution changes:
      1. Alaska : 3 km NMMB, 3.5 km WRF-ARW
      2. CONUS : 3.6 km NMMB, 4.2 km WRF-ARW
      3. Hawaii/Puerto Rico/Guam : 3.0 km NMMB, 3.8 km WRF-ARW
      4. Increase the number of vertical levels from 35 to 40
    6. Replace WSM3 microphysics in ARW with WSM6 (includes graupel; more appropriate for sub-10 km resolution)
    7. Upgraded Ferrier microphysics in NMMB
    8. RRTM radiation in the NMMB
    9. RAP replaces NAM as inititalization source for CONUS runs
    10. GFS replaces NAM for Hawaii and Puerto Rico initializations
    11. New output on 2.5-3 km NDFD grids with smartinit downscaling
    12. Additional isobaric level output and selected new fields for aviation (simulated radar VIL) and fire weather
  • 2 April 2014
  • Changes to the Short-range Ensemble Forecast System (SREF):
    1. Replace GFS land states with NDAS land states in NMM and ARW members
    2. Revise NDAS land states in NMMB members to fix a bug related to ice cover in the Great Lakes
    3. Replace global initial conditions with RAP initial conditions for the ARW members
    4. Fix bugs in NOAH Land Surface Model (LSM):
      1. Eliminate negative soil moisture fractions for NMM and ARW members
      2. Eliminate "urban swamp" (causing too cold surface temperature over urban regions during heat wave periods) for NMMB members
    5. Correct GFS physics in 2 NMMB members to produce compatible cloud & ceiling guidance with the rest of SREF members
    6. Fix post-processor to remove use of snow in diagnosing cloud base height
    7. Correct a mapping bug (eastward shift) in NMM member’s pressure-grib output files
    8. Use the model lowest-level values for the 2m T, Td q, RH and 10m u and v fields for the 7 NMMB members at initial time f00; these fields do not have correct values in the current operational SREF.
    9. Switch the hypsometric option in the ARW model back to the version in the original wrf3.3 version from option 2 (height is derived from log pressure) to option 1 (derived from pressure); this will make the model more reliable.
    10. New output products:
      1. Rime Factor at the lowest model level above the surface
      2. Snow depth
      3. Percent of frozen precipitation for all 21 members
      4. Water equivalent of accumulated snow for all 7 ARW members.
      5. Begin disseminating 2m temperature and 3-hourly accumulated precipitation for all 21 SREF members on the 32km North American domain (grid 221) via NOAAPORT. More details about these products, including WMO headers, can be found in NWS TIN 13-44.
      6. Modify the clustering algorithm to preserve time-continuity within a cluster over each of the three pre-selected forecast periods (00-39hr, 42-63hr, 66-87hr). This change will make available a larger number of cluster files. Also, some of the spacing in the sref_cluster_info text file will change.
      7. Modify the list of stations for which SREF BUFR output is generated. The details of the additions, replacements and eliminations of stations are listed below. There were 68 sites added.
  • 25 February 2014
  • Changes to the Rapid Refresh (RAP) Modeling System:
    1. Model changes
      1. Updated version of WRF-ARW model code
      2. Increase the number of soil layers from 6 to 9; with modified roughness length for some land-use classes
      3. Modifications to the Thompson microphysics
      4. Switch PBL scheme from MYJ to MYNN
    2. Analysis/assimilation changes
      1. Updated version of GSI analysis code
      2. Use hybrid variational ensemble analysis with global EnKF
      3. Adjustment of soil temperature/moisture inside GSI analysis based on atmospheric low-level temperature and moisture increments
      4. Improvement in assimilation of GPS precipitable water data
      5. Assimilation of lightning data as proxy for radar reflectivity
      6. Addition of PBL-based pseudo-innovations for surface moisture observations
      7. Retaining cloud fraction from METAR and satellite cloud data and other cloud assimilation improvements
      8. Modification to radar hydrometeor specification and adding a surface temperature tendency
  • 28 January 2014
  • Changes to the NCEP Real-Time Mesoscale Analysis (RTMA) System:
    1. Unified version of RTMA for all domains
    2. Five domains now run:
      1. CONUS 2.5 km
      2. Alaska 3 km
      3. Hawaii 2.5 km
      4. Puerto Rico 2.5 km
      5. Guam 2.5 km
    3. Extend CONUS 2.5 km domain northward to provide support for the Northwest River Forecast Center
    4. Additional of Unrestricted Mesoscale Analysis (URMA)
      1. Identical to RTMA but with 6-h delay
      2. Run for extended CONUS 2.5 km domain only
      3. Includes remapped Stage IV precipitation every 6-h
    5. GSI changes
      1. Improved background error covariance model
      2. Bias correct 2-m temperature
      3. Use low-level satellite winds
      4. Routinely compute cross-validation for CONUS 2.5 km
      5. First guess : blend HWRF for tropical storm winds, blend RAP and NAM Alaska nest for Alaska 3 km RTMA
      6. Use diurnal reject lists for mesonet T, Td and direction-dependent accept lists for mesonet winds
  • 3 December 2013
  • Mesoscale Modeling Branch 2013 Production Review
    1. North American Mesoscale (NAM) and HiResWindow Systems
    2. Short-range Ensemble Forecast (SREF) System
    3. Rapid Update Cycle (RAP) / High Resolution Rapid Refresh (HRRR)
  • 5 December 2012
  • Mesoscale Modeling Branch 2012 Production Review
  • 21 August 2012
  • Changes to the NCEP Short-Range Ensemble Forecast System (SREF):
    1. Model changes:
      1. Eliminate Eta and RSM members, add more WRF-NMM/ARW members, and add NEMS-NMMB members (still 21 members total)
      2. Upgrade WRF cores from v2.2 to v3.3
      3. Increase horizontal Resolution from 32km/35km to 16km
      4. All models run with 35 levels in the vertical and 50 mb model top pressure
    2. Changes to initial condition diversity
      1. More control initial conditions (NDAS for NMMB members, GDAS for-> WRF-NMM, RAP blended @ edges w/GFS for WRF-ARW)
      2. More IC perturbation diversity (blend of regional breeding and downscaled ETR)
      3. Diversity in land surface initial states (NDAS, GFS, and RAP).
    3. More diversity of phyiscs schemes (flavors from NAM, GFS, NCAR, and RAP)
    4. New capabilities of post-processing and product generation:
      1. Precipitation bias correction (individual members and ensemble mean)
      2. Clustering and associated mean/prob/spread within a cluster
      3. Member performance ranking (different weights for different members)
      4. Downscaling to 5km using RTMA and associated ensemble products
    5. New ensemble products :
      1. Max/min, mode, 10-25-50-75-90% forecasts
      2. Probability of severe thunderstorms, lightning, dry lightning, fire weather (SPC) as well as LLWS, composite reflectivity, echo top, ceiling and visibility
      3. Addition of hourly ensemble product output from 1-39 hr.
      4. Ensemble mean station data in BUFR format
      5. A new 16km output grid covering North America (g132)
  • 1 May 2012
  • Rapid Update Cycle (RUC) upgraded to Rapid Refresh (RAP):
    1. Increase in domain coverage compared to the RUC, including Alaska and the Caribbean basin and almost all of North America.
    2. Use of the WRF modeling framework, with the Advanced Research WRF (ARW) forecast model with RUC physics.
    3. Major upgrades to the prediction model (updated versions of the cloud microphysics, Grell convection, and RUC land-surface schemes)
    4. Modifcations to the data analysis and assimilation system:
      1. Begin use of Grid-point Statistical Interpolation (GSI) analysis
      2. Assimilate satellite radiances (including AMSU-A and AMSU-B)
      3. Use aircraft moisture observations from UPS and Southwest Airlines
      4. Use 915-MHz profiler wind observations
      5. GOES cloud pressure/temperature from NASA Langley over full RAP domain added to NESDIS cloud data already assimilated in RUC
    5. Match most existing RUC products and add new ones to cover the expanded domain.
    6. Introducing the experimental North American Rapid Refresh Ensemble using Time Lagged (NARRE-TL) forecast.
    7. Modifying some product output and changing the names of all directories and output filenames from *ruc* or *ruc2a* to *rap*.
  • 7 December 2011
  • Mesoscale Modeling Branch 2011 Production Review
  • 18 October 2011
  • Changes to the NAM/DGEX:
    1. Non-hydrostatic Multiscale Model on B-grid in NEMS format (NEMS-NMMB) replaces the WRF-NMM as the forecast model in the NDAS/NAM/DGEX
    2. Addition of nested domains that run inside the 12 km NAM domain from 0-60 h:
      1. 4 km CONUS
      2. 6 km Alaska
      3. 3 km Hawaii
      4. 3 km Puerto Rico
      5. From 0-36 h, run a placeable 1.333 km nest inside the CONUS nest or a 1.5 km nest inside the Alaska nest for support of fire weather meteorologist and the NCEP Centers
      6. All nests run with new convection option ("BMJ_DEV") with reduced convective triggering
    3. Specific dynamics changes in the NMMB:
      1. Janjic's Eulerian passive tracer advection of scalars
      2. New generalized hybrid vertical coordinate
      3. Boundary condition treatment changed to specify 5 boundary rows instead of one row
      4. Modified vertical level distribution with more layers in the stratosphere (twice as many levels above 200 mb)
      5. Diffusion of specific humidity/cloud water increased by 4x
    4. Physics changes
      1. Microphysics changes to increase radar reflectivities, rain rates and produces higher rain amounts:
        1. Use expanded rain look up tables, increasing the maximum size of raindrops from 0.45 to 1.0 mm.
        2. Parameterizes sedimentation of 50-micron ice crystals.
        3. New cloud water to rain autoconversion (PRAUT) scheme following work of Liu & Daum et al. This new scheme no longer requires an autoconversion threshold, and the functional dependence of cloud water mixing ratio is quite different from the original Kessler-based formulation.
        4. NCW increased from 100 to 200 cm^-3.
        5. T_ice_init=0 results in faster initiation of ice. In 1D column runs it produced higher maximum surface rainfall rates.
        6. FLARGE2=0.07 based on tests by JMA visiting scientist Nakagawa in his global runs. The parameter determines the number fraction of large precipitation ice particles.
        7. VEL_INC~VRIMEF**2 – even faster rimed ice fall speeds than in the HAIL microphysics.
        8. Changes to improve cloud fraction (reduce coverage associated with cold, high clouds)
      2. Change from USGS to MODIS_IGBP land-use definitions
    5. Analysis/assimilation changes
      1. Upgrade to latest version (March 2011) of Grid-point Statistical Interpolation (GSI) analysis code
      2. Add GSI analysis job for all 5 NAM nests
      3. Begin use of dynamic reject list (from RTMA) for mesonet data
      4. New observation types:
        1. ACARS humidity
        2. WDSATR : superob'ed Scatterometer winds over oceans
        3. HIRS and AMSU-A radiances from NOAA-19,
        4. IASI radiances from METOP
        5. AMSU-A radiances from AQUA
        6. RASS virtual temperatures
        7. MAP winds
        8. ASCAT winds
        9. Improved assimilation of GPS radio occultation (COSMIC) data
      5. Analysis will now update the first guess 2-m temperature/specific humidity and 10-m wind (12 km NAM domain only)
    6. Switch SST analysis from MMAB 1/2 degree RTG_SST to 1/12th degree RTG_SST_HR
  • 29 March 2011
  • Changes to the NCEP HiResWindow Modeling System:
    1. The HIRESW model will be updated from Weather Research and Forecasting (WRF) version 2.2 code to WRF version 3.2 code for both the Advanced Research WRF (ARW) and the Nonhydrostatic Mesoscale Model (NMM) members of the system. Both the ARW and NMM models will use better conserving moisture advection..
    2. The Puerto Rico domain will be expanded by approximately 50% to provide full coverage to Hispaniola. A new domain will be added to run over Guam twice daily at 00 and 12 UTC. The model grid spacing will remain unchanged at 5.15 km for ARW and 4.0 km for NMM for all domains. With the addition of Guam, the revised run schedule will be:

      00 UTC: East, Hawaii , Guam

      06 UTC: West, Puerto Rico

      12 UTC: East, Hawaii , Guam

      18 UTC: Alaska, Puerto Rico

    3. BUFR-formatted point forecasts for select locations are now available
    4. New high-resolution, hybrid ensemble output will be created that combines uncertainty information from the Short Range Ensemble Forecast (SREF) with deterministic forecasts from the HIRES. Output products from this HIRES ensemble will include mean, spread, and probabilistic guidance.
  • 8 December 2010
  • Mesoscale Modeling Branch 2010 Production Review
  • 28-29 September 2010
  • Changes to the NCEP Real-Time Mesoscale Analysis (RTMA) System:
    1. Add 2.5 km RTMA for Guam; use downscaled GFS for first guess
    2. Begin running 2.5 km CONUS RTMA, new features:
      1. Extended assimilation time window (+/-30 min; 5 km RTMA uses +/-12 min)
      2. Use First Guess at the Appropriate Time (FGAT)
      3. Apply sequential bias-correcton algorithm for background temperature
      4. Improved quality control
      5. Add ocean surface WindSat and ASCAT winds and low-level satellite drift winds
    3. Slight realignment of the Hawaii 2.5 km RTMA grid
  • 6 July 2010
  • Changes to the preemption schedule for the operational HIRESW forecasts when the NCEP Hurricane model is running:
    1. Two or less hurricane runs : All HIRESW forecasts made
    2. Three hurricane runs : Large domain (East CONUS, West CONUS, Alaska) NMM and ARW runs cancelled
    3. Four hurricane runs : All HIRESW forecasts cancelled
  • 2 March 2010
  • Changes to the NCEP Rapid Update Cycle Forecast:
    1. Forecast extended to 18 hours for all cycles
  • Changes to the NCEP Rapid Update Cycle Analysis/Preprocessing:
    1. Assimilation will use Canadian aircraft (AMDAR) data
    2. Fixed bug in cloud-building code that will impact virtual potential temperature in cloudy areas
    3. Aircraft reject list updated
    4. The removal of snow at grid points where the NESDIS snow analysis does not support its presence is changed from once pre day at 19Z to twice per day at 17Z and 23Z. A land-sea mask will also be incorporated into this algorthim due to the difference in resolution between the NESDIS analysis and the RUC.
  • 8 December 2009
  • Mesoscale Modeling Branch 2009 Production Review
  • 3 November 2009
  • Minor changes to the NAM/DGEX:
    1. Fixed a bug in the horizontal advection of W and height in the non-hydrostatic module; missing factor of 2 added.
    2. Removed the addition of rain water mixing ratio to the input cloud water mixing ratio array used by the GFDL radiation code. This change should make the clouds less opaque to SW and LW radiation at grid points where rain is falling in the column.
    3. Bug fix in turbulence routine to declare and define CAPA (R/Cp).
    4. The surface (skin) temperature is constrained to be no greater than 350K. This fix will eliminate spurious values at the NAM lateral boundary. These spurious values were not used in the NAM integration, but they did cause the SREF failures in early April, late May, and late October 2009
    5. The assumed fraction of large, precipitating ice particles to the total number concentration of ice particles is reduced from 0.2 to 0.03, which acts to increase the number of small, nonprecipitating ice particles. This change improves NAM simulated GOES brightness temperatures.
    6. Enforce a minimum number concentration for large ice particles (1 per liter) at all temperatures, rather than not enforcing it at >0C in the operational code where a fixed mean diameter is assumed.
    7. When initiating ice in water saturated conditions, growth rates are calculated by combining the number concentrations of ice initiation from eq. (2.4) of Meyers et al. (JAM, 1992) with estimated mass growth rates of ice crystals using the calculations of Miller and Young (JAS, 1979). The Miller-Young calculations were in cgs units (g per unit time), so the values in the model need to be multiplied by 1e.-3 to convert to mks units (kg per unit time) in subroutine MY_GROWTH_RATES.
    8. Added radar echo top height to some NAM output grids
    9. Fixed a bug in the computation of dew point temperature in the post-processing routine that determines categorical precipitation type.
  • 27 October 2009
  • Changes to the NCEP Short-Range Ensemble Forecast (SREF) System:
    1. Three of the four models used in the SREF (NMM, ARW, and RSM) are upgraded; NMM and ARW from WRF V2.0 to WRF V2.2, RSM from v2003 to v2008.
    2. The horizontal resolution of the WRF members is increased 40 km to 32 km, and the RSM members from 45 km to 35 km
    3. The number of WRF-NMM and WRF-ARW members are increased from 3 to 5; the number of Eta members is reduced from 10 to 6, and members n3, n4, and p3 and p4 removed.
    4. Introduce more physics diversity by switching from Zhao cloud scheme to Ferrier cloud scheme in three out of five RSM members.
    5. GRIB forecast output frequency will increase from 3-hourly to hourly for the first 39 hours (CONUS grid only).
    6. Four new aviation products are added:
      1. Icing (probability products only)
      2. Clear air turbulance (probability products only)
      3. Ceiling (mean and probability products)
      4. Flight restriction (probability products only)
    7. Three new products will be added to the individual member output for some members:
      1. Richardson number-based PBL height (Richardson number = 0.25)
      2. Simulated composite radar reflectivity
      3. Radar echo top height (= 18.3dbz)
    8. BUFR sounding output from each SREF member will be broken out into individual station time series.
  • 31 March 2009
  • Changes to the NCEP Rapid Update Cycle (RUC):
    1. Introducing the NESDIS snow analysis to eliminate snow cover at model points where the analysis indicates no snow is present. The new code will introduce the NESDIS analysis once per day at 1900 UTC and will eliminate snow cover at any point where 1) the analysis shows no snow, 2) the model surface temperature is above 274 K, and 3) no precipitation has fallen during the previous one hour forecast.
    2. Changing the call to the analysis of cloud data so it occurs near the end of the analysis process. This will prevent non- cloud observations from causing subsaturation at grid points where clouds exists. A final check is made to make certain that any grid point with analyzed cloud is saturated.
    3. Modifications to the code to allow GOES satellite cloud data to supercede any METAR report of clear skies.
  • 3 March 2009
  • The NCEP operational Nested Grid Model (NGM) was turned off as of this cycle.
  • 26 January 2009
  • Change to the land-surface physics in the WRF-NMM model running in the NDAS/NAM:
    1. At the start of the first (tm12) forecast of each NDAS run, the WRF-NMM forecast model, instead of cycling the frozen soil moisture from the previous NDAS run, was recomputing it using the explicit Flechinger equation. This led to inconsistencies between the frozen soil moisture and both the total (liquid+frozen) soil moisture and the soil temperatures, leading to warm 2-m temperature biases in cold regions. As of this date the error has been fixed.

      Note : This code error, in the forecast code since the unified Noah land-surface physics was implemented on 31 March 2008, was never invoked in the operational NDAS until it began to be initialized from the GDAS first guess on 16 December 2008.

  • 16 December 2008
  • Changes to the NAM forecast system:
    1. The background for the first (tm12) analysis in each NDAS run is now from the GDAS instead of the previous NDAS run (so-called "partial cycling"). Land states are still fully cycled from the previous NDAS cycle.
    2. WRF-NMM Model changes (also implemented into the DGEX):
      1. The PBL/turbulance schemes were modified to mix each hydrometeor species in the vertical.
      2. To apply vertical diffusion for separate water species, the model was changed so that (a) it can apply vertical diffusion to an arbitrary number of species, (b) the counter gradient option can be applied to some or all of the species if desired, and (c) option to set to zero some or all of the surface fluxes is also made available.
      3. In the radiation parameterization, the absorbtion coefficients for water and ice have been doubled to 1600 and 1000, respectively
      4. Changes to land-sfc physics:
        1. Let the potential evaporation decrease linearly with Bulk Richardson number under stable condition, and weighted by snow coverage.
        2. Let the slope of saturated humidity function wrt temperature decrease linearly with snow coverage.
    3. Changes to GSI analysis
      1. Use latest (1Q 2008) version of the GSI analysis code
      2. Assimilate METOP radiance data
      3. Assimilate TAMDAR/AMDAR aircraft data
      4. New version of Community Radiative Transfer Model
    4. Use AFWA 1/16 bedient snow depth analysis
    5. Use WPS (instead of WRF-SI) codes to process GDAS first guess input files, which are used as a first guess to the first (tm12) GSI analysis in the NDAS
  • 9 December 2008
  • Mesoscale Modeling Branch 2008 Production Review
  • 17 November 2008
  • Changes to the NCEP Rapid Update Cycle (RUC):
    1. Changes to the RUC analysis:
      1. Include processing of three-dimensional radar reflectivity mosaic data to produces a latent heat specification to be used in the model digital filter
      2. It is also being modified to include an assimilation of TAMDAR and MESONET wind data
      3. Revision to observation and background error for moisture data
      4. Improved quality control based on mean observation-background differences for a given platform within the analysis window
    2. Changes to the RUC forecast model:
      1. Change the longwave radiative scheme from Dudhia to Rapid Radiative Transfer Model (RRTM)
      2. Modify the snow component of the land-surface model to avoid excessively cold temperatures over fresh snow at night as well as during warm advection events over snow cover
      3. Modify the convective scheme to reduce the excessive generation of light precipitation areas.
      4. Specify three-dimensional latent heating in the diabtic digital filter initialization.
    3. Changes to the RUC post-processing:
      1. Add simulated reflectivity products
      2. Add relative humidity computed with respect to precipitable water in a saturated column to the pressure level output files
      3. Add four new land-surface fields (soil type, vegetation type, land/water mask, and ice cover) to the native level output files.
      4. Modify post-processing code to correct the GRIB PDS (product description section) time descriptors for very short-range precipitation forecasts.
  • 7 October 2008
  • Operational implementation of the Real-time Mesoscale Analysis (RTMA) over Hawaii and Puerto Rico.
  • 13 May 2008
  • Changes to the NCEP Air Quality Model:
    1. Point, area and mobile emissions will be upgraded based upon recent EPA National Emissions Inventory (NEI, 2005) and then projected for the current year. EGU sources will use 2006 CEM data projected for 2008.
    2. For mobile sources, the EPA Office of Transportation and Air Quality (OTAQ) estimates will be used in addition to 2005 NEI v1 emission data sets. Use of OTAQ on-road emission estimates is
    3. Use of OTAQ on-road emission estimates is a departure from the temperature dependent regression approach used in previous years.
  • 22 April 2008
  • Begin assimilation of AIRS radiance data in NDAS/NAM GSI analysis. This was not implemented on 31 March 2008 as intended due to a script error.
  • 15 April 2008
  • Operational implementation of the Real-time Mesoscale Analysis (RTMA) over Alaska.
  • 31 March 2008
  • Changes to the WRF-NMM forecast model running in the North American Mesoscale (NAM) Analysis and Forecast System and the DGEX:
    1. The computational domain of the NAM was increased by ~18%, click here to see a comparison with the old NAM computational domain.
    2. WRF-NMM Model changes:
      1. Run with WRF-NMM V2.2 code (August 2007 Repository version) with IJK array indexing
      2. Use gravity wave drag/mountain blocking. Run with SIGFAC=0: gravity wave drag responds only to ELEVMAX, the maximum elevation within the grid box only. No further inflation is done based on the standard deviation of the 30" heights in the grid box.
      3. Use new Unified (with NCAR) Land-Surface Physics module. This module now uses total soil moisture rather than liquid soil moisture (as in the previous NCEP/noahlsm) to determine bare-soil evaporation, which results in greater moisture fluxes (and thus higher near-surface dew point temperatures) over regions of frozen, bare soil with patchy or no snow cover.
      4. Use of new passive advection with the requirement for exact conservation of specific humidity, TKE, and cloud water relaxed in the advection step. The exact conservation is still required in the antifiltering step following the advection step.
      5. Stratospheric ozone fix in the computation of latitude: the error led to using climatological ozone values valid at the equator at all latitudes.
      6. Remove two modifications to longwave radiation made for the June 2006 WRF-in-NAM implementation
        1. Remove averaging of longwave temperature tendencies from the lowest two model layer
        2. Compute the upward LW at the surface was based on the ground (skin) temperature instead of the average of the skin and lowest model layer temperatures.
    3. GSI analysis changes:
      1. New (August 2007) version of GSI code
      2. Retuned background errors (gives improved obs fit to first guess)
      3. Use AIRS radiance data
      4. Use GOES 1X1 radiance data
      5. New SATWND data (eumetsat and modis)
      6. MESONET uv (winds with uselist)
    4. Use new terrain with "3x3" (smoothed-desmoothed) smoothing, a smaller (more realistic) Great Salt Lake, better depiction of the Channel Islands off the California coast, and spurious waterfalls removed; use climatological water temperatures for Lake Champlain.
    5. Use 12-36 h forecast precipitation from the 00z ops NAM run to fill in for the CONUS-based Stage II/IV analysis as a driver for NDAS soil moisture outside of the CONUS (OCONUS)
  • 12 December 2007
  • Changes to Short-range Ensemble Forecast System:
    1. Introduce bias correction scheme for basic meteorological fields (except QPF)
    2. Expand RSM domain to fully cover Alaska
    3. Add aviation-related ensemble products (icing, CAT, flight restriction, ceiling height)
    4. Add BUFR sounding output to the 6 WRF members
  • 11 December 2007
  • Mesoscale Modeling Branch 2007 Production Review
  • 17 September 2007
  • Changes to the NCEP Air Quality Model:
    1. Expanded domain (5X) to cover Continental U.S.
    2. Common WRF-NMM hybrid sigma-P vertical coordinate
    3. NAM clear sky radiation prediction used to scale CMAQ photolysis
    4. Asymmetric Convective Model used to drive CMAQ moist convection mixing
    5. Asymmetric Convective Model-2 used to drive CMAQ PBL mixing
    6. Constant, static Ozone Lateral Boundary conditions for all CMAQ levels (turned off use of GFS ozone at CMAQ Lateral boundary top)
    7. Updates to CMAQ V4.6 with bug corrections to deposition, optimized advection scheme and plume rise
  • 11 September 2007
  • Changes to the NCEP HiResWindow Modeling System:
    1. WRF-NMM
      1. Upgrade from WRF version 1.3 to WRF version 2.2
      2. Increase resolution from 5.2 km to 4.0 km
    2. WRF-ARW
      1. Upgrade from WRF version 1.3 to WRF verison 2.2
      2. Increase resolution from 5.8 km to 5.1 km
    3. Expand large domains (Click here to see new HIRESW domains)
      1. Western and Eastern U.S. domains roughly doubled in size
      2. 3 CONUS nests reduced to 2 overlapping domains (West-Central & East-Central)
      3. New HIRESW schedule (see below) to run the new East/Central domain at 00z and 12z for NCEP's Storm Prediction Center
    4. New HIRESW run schedule:
      1. 0000Z : East/Central U.S., Hawaii
      2. 0600Z : West/Central U.S., Puerto Rico
      3. 1200Z : East/Central U.S., Hawaii
      4. 1800Z : Alaska, Puerto Rico
    5. The operational HIRESW forecasts are subject to cancellation by NCEP Central Operations (NCO) if the NCEP Hurricane model is running. This is the production HIRESW configuration when the NCEP hurricane model is running
      1. No hurricane runs : Both large and small NMM and ARW domains are run by NCO
      2. One hurricane run : Large domain ARW run cancelled by NCO
      3. Two or three hurricane runs : Both large domain NMM and ARW runs cancelled by NCO
      4. Four hurricane runs : All WRF HIRESW cancelled by NCO
    6. Due to computing resource constraints EMC will no longer run the cancelled HIRESW WRF-NMM forecast on the development computer at this time.
  • 26 June 2007
  • Changes to the Real-time Mesoscale Analysis (RTMA):
    1. Tuned observation and background error covariances for improved fit to obervations
    2. Reduced spatial scales of anisotropic filter to allow the for better resolution of mesoscale features
    3. Elevation gradient near coastlines made artifically large to onbain sharper background error covriances, which reduced influence of coastal land stations on the analysis of temperatures over water.
  • 19 June 2007
  • Changes to the WRF-NMM model running in the NAM and DGEX:
    1. Under stable conditions, modify roughness length for heat so that it is only a function of surface-layer bulk Richardson number, removing the dependence on surface elevation.
    2. The minimum canopy resistance was increased for evergreen needleleaf forest (doubled from 125.0 to 250.0, units of s/m) and for mixed forest (from 125.0 to 150.0).
  • 19 December 2006
  • Changes to the WRF-NMM forecast model running in the North American Mesoscale (NAM) Analysis and Forecast System and the DGEX:
    1. The divergence damping routine, which damps all gravity-inertia and external modes, is changed to increase damping of the external mode.
    2. During the NDAS, divergence damping is increased to 5x that used during the 84 hr NAM free forecast.
    3. Numerous changes are made to convective parameterization:
      1. Triggering of deep and shallow convection is considered only for grid points with positive cape throughout a parcel's ascent; the search for parcel instability is extended to include not only whether the most unstable (highest theta-e) parcel can support convection, but also whether parcels originating at higher levels become positively buoyant when lifted to their LCL. Convective adjustments are made with respect to the parcel associated with the greatest instability (largest CAPE)
      2. The search for the most unstable parcel is extended from the lowest twenty percent of the atmosphere to the lowest 40 percent of the atmosphere.
      3. Water loading effects are now included in assessing the buoyant instability of parcels from which a revised (lower) cloud top is determined to be at the highest level of positive buoyancy.
      4. The latent heat of vaporization used to calculate equivalent potential temperatures during model integration is made to be consistent with the value used in generating the initial lookup tables.
      5. When a grid point fails the entropy check for deep convection but still has positive CAPE, changes in temperature and moisture by shallow convection are then considered at these so-called "swap" points. The first-guess estimate for the top of shallow convection is based on the highest level where the parcel remains positively buoyant (this is more restrictive than positive CAPE), and the vertical extent of shallow convection is not to exceed 0.2 times the atmospheric pressure depth (e.g., 200 hPa for a surface pressure of 1000 hPa). A final adjustment is made to the top of shallow convection in which it can extend to higher altitudes if the mean ambient relative humidity (RH) in the cloud layer exceeds a threshold RH while remaining positively buoyant (i.e. CAPE greater than 0). The threshold RH is based on the RH at cloud base that is consistent with a deficit saturation pressure of 25 mb (usually near 90%). The maximum cloud top height for shallow convection is still limited to 450 hPa.
      6. The first-guess reference temperatures in the upper-half of shallow convective clouds are limited to be no more than 1 deg C colder than the ambient temperature.
    4. Three changes are made to the cloud microphysics:
      1. During melting precipitation ice particles are assumed to have the same mean diameter (1 mm) as at the freezing level.
      2. Two changes intended to increase the presence of supercooled liquid water and improve forecast products for use in aircraft icing algorithms:
        1. The temperature at which small amounts of supercooled liquid water, if present, are assumed to be glaciated to ice was lowered from -30C to -40C.
        2. The temperature at which ice nucleation is allowed to occur was lowered from -5C to -15C based on aircraft icing observations
    5. Allow horizontal diffusion between neighboring grid points with a slope of less than or equal to 54 m / 12 km (9x that in previous operational NAM).
  • 12 December 2006
  • Mesoscale Modeling Branch 2006 Production Review
  • 5 September 2006
  • Changes to the North American Mesoscale (NAM) Analysis and Forecast System:
    1. Increased Smagorinsky constant for lateral diffusion from 0.27 to its maximum value of 0.4; this was inadvertently left out of the 8/15 changes for the NAM, it was implemented in the DGEX on 8/15
    2. Revert back to using the 1/2 degree RTG_SST analysis used in the NAM-Eta due to problems with a persistent cold bias in the hi-res (1/12th degree) RTG_SST analysis in and north of the Bering Strait and in Hudson's Bay.
  • 15 August 2006
  • Changes to the North American Mesoscale (NAM) Analysis and Forecast System and the DGEX:
    1. Remove any restrictions to horizontal diffusion between water points at different elevations (e.g., between erroneously sloping water points and water points at sea-level)
    2. Redefine roughness length z0=z0base (veg component) + z0land, removing terrain height component
    3. Code changes to allow horizontal diffusion at grid points along coastal/ice boundaries where the slope between neighboring grid points is > 6 m
    4. Increases Smagorinsky constant for lateral diffusion from 0.27 to its maximum value of 0.4
    5. Enhanced vertical diffusion
    6. Turned on assimilation of surface temperature data over land in the GSI analysis
    7. Modified the SST preprocessing job to use new climatological values for Great Salt Lake water temperatures from the University of Utah; a cosine fit to the bimonthly observational data from Saltair Boat harbor (from 1972-1989). From Steenburgh et al., 2000: Climatology of Lake-Effect Snowstorms of the Great Salt Lake. Monthly Weather Review, 128, 709-727.
    8. Modified the SST preprocessing job to use monthly climatological values of water temperature for the Salton Sea in southern California
    9. Modified the SST preprocessing job to use monthly climatological values of water temperature (obtained from the Army Corps of Engineers) for Fort Peck Reservoir in Montana
  • 6 August 2006
  • Operational implementation of the Real-time Mesoscale Analysis (RTMA) over the CONUS.
  • 11 July 2006 (Summary of Changes)
  • Numerous RUC model/analysis/output changes (click on "Summary of Changes" for details)
  • 27 June 2006
  • Changes to the Short-range Ensemble Forecast (SREF) system:
    1. Added 03Z and 15Z runs
    2. Expanded integration domain to cover Alaska
  • 20 June 2006 (NCEP/EMC documentation, PDF format)
    20 June 2006 (COMET documentation)
  • Changes to the North American Mesoscale (NAM) Analysis and Forecast System:
    1. Eta step-mountain coordinate model replaced with the WRF version of the Non-hydrostatic Mesoscale (WRF-NMM) model in the NDAS, NAM, and DGEX; WRF-NMM model characteristics:
      1. Uses WRF common modeling infrastructure
      2. Non-hydrostatic dynamics
      3. Uses hybrid sigma-pressure vertical coordinate with model top pressure of 2 mb for NAM (DGEX has 30 mb model top)
      4. Refined advection, diffusion, numerics, and physics
    2. Eta 3D-Variational analysis replaced with the Gridpoint Statistical Interpolation (GSI) analysis:
      1. Unified 3D-Variational analysis adapted to WRF infrastructure
      2. Uses background errors based on WRF-NMM forecasts
      3. Uses new variable (normalized RH) for moisture analysis
      4. Uses tendency in constraint term
      5. Uses dynamically retuned observation error covariances
    3. Changes to model initialization:
      1. Use of new unified package to bring external fields (SST, snow, sea ice) into WRF-NMM forecast
      2. Begin use of high resolution (1/12th degree lat/lon) RTG_SST analysis
      3. Begin use of high resolution (NESDIS 4km, 1/96th bedient) snow/sea ice analysis
    4. Data assimilation changes:
      1. Turn off nudging of temperature, mositure and cloud during assimiltion of observed precipitation, but continue use of bias-corrected observed precipitation analysis to drive the WRF-NMM land-surface physics
      2. Begin use of new observation types: WSR-88D Level II radial wind data, GPS-Integrated Precipitable Water (IPW) data, and NOAA-18 radiances.
      3. Drop use of GOES and SSM/I Precipitable Water retrievals
  • 6 December 2005
  • Mesoscale Modeling Branch 2005 Production Review
  • 6 December 2005
  • Changes to Short-range Ensemble Forecast System:
    1. Added 6 new members:
      1. Three with 40km/50lev WRF-NMM w/EMC physics (control, n5, p5 perturbations)
      2. Three with 45km/35lev WRF-ARW w/NCAR physics (control, n1, p1 perturbations)
    2. Begin use of common ensemble product generator
  • 31 August 2005
  • Changes to NCEP Air Quality Model run;
    1. Northeast US operational forecasts replaced with Eastern U.S. (3X) runs.
    2. The 3X operational forecasts were the same as the NE U.S. runs except for:
      1. Larger CMAQ domain: 268x259x22
      2. Lateral Boundaries are static except at CMAQ top layer where GFS ozone is specified
      3. Above-cloud downward convective mixing turned off
  • 30 August 2005
  • Changes to Short-range Ensemble Forecast (SREF) System;
    1. Upgrade 10 Eta members so they are initialized using land states from 12 km NDAS
    2. Lateral boundary conditions from GFS 3-h old forecast (previously 9-hour)
    3. Forecast length increased from 63 to 87 h
  • 28 June 2005
  • Resolution of WRF-NMM in HIRESW system changed from 8km/60levels to 5.1km/35 levels
  • Resolution of WRF-EM (ARW) in HIRESW system changed from 10km/50levels to 5.8km/35 levels
  • Convective parameterization turned off in both HIRESW NMM and ARW
  • 28 June 2005 (Summary of Changes)
    28 June 2005 (Powerpoint)
  • Resolution of RUC increased from 20 km to 13 km
  • Numerous model/analysis/output changes
  • 3 May 2005
  • Changes to NE US Air Quality Model run:
    1. PREMAQ updated to use NAM-12 1 km landuse data
    2. Minor CMAQ updates to version 4.4
    3. 2002 Point/Area Source Emissions projected for 2005
    4. Updated Mobile 6 source emissions
    5. GFS ozone for CMAQ LBCs above 6 km
  • 3 May 2005 (low-res version)
    3 May 2005 (Powerpoint file)
  • Changes to NAM/DGEX:
    1. Eta 3DVAR:
      1. Turned on use of on-time overland surface temperature observations in Eta 3DVAR using 2DVar with anisotropic covariance tied to terrain
      2. Use of Level II.5 (on-site derived superobs) WSR-88D radial velocity data
    2. Precipitation assimilation:
      1. Cease attempts to create precipitation when model precipitation is less than observed
      2. Continue to reduce latent heat and moisture fields when model precipitation is greater than observed
      3. Use observed precipitation directly in driving the land surface physics
    3. Eta Model : Land-surface model changes:
      1. Use high-resolution (1-km vs 1 deg) vegetation and soils data bases with more classes
      2. Retuned canopy conductance and other vegetation parameters - ops had been tuned to higher values to maintain reasonable evaporation rates given low soil moisture bias which is removed by new precipitation assimilation procedures
      3. Lowered roughness length for heat to reduce skin temperature, and hence lower diagnosed 2-m air temp
      4. Parameter changes over patchy snow cover (higher snow albedo, reduced snow sublimation, less snow depth for 100% cover)
      5. Surface emissivity over snow changed from 1.0 to 0.95
      6. In very stable conditions when PBL depth is diagnosed at the lowest Eta model level, impose lower limit on eddy diffusivity up to (and one level above) inversion height
    4. Eta Model : Clouds / radiation:
      1. Radiation scheme modified to "see" thicker clouds by removing the upper limit for cloud water mixing ratio when computing optical depths
      2. Modified cloud cover fraction formulation to allow for more partial cloudiness (had been too binary)
  • 25 January 2005
  • Operational Eta forecast system officially renamed North American Mesoscale (NAM) forecast system; Eta Data Assimilation System (EDAS) renamed NAM Data Assimilation System (NDAS).
  • 7 December 2004
  • Mesoscale Modeling Branch 2004 Production Review
  • 29 November 2004
  • Changes to WRF-NMM and WRF-ARW runs in HIRESW system:
    1. WRF-ARW:
      1. The "masked" horizontal interpolation of SST data was generating spurious 290K temperatures over parts of the Arctic Ocean, leading to unrealistically warm near-surface temperatures.
      2. Native-grid GRIB output from the HI and PR WRF-ARW runs were being labeled as Lambert Conformal, when the integration domain is actually Mercator. Improper hardwiring of the map type to a Lambert Conformal projection was removed from, and the problem that necessitated the hardwiring was eliminated.
      3. Made modifications so an initial snowcover would be properly defined within the WRF-ARW.
      4. Definition of sea-ice points are changed from water to land, and the Land-sfc physics can now handle sea-ice properly
    2. WRF-NMM:
      1. Modify vertical advection to use an off-centered Crank-Nicholson scheme, which remedied recent failures of the WRF-NMM over Alaska
      2. Divergence damping parameter CODAMP set back to 6.4 for all domains
      3. Removed faulty logic in generating the initial skin temperature
    3. WRF Post-processor:
      1. The reduced sea-level pressure in the WRF-ARW was in poor agreement with the initializing Eta model data at the initial time (up to 5 hPa too low relative to the Eta), and would continue to have a low bias through the forecast period. A moisture component of pressure that is subtracted out during initialization of the WRF-ARW was added back in the post.
      2. Fixes which ensure that output from both WRF cores will produce bit-identical answers regardless of the number of processors applied to the task.
      3. Modified two routines to process properly the snow and snowcover fields now coming out of the WRF-ARW.
  • 21 September 2004
  • Replace single run of NCEP Non-hydrostatic Meso Model (NMM) in the HiResWindow suite with two runs : 1) The WRF version of the NMM (WRF-NMM), and the WRF version of the Eulerian Mass core (WRF-ARW) with physics chosen by NCAR:


    Physics module








    Mellor-Yamada-Janjic (Eta)


    MRF scheme

    Monin-Obukhov (Janjic Eta) scheme

    Surface layer


    OSU land-surface


    OSU land-surface

    GFDL (Eta)



  • The WRF version of the NMM has been upgraded with these changes to the model dynamic core:
    1. The Matsuno vertical advection scheme has been replaced with the neutral, unconditionally stable Crank-Nicholson scheme
    2. The Smagorinsky constant in the lateral diffusion is reduced by 70%
    3. The effect of horizontal shear of vertical velocity has been added to the lateral diffusion scheme.
    4. The fundamental time step has been reduced by 10%.
  • The NCEP physics for the WRF-NMM have these changes:
    1. Input data on surface conditions (soil and vegetation type) have been refined
    2. Soil heat capacity has been increased which results in larger ground fluxes
    3. The dependence of roughness length (z0) on the height of topography has been removed, significantly reducing z0 over elevated terrain
    4. The countergradient heat flux has been added to the turbulent kinetic energy (TKE) equation and in the vertical heat diffusion
    5. The diagnostic mixing length has been increased
    6. The floor values for TKE and mixing length have been significantly reduced
    7. Increased residual turbulent mixing has been introduced in case of strong stability between the top of the surface layer and the layer above the inversion
    8. The effect of entrainment has been incorporated into the procedure for finding convective cloud top pressure.
    9. The entropy change threshold for triggering deep convection has been reduced
  • 15 September 2004
  • Operational Implementation of the Northeast US Air Quality Model run
  • 17 August 2004
  • Replace 48-km SREF (10 Eta members, 5 RSM members) with a 15-member Eta/RSM system at 32 km resolution with physics diversity:
    1. Eta, Betts-Miller-Janjic convection, ops Ferrier microphysics, control
    2. Eta, Kain-Fritsch convection, ops Ferrier microphysics, control
    3. Eta, Betts-Miller-Janjic convection, ops Ferrier microphysics, negative perturbation
    4. Eta, Betts-Miller-Janjic convection, ops Ferrier microphysics, positive perturbation
    5. Eta, Kain-Fritsch convection, ops Ferrier microphysics, negative perturbation
    6. Eta, Kain-Fritsch convection, ops Ferrier microphysics, positive perturbation
    7. Eta, Betts-Miller-Janjic convection w/saturated vapor pressure profiles, experimental Ferrier microphysics, negative perturbation
    8. Eta, Betts-Miller-Janjic convection w/saturated vapor pressure profiles, experimental Ferrier microphysics, positive perturbation
    9. Eta, Kain-Fritsch convection w/full cloud detrainment, experimental Ferrier microphysics, negative perturbation
    10. Eta, Kain-Fritsch convection w/full cloud detrainment, experimental Ferrier microphysics, positive perturbation
    11. RSM, simplified Arakawa-Schubert convection, Zhou GFS microphysics, control
    12. RSM, simplified Arakawa-Schubert convection, Zhou GFS microphysics, negative perturbation
    13. RSM, simplified Arakawa-Schubert convection, Zhou GFS microphysics, positive perturbation
    14. RSM, relaxed Arakawa-Schubert convection, Zhou GFS microphysics, negative perturbation
    15. RSM, relaxed Arakawa-Schubert convection, Zhou GFS microphysics, positive perturbation
  • 1 June 2004
  • Initial implementation of the Downscaled GFS with Eta Extension (DGEX) over the CONUS (06Z/18Z cycles) and Alaska (00Z/12Z cycles)
  • 16 March 2004
  • Use of daily gauge data for precipitation assimilation bias adjustment
  • Assimilation of GOES cloud top radiances
  • Eta Land-surface model precipitation type now based on model microphysics
  • Post-processing changes
  • 9 December 2003
  • Mesoscale Modeling Branch 2003 Production Review
  • 10 September 2003
  • To improve the quality of the Eta initial conditions: 1) surface temperatures over land are not used in the Eta 3DVAR analysis, and 2) all surface data that is not within 6 minutes of the analysis time is excluded.
  • 2 September 2003
  • SREF increased from 10 to 15 members with the addition of 5 Eta forecasts with Kain-Fritsch convective parameterization
  • 8 July 2003 (TPB)
    8 July 2003 (Powerpoint briefing)
  • Extension of the "off-time" (06/18Z) runs to 84 hours
  • Addition of hourly output on selected grids to 36 hours
  • Modifications to the cloud physics and radiation
  • Assimilation of GOES cloud top pressure, Stage IV precipitation data, and super-observations of NEXRAD radial wind data.
  • 27 May 2003
  • A 3-d variational (3DVAR) analysis was implemented replacing the previous optimal interpolation (OI) analysis in the 20 km RUC
  • 15 April 2002
  • Resolution of the Rapid Update Cycle changed from 40km to 20km
  • Improved cloud microphysics, convection, land-surface physics
  • 22 February 2002
  • Eta land-surface physics changed to increase the thermal conductivity through snow; change lessened Eta forecast 2-m temperature bias over snow cover
  • Upgrade to the NCEP HiResWindow (HIRESW) runs with the Non-hydrostatic Meso Model (NMM)
  • 27 November 2001 (TPB)
    27 November 2001 (Powerpoint briefing)
  • Increased horizontal and vertical resolution from 22 km/50 levels to 12 km/60 levels
  • New cloud microphysics scheme
  • Improvements to the 3DVAR initialization
  • 24 July 2001 (TPB)
    24 July 2001 (Powerpoint briefing)
  • Eta 3DVAR analysis modified for improved mass-wind balance constraint
  • Assimilation of the 4-km NCEP National Precipitation Analysis (stage II) in the EDAS
  • Extensive modifications to the Eta model land-surface physics (NOAH LSM version 2.3
  • 5 June 2001
  • Initial implementation of NCEP Short-range Ensemble Forecasting System
  • 22 March 2001
  • Extension of 00z/12z Eta runs to 84-h
  • Introduction of nested Eta HiResWindow (HIRESW) runs
  • 26 September 2000 (TPB)
    26 September 2000 (Powerpoint briefing)
  • Eta model resolution increased to 22-km and 50 vertical levels
  • Improvements to Eta 3DVAR analysis
  • Vertical advection of cloud ice/water has been added, and slight modifications to the convective scheme
  • 29 March 2000
  • The 00Z and 12Z runs have been extended to 60 hours
  • The convective scheme has been modified to reduce the dry bias in the western U.S. and the moist bias along the Gulf and southeast U.S. coast
  • VAD winds are now being used a new quality control code
  • Balloon drift is now accounted for in the processing of radiosonde data
  • 15 March 2000
  • Nested Grid Model initialization changed to use the 00-h Eta analysis over North America and a 6-h GDAS forecast over the rest of the Northern Hemisphere in place of the Regional Data Assimilation System
  • 3 June 1998
  • Changes to the Eta Model and Eta Data Assimilation System (EDAS):
    1. The 03Z run of the Eta-29 (Meso Eta) was replaced by an 03Z run of the Eta-32. This forecast will will be the same length as the Eta-29 (33-h). It will be initialized by a 3-h EDAS assimilaition starting at 0000 UTC using the Eta 3DVAR analysis and an EDAS first guess.
    2. The 15Z run of the Eta-29 will be replaced by an 1800 UTC run of the Eta-32. Forecast length will be 30-h, with the 1800 UTC Eta 3DVAR analysis created using a 6-h EDAS run starting at 12Z
    3. The EDAS will run in full cycling mode, with all 3-d atmospheric variables cycled from the previous EDAS, instead of just soil states/TKE/cloud parameters
  • 13 May 1999
  • Eta 3DVAR modified to improve mass/wind balance
  • April 1998
  • Implementation of the new 40-km Rapid Update Cycle (RUC2)
  • 9 February 1998
  • Increase resolution of Early Eta from 48km/38levs to 32km/45levs
  • Replaced Eta OI analysis with Eta 3-d variational (3DVAR) analysis
  • 2 October 1995
  • Changes to the Early Eta System:
    1. Increase horizontal resolution from 80 km to 48 km
    2. Early Eta initialized from a 12-h intermittent data assimilation system (Eta Data Assimilation System, or EDAS) with 3 hourly analysis update. First EDAS analysis at 12-h prior to cycle time uses GDAS as a first guess
    3. Assimilate SSM/I precipitatble water data in Eta OI analysis
    4. Use 0.5 deg lat/lon SST analysis from NESDIS, merged with a 14-km analysis over the Great Lakes provided by GLERL
  • 7 February 1995
  • Initial implementation of the 29 km/50 level "Meso" Eta forecast over the CONUS
    1. Run from 03z/15z initial conditions, forecast length = 33-h
    2. Initialzied by a 3-h "mini" data assimilation: use GDAS first guess valid 00z/12z as first guess, perform a 29 km Eta OI analysis, run a 3-h Meso Eta forecast to 03z/15z, use this Meso Eta forecast as first guess to the 03z/15z Eta OI analysis
  • 27 September 1994 (TPB on Verification and Evaluation of RUC-1)
  • Initial implementation of the 80-km Rapid Update Cycle (RUC-1)
  • September 1994
  • Changes to the Early Eta System:
    1. Replace silhouette orography with "silhouette-mean" orography: at points where the observed topography is concave, replace silhouette elevation with average elevation
    2. Numerous changes to the Eta OI analysis
  • 8 June 1993
  • Limited-area Fine Mesh (LFM) model replaced with 80 km/38 level Eta model ("Early Eta"), initialzed with the Eta OI analysis using the GDAS as a first guess
  • Back to Table of Contents


    Contents of NDAS/NAM archive on HPSS

    Link to log of all operational NAM (formerly Eta) model changes since 1995

    Link to reference page and domain size graphics for NCEP output grids

    Link to Mesoscale Modeling Branch NAM parallel log

    Link to NCEP Environmental Modeling Center Home Page

    Link to Mesoscale Modeling Branch Home Page


    Eric Rogers
    NCEP/EMC Mesoscale Modeling Branch