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NMME User's Guide

  1. What is this?

  2. What is the NMME?

  3. When is this page updated?

  4. What is available on this website?

  5. Hindcasts

  6. Data access

  7. Frequently asked questions

  8. Different view options

  9. Archived forecasts

  10. More information about climate modeling


1. What is this?
This is the North American Multi-Model Ensemble (NMME) forecasting project web home. (Originally known as the "National Multi-Model Ensemble".)
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2. What is the NMME?
  1. The North American Multi-Model Ensemble (NMME) is a collaboration between several climate modeling centers. Several studies have found that multi-model ensembles (MME) have higher skill at forecasting weather and climate, and allow for better characterization of prediction uncertainty. (See the BAMS article for MME references.) In 2010, a report by the National Academies of Science recommended the development of a National MME capability. The NMME was planned in two workshops in early 2011, and realtime forecasting began in August, 2011. There is both a research component and a real-time experimental-operational seasonal prediction component. Resarch for the community is helped by free data distribution [see points 6 and 9], while CPC/NCEP runs the real-time application (i.e. the forecasts on this website.)
  2. BAMS article
  3. What models are involved?
    1. NOAA NCEP CFSv1 (retired October, 2012)
    2. NOAA NCEP CFSv2
    3. IRI ECHAMA and ECHAMF (retired August, 2012)
    4. NASA Goddard Space Flight Center (GSFC) GEOS5
    5. NCAR/University of Miami CCSM3.0
    6. GFDL CM2.1
    7. GFDL CM2.5 [FLORa06 and FLORb01] (joined March, 2014)
    8. Environment Canada CanCM3 and CanCM4 (joined September, 2012)
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3. When is this page updated?
The models are run at their respective centers before the 8th of each month, and delivered to CPC by 5:00 p.m. Eastern time on the 8th. Forecast graphics and data are updated to the website on the 9th of each month. Back to top



4. What's available on this website?
  1. Spatial anomaly forecasts
    1. one-month: ensemble mean monthly anomaly forecasts for each model based on their climatology from the hindcasts. The models are equally weighted, meaning the ensemble means for each model are calculated first, then averaged together to form the multi-model mean. Forecasts for the following seven months are available.
    2. three-month: ensemble mean three-month average of monthly anomalies (also called "seasonal"). The three-month averages are calculated, then the ensemble means for each model, then the multi-model ensemble mean. Forecasts are available for the five three-month periods following the current month.
  2. Skill maps are based on the monthly/three-month anomaly correlation for each variable's ensemble mean from the 1982-2010 hindcasts. Skill maps are available for the individual models and for the NMME.
  3. Niņo 3.4 plumes: area-averaged sea-surface temperature over the Niņo 3.4 region (-5° S to 5°N latitude, 190° to 240° longitude). This area is a key indicator of El Niņo/La Niņa Southern Oscillation (ENSO).
  4. International MME: The EuroSIP (European Seasonal-to-Interannual Prediction) project is presently a collaboration of ECMWF, MeteoFrance, UKMet Office, and NCEP. Raw data from IMME is not available. IMME is not currently included in NMME, but is provided on the NMME webpage for informative purposes. More information on EuroSIP.
  5. Experimental probability forecasts: probability forecasts are a different representation of the model data, and are prepared in parallel to the the anomaly forecasts. Forecasts are categorized for each model by counting the occurrence of above/below/near normal, and all models are added together, hence, only the NMME is shown. Here, each member has equal weight. More information.
  6. Preview of additional variables: Five variables are available in "preview" mode: 200 mb height, maximum and minimum 2 m surface temperature, runoff, and soil moisture. These five were added as "Phase I plus"; more variables will be available for research with NMME Phase II.
  7. Preliminary real-time verification: Skill assessments of the real-time forecasts are updated monthly between the 6th - 8th. Pattern correlation of the anomaly forecasts are calculated using the anomaly correlation coefficient for each model and the NMME. Annual summaries (August - July) are also available.
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5. Hindcasts
Each model has a complete set of retrospective forecasts for 1982-2010. These hindcasts are used for model calibration and for studies. Information on accessing the hindcasts available below. Only monthly means are available, for the three variables: sea-surface temperature, 2 meter temperature, and precipitation rate, at a global, 1-degree latitude by 1-degree longitude resolution.
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6. Data access
  1. Forecast data for the current month is available here.
  2. Hindcast data is hosted by IRI. Monthly means for 1982-2010 are available for all models and leads, except for CFSv1 (1982-2009). This site also has a data viewer option.
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7. Frequently asked questions
  1. Why does the CFSv2 forecast look different here than on the CPC's CFSv2 page? The CFSv2 forecast for the NMME is based on initial conditions from the 1st - 8th of the month. CPC's CFSv2 page shows three ensembles, from initial conditions over the previous three ten-day periods. As well, there may be differences in the climatology subtracted to form the anomalies. Read the description of the CFSv2 from this page for more details.
  2. I want a different variable! Many new variables will be released as part of NMME Phase II. The database, which will ultimately house more than petabyte of data, is currently being populated. Target release date is August, 2014. More information, including a list of parameters, available here.
  3. I want subseasonal forecasts! Subseasonal (45-day forecasts, including 6-hourly) will be available as part of Phase II, but will not be available in realtime any time soon. More information, including a list of parameters, available here.
  4. Where can I get the data represented in these maps? Data for current forecasts available via ftp here.
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8. Different view options
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9. Forecast Archive
Forecast images from August, 2011 initial conditions through last month are available here.
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10. More information about climate prediction
  1. What's a climate model?
  2. NOAA's Climate.gov
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