Numerical Weather Models are often the first layer of the weather forecasting cake. Several times a day, weather service computers are crammed full with all the latest surface, upper air, radar and satellite weather data, then they whir and shake for a while as a complicated mathematical model is applied, and eventually they spit out forecast weather elements for an evenly spaced grid over the Earth. The forecast at this point has
not been adjusted by any humans.
Pros: The grid coverage allows for the creation of forecasts at any location within the model (i.e. your favorite fishing spot), not just for the nearest town or city. The grid coverage also allows your local TV station to make those fancy maps.
Cons: Your Spot may not be properly represented by the model grid cell in which it falls. The average elevation of the model cell may not represent your Spot elevation, or the cell may fall mostly over water while your Spot is over land. Zoom in on the map when selecting your Spot to view the extent of the model grid cells. The model elevation and land proportion is also shown below the forecast graphs.
Read more about numerical models in Wikipedia.
Numerical Models currently shown on Spotwx.com:
Regional Deterministic Prediction System (RDPS) / Global Environmental Multiscale (GEM) Regional
Agency: Environment and Climate Change Canada
Spatial Resolution: 10 kilometers
Temporal Resolution: 1 hour
Model runs: 00/06/12/18 Zulu
Forecast Range: 84 hours
Geographic Extent: map
References: CMC for details.
Global Deterministic Prediction System (GDPS) / Global Environmental Multiscale (GEM) Global
Agency: Environment and Climate Change Canada
Spatial Resolution: 15 kilometers
Temporal Resolution: 3 hours
Model Runs: 00/12 Zulu
Forecast Range: 240 hours
Geographic Extent: Global
References: CMC for details.
High Resolution Deterministic Prediction System (HRDPS) / Global Environmental Multiscale (GEM) Limited Area Model (LAM) - Continental Domain
Agency: Environment Canada
Spatial Resolution: 2.5 kilometers
Temporal Resolution: 1 hour
Model Runs: 00/06/12/18 Zulu
Forecast Range: 48 hours
Geographic Extent: map.
References: CMC for details.
High Resolution Deterministic Prediction System (HRDPS) / Global Environmental Multiscale (GEM) Limited Area Model (LAM) - 1km West Domain
Agency: Environment Canada
Spatial Resolution: 1 kilometer
Temporal Resolution: 1 hour
Model Runs: 00/12 Zulu
Forecast Range: 48 hours
Geographic Extent: map.
References: CMC for details.
North American Mesoscale Model (NAM)
Agency: National Centers for Environmental Prediction, NOAA
Spatial Resolution: 12 kilometers
Temporal Resolution: 1 hour increments to 36 hours, then 3 hour increments
Model Runs: 00/06/12/18 Zulu
Forecast Range: 84 hours.
Geographic Extent: Much of North America, from central Mexico to around the 60th parallel.
References: Wikipedia for details.
Global Forecast System (GFS)
Agency: National Centers for Environmental Prediction, NOAA
Spatial Resolution: 0.25 degrees
Temporal Resolution: 1 hour to hour 120, then 3 hours to hour 384
Model Runs: 00/06/12/18 Zulu
Forecast Range: 384 hours.
Geographic Extent: Global
References: Wikipedia for details.
Rapid Refresh (RAP)
Agency: National Centers for Environmental Prediction, NOAA
Spatial Resolution: 13 kilometers
Temporal Resolution: 1 hour
Model Runs: Hourly
Forecast Range: 21 hours, except 51 hours at 03/09/15/21 Zulu
Geographic Extent: Much of North America (solid line on this map).
References: NOAA link for details.
High-Resolution Rapid Refresh (HRRR)
Agency: National Centers for Environmental Prediction, NOAA
Spatial Resolution: 3 kilometers
Temporal Resolution: 1 hour
Model Runs: Hourly
Forecast Range: 18 hours, except 48 hours at 00/06/12/18 Zulu
Geographic Extent: Lower 48 states and southern Canada (CONUS coverage on this map).
References: NOAA link for details.
Short Range Ensemble Forecast (SREF)
Agency: National Centers for Environmental Prediction, NOAA
Spatial Resolution: 16 kilometers
Temporal Resolution: 3 hours
Model Runs: 03/09/15/21 Zulu
Forecast Range: 87 hours
Geographic Extent: North America, plus a bit (Solid black line on this map).
References: NOAA link for details.
CMC GEPS Ensemble
Agency: Environment Canada
Spatial Resolution: 0.5 degree
Temporal Resolution: 3 hours to hour 192, then 6 hours to hour 384
Model Runs: 00/12 Zulu
Forecast Range: 384 hours (16 days)
Geographic Extent: Global
References: CMC for details.