Model spread, mapped
GFS, ECMWF, ECMWF AIFS, GEM · Run 00Z 1 Oct · +18 h · Valid Thu 18Z 1 Oct
Gap between the warmest and coolest of these models
Region Northern Plains
The readings under the map are for the whole map, not only the part shown.
GFS, ECMWF, ECMWF AIFS, GEM · Run 00Z 1 Oct · +18 h · Valid Thu 18Z 1 Oct
Gap between the warmest and coolest of these models
Widest gap 20.8 °F, 45 mi WSW of St. Charles, Missouri · unshaded ground is where all 4 land within 2 °F of each other
Thin lines are temperature itself, every 10 °F — the per-cell median of the 4, so a line no single model forecast.
Shows where the models disagree about the temperature at 18Z 1 Oct — the day you choose, always at the same hour so that successive days compare.
Methodology
Across-model 2 m temperature spread from GFS, ECMWF, ECMWF AIFS, GEM — four models and three centres, named because a roster is a fact about a chart: two of these are ECMWF's, and where those two agree they agree partly for family reasons. Uncorrected model output on every side, unlike the city forecasts elsewhere on this site, so the comparison is what it says it is.
Nothing here is smoothed. The shading, the contours and the widest gap are all read from the models' own grids at their own resolution, because averaging a cell into its neighbours fills in exactly the extremes this map exists to show — and a number printed over a colour has to agree with it. The widest gap comes from the drawn frame only: the store reaches further west than this map does, and naming a coordinate a reader cannot find is worse than naming a nearer one.
Valid at 18Z on purpose, and the same hour every day so successive maps compare: mid-afternoon is well mixed, and the models' own terrain heights explain a sixth as much of this picture then as they do at dawn.
Shaded ground is a disagreement rather than an error — none of these models is the truth here, and the map cannot say which is right. For who has actually been closest, the model leaderboards are the place.
This map is drawn from model output we store ourselves, not from anyone's picture of it, and is based on data and products of NOAA, the European Centre for Medium-Range Weather Forecasts (ECMWF) and Environment and Climate Change Canada. The per-city read of the same day — which cities the models are fighting about, and what the discussion makes of it — is on the national page.
Sources and licences
- NOAA: GFS, from NOAA's NOMADS server. US government data, not subject to copyright (NOAA/NWS terms of use).
- ECMWF: IFS and AIFS Single, from ECMWF's open data. This service is based on data and products of the European Centre for Medium-Range Weather Forecasts (ECMWF). Source: www.ecmwf.int. This ECMWF data is published under a Creative Commons Attribution 4.0 International (CC BY 4.0). ECMWF does not accept any liability whatsoever for any error or omission in the data, their availability, or for any loss or damage arising from their use.
- Environment and Climate Change Canada: GEM, from the MSC Datamart. Data Source: Environment and Climate Change Canada, under its Data Services End-use Licence.
What we change: each field is cropped to the frame these maps share when we download it, and each map then smooths, contours, differences or ranks those numbers as its Methodology says. These are our maps of the providers' numbers, not their products, and none of them has reviewed or endorsed this site.
Coastlines, borders, lakes and place names: Natural Earth, public domain.