Ensemble charts

Super Ensemble

The Super Ensemble tab overlays GFS, EC, GEM and MOGREPS in their model colours: pink, teal, blue and green. Up to 121 member lines include the four controls. Use Show members to hide all member lines, the individual switches to hide one model’s members, or Line opacity to fade the lines. Means only keeps the four model means; Show all members restores every model’s members. Model means and the optional 10–90% ranges are separate controls. These settings are independent of the individual ensemble views.

Each model keeps its own mean, member count, run information and forecast endpoint. No pooled mean or combined probability is calculated. Missing data remain gaps. Snowfall signal remains four separate model agreement curves. The cumulative precipitation curves retain their separate model totals and line styles. Image exports reflect the selected visibility; CSV exports retain all available members from all four models.

Near-surface temperature

The 2 m temperature graph shows instantaneous air temperature in °C, with member lines, the ensemble mean and 10–90% range. GFS, GEM and ECMWF supply temperature at 2 m above ground. MOGREPS-G supplies its native 1.5 m screen temperature, identified in the graph and exports; it is not adjusted or relabelled as a 2 m measurement. The time interval selects forecast samples and never sums temperatures.

Read the ensemble

Each thin line is an individual ensemble member. The pink line is the arithmetic mean of the available members; the shaded band spans the 10th to 90th percentiles. It is an ensemble range, not a calibrated confidence interval. Missing values are gaps, never zeros.

Click or hover to inspect the same time in every panel. Drag horizontally to zoom all charts together. Use the time slider for keyboard inspection. On phones, each chart has clearer day and time markers, its visible UTC range, and a linked time slider so you can inspect the forecast without scrolling back to the top. Each panel also has its own optional minimum and maximum.

Right-click a chart or use its image button to Copy image, Save PNG or Save SVG. Images include the visible UTC window, location, model run information and cumulative precipitation context. If direct copying is unavailable, a PNG preview lets you hold or right-click the image to copy it, or save it.

Cumulative precipitation

The blue line uses the right-hand millimetre scale and sums the available-member ensemble mean for each complete period inside the visible window. It starts at zero at the first period boundary at or after the left edge; rain before that boundary and partial periods at the edges are excluded. The bottom readout states the exact counted UTC span, the total and member availability. Zooming or changing the forecast window recalculates the total. A missing mean stops the line and makes the full-window total unavailable. Compare means shows separate blue cumulative curves and totals for each model, distinguished by line style; forecasts are never blended.

Snow signal

The snow panel shows the share of available members forecasting at least 0.1 cm of snowfall in the selected accumulation period. This is model agreement, not a calibrated probability or a prediction of settling snow.

Source & timing

GFS and GEM ensemble data: Open-Meteo Ensemble API. Every model card checks the latest published initialization as the page opens, independently of forecast loading, in UTC (00Z, 06Z, 12Z or 18Z). These small run checks refresh when you use Refresh and every five minutes while the page is visible. Each model card shows one latest feed run. Each loaded chart keeps the run information checked with its own forecast. GEFS combines 0.25° and 0.5° data; if their runs differ, the card shows the newest reported run and its tooltip lists both. Its upper-air temperatures use the 0.5° feed; 2 m temperature, precipitation, snowfall and mean sea level pressure can use both. These are rolling forecasts and may retain an older run at longer lead times. Chart labels and model-card tooltips include update status and any uncertainty in the timing. Retrieval time is shown separately.

EC ENS uses ECMWF Open Data directly: 50 perturbed members plus IFS CTRL, all from one verified 00Z or 12Z initialization. The native 0.25° grid covers the UK and Ireland area (49–62°N, 12°W–4°E). Complete runs extend to +360 hours, with 3-hour steps through +144 hours and 6-hour steps thereafter. Choose 6-hour totals for the full forecast; 3-hour precipitation and snow values after day 6 remain unavailable. Hourly totals are disabled. Pressure-level temperatures below the model surface are masked. Snow water equivalent uses the same fixed 7:1 conversion as the other charts. The publisher checks for new runs every five minutes; a new run replaces the previous one after all fields and members pass validation. GitHub scheduling and processing can add delay.

Open-Meteo hourly values may be interpolated from coarser model output. Temperatures and mean sea level pressure (hPa) are instantaneous values sampled at the displayed times. Precipitation and snowfall are summed over complete preceding 1-, 3- or 6-hour windows; incomplete windows remain missing. Forecast availability differs by model and variable.

MOGREPS-G uses the free Met Office AWS dataset: 18 members, both pressure-level temperatures, native 1.5 m screen temperature, precipitation, snowfall and mean sea level pressure from the same run, out to +246 hours. The latest complete run is checked every 3 hours. Publication is delayed after initialization; its actual run time is shown above. A new location can take around a minute to load, then benefits from caching.

MOGREPS is read on its native global grid, at 3-hour intervals. Six-hour totals combine two complete 3-hour periods; hourly totals are disabled when MOGREPS is displayed. Pressure-level temperatures below the surface are masked. Snow water equivalent is converted to centimetres using a fixed 7:1 ratio, matching Open-Meteo’s snowfall convention; actual snow density varies. Comparisons align valid times, not initialization times.

The separate operational GFS line in the reference image is not included: this view uses ensemble members and their control only.