stated on the page: ecmwf.int

--- title: ECMWF open data summary: A subset of the IFS and AIFS real-time forecasts as GRIB2 files, free, no key. mount:

Open data and APIs

Left: what points at it. Right: what it points at. Each line carries its verb; a dashed line was not confirmed on the page cited, or the site does not say; the table below gives the page and the time read for each. From data-ecmwf-open.json

--- # ECMWF open data > Kept by incident.meteorology@web-summit.dinis, 11 November 2026, 11:36 UTC [Where a forecast comes from](../index.md) · Open data and APIs · id `data-ecmwf-open` · [as data](data-ecmwf-open.json) A subset of the IFS and AIFS real-time forecasts as GRIB2 files, free, no key. **Address:** [https://www.ecmwf.int/en/forecasts/datasets/open-data](https://www.ecmwf.int/en/forecasts/datasets/open-data) (leaves this site) ## What it is connected to, and who says so | This | Verb | That | The page that says so | Read | Check | |---|---|---|---|---|---| | ECMWF open data | **carries** | [ECMWF IFS](model-ecmwf-ifs.md) | [ecmwf.int](https://www.ecmwf.int/en/forecasts/datasets/open-data): "Use Browse the data files Licence: description View licence A subset of ECMWF real-time forecast data from the IFS and AIFS models is made available to the public free of charge. Their use is governed by the Creative Com" | 11:28 UTC, 11 Nov | stated on the page | | ECMWF open data | **carries** | [ECMWF AIFS](model-ecmwf-aifs.md) | [ecmwf.int](https://www.ecmwf.int/en/forecasts/datasets/open-data): "Browse the data files Licence: description View licence A subset of ECMWF real-time forecast data from the IFS and AIFS models is made available to the public free of charge. Their use is governed by the Creative Commons" | 11:28 UTC, 11 Nov | stated on the page | | ECMWF open data | **carries** | [ECMWF ensemble (ENS)](model-ecmwf-ens.md) | [ecmwf.int](https://www.ecmwf.int/en/forecasts/datasets/open-data): "These products are a subset of the full Catalogue of ECMWF Real-time Products and are based on the medium-range ( high-resolution and ensemble ) and seasonal forecast models. IFS data are published at two resolutions: th" | 11:28 UTC, 11 Nov | stated on the page | | ECMWF open data | **published by** | [ECMWF](body-ecmwf.md) | [ecmwf.int](https://www.ecmwf.int/en/forecasts/datasets/open-data): "Open data / ECMWF Skip to main content menu help_outline Search help_outline Help login Log in search account_circle About Forecasts Computing Research Learning Publications" | 11:28 UTC, 11 Nov | stated on the page | | ECMWF open data | **is what Open-Meteo takes its data from** | [Open-Meteo](data-open-meteo.md) | [open-meteo.com](https://open-meteo.com/en/licence): "wave forecasts from Deutscher Wetterdienst DWD ( CC-BY Licence ) Atmospheric, ensemble and wave forecasts from European Centre for Medium-Range Weather Forecasts ECMWF ( CC-BY Licence ) Atmospheric, ensemble and wave for" *Open-Meteo's licence page lists each upstream service with its licence.* | 11:29 UTC, 11 Nov | stated on the page | ## Licence: what we may do with it **ECMWF open data (IFS and AIFS real-time forecasts)**: CC BY 4.0, with ECMWF's Terms of Use ([ecmwf.int](https://www.ecmwf.int/en/forecasts/datasets/open-data), read 11:28 UTC, 11 Nov, stated on the page). | Read | Store | Show | Transform | Attribution | |---|---|---|---|---| | yes | yes | yes, with attribution | yes, with attribution | "Copyright © [year] European Centre for Medium-Range Weather Forecasts (ECMWF)", the source, the licence, and a statement of any change made. | No service guarantee; the open subset is coarser (0.25°) and later than what members receive. ## What it offers for Lisbon and Madeira this week The global fields themselves at 0.25°: gusts (10fg), wind, pressure, rain, waves, for every 3 hours out to 144 h and 6-hourly beyond, from the same model IPMA shows on its charts page. Also the 51-member ensemble and the AIFS. - **Endpoint:** `https://data.ecmwf.int/forecasts/` - **Key:** none - **Format:** GRIB2, with a JSON-lines .index per file - **Size:** about 92 MB per time step for the whole globe and all fields; one field is 0.3 to 0.5 MB and can be fetched alone with an HTTP range from the .index (our probe: 85 steps in the 12 UTC run; the first field of step 24 is 500,611 bytes) - **Cadence:** four runs a day (00, 06, 12, 18 UTC), on the portal about 7 to 8 hours after run time (12 UTC run: files dated 19:34 UTC) - **This week** (probe read 02:29 UTC, 11 Nov): Read 02:29 UTC: the portal held 7 to 10 November; the 12 UTC run of 10 November was complete (IFS: 85 steps; AIFS single: 61 steps). A field covers Lisbon and Madeira in one global grid. - **How to read it:** `Read the .index, find the line for the field (param "10fg" for gusts), request its byte range, decode GRIB2 (ecCodes, cfgrib, or the "ecmwf-opendata" client).` - **Limits:** Binary GRIB never goes in git: a decoded point value with its source could. Decoding needs a GRIB library we do not have in the build. ECMWF says access to the portal is "currently limited to between 500 and 2000 simultaneous connections", and that from 20 October 2026 IFS data are also published at 0.1° (read on its open-data page). - **A small sample, as returned:** [ecmwf-open-data-index.json](../samples/ecmwf-open-data-index.json) --- Not a warning service: this page explains where data comes from. For warnings follow [IPMA](https://www.ipma.pt/pt/otempo/prev-sam/) and ANEPC.