What this is
Twice a day, at about 03 and 15 UTC, an AI model (OpenAI's GPT or Anthropic's Claude) scans the latest ECMWF forecasts on
ECMWF Open Data
for interesting weather and picks about a dozen highlights. At those times the newest forecasts are the 18 and
06 UTC runs; "chance of …" maps come from the most recent ensemble, run at 00 or 12 UTC. The model writes a short
explanation for each highlight and sets up one or more animated scenes from the forecast. The new highlights
appear here within about an hour. People using the companion iPhone app can also request an event; those appear
under Requested for two days.
This is model guidance, chosen and written automatically, not an official forecast or warning. For those, see
your National Meteorological Service.
Choosing what to watch
- Highlights (left, or across the top on a phone): pick an event. Each says where it is and how many scenes it has.
- Scenes (the numbered tabs above the map): each scene shows a different side of the event, such as pressure and
upper-air pattern, then gusts, then the ensemble's view. Work through them in order.
- The panel below or beside the map explains what's happening, why it's interesting, and where the information came from.
- Items tagged Explainer aren't news: they are textbook examples of how the atmosphere works (a Greenland tip jet,
a bora, a burst of tropical thunderstorms…) picked because the forecast shows them clearly right now.
Playing the forecast
- ▶ / ❚❚ plays or pauses; drag the slider to move through time. Under the time is the forecast's lead time and
the model run it comes from.
- 2× changes the speed: ½×, 1×, 2× or 4×. 1× plays one frame a second, and frames are usually 3 hours
apart, so the starting speed of 2× shows 6 forecast hours a second. Your choice is remembered.
- Captions on the map point out what to look for as the forecast unfolds.
Moving around the map
- Drag to pan; scroll, pinch or use + and − to zoom.
- Target button: back to the whole scene.
- Full screen button: the map and timeline fill the screen (Esc or the same button to return).
- Layers button: dark, light, satellite or relief background (satellite imagery: NASA Blue Marble).
- Relief shows the lie of the land, lit from the north-west: greens for low ground, browns for hills and
mountains, pale grey and white for the highest ground and the ice sheets of Greenland and Antarctica, and darker
blues for deeper sea. Use it to see how mountains and coasts shape the weather: winds funnelled through gaps and
down slopes (such as the bora), rain piled up on windward ranges, or a low-level jet running along the foot of the
Rockies or the Andes. The background never changes by itself. (Heights: NOAA ETOPO 2022.)
- Tap or click anywhere on the map for the value at that point.
Reading the map
- Colours: the field named in the key at the top left, such as wind gusts, rain or temperature.
- Lines: isobars (mean sea level pressure, every 4 hPa) or 500 hPa height, with values along them.
- H and L: centres of high and low pressure, with their central pressure.
- Moving streaks: wind direction and speed (at 10 m, or higher up where the key says so).
- Precipitation type: rain, freezing rain, snow, wet snow, sleet (rain and snow), ice pellets and freezing
drizzle, in the colours of ECMWF's OpenCharts; each is darker when light and at its brightest when heavy.
- Cloud tops: a satellite-like view from the outgoing infrared radiation; the brightest white is the coldest,
highest cloud, such as thunderstorm tops.
- Storm energy (CAPE): the energy available to thunderstorms; above about 2000 J/kg storms can be strong.
- "Chance of …" layers come from the ECMWF ensemble (IFS ENS): the percentage of its 51 forecasts showing the event.
- Projection: an equal-area map centred on the middle of the view (Lambert azimuthal), so areas are true
and shapes stay close to true across a scene, even near the poles. Panning turns the globe, and north is straight
up through the centre; meridians away from it lean. Dashed lines mark latitude and longitude, so north can be read
anywhere. Satellite and relief backgrounds stop at 85° north and south.
Units and times
Units follow your device's time zone: for example °F, mph and inches in the US; °C, mph and mm in the UK; °C, km/h and mm
in most other places. Change any of them with the units button at the top. Figures in the text change to match.
Times are shown in your own time zone, by its usual name such as NZDT, CET or EDT. Choose UTC under Time zone
in the same menu if you prefer. Times in the text that include a date change too. Model
runs keep their UTC names (for example "00 UTC run"), as do times written without a date. Your choices are remembered
in this browser.
Sharing and saving
- 3D (tropical cyclones) opens a 3D model of the storm that you can turn, tilt and zoom: clouds and the warm
core from humidity and temperature on 12 pressure levels, winds spiralling in near the sea and out at the top, rain,
and the sea coloured by wind speed with isobars. It starts at the moment you were looking at, and can make its own video.
Heights are exaggerated, and the clouds are inferred from humidity rather than taken from the model's cloud. It needs
a download of about 10 MB.
- Share creates a link to exactly what you're looking at: the highlight, the scene, the moment, the map style
and your view. Whoever opens it sees their own units and time zone. Links keep working for a week after a highlight is replaced.
- Video makes an MP4 of the current scene from start to end at your chosen speed, square, portrait or
landscape, with the title, time, key, caption and ECMWF credit drawn in. Use it for social media. It's made in
your browser and takes a few seconds to a minute. It needs a recent browser; where it isn't supported the button doesn't appear.
- Save downloads one web page file, either this highlight or all current ones, that plays with no
connection. Open it in a browser on a computer. Satellite backgrounds still need the internet.
Data
Forecasts: ECMWF IFS (HRES and ENS) from ECMWF Open Data, © ECMWF, CC BY 4.0, regridded and converted. Map outlines:
Natural Earth. Relief: NOAA ETOPO 2022. Satellite imagery: NASA Blue Marble via GIBS. New highlights appear at
about 04 and 16 UTC.
Visits are counted anonymously with GoatCounter (no cookies, nothing that identifies you), so we can see which
highlights people look at.
About
A prototype developed by Neil Gordon as an ECMWF Visiting Scientist, with ECMWF's support; not an official ECMWF
product or service. The code was written by Claude Opus 5.5 (Anthropic), provided through ECMWF's enterprise
account, at Neil Gordon's direction, and is open source under the MIT Licence:
web viewer and
backend.