Where each model takes its lows
GFS, ECMWF, AIFS, GEM, AIGFS · Valid Mon 18Z 12 Oct each model's newest run
Each model's lows, followed through its own run
Region Lower 48
United States
Europe
The readings under the map are for the whole map, not only the part shown.
GFS, ECMWF, AIFS, GEM, AIGFS · Valid Mon 18Z 12 Oct each model's newest run
Each model's lows, followed through its own run
Every low in each model's newest run that lasts 24 hours or more, followed through the run. No line joins one model's low to another's: which lows are the same is left to the eye.
- a low's track, a dot every 6 hours
- where it forms
- where it is at the time chosen, with its central pressure (hPa; height in dam for 500 mb lows)
- where it goes after that
- a jump the run's own motion does not explain: possibly a different low
Each model's newest run, to day 5: the time slider puts every track's marker at one moment, and the track after it is drawn fainter.
Runs: GFS 12Z 10 Oct, ECMWF 06Z 10 Oct, AIFS 12Z 10 Oct, GEM 12Z 10 Oct, AIGFS 12Z 10 Oct.
Choose models with the chips. The depth control keeps only the lows that get at least that deep at some point in their life, so a low does not come and go as the time moves. Hover a track for its model, run, life and both depths.
Methodology
The lows are found in each model's own sea-level pressure and 500 mb heights as each run is stored, and followed lead by lead through the run, six hours a step, to day 5. Uncorrected model output on every side.
The depth control measures one of two ways. Below surroundings (the default) is how far the low stands below the pressure around it: for a surface low, its central pressure against the average over a box 10 degrees of latitude and longitude on a side centred on it (about 1,100 km north to south, narrower east to west the further north it is), in hPa; for a 500 mb low, how far even the lowest point on a ring about 440 km out stands above the centre, in dam. A compact, well-wound low stands out; a broad one sitting in generally low pressure does not. At the centre is the low's lowest central pressure (height, for 500 mb lows), the number on its marker. It carries the climate with it: 1000 hPa is a strong low over the Gulf and an ordinary one near the Aleutians.
A dotted step is one the run's own motion does not explain, where the tracker may have joined two different lows.
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. Every model's full forecast for any of these cities, or anywhere else, is in the beta: request an invite; it's free during the beta.
Sources and licences
- NOAA: GFS and AIGFS, 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.