ECMWF
Also called: European model, Euro, IFS
ECMWF is the European Centre for Medium-Range Weather Forecasts, an intergovernmental organization supported by 35 states, and the name commonly given to its global weather model, often called the European model or the Euro. Its physics-based Integrated Forecasting System (IFS) runs on a global grid of about 9 km and forecasts up to 15 days ahead.
Why It Matters
The ECMWF model is one of the main global models forecasters consult for the medium range, days 3 to 15, usually alongside the American GFS. Because it is an ensemble, it shows a range of outcomes as well as a single forecast.
ECMWF was established in 1975. It is headquartered in Reading in the United Kingdom, with sites in Bologna, Italy, and Bonn, Germany.
ECMWF Forecast Systems
| System | Type | Grid spacing | Details |
|---|---|---|---|
| IFS ensemble (ENS) | Physics-based | About 9 km | 51 members (1 control and 50 perturbed), up to 15 days ahead. Main runs start at 00 and 12 UTC, with shorter runs at 06 and 18 UTC. |
| AIFS | Machine learning | 28 km at launch | Operational since 25 February 2025. It runs alongside the IFS from the same initial conditions. |
Source: ECMWF: Medium-Range Forecasts
Frequently Asked Questions
What is the difference between the IFS and the AIFS?
The IFS (Integrated Forecasting System) is ECMWF's physics-based model: it applies the laws of physics to the atmosphere on a 9 km global grid. The AIFS (Artificial Intelligence Forecasting System) is a machine-learning model trained on past weather. It became operational on 25 February 2025 and runs alongside the IFS from the same initial conditions.
How far ahead does the ECMWF model forecast?
The medium-range ensemble forecasts up to 15 days ahead, with 51 members: one control forecast and 50 perturbed forecasts.
How often does the ECMWF model run?
The main runs start from conditions at 00 and 12 UTC, with shorter supplementary forecasts from 06 and 18 UTC. Forecasts become available several hours after those times.
Related Terms
GFS
Global Forecast System, the primary American global weather model run by NOAA. The GFS provides forecasts out to 16 days and is widely used for medium-range forecasting. It runs four times daily with global coverage.
Ensemble Forecast
A collection of multiple model runs with slightly different initial conditions, showing the range of possible outcomes. Ensemble forecasts help quantify uncertainty and are especially valuable for medium-range predictions.
HRRR
High-Resolution Rapid Refresh, a real-time 3km resolution weather model updated hourly. The HRRR excels at short-range (0-18 hour) forecasts of convection, precipitation, and aviation weather across the contiguous United States.
NAM
North American Mesoscale Model, a regional weather model covering North America at 3-12 km resolution and NCEP's short-range workhorse for mesoscale features like fronts, lake-effect snow, and sea breezes. Its successor is the Rapid Refresh Forecast System (RRFS) with its ensemble REFS, and the same changeover ends SREF, HREF, HiresW, and NAM MOS. The National Weather Service notice of October 2, 2026 set the changeover date as November 3, 2026, moved from October 14.
Probability of Precipitation
Probability of precipitation (PoP) is the chance that a given point receives measurable precipitation, at least 0.01 inch, during the forecast period. A 40% chance of rain means a 4 in 10 chance of at least 0.01 inch at your location. It does not mean rain over 40% of the area or for 40% of the time.
Zulu Time
Zulu time, written with a Z, is the name used in aviation and meteorology for Coordinated Universal Time (UTC), the time at the Greenwich prime meridian. Weather observations, model runs, and aviation reports all use it so that a time means the same thing everywhere. 12Z is 8 in the morning Eastern Daylight Time and 7 in the morning Eastern Standard Time.
ECMWF: Guides and Explainers
These explainers connect this definition to real-world forecasting and decision-making.
In-depth guide
GFS vs HRRR vs NAM: Which Weather Model Should You Trust?
Learn the differences between GFS, HRRR, NAM, and the Euro model. Understand which forecast model to trust for different situations and how weather enthusiasts can interpret model data.
Weather Education
Spaghetti Models Explained: What Those Tangled Hurricane Lines Actually Mean
Spaghetti models are a tangle of individual forecast tracks, not a forecast. Here is what each line is, what the labels like AVNO and EMX stand for, and how to read the spread instead of the scariest strand.
Weather Education
El Niño 2026: How Strong It Is, and What It Actually Means
El Niño is strengthening in 2026, with NOAA calling a strong-to-very-strong event likely through winter and 83% odds of a historic peak that exceeds every event since 1950. What that means for hurricane season and winter.
Helpful Tools and Hubs
Use these pages to apply the concept, compare conditions, or follow related weather workflows.
Tool
Pressure Tendency Calculator
Calculate 3-hour barometric pressure tendency from rising or falling readings.
Guide
Understanding Snow Totals
Why snow forecasts give ranges instead of exact numbers: snow ratios, banding, and elevation effects.
Guide
How to Read Weather Radar
Learn the basics of radar interpretation so you can tell where storms are headed and how intense they may become.
Guide
Weather Radar Colors Explained
Understand what green, yellow, red, and purple radar returns usually mean in real-world storms.
Sources
Explore Other Terms
Sleet
Frozen raindrops that bounce when hitting the ground. Sleet forms when snowflakes partially melt falling through a warm layer, then refreeze in a cold layer near the surface. Unlike freezing rain, sleet is frozen before it hits the ground.
Wind Shear
A change in wind speed or direction over a short distance, either horizontally or vertically. Strong wind shear is essential for supercell and tornado development but is also a significant hazard to aircraft during takeoff and landing.
Velocity
Doppler radar measurement of how fast precipitation is moving toward or away from the radar. Velocity data reveals wind patterns, rotation in thunderstorms, and potential tornado signatures that reflectivity alone cannot show.
IFR
Instrument Flight Rules govern flights conducted under instrument procedures and can be used in clear weather too. Separately, the IFR weather category means a ceiling from 500 to less than 1,000 feet and/or visibility from 1 to less than 3 statute miles, with lower values classified as LIFR. Legal operating requirements depend on airspace, regulations, equipment, and pilot qualifications.
Tropical Depression
An organized system of clouds and thunderstorms with defined circulation and maximum sustained winds of 38 mph or less. Tropical depressions can strengthen into tropical storms and eventually hurricanes.
Alberta Clipper
A fast-moving low-pressure system that originates near Alberta, Canada, and tracks southeast across the northern United States. Clippers typically bring light snow (1-4 inches) followed by bitter cold and gusty winds.
Browse by Category
In the WeatherAI App
WeatherAI Forecast, the app's own free forecast, blends multiple traditional and AI weather-model inputs. ECMWF's IFS and AIFS are among the guidance it can draw on, and the mix varies by location, forecast range, and data availability.
Availability, coverage, update frequency, and alert delivery vary by data source, region, subscription plan, device permissions, and service conditions.