EPT-1.5 to EPT-2
This guide helps you transition your applications from using EPT-1.5 to EPT-2.
Key Differences
API Changes
API endpoints remain the same
Change in parameter ordering in some responses
Enhanced error handling with more descriptive error messages
Data Format Changes
Grid dimensions changed from 2220x4440 to 2160x4320
Data chunking parameters are different:
(time: 1, prediction_timedelta: 144, lat: 120, lon: 240)File access paths now include version information in the path
Hindcast Parameter Naming Changes
EPT-2 hindcasts use human-readable parameter names instead of ECMWF shortnames
While EPT-1.5 hindcasts used ECMWF shortnames like
2t,10si, etc., EPT-2 hindcasts exclusively use longnames likeair_temperature_at_height_level_2m,wind_speed_at_height_level_10mNote that the API parameter names have not changed, this only affects the hindcast data files
Advantages of EPT-2
EPT-2 offers significant improvements over EPT-1.5:
Performance Improvements
Strong accuracy improvements on all parameters, outperforming all open and closed global weather models in our benchmarks (on RMSE)
Improved architecture with more training data and more parameters
Operational Enhancements
Faster dissemination times
Phased roll-out in different versions, with increased resolution and update rate
Slight update on the grid for improved geographical coverage
Temporal Resolution
Hourly predictions for the first 10 days
6-hourly predictions from days 10 to 20 (changed from hourly in EPT-1.5)
Migration Steps
1. Update Hindcast Data References
If you're using the hindcast data directly, update your code to handle the new parameter names:
# EPT-1.5 hindcast (old)
temperature = data['2t'] # ECMWF shortname
# EPT-2 hindcast (new)
temperature = data['air_temperature_at_height_level_2m'] # Human-readable longname2. Hindcast Parameter Names Reference
Here is a reference table for the parameter name changes in hindcast data:
2t
air_temperature_at_height_level_2m
Air temperature at 2m
10si
wind_speed_at_height_level_10m
Horizontal wind speed at 10m
10wdir
wind_direction_at_height_level_10m
Horizontal wind direction at 10m
100si
wind_speed_at_height_level_100m
Horizontal wind speed at 100m
100wdir
wind_direction_at_height_level_100m
Horizontal wind direction at 100m
msl
air_pressure_at_mean_sea_level
Mean Sea-level Pressure
z_500
geopotential_at_pressure_level_50000Pa
Geopotential at 50000 Pa
Additional parameters available on request:
tcwv
atmosphere_mass_content_of_water_vapor
Total column water vapor
2d
dew_point_temperature_at_height_level_2m
2m dewpoint temperature
t
air_temperature_at_pressure_level
Temperature (pressure levels)
u
eastward_wind_at_pressure_level
U component of wind
v
northward_wind_at_pressure_level
V component of wind
q
specific_humidity_at_pressure_level
Specific humidity
z
geopotential_at_pressure_level
Geopotential
3. Update File Access Paths
# EPT-1.5 (old)
path = "https://data.jua.ai/hindcasts/ept-1.5-early/europe/2024.zarr" # Example for Europe 2024
# EPT-2 (new)
path = "https://data.jua.ai/hindcasts/ept-2/v2/global/2023-01-01-to-2024-12-28.zarr"4. Adjust for Grid Size Differences
If your application depends on specific grid positions, you'll need to adjust for the new grid dimensions:
# EPT-1.5 (old)
# Grid size: 2220x4440
# EPT-2 (new)
# Grid size: 2160x43205. Update Data Loading Code
# EPT-1.5 (old)
ds = xr.open_zarr("https://data.jua.ai/hindcasts/ept-1.5-early/europe/2024.zarr")
# For live forecast data e.g. 2025-04-24 06:00:00: ds = xr.open_zarr("https://data.jua.ai/forecasts/ept-1.5/2025042406.zarr")
# EPT-2 (new)
ds = xr.open_zarr("https://data.jua.ai/hindcasts/ept-2/v2/global/2023-01-01-to-2024-12-28.zarr")
# For live forecast data e.g. 2025-04-24 06:00:00: ds = xr.open_zarr("https://data.jua.ai/forecasts/ept-2/2025042406.zarr")
# Note the chunking differencesTesting Your Migration
We recommend running your application against both EPT-1.5 and EPT-2 in parallel during the transition period to validate output and ensure compatibility.
For any migration issues, please contact our support team.
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