AIGEFS#

In December 2025, NOAA announced the release of three AI global forecasting systems.

NOAA deploys new generation of AI-driven global weather models

All three models are available for download in Herbie:

  • model="aigfs"

  • model="aigefs"

  • model="hgefs"

This notebook demonstrates how to download and use AIGEFS data using Herbie.

[3]:

from herbie import Herbie
from herbie.toolbox import EasyMap, pc, ccrs
from herbie import paint

import matplotlib.pyplot as plt

There are two available products:

  • product="sfc"

  • product="pres"

You must specify the extra argument member=. Herbie will tell you the list of valid members…

[4]:

H = Herbie("2026-02-01", model="aigefs", product="sfc", member="what?")
H

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[4], line 1
----> 1 H = Herbie("2026-02-01", model="aigefs", product="sfc", member="what?")
      2 H

File ~/GITHUB/Herbie/src/herbie/core.py:277, in Herbie.__init__(self, date, valid_date, model, fxx, product, priority, save_dir, overwrite, verbose, **kwargs)
    269     setattr(self, key, value)
    271 # Get details from the template of the specified model.
    272 # This attaches the details from the `models.<model>.template`
    273 # class to this Herbie object.
    274 # This line is equivalent to `model_templates.gfs.template(self)`.
    275 # I do it this way because the model name is a variable.
    276 # (see https://stackoverflow.com/a/7936588/2383070 for what I'm doing here)
--> 277 getattr(model_templates, self.model).template(self)
    279 # Specify the suffix for the inventory index files.
    280 # Default value is `.grib2.idx`, but some have weird suffix,
    281 # like archived RAP on NCEI are `.grb2.inv`.
    282 self.IDX_SUFFIX = getattr(self, "IDX_SUFFIX", [".grib2.idx"])

File ~/GITHUB/Herbie/src/herbie/models/gefs.py:258, in aigefs.template(self)
    256 _member = valid_members.get(self.product)
    257 if _member is not None and self.member not in _member:
--> 258     raise ValueError(
    259         f"For AIGEFS product {self.product}, member must be one of {_member}"
    260     )
    262 self.SOURCES = {
    263     "nomads": f"https://nomads.ncep.noaa.gov/pub/data/nccf/com/aigefs/prod/{filepath}.grib2"
    264 }
    266 self.IDX_SUFFIX = [".grib2.idx"]

ValueError: For AIGEFS product sfc, member must be one of ['mem000', 'mem001', 'mem002', 'mem003', 'mem004', 'mem005', 'mem006', 'mem007', 'mem008', 'mem009', 'mem010', 'mem011', 'mem012', 'mem013', 'mem014', 'mem015', 'mem016', 'mem017', 'mem018', 'mem019', 'mem020', 'mem021', 'mem022', 'mem023', 'mem024', 'mem025', 'mem026', 'mem027', 'mem028', 'mem029', 'mem030', 'control', 'spr', 'avg']

Let’s get the ensemble mean…

[5]:

H = Herbie("2026-02-01", model="aigefs", product="sfc", member="avg")
H

✅ Found ┊ model=aigefs ┊ product=sfc ┊ 2026-Feb-01 00:00 UTC F00 ┊ GRIB2 @ nomads ┊ IDX @ local

[5]:

▌▌Herbie AIGEFS model sfc product initialized 2026-Feb-01 00:00 UTC F00 ┊ source=nomads

[6]:

# Show all available sources
H.SOURCES

[6]:

{'nomads': 'https://nomads.ncep.noaa.gov/pub/data/nccf/com/aigefs/prod/aigefs.20260201/00/ensstat/products/atmos/grib2/aigefs.t00z.sfc.avg.f000.grib2'}

[7]:

H.inventory()

[7]:
grib_message start_byte end_byte range reference_time valid_time variable level forecast_time ? search_this
0 1 0 860132.0 0-860132 2026-02-01 2026-02-01 UGRD 10 m above ground anl ens mean :UGRD:10 m above ground:anl:ens mean:
1 2 860133 1680784.0 860133-1680784 2026-02-01 2026-02-01 VGRD 10 m above ground anl ens mean :VGRD:10 m above ground:anl:ens mean:
2 3 1680785 2132284.0 1680785-2132284 2026-02-01 2026-02-01 TMP 2 m above ground anl ens mean :TMP:2 m above ground:anl:ens mean:
3 4 2132285 NaN 2132285- 2026-02-01 2026-02-01 PRMSL mean sea level anl ens mean :PRMSL:mean sea level:anl:ens mean:

Now, let’s look at the 1st member for the pressure fields…

[8]:

H = Herbie("2026-02-01", model="aigefs", product="pres", member="mem001")
H.inventory()

✅ Found ┊ model=aigefs ┊ product=pres ┊ 2026-Feb-01 00:00 UTC F00 ┊ GRIB2 @ nomads ┊ IDX @ nomads
Downloading inventory file from self.idx='https://nomads.ncep.noaa.gov/pub/data/nccf/com/aigefs/prod/aigefs.20260201/00/mem001/model/atmos/grib2/aigefs.t00z.pres.f000.grib2.idx'

[8]:
grib_message start_byte end_byte range reference_time valid_time variable level forecast_time ? search_this
0 1 0 654388.0 0-654388 2026-02-01 2026-02-01 HGT 50 mb anl P-ENS=1 :HGT:50 mb:anl:P-ENS=1:
1 2 654389 1301679.0 654389-1301679 2026-02-01 2026-02-01 HGT 100 mb anl P-ENS=1 :HGT:100 mb:anl:P-ENS=1:
2 3 1301680 1945841.0 1301680-1945841 2026-02-01 2026-02-01 HGT 150 mb anl P-ENS=1 :HGT:150 mb:anl:P-ENS=1:
3 4 1945842 2584759.0 1945842-2584759 2026-02-01 2026-02-01 HGT 200 mb anl P-ENS=1 :HGT:200 mb:anl:P-ENS=1:
4 5 2584760 3214315.0 2584760-3214315 2026-02-01 2026-02-01 HGT 250 mb anl P-ENS=1 :HGT:250 mb:anl:P-ENS=1:
... ... ... ... ... ... ... ... ... ... ... ...
73 74 73796507 74454217.0 73796507-74454217 2026-02-01 2026-02-01 VVEL 600 mb anl P-ENS=1 :VVEL:600 mb:anl:P-ENS=1:
74 75 74454218 75121374.0 74454218-75121374 2026-02-01 2026-02-01 VVEL 700 mb anl P-ENS=1 :VVEL:700 mb:anl:P-ENS=1:
75 76 75121375 75807680.0 75121375-75807680 2026-02-01 2026-02-01 VVEL 850 mb anl P-ENS=1 :VVEL:850 mb:anl:P-ENS=1:
76 77 75807681 76460214.0 75807681-76460214 2026-02-01 2026-02-01 VVEL 925 mb anl P-ENS=1 :VVEL:925 mb:anl:P-ENS=1:
77 78 76460215 NaN 76460215- 2026-02-01 2026-02-01 VVEL 1000 mb anl P-ENS=1 :VVEL:1000 mb:anl:P-ENS=1:

78 rows × 11 columns

[9]:

ds = H.xarray(":TMP:700 mb")
ds

[9]:

<xarray.Dataset> Size: 4MB
Dimensions:              (latitude: 721, longitude: 1440)
Coordinates:
  * latitude             (latitude) float64 6kB 90.0 89.75 89.5 ... -89.75 -90.0
  * longitude            (longitude) float64 12kB 0.0 0.25 0.5 ... 359.5 359.8
    number               int64 8B 1
    time                 datetime64[ns] 8B 2026-02-01
    step                 timedelta64[ns] 8B 00:00:00
    isobaricInhPa        float64 8B 700.0
    valid_time           datetime64[ns] 8B 2026-02-01
    gribfile_projection  object 8B None
Data variables:
    t                    (latitude, longitude) float32 4MB 243.6 243.6 ... 242.5
Attributes:
    GRIB_edition:            2
    GRIB_centre:             kwbc
    GRIB_centreDescription:  US National Weather Service - NCEP
    GRIB_subCentre:          2
    Conventions:             CF-1.7
    institution:             US National Weather Service - NCEP
    model:                   aigefs
    product:                 pres
    description:             AI Global Ensemble Forecast System (AIGEFS)
    remote_grib:             https://nomads.ncep.noaa.gov/pub/data/nccf/com/a...
    local_grib:              /home/blaylock/data/aigefs/20260201/subset_afef7...
    search:                  :TMP:700 mb
[10]:

ax = EasyMap(crs=ds.herbie.crs, figsize=[10, 8]).ax
p = ax.pcolormesh(
    ds.longitude,
    ds.latitude,
    ds.t - 273.15,
    transform=pc,
    **paint.NWSTemperature.kwargs2,
)
plt.colorbar(
    p, ax=ax, orientation="horizontal", pad=0.05, **paint.NWSTemperature.cbar_kwargs2
)

ax.set_title(
    f"member={ds.number.item()} {ds.t.GRIB_name} @ {ds.t.isobaricInhPa.item()} hPa",
    loc="right",
)
ax.set_title(f"{ds.model.upper()}: {H.product_description}", loc="left")

[10]:

Text(0.0, 1.0, 'AIGEFS: pressure fields, 0.25 degree resolution')
../../_images/gallery_noaa_models_aigefs_11_1.png

Now, just for fun, let’s plot the difference between member 1 and the ensemble average for the 24 hour forecast…

[11]:

H1 = Herbie("2026-02-01", model="aigefs", product="pres", member="mem001", fxx=24)
H2 = Herbie("2026-02-01", model="aigefs", product="pres", member="avg", fxx=24)

diff = H2.xarray("TMP:700 mb").t - H1.xarray("TMP:700 mb").t

ax = EasyMap(figsize=[8, 8]).ax
p = ax.pcolormesh(
    diff.longitude,
    diff.latitude,
    diff,
    transform=pc,
    vmax=2,
    vmin=-2,
    cmap="bwr",
)

plt.colorbar(
    p,
    ax=ax,
    orientation="horizontal",
    pad=0.05,
    shrink=0.8,
    extend="both",
)

plt.title("Difference between Member 1 and Ensemble Mean")

✅ Found ┊ model=aigefs ┊ product=pres ┊ 2026-Feb-01 00:00 UTC F24 ┊ GRIB2 @ nomads ┊ IDX @ nomads
✅ Found ┊ model=aigefs ┊ product=pres ┊ 2026-Feb-01 00:00 UTC F24 ┊ GRIB2 @ nomads ┊ IDX @ local
Downloading inventory file from self.idx='https://nomads.ncep.noaa.gov/pub/data/nccf/com/aigefs/prod/aigefs.20260201/00/mem001/model/atmos/grib2/aigefs.t00z.pres.f024.grib2.idx'

[11]:

Text(0.5, 1.0, 'Difference between Member 1 and Ensemble Mean')
../../_images/gallery_noaa_models_aigefs_13_2.png