NOAA adds AI GFS hurricane-track products to ens_tracker

NOAA/NCEP implemented ens_tracker v1.3.8 on April 8, 2026 at 1200 UTC. The release adds tropical-cyclone track products for NOAA's operational AI global model family:

• AIGFS: deterministic AI global forecast model
• AIGEFS: 31-member AI ensemble
• HGEFS: 62-member hybrid ensemble, combining 31 AIGEFS members with 31 operational GEFSv12 members

This is a follow-up to NOAA's December 2025 operational rollout of AIGFS, AIGEFS, and HGEFS. The new notice is narrower: it adds tropical-cyclone track products to the ens_tracker package and fixes a folder issue for GFS tracker output.

What changed

The new AI-model track data are published under ens_tracker on NOMADS:

https://nomads.ncep.noaa.gov/pub/data/nccf/com/ens_tracker/prod/aigfs.YYYYMMdd/CC/tctrack/
https://nomads.ncep.noaa.gov/pub/data/nccf/com/ens_tracker/prod/aigefs.YYYYMMdd/CC/tctrack/
https://nomads.ncep.noaa.gov/pub/data/nccf/com/ens_tracker/prod/hgefs.YYYYMMdd/CC/tctrack/

NOAA says NCEP evaluated hurricane-track forecasts from the AI models for the 2025 hurricane season before this implementation.

File families to expect

For AIGFS, NOAA lists deterministic track files:

agfs.tCCz.cyclone.trackatcfunix
agfsp.tCCz.cyclone.trackatcfunix

For AIGEFS, NOAA lists member-level track files for members 000 through 030:

a{mem}p.tCCz.cyclone.trackatcfunix
a{mem}.tCCz.cyclone.trackatcfunix

It also lists ensemble statistics and probability files using the aimn prefix:

aimn.tCCz.cyclone.trackatcfunix
aimn.tCCz.cyclone.trackmode
aimn.tCCz.cyclone.trackspread
aimn.tCCz.cyclone.trackstd
aimn.trkprob.YYYYMMdd.65.ctlinfo.txt
aimn.trkprob.{BasinID}.65nm.YYYYMMdd.accum.ieee
aimn.trkprob.{BasinID}.65nm.YYYYMMdd.indiv.ieee

For HGEFS, NOAA lists equivalent ensemble-statistics and probability files using the ahmn prefix:

ahmn.tCCz.cyclone.trackatcfunix
ahmn.tCCz.cyclone.trackmode
ahmn.tCCz.cyclone.trackspread
ahmn.tCCz.cyclone.trackstd
ahmn.trkprob.YYYYMMdd.65.ctlinfo.txt
ahmn.trkprob.{BasinID}.65nm.YYYYMMdd.accum.ieee
ahmn.trkprob.{BasinID}.65nm.YYYYMMdd.indiv.ieee

In those patterns, CC is the cycle, mem is the ensemble member, and BasinID is the two-letter basin plus two-digit storm number.

GFS tracker files moved

The same release corrects a GFS/GEFS layout issue. NOAA says these GFS files were previously listed under the GEFS folder and are moving to the GFS folder:

genesis/storms.gfso.atcf_gen.altg.YYYYMMddHH
tctrack/avnx.tCCz.cyclone.trackatcfunix
tctrack/kwbc_YYYYMMddHH0000_GFS_glob_prod_sttr_glo.xml

Old location:

https://nomads.ncep.noaa.gov/pub/data/nccf/com/ens_tracker/prod/gefs.YYYYMMdd/CC

New location:

https://nomads.ncep.noaa.gov/pub/data/nccf/com/ens_tracker/prod/gfs.YYYYMMdd/CC

That path change matters if your tracker ingest has hard-coded the older gefs.YYYYMMdd/CC location for GFS files.

What this means for GribStream users

GribStream supports GFS, GEFS Atmosphere, and GraphCast GFS, but these ens_tracker products are not core gridded forecast fields. They are tropical-cyclone track and probability products published through a separate NOMADS tree.

So this release does not change the gridded GFS, GEFS, or GraphCast datasets GribStream serves. It does matter indirectly, because NOAA is adding operational tropical-cyclone products derived from the same AI/GFS/GEFS model families and correcting the path layout for GFS tracker outputs.

The practical impact is mostly for tropical-cyclone workflows:

• AI-model track output is now in the same operational tracker package as other NCEP tropical-cyclone guidance.
• AIGEFS and HGEFS expose ensemble track spread and probability products, not just deterministic tracks.
• GFS tracker ingest code should use the corrected gfs.YYYYMMdd/CC location.

GribStream's NOMADS expansion is focused on GRIB products. The tracker files in this notice are ATCF text, XML, and probability/statistics files rather than gridded GRIB fields. For now, this is best treated as an operational NOMADS tracker-product change, not an automatic extension of the existing gridded GFS, GEFS, or GraphCast model pages.

Sources

• NWS SCN 26-37, "Implementation of the Ens_Tracker package" (Apr 3, 2026): https://www.weather.gov/media/notification/pdf_2026/scn26-37_ENS_tracker_v1.3.8.pdf
• NWS SCN 25-89, "Implementation of AIGFS, AIGEFS, and HGEFS" (Dec 9, 2025): https://www.weather.gov/media/notification/pdf_2025/scn25-89_AIGFS_AIGEFS_and_HGEFS.pdf
• NWS notification index: https://www.weather.gov/notification/