NOAA GTGN turbulence nowcast data is now available on GribStream

Update, August 2, 2026: NOAA's GTGN production feed is operational, and GribStream now serves it through GTGN. The operational product retains the same 15-minute cadence, 3 km HRRR CONUS domain, EDPARM field, and 51 altitude levels evaluated through the earlier parallel feed. This is an operational-status transition, not a change to the published science or the gtgn dataset identity.

Earlier update, July 4, 2026: NOAA replaced the earlier June implementation notice with NWS SCN 26-62 and scheduled operational implementation on or about July 28, 2026 at 1200 UTC. GribStream made the evaluation feed available ahead of that transition.

NOAA/NWS originally scheduled the Graphical Turbulence Guidance Nowcast (GTGN) for operational implementation on or about June 29, 2026 at 1200 UTC.

The useful change is operational: GTGN turns turbulence guidance into a 15-minute nowcast, built for conditions that can evolve faster than a standard forecast cycle.

What GTGN Adds

GTGN starts from a short-term Graphical Turbulence Guidance (GTG) forecast, then blends in recent turbulence observations to produce a near real-time analysis. NOAA says the product is meant to support the aviation community, but it is not a substitute for forecaster-issued turbulence SIGMETs.

The notice lists these inputs:

• pilot reports
• automated in situ eddy dissipation rate reports
• radar-derived EDR from NCAR's Turbulence Detection Algorithm
• estimated EDR from lightning data
• METAR data

The output is EDR, an aircraft-independent turbulence metric. NOAA says the horizontal domain follows the 3 km HRRR CONUS domain used by GTG, with vertical output from 100 feet and then every 1,000 feet up to 50,000 feet.

Timeline and Access

NWS SCN 26-62 scheduled the operational start for July 28, 2026 at 1200 UTC. GribStream verified current production output and completed its source transition on August 2, 2026.

NOAA also documents a NCEP/NOMADS data path for the operational product:

https://nomads.ncep.noaa.gov/pub/data/nccf/com/gtgn/prod/gtgn.YYYYMMDD/

That distribution detail matters because GTGN can be monitored, archived, and exposed through tools rather than only viewed on a web display. The notice identifies the turbulence field as Eddy Dissipation Parameter (EDPARM).

Why this matters for aviation workflows

GTGN is useful when the question is not "what might turbulence look like in several hours?" but "what is the best current analysis after the latest reports and observations?" That makes it relevant for dispatch dashboards, route monitoring, pilot briefings, event review, and comparing recent turbulence reports against the model background.

The 15-minute cadence is the key operational feature. It lets the product react to newly observed turbulence signals while still staying tied to the physically consistent GTG forecast field.

Why this matters for GribStream

GribStream already serves HRRR and NOAA aviation guidance such as DAFS GTG. GTGN adds a different layer: a high-frequency turbulence nowcast that can sit alongside forecast guidance in the same aviation workflow.

GTGN is now operational through GribStream under the gtgn dataset code. The move from evaluation to production did not change the published cadence, grid, parameter, or altitude levels, so the scientific description above remains current.

Sources

• NWS Service Change Notice 26-62, "Implementation of the Graphical Turbulence Guidance Nowcast (GTGN)": https://www.weather.gov/media/notification/pdf_2026/scn26-62_GTGN_v1.0.pdf
• NWS Service Change Notice 26-46, earlier GTGN implementation notice: https://www.weather.gov/media/notification/pdf_2026/scn26-46_gtgn_implementation.pdf
• NWS Public Information Statement 26-08, experimental GTGN comment period: https://www.weather.gov/media/notification/pdf_2026/pns26-08_ExpGTGN.pdf
• NOMADS GTGN production data: https://nomads.ncep.noaa.gov/pub/data/nccf/com/gtgn/prod/
• GTGN display location listed by NOAA: https://aviationweather.gov/gfa/#obs