GribStream Blog
NBM percentile thinning proposed for Spring 2026
NWS proposes reducing NBM percentile output to 5th-95th (step of 5) plus min/max, to manage data volume as the blend adds new probabilistic fields.
On July 31, 2025, NOAA/NWS proposed a reduction in the number of percentiles disseminated in the National Blend of Models (NBM). The change is targeted for Spring 2026, with public comments requested through October 6, 2025.
What is proposed
Today, many NBM products publish 1st-99th percentiles (and in some cases 0th/100th). The proposal would thin output to:
- 5th-95th percentiles in steps of 5 (5, 10, 15, ..., 95)
- Minimum and maximum retained as 0th and 100th percentiles
The motivation: upcoming NBM upgrades add more probabilistic parameters, and the full percentile set pushes file sizes and bandwidth to an unsustainable level.
Why it matters
- Smaller data volumes and faster transfers for full-grid users.
- Less percentile granularity for workflows that depend on 1-99 percentiles.
- If you derive continuous distributions, you may need interpolation or updated calibration.
What this means for GribStream users
GribStream already supports NBM. If this change is implemented, we will align our feeds as soon as NOAA publishes updated data through the AWS Open Data program and document any schema changes clearly.
Suggested planning steps:
- Identify any models or dashboards using full percentile sets.
- Adjust plots or thresholds to the 5-step percentiles.
- Consider interpolating between percentiles if you need higher resolution.
Sources
- NWS Public Information Statement 25-53 (Jul 31, 2025): https://www.weather.gov/media/notification/pdf_2025/pns25-53_Thinning_of_NBM_Percentiles.pdf