GribStream Blog
NOAA SPC HREF convective probability guidance is now on GribStream
GribStream now serves NOAA Storm Prediction Center HREF thunderstorm, lightning-density, hail, tornado, and severe-wind probability guidance for CONUS severe-weather workflows.
We added six NOAA Storm Prediction Center post-processed HREF probability datasets to GribStream. Together they provide point-queryable CONUS guidance for thunderstorms, lightning-density risk, hail, tornadoes, and severe convective wind.
These are not broad outlook categories. They are gridded probability fields designed to support short-range convective decision making. That makes them useful for operations teams that need site-level or route-level severe-weather risk signals before warnings exist and after a general outlook needs to be localized.
What is included
- SPC HREF Thunderstorm Probability 1 Hour:
spctstm1hr - SPC HREF Thunderstorm Probability 4 Hour:
spctstm4hr - SPC HREF Lightning-density Probability 4 Hour:
spcltg4hr - SPC HREF Calibrated Hail Probability 4 Hour:
spchail4hr - SPC HREF Calibrated Tornado Probability 4 Hour:
spctor4hr - SPC HREF Calibrated Severe Wind Probability 4 Hour:
spcwind4hr
The one-hour thunderstorm product is the sharper nowcasting-style layer. The four-hour products are better for operational planning windows: staffing, dispatch, event delay decisions, utility crew posture, aviation ground operations, and transportation risk screening.
Why the SPC HREF products are useful
The Storm Prediction Center HREF viewer describes two related pieces of science behind this family.
For calibrated severe hazards such as tornado, hail, and wind, SPC pairs storm-scale HREF evidence with larger-scale environmental ingredients and then uses historical report frequency near a grid point to produce calibrated hazard probabilities. That matters because raw severe-weather ingredients are not probabilities. Calibration is what makes the field more useful for thresholds, ranking, and automated decision support.
For thunderstorm and lightning-oriented products, SPC uses ensemble evidence from simulated reflectivity, accumulated precipitation, and instability signals, with calibration against observed cloud-to-ground lightning. That is why these fields are often a better input for outdoor safety and lightning-aware operations than a generic precipitation field.
Common uses
These datasets are a good fit for:
- severe-weather dashboards
- outdoor-event and venue safety systems
- utility and field-crew planning
- aviation ramp and ground operations
- logistics and route risk scoring
- emergency-management triage
- insurance and asset exposure screening
- automated alert pipelines that need probability thresholds
They also pair well with physics-model context from HRRR, HRRR sub-hourly, and RAP. The probability fields can tell you where calibrated risk is elevated, while the underlying forecast models help explain storm structure, boundaries, wind fields, and timing.