NWS runs a national verification program (NVP) that provides feedback to forecasters and managers. This feedback is used to improve the quality of forecasts and services. The data from the NVP provide long-term trends in forecast accuracy and assist managers in establishing baselines of forecast accuracy . From these baselines, improvements in forecast accuracy resulting from scientific advances and new technologies are measured. The program also provides information on the quality of forecasts to NWS customers. Below is a list of NWS products that are verified:
Severe Thunderstorm Warnings and Watches
- All severe thunderstorms – A severe thunderstorm is defined as any thunderstorm that
- Spawns a tornado or
- Generates winds exceeding 57 miles per hour or
- Produces hail at least 0.75” in diameter.
- Only severe thunderstorms that spawn tornadoes
- Only severe thunderstorms that do not spawn tornadoes
Severe Weather Warnings
- Flash floods
- Winter storms
- High winds
- Special marine conditions, associated with thunderstorms and/or strong winds
- Coastal and lakeshore floods
Public Forecast Elements: verified out to 7 days in advance
- Daily maximum and minimum temperature
- Probability of precipitation for each 12-hour period of the forecast.
Aviation Forecast Elements: verified out to 24 hours in advance
- Ceiling
- Visibility
- Wind direction, speed and gusts
- Significant weather types
- Icing
- Turbulence
- Thunderstorms
Marine Forecast Elements: verified out to 5 days in advance:
- Wind speed
- Wind direction
- Wave height
- Warnings and advisories issued due to expected high wind speeds or wave heights
Hydrology Forecasts: verified out to 3 days in advance:
- River stage forecasts
- Quantitative precipitation forecasts: precipitation amount
Tropical Cyclone and Hurricane Forecast Elements: verified out to 5 days in advance:
Climate Forecasts Verified
- 6 to 10 day outlooks
- 8 to 14 day outlooks
- Monthly (30 day) outlooks
- Seasonal (3-month) outlooks
- 3- to 14-day hazard assessments for heavy precipitation, tornadoes, damaging winds and hail
For more information on NWS Verification program, see the official policy directive.