Reid Wind Scale

Independent tornado wind-intensity classification project

Reid Wind Scale (RWS)

RWS is a 0-6 tornado intensity scale based on the best-supported physical wind speed. It records the evidence behind the estimate and keeps human impact separate from wind intensity.

Basic idea: rate the wind first, then describe how certain the estimate is and what the tornado affected.
RatingWindDescription
RWS0<85 mphWeak
RWS185-109 mphModerate
RWS2110-139 mphStrong
RWS3140-169 mphSevere
RWS4170-199 mphExtreme
RWS5200-249 mphViolent
RWS6250+ mphExceptional

Scale & Key

Definitions, evidence codes, confidence rules and comparison scales.

Read the documentation

Calculator

Classify wind evidence and produce an RWS result with a confidence assessment.

Open the calculator

Database

Browse notable tornadoes and the evidence currently attached to each classification.

Browse the database

What RWS does differently

An RWS rating is not raised because a tornado killed more people or struck a city. Fatalities, injuries, width and track length are recorded as secondary characteristics. Radar, direct measurements, photogrammetry, engineering analysis, damage estimates and theoretical reconstructions can all be recorded without treating them as equally certain.