Supercell tornadoes are much stronger and wider than damage-based ratings indicate

Area of Science:

• Atmospheric Science and Meteorology
• Severe Weather Phenomena
• Tornado Climatology

Background:

• Tornado intensity and size are critical for hazard assessment but traditionally rely on post-event damage surveys.
• Existing damage-based assessments are suspected to underestimate true tornado wind speeds and dimensions.
• Accurate quantification of tornado wind hazards is essential for public safety and infrastructure resilience.

Purpose of the Study:

• To investigate and quantify the actual wind speeds and sizes of tornadoes using direct radar measurements.
• To compare radar-derived tornado characteristics with conventional damage-based intensity ratings.
• To re-evaluate tornado wind hazards and inform future engineering standards.

Main Methods:

• Analysis of Doppler On Wheels (DOW) radar data from 120 supercell tornadoes during their peak intensity.
• Mapping of low-level tornado wind speeds and estimation of tornado diameters from radar observations.
• Comparison of DOW-measured wind speeds and sizes against National Weather Service (NWS) damage-based ratings.

Main Results:

• Median peak tornado wind speeds were approximately 60 m/s, indicating EF-2 to EF-3 intensity.
• 20% of observed tornadoes possessed winds capable of EF-4/EF-5 damage.
• NWS intensity ratings were 1.2 to 1.5 categories (approx. 20 m/s) lower than DOW observations; median diameter ranged from 250-500m, with 10-15% exceeding 1km.

Conclusions:

• Supercell tornadoes are demonstrably stronger and wider than indicated by traditional damage assessments.
• Direct wind-speed measurements reveal a higher prevalence of intense tornado winds than previously understood.
• Wind engineering models and building standards may need upward revision to account for underestimated tornado wind risks.