Fujita Manual

The Fujita Manual provides comprehensive guidelines and procedures for the Fujita scale classification system used in tornado intensity assessment. Developed by Dr. Tetsuya Theodore Fujita, this manual outlines the detailed criteria for categorizing tornado damage and estimating wind speeds based on observed destruction patterns. Below are key sections covering the scale overview, classification criteria, assessment methodology, application procedures, and reference materials.

Fujita Scale Overview

The Fujita scale categorizes tornado intensity based on damage severity, ranging from F0 (light damage) to F5 (incredible damage). Each category corresponds to estimated wind speeds and specific damage characteristics.

F-Scale	Wind Speed (mph)	Damage Description
F0	40-72	Light damage: broken branches, shallow-rooted trees pushed over
F1	73-112	Moderate damage: roofs severely stripped, mobile homes overturned
F2	113-157	Considerable damage: roofs torn off frame houses, large trees snapped
F3	158-206	Severe damage: walls torn from well-constructed houses, trains overturned
F4	207-260	Devastating damage: well-constructed houses leveled, cars thrown
F5	261-318	Incredible damage: strong frame houses lifted off foundations, steel-reinforced structures damaged

Damage Indicators

Standardized damage indicators used to assess tornado intensity and assign F-scale ratings.

1. Residential Structures: Single-family homes, apartments, mobile homes
2. Commercial Buildings: Shopping centers, office buildings, warehouses
3. Educational Facilities: Schools, universities, administrative buildings
4. Industrial Structures: Factories, manufacturing plants, storage facilities
5. Infrastructure: Power lines, communication towers, transportation systems
6. Vegetation: Trees, shrubs, agricultural crops
7. Vehicles: Cars, trucks, trains, aircraft

IMPORTANT! Always use multiple damage indicators for accurate classification; single indicators may be misleading.

Assessment Procedures

Systematic approach to tornado damage assessment and F-scale classification.

1. Initial Survey: Conduct aerial reconnaissance to identify damage path
2. Ground Verification: Perform detailed ground-level inspections
3. Damage Documentation: Photograph and record all significant damage
4. Indicator Matching: Compare observed damage with standard indicators
5. Intensity Assignment: Assign F-scale rating based on worst damage
6. Quality Control: Review assessment with team members

CAUTION! Ensure safety during assessments; avoid unstable structures and hazardous conditions.

Classification Criteria

• F0 Classification: Minor damage to structures and vegetation
• F1 Classification: Moderate structural damage, mobile home destruction
• F2 Classification: Significant structural damage, tree debarking
• F3 Classification: Severe structural failure, vehicle displacement
• F4 Classification: Complete destruction of well-built structures
• F5 Classification: Extraordinary damage with ground scouring
• Construction Quality: Consider building materials and construction methods
• Damage Consistency: Evaluate damage patterns across multiple structures

Wind Speed Estimation

Wind speed estimation methodology based on damage observations and engineering analysis.

Engineering Analysis: Structural failure analysis, material strength considerations, wind loading calculations.

Estimation Methods: Empirical correlations, computational fluid dynamics, historical comparisons. Adjustment Factors: Terrain effects, exposure conditions, structural response characteristics. Uncertainty Ranges: ±10-15 mph for well-documented cases, higher for limited data.

Field Survey Guidelines

Comprehensive guidelines for conducting field surveys and damage assessments.

1. Team Preparation: Assemble qualified personnel with proper equipment
2. Safety Protocols: Establish safety procedures and emergency contacts
3. Data Collection: Use standardized forms and digital recording methods
4. Photographic Documentation: Systematic photography with scale references
5. Interview Procedures: Conduct witness interviews following established protocols

Tip: Maintain detailed field notes and backup all digital data regularly.

Documentation Standards

Standardized documentation requirements for tornado damage assessments.

1. Damage Maps: Create detailed maps showing damage intensity contours
2. Photographic Logs: Maintain organized photographic documentation
3. Structural Analysis: Document engineering assessments of key structures
4. Witness Statements: Record and verify eyewitness accounts
5. Meteorological Data: Correlate damage with radar and weather data
6. Final Reports: Prepare comprehensive assessment reports
7. Archiving: Maintain permanent records for research and reference

WARNING! Ensure all documentation meets legal and scientific standards for potential use in research and litigation.

Case Studies

Historical case studies demonstrating F-scale application and classification challenges.

Reference Tables

Comprehensive reference tables for damage indicators, wind speed correlations, and classification criteria.

CAUTION! Reference tables should be used as guidelines; professional judgment is required for accurate classification.

Regulatory Framework

Regulatory standards and professional guidelines governing tornado damage assessment and F-scale usage. Compliance Requirements: National Weather Service standards, engineering codes, scientific protocols. Professional Certification: Requirements for qualified damage assessors. Data Sharing: Protocols for sharing assessment data with meteorological organizations. Copyright © 2025 Fujita Manual; all rights reserved. For technical support and updates, contact the National Severe Storms Laboratory or visit www.fujitamanual.gov.

Troubleshooting & FAQ

Issue	Possible Cause	Corrective Action
Inconsistent damage ratings	Varied construction quality	Use multiple indicators; consider local building practices
Wind speed uncertainty	Limited damage evidence	Correlate with meteorological data; use engineering analysis
Classification disputes	Subjective interpretation	Consult multiple experts; review historical precedents
Missing data	Incomplete surveys	Conduct supplemental investigations; use remote sensing
Scale limitations	Extreme damage cases	Document thoroughly; note exceptional characteristics

Technical Support: Contact meteorological services or engineering consultants for complex cases.

Updates: www.fujitamanual.gov; National Weather Service regional offices