Fujita scale

Fujita scale
Name	Tetsuya Fujita
Birth date	1920
Death date	1998
Nationality	Japanese-American
Known for	Tornado research, damage scale

Fujita scale The Fujita scale is a damage-based system for rating the intensity of tornadoes and wind events, developed to relate observed destruction to estimated wind speeds. It connects structural impacts in cities such as Oklahoma City, Dallas, and Moore, Oklahoma to meteorological analyses by researchers affiliated with institutions like the University of Chicago, Texas Tech University, and the National Oceanic and Atmospheric Administration. The scale informed operational practice at agencies including the National Weather Service, Storm Prediction Center, and influenced international organizations such as the World Meteorological Organization.

Overview

The Fujita scale classifies tornadoes into categories originally labeled F0 through F5 based on damage to structures, trees, and vehicles observed in locations like Joplin, Missouri, Greensburg, Kansas, and Hallam, Nebraska. It was intended to bridge field surveys conducted by teams from University of Oklahoma, Pennsylvania State University, and the Air Force with theoretical work by engineers at institutions such as Massachusetts Institute of Technology and the Iowa State University. The scale became a reference for historical assessments including the Tri-State Tornado, the Super Outbreak (1974), and the El Reno tornado.

History and Development

The Fujita scale was proposed by Tetsuya Fujita of the University of Chicago in the early 1970s after studies of tornado damage in areas like Tuscaloosa, Alabama and Xenia, Ohio. Fujita collaborated with colleagues from Argonne National Laboratory, researchers associated with Project NIMROD, and analysts from the National Severe Storms Laboratory. Early development drew on comparisons with wind damage data from events such as the Great Natchez Tornado and engineering assessments by teams at the University of Illinois and Cornell University. The scale was adopted into operational use by the National Weather Service and cited in reports by the Federal Emergency Management Agency.

Scale Classification and Criteria

Categories F0–F5 describe increasing degrees of damage: lightweight damage in towns like Mayfield, Kentucky at lower ratings to catastrophic destruction in municipalities such as Joplin, Missouri at the upper end. Fujita's original criteria referenced construction types studied by civil engineers at Purdue University and damage surveys from storms documented by researchers at Colorado State University. Each category implied an estimated wind speed range that investigators compared with structural standards from organizations such as the American Society of Civil Engineers and codes adopted in jurisdictions like Miami-Dade County, Florida. Classifications relied on field indicators including failure modes documented in reports to bodies like the American Meteorological Society.

Measurement Methods and Limitations

The Fujita scale uses post-event damage surveys carried out by teams from National Oceanic and Atmospheric Administration, state climatologists, and university researchers to infer wind speeds indirectly. Surveyors referenced engineering analyses from Stanford University and University of California, Berkeley when assessing debris patterns in places like Pampa, Texas and Wichita, Kansas. Limitations included variability in construction quality across regions such as New England, Midwest United States, and Great Plains, inconsistent documentation in remote areas like parts of Nebraska and Kansas, and lack of direct wind measurements from instruments deployed by programs like VORTEX and probes used by Doppler radar teams from NCAR. These constraints led to potential overestimation or underestimation when comparing to datasets compiled by agencies such as the National Climatic Data Center.

Applications and Usage

Emergency managers in counties surrounding Oklahoma City, Wichita, and Dallas–Fort Worth used Fujita ratings to prioritize recovery after events like the May 3, 1999 tornado outbreak and the 2011 Super Outbreak. Researchers at Iowa State University, Louisiana State University, and University of Alabama employed the scale for climatological studies, risk assessments, and insurance analyses involving companies headquartered in New York City and Chicago. International meteorological services in countries such as Japan, Australia, and Canada referenced Fujita-style assessments when documenting severe convective storms alongside guidance from the World Meteorological Organization.

Criticism and Revisions

Critics from engineering departments at Virginia Tech, University of Michigan, and University of Texas at Austin noted that inferred wind speeds lacked empirical validation and depended heavily on construction standards found in places like Midwest United States and Southeastern United States. Concerns raised by scholars publishing in journals associated with the American Geophysical Union and the American Meteorological Society prompted revisions and the development of alternatives, including enhanced damage scales and methodologies used by National Weather Service personnel and projects such as VORTEX2. Debates about retrospective rating of historical events like the Tri-State Tornado and methodological updates influenced policy discussions in bodies such as the United States Congress and panels convened by the National Academy of Sciences.

Category:Severe weather