Fujita Tornado Intensity Scale: A Critique Based on Observations of the Jarrell Tornado of May 27, 1997.
Fujita Tornado Intensity Scale: A Critique Based on
Observations of the Jarrell Tornado of May 27, 1997.
Phan, L. T.; Simiu, E.
NIST TN 1426; 23 p. July 1998.
Available from: National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
1-800-553-6847 or 703-605-6000;
Order number: PB98-175136
tornadoes; building technology; Fujita intensity scale;
meteorology; structural engineering; wind engineering;
On May 27, 1997, several tornadoes hit the Central Texas
area in the counties of McLennan, Bell, Williamson, and
Travis. The most destructive of these tornadoes swept
through a housing area on the outskirts of Jarrell,
Texas. Jarrell is a Central Texas town with a population
of 410 located approximately 60 km north of Austin,
Texas. The Jarrell tornado destroyed about 40
single-family residences and other structures, killing
27 people. A post-storm damage survey was made at
Jarrell by a team coordinated by the Office of the
Federal Coordinator for Meteorological Services and
Supporting Research (OFCM). We report damage
observations and conclude on their basis that the worst
damage can be explained by wind speeds corresponding to
an F3 rating on the Fujita tornado intensity scale (wind
speeds of 71 m/s to 92 m/s). An F4 (93 m/s to 116 m/s)
rating, or the F5 (117 m/s to 142 m/s) rating officially
issed by the National Weather Service (NWS), need not be
assumed to explain that damage. We ascribe the NWS
rating to the failure of the Fujita tornado intensity
scale to account explicitly for the dependence of wind
speeds causing specified types of damage or destruction
upon the following two structural engineering factors:
(1) quality of construction, defined as degree of
conformity to applicable standards requirements, and (2)
the basic design wind speed at the geographical location