The Enhanced Fujita scale rates the strength of tornadoes in the United
States and Canada based on the damage they cause.
Implemented in place of the Fujita scale introduced in 1971 by Tetsuya Theodore
Fujita, it began operational use in the United States on February 1, 2007,
followed by Canada on April 1, 2013. The scale has the same basic design as the
original Fujita scale—six categories from zero to five, representing
increasing degrees of damage. It was revised to reflect better examinations
of tornado damage surveys, so as to align wind speeds more closely with
associated storm damage. Better standardizing and elucidating what was
previously subjective and ambiguous, it also adds more types of structures and
vegetation, expands degrees of damage, and better accounts for variables such
as differences in construction quality. The new scale was publicly unveiled by
the National Weather Service at a conference of the American
Meteorological Society in Atlanta on February 2, 2006. It was developed from
2000 to 2004 by the Fujita Scale Enhancement Project of the Wind Science
and Engineering Research Center at Texas Tech University, which brought together
dozens of expert meteorologists and civil engineers in addition to its own
resources. As with the Fujita scale, the Enhanced
Fujita scale remains a damage scale and only a proxy for actual wind speeds.
While the wind speeds associated with the damage listed have not undergone
empirical analysis owing to excessive cost, the wind speeds were obtained
through a process of expert elicitation based on various engineering studies
since the 1970s as well as from field experience of meteorologists and
engineers. In addition to damage to structures and vegetation, radar data,
photogrammetry, and cycloidal marks may be utilized when available.
The scale was used for the first time in the United States a year after its
public announcement when parts of central Florida were struck by multiple
tornadoes, the strongest of which were rated at EF3 on the new scale. It was
used for the first time in Canada shortly after its implementation there
when a tornado developed near the town on Shelburne, Ontario on April 18, 2013,
causing up to EF1 damage. Parameters
The six categories for the EF scale are listed below, in order of increasing
intensity. Although the wind speeds and photographic damage examples are
updated, the damage descriptions given are those from the Fujita scale, which
are more or less still accurate. However, for the actual EF scale in
practice, damage indicators are predominantly used in determining the
tornado intensity. = Damage indicators and degrees of
damage= The EF scale currently has 28 damage
indicators, or types of structures and vegetation, each with a varying number
of degrees of damage. Larger degrees of damage done to the damage indicators
correspond to higher wind speeds. The links in the right column of the
following table describe the degrees of damage for the damage indicators listed
in each row. Differences from the Fujita scale
The new scale takes into account quality of construction and standardizes
different kinds of structures. The wind speeds on the original scale were deemed
by meteorologists and engineers as being too high, and engineering studies
indicated that slower winds than initially estimated cause the respective
degrees of damage. The old scale lists an F5 tornado as wind speeds of 261–318
mph, while the new scale lists an EF5 as a tornado with winds above 200 mph,
found to be sufficient to cause the damage previously ascribed to the F5
range of wind speeds. None of the tornadoes recorded on or before January
31, 2007, will be re-categorized. Essentially, there is no functional
difference in how tornadoes are rated. The old ratings and new ratings are
smoothly connected with a linear formula. The only differences are
adjusted wind speeds, measurements of which were not used in previous ratings,
and refined damage descriptions; this is to standardize ratings and to make it
easier to rate tornadoes which strike few structures. Twenty-eight Damage
Indicators, with descriptions such as "double-wide mobile home" or "strip
mall", are used along with Degrees of Damage to determine wind estimates.
Different structures, depending on their building materials and ability to
survive high winds, have their own DIs and DODs. Damage descriptors and wind
speeds will also be readily updated as new information is learned.
Since the new system still uses actual tornado damage and similar degrees of
damage for each category to estimate the storm's wind speed, the National Weather
Service states that the new scale will likely not lead to an increase in a
number of tornadoes classified as EF5. Additionally, the upper bound of the
wind speed range for EF5 is open—in other words, there is no maximum wind
speed designated. Rating classifications
For purposes such as tornado climatology studies, Enhanced Fujita scale ratings
may be grouped into classes. See also
Beaufort scale Saffir–Simpson hurricane wind scale
TORRO scale Tornado intensity and damage
Wind engineering List of tornadoes and tornado outbreaks
List of F5 and EF5 tornadoes Severe weather terminology
Fujita–Pearson scale References
Edwards, Roger; J. G. LaDue; J. T. Ferree; K. Scharfenberg; C. Maier; W. L.
Coulbourne. "Tornado Intensity Estimation: Past, Present, and Future".
Bull. Amer. Meteor. Soc. 94: 641–53. Bibcode:2013BAMS...94..641E.
doi:10.1175/BAMS-D-11-00006.1. External links
National Oceanic and Atmospheric Administration
NOAA National Weather Service Improves Tornado Rating System at NOAA News
The Enhanced Fujita Scale at Storm Prediction Center
EF-Scale Training at The Warning Decision Training Branch of National
Weather Service The Enhanced Fujita Tornado Scale at
National Climatic Data Center The Tornado: An Engineering-Oriented
Perspective A Guide for Conducting Convective
Windstorm Surveys Fujita Scale Enhancement Project
Symposium on the F-Scale and Severe-Weather Damage Assessment at
American Meteorological Society A Guide to F-Scale Damage Assessment,
MetEd, University Corporation for Atmospheric Research
Mitigation Assessment Team Report: Midwest Tornadoes of May 3, 1999
{(Federal Emergency Management Agency)