unit
of measure
conversions
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The
classification of the tornado and the Fujita scale
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The
Fujita Scale (also known as the Fujita-Pearson Scale)
may not be a perfect system for linking damage to wind speed,
but it had distinct advantages over what had gone on before
its inception. And it was simple enough to use in daily
practice without involving much additional expenditure of
time or money. From a practical point of view, it is doubtful
that any other system would have found its way into widespread
accepted use, even to this day.
The entire premise of estimating wind speeds from damage
to non-engineered structures is very subjective and is difficult
to defend from various meteorological perspectives. Nothing
less than the combined influence and and prestige of the
late Professor Fujita and Allen Pearson, director of NSSFC
(National Severe Storm Forecast Center) in 1971 could have
brought this much needed system into widespread use. The
FPP scale rates the intensity of the tornado, and measured
both the path length and the path width.
The Fujita part of the scale is as follows:
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Fujita-Pearson scale
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F
scale
|
intensity
|
wind
speed
|
type
of damage
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F0
|
gale
tornado
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40-72
mph
|
Some
damage to chimneys; breaks branches off trees; pushes over
shallow-rooted trees; damages sign boards.
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F1
|
moderate
tornado
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73-112
mph
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The
lower limit is the beginning of hurricane wind speed; peels
surface off roofs; mobile homes pushed off foundations or
overturned; moving autos pushed off the roads; attached
garages may be destroyed.
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F2
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significant
tornado
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113-157
mph
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Considerable
damage. Roofs torn off frame houses; mobile homes demolished;
boxcars pushed over; large trees snapped or uprooted; light
object missiles generated.
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F3
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severe
tornado
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158-206
mph
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Roof
and some walls torn off well constructed houses; trains
overturned; most trees in fores uprooted
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F4
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devastating
tornado
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207-260
mph
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Well-constructed
houses leveled; structures with weak foundations blown off
some distance; cars thrown and large missiles generated.
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F5
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incredible
tornado
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361-318
mph
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Strong
frame houses lifted off foundations and carried considerable
distances to disintegrate; automobile sized missiles fly
through the air in excess of 100 meters; trees debarked;
steel re-inforced concrete structures badly damaged.
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F6
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inconceivable
tornado
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319-379
mph
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These
winds are very unlikely. The small area of damage they might
produce would probably not be recognizable along with the
mess produced by F4 and F5 wind that would surround the
F6 winds. Missiles, such as cars and refrigerators would
do serious secondary damage that could not be directly identified
as F6 damage. If this level is ever achieved, evidence for
it might only be found in some manner of ground swirl pattern,
for it may never be identifiable through engineering studies.
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other
scale of classification for tornado hurricane cyclone
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