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Tornado Facts and Information
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Tornado Facts and Information
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| TORNADO SAFETY IN
SCHOOLS | MORE INFORMATION FOR TEACHERS
AND KIDS | SAFE ROOMS BEST
BET FOR SURVIVING TWISTER FURY |
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The twister that struck Seward in 2000. It completely leveled
one home in its path leaving only the basement with nothing left standing
above ground.
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New technology offers people an opportunity
to construct safe rooms in either existing or new construction homes.
The relatively inexpensive technology will offer protection from even
the strongest storms.
Tornadoes with ratings of F-4 or F-5 will
destroy everything in their paths. Emergency management officials
say the only sure-fire way to escape the fury of these storms is to get
below ground level and into a structure that will protect you from not
only the howling winds, but the debris that is tossed around by these
killer storms.
Anyone caught unprotected above ground in
powerful twisters with winds exceeding 200 mph seldom survives without
at least major injuries.
Emergency management officials have been
advising people for years to seek shelter in a basement or if that isn't
possible in an interior room away from windows. That is still the
recommended procedure, but people should also consider building a safe
room or some kind of hardened structure to protect them from harm.
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This is a typical scene of a basement following a tornado.
Flying debris is still a serious concern for those who seek the recommended
shelter. |
Fortunately for the owners of the home shown
to the left, they were gone when the relatively mild twister tore their
house apart in Jackson last year. Flying debris is responsible for most
of the deaths and injuries from tornadoes.
Texas Tech University has pioneered research into safe rooms. An illustrated
brochure, Taking Shelter from the Storm: Building a Safe Room Inside Your
House, can be obtained from FEMA at www.fema.gov.
The solution might be to merely strengthen a room in your basement with
reinforced building block construction. Something big enough for your
entire family to get into, below ground, with enough support to shelter
you from the fury of the biggest tornadoes that nature can throw at you.
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| In 2002, the number of tornadoes in the
state, 28, was below the normal of 40 for the first time since 1997 and
was the lowest total since 1995. The strongest tornado in 2002 was only
an F1 and property damage was extremely low as most twisters remained in
open country.
The first tornado in 2002 occurred on April 27 in Saline County, the
last touchdown was in Sheridan County on August 26. May and July had the
most tornadoes, eight each.
Nebraska ranks fifth in the nation in the number of tornadoes. The most
number of twisters occurred in 1990 when 88 of them snaked across the
state. That was the year when 13 tornadoes touched down in one day in
March! 1966 remains the year with the fewest tornadoes - 10.
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NEBRASKA'S WORST TORNADOES
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| 1. Omaha - March 23, 1913 |
83 Deaths/350 Injuries |
| 2. Arcadia - June 7, 1953 |
11 Deaths/5 Injuries |
| 3. Madison County - May 30, 1954 |
6 Deaths/23 Injuries |
| 4. Hebron - May 9, 1953 |
5 Deaths/80 Injuries |
| 5. Grand Island - June 3, 1980 |
5 Deaths/193 Injuries |
| 6. Primrose - May 8, 1965 |
4 Deaths/133 Injuries |
| 7. Omaha May 6, 1975 |
3 Deaths/133 Injuries |
The strongest tornado reported in the state in 1999 was rated F3 on
the Fujita Scale. It occurred in Valley County in June. |
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FUJITA SCALE
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| Scale Value |
Wind Speed |
Damage |
| F0 |
40-72 mph |
Light Damage |
| F1 |
73-112 mph |
Moderate Damage |
| F2 |
113-157 mph |
Considerable Damage |
| F3 |
158-206 mph |
Severe Damage |
| F4 |
207-260 mph |
Devastating Damage |
| F5 |
261-318 mph |
Incredible Damage |
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| TORNADO WARNINGS - WHAT WORKS BEST?
The National Weather Service (NWS) has verified that outdoor warning
systems delayed warning time in a recent Kansas tornado event. The NWS
reports that NOAA weather transmitters are a more ideal warning method.
The NWS is also reported to have the empirical data to support their contentions.
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This overpass near Wichita Falls, Texas, is similar
to the one in the celebrated video from Kansas where several people
survived a dangerous tornado. Note the ample crawl space under the
roadbed for people to seek shelter and the heavy I-beam construction.
Traffic was blocked for several minutes before the
F-5 tornado lowered from the cloud in the background. If people
had been allowed to continue, they would have cleared the area before
the storm hit, according to this report. The authors also say the
police were acting in the best interest of the public when they
closed the highway.
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HIGHWAY OVERPASSES NOT THE BEST SHELTER FROM TWISTERS
Highway overpasses might not be the best shelters from tornadoes.
In fact, a study by the National Weather Service indicates overpasses
might have contributed to deaths and injuries in Kansas and Oklahoma
during a supercell outbreak in May of 1999.
Video footage shot by a television station in Kansas in 1991 of
people seeking shelter under an interstate overpass has contributed
to people's beliefs that these are ideal places to seek shelter.
In Nebraska's Severe Weather Awareness Poster Contest in the past
couple of years, several fourth grade students submitted drawings
showing people taking shelter under overpasses.
"It appears that highway overpasses offer, at best questionable
shelter not only from tornadoes, but severe storms in general,"
says Dan Miller, lead author of the report and forecaster at the
NWS forecast office in Norman, Oklahoma.
In Oklahoma in 1999, three deaths and many injuries occurred when
people sought shelter under three separate underpasses during a
severe tornadic outbreak. According to the authors of the study,
these people would have been wiser to either seek shelter elsewhere
or to stay in their vehicles and try to drive at right angles to
the storms. Better yet, they should not have been travelling during
tornado watches and warnings.
In most cases, safety experts advise people to seek shelter from
tornadoes when driving and to not try to outrun a twister. In this
case, however, the overpass was not suitable as a shelter. The authors
maintain the overpass might have actually increased the strength
of the winds by acting like a wind tunnel.
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TRAFFIC CONGESTION CONTRIBUTES TO DANGER
Another factor contributing to potential deaths and injuries when
people seek shelter under overpasses is traffic congestion can get
so bad, people have no choice but to abandon their vehicles.
The authors of the study concluded that this is exactly what happened
in Oklahoma City in 1999. The state police actually closed off an
interstate in both directions. The conclusion by the authors is
the people would have been able to get through the danger area if
the interstate had been left open.
WHAT TO DO?
The authors contend that with adequate warnings available to the
public today, people should stay where they are. First, they recommend
that people stay abreast of storm watches and warnings. If tornado
watches are issued, don't travel. If you are travelling and see
approaching storm clouds, tune in to the local media and seek shelter
if necessary.
The recommended course of action when storms are approaching is
to seek shelter in a basement or on the lowest level in an interior
room, wherever you are. Do not get in your vehicle and travel when
tornadoes are forecast.
The promotion of ditches, overpasses and vehicles are "options
of absolute last resort," conclude the authors.
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SIMPLE STEPS CAN PROTECT HOMES, BUSINESSES FROM TORNADO
DAMAGE
According to a comprehensive FEMA study of the tornadoes that devastated
Oklahoma and Kansas in 1999, there are simple, relatively inexpensive
things people can do to protect their homes and businesses from significant
structural damage from even powerful tornadoes.
Much of the structural damage found by FEMA investigators after the 1999
storms was avoidable reported FEMA Director James Lee Witt.
"Our teams saw significant damage to thousands of single-family
homes, multi-family housing and manufactured homes," Witt said. "They
saw building failures that resulted from wind-borne debris and high winds
that produced forces on buildings they were not designed to withstand.
They saw building failures that resulted from improper construction techniques,
poor selection of construction materials and ineffective detailing of
connections of homes to foundations, floors to walls and walls to roofs."
Double-Wide Garage Doors Singled Out
A major culprit, Witt said, was poorly designed double-wide garage doors,
which allowed the tornadoes' winds to penetrate into the interior of houses,
resulting in "tremendous internal pressure" that ripped off
roofs and other parts of the homes.
Witt is urging homeowners to get their garage doors inspected and bring
them up to, or above, code.
The breaches of windows and entry doors also caused significant damage,
but the breaches were not as dramatic as those associated with garage
doors, which are larger.
Another problem was the failure of masonry chimneys, even in winds as
low as 75 mph. The collapse of the chimneys "caused considerable
damage to homes that otherwise had very minor wind damages [and] ... placed
the people inside at significant risk of death and injury from falling
masonry debris," Witt said. For homeowners with masonry chimneys
higher than six feet above the roof, Witt urges retrofitting them with
continuous vertical reinforcing steel in the corners to help resist high
winds.
Witt estimates the average minimum retrofit would cost a homeowner around
$1,000 to $2,000. Such a retrofit could include anchoring the foundation,
properly linking the roof to the housing structure and making sure doors
and windows are secure against wind and debris.
However, to save lives, Witt emphasized that the best thing a homeowner
can do is to build a "safe room." It is the only structure that
can withstand violent storms up to an F-5 tornado.
For more detailed information please see The Building Performance
Assessment Report (BPAT), Oklahoma and Kansas: Midwest Tornadoes of May
3, 1999. The report is available on FEMA's web site at www.fema.gov.
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