Localized Storms - Natural Hazards - page 100

War ning Resp onse

(Golden & Adams, 2000) (Sims & Baumann, 1972; Oliver, 1981)

Tornado prediction in the United States has dramati-
cally improved since 1970 with the explosion in private
meteorological forecasting and improved federally
funded technology. In the 1950s, the US Air Force
instigated tornado forecasting. A radar network was
established in which tornadoes could be detected
based upon their 'hock echo' signature on a radar map.
However, in most cases, these identified only tornadoes
that had already touched down. In the 1970s, lightning
detectors were established to detect tornado-bearing
storms. In the 1990s, infrasound and seismic ground
detector systems augmented a range of remote sensing
systems. The latter included precursor Geostationary
Operational Environmental Satellites (GOES) 8 and 10
forecasting in tandem with 161 WSR88-Doppler radar
installations, all of which were backed up by improved
personnel training, increased numbers of local storm
spotters and enhanced public awareness. The satellite
monitoring permits severe convective systems to be
detected days in advance. No longer is a simple vortex
approach used to model tornadoes. Instead, satellite
detection and computer modelling provides, hours in
advance, evidence of mesocyclones favorable to
tornadoes. The Doppler radar network monitors the
instantaneous development of severe thunderstorms,
large hail, heavy rain, and high winds associated with
tornadoes. These signals are processed locally using
sophisticated algorithms at over 1200 sites using
the Automated Surface Observing System. In 1978, the
probability of detecting a tornado was 22 per cent with
a lead time of three minutes. In 1998 this probability
had risen to 65 per cent with a lead time of 11 minutes.
The events that occurred on 3 May 1999 around
Oklahoma City provide an example of how effective
recent procedures have become. That night 116
warnings, with lead times of 20-60 minutes, were
issued for 57 tornadoes. No warning is useful unless it
can be communicated effectively to the public. Radio
messages can be transmitted by a network of 504
transmitters to 80-85 per cent of the US population.
About 25 per cent of households can automatically
receive these signals. Many TV stations also receive
these automatic warnings and display them on tele-
vision screens as either a text crawler or a flashing icon.
In the United States the fear of tornadoes occurring
without any warning has virtually disappeared.

For most of the world, tornadoes can be put into the
'act of God' category. For instance, in Australia, it is
just bad luck if a tornado strikes you or your property.
In the United States, especially in 'tornado alley',
tornadoes are a frequent hazard. While it is difficult
to avoid their occurrence, there are many ways to
lessen their impact. For instance, in the United States
Midwest, schoolchildren are taught at an early age how
to take evasive action if they see, or are warned about,
the approach of a tornado. I can remember, as a
schoolchild living in southern Ontario, being sent
home from school one day when tornadoes were
forecast. Southern Ontario, then, was not considered
highly vulnerable; but the school authorities were
aware that a tornado hitting a school full of children
would generate a major disaster. We were sent home to
minimize the risk. We were also drilled in procedures
to take if a tornado did strike during school hours - the
same procedures we would have taken if a nuclear
attack were imminent! We knew that tornadoes
traveled mainly north-east; so, if we could see a
tornado approaching and were caught in the open, we
were instructed to run to the north-west. In the United
States Midwest, most farms or homes have a basement
or cellar separate from the house that can be used as
shelter. All public buildings have shelters and workers
are instructed in procedures for safe evacuation. Safety
points in buildings, and in the open, are well sign-
posted. In the worst threatened areas such as 'tornado
alley', tornado alerts are broadcast on the radio as part
of weather forecasts. The actual presence of a tornado
can be detected using Doppler radar or tornado
watches maintained by the Weather Service. The
weather watch consists of a network of volunteer
ham radio operators known as the Radio Emergency
Associated Citizen Team (REACT), who will move to
vantage points with their radio equipment on high-risk
days. Immediately a tornado is detected, local weather
centers, civil defense and law enforcement agencies
are alerted and warnings then broadcast to the public
using radio, television, and alarm sirens.
For many rural communities in the Midwest, a
tornado is the worst disaster that can strike the area.
State governments will declare a state of emergency
and, if outbreaks of tornadoes occur over several states,
federal assistance may be sought through the Federal