Top
PAPERS
Analysis of the Tornado Detection, Warning and
Communication System in Canada
Samanthi W. DURAGE1, Janaka RUWANPURA2 and S.C. WIRASINGHE3
1Graduate Student
(Schulich School of Engineering, University of Calgary, Canada)
E-mail:[email protected]
2,3Professor
(Schulich School of Engineering, University of Calgary, Canada)
E-mail:[email protected]; [email protected]
Tornadoes are one of the most powerful weather events associated with destructive forces of nature. The
frequency of occurrence of tornadoes is highest in North America especially in the US. Canada is second
only to the US and approximately 80 occurrences are reported annually. Communities are impacted only
when and if a tornado touches down on the ground. Early recognition of tornadoes and proper communication of warnings at the pre-touch down phase helps the public to be ready and respond appropriately and
effectively. Given that tornadoes are hard to predict and the warnings give a very brief window of opportunity to prepare for evacuation to a secure underground or other location, each activity in the detection
and warning phases is critically important to enable effective response actions to be taken before impacts on
lives and property occur. This paper presents a detailed analysis of the tornado detection and warning
system in Canada. The sequence of activities, their interrelationships in the tornado detection, warning and
communication system are identified and developed as a network taking the City of Calgary, Alberta as a
case study. The time durations of activities in the network are estimated and represented via triangular
probability distributions. Developing the activity network is a continuous process of refinement based on
information gathered from different sources such as Environment Canada and emergency management
officials at provincial and local levels based on how they are associated with tornado detection, warning and
communication. The network is modeled using the simulation-based schedule networking tool DSSS in the
Simphony software. Based on the simulation output results, improvements to the existing tornado detection, warning and communication system in Canada are proposed. A brief discussion on how the model and
results can be improved is presented.
Key Words: tornado warning, Canada, network modeling, simulation
1. INTRODUCTION
7RUQDGRHVDUH³1DWXUH¶VPRVWYLROHQWwind VWRUPV´ZLWKKXJHGHVWUXFWLYHIRUFHV12$$There are
reports of tornadoes on all continents except Antarctica. However, the frequency of occurrence is highest in
North America especially in the US. Tornadoes have a high potential to create enormous damage to property
and large numbers of deaths and injuries. Although it is difficult to avoid property damage due to the sudden
onset of a tornado, deaths and injuries could be minimized by taking appropriate actions at the pre-touch down
phase.
Proper early warning and communication systems can provide time and information to attain a safe location
during a tornado subject to proper pre-planning of safe places within structures. +RZHYHU³:DUQRQGHWHFWLRQ´
or detection based tornado warnings give a very brief window of opportunity to plan for evacuation. Therefore,
each minute in the warning lead-time is important to launch proper warning and evacuation strategies.
$FFRUGLQJWRWKH,QVWLWXWHIRU&DWDVWURSKLF/RVV5HGXFWLRQ³XQWLODQHIIHFWLYHearly warning communication
PRGHOLVLPSOHPHQWHG&DQDGLDQFLWL]HQVZLOOEHVXEMHFWHGWRKLJKHUOHYHOVRIULVN´0XUSK\HWDO
－ 457 －
Top
PAPERS
Although there are studies that have discussed tornado climatology related issues, no work has appraised or
evaluated the process from detection to warning communication that is an important aspect of tornado disaster
mitigation (Durage et al., 2011). This research focuses on the proactive phase related to a tornado disaster.
Here attention is paid to emergency preparedness activities especially the detection, warning decision-making
and communication systems. The sequence of activities are identified and developed as a network. The network modeling approach using the Decision Support Simulation System (DSSS) template in the Simphony
Legacy software (Ruwanpura et al., 2009) is used to model and simulate network. Our study is timely given
that global warming could increase the frequency of tornadoes in Canada (Etkin, 1995). Overall, this research
provides an analysis of the tornado warning and communication system in Canada.
2. TORNADO RISK IN CANADA
Canadian provinces that are ORFDWHGERUGHULQJWKH³WRUQDGRDOOH\´LQ1RUWK$PHULFDDUHmore susceptible to
tornadoes. In fact, Canada is second only to the US in occurrence of tornadoes. A comparison of the Canadian
and US tornado mitigation systems has been given in Durage et al (2012). According to Environment Canada
(EC), the responsible authority for tornado warning, approximately 80 tornadoes are reported on average
annually. Historical records of tornadoes show two main clusters of tornado prone regions: the central part of
Canada that includes Southern Ontario and Quebec, and the Canadian Prairie region that includes the Provinces of Alberta, Saskatchewan and Manitoba. This distribution pattern is associated with the bordering regions in the US where tornado alley is located.
Although tornado risk is there, the significance of the risk is generally insufficiently appreciated by disaster
management authorities as well as the public. As the tornado season is limited to summer months, and given
the low probability of occurrence (Dore, 2003), the attention and readiness for such an event by weather officials, disaster management authorities, or individuals, is inferior compared to preparedness in the U.S..
Timely detection of isolated tornado events is a challenging task for meteorologists. These events can easily go
undetected from radar observations. Dissemination of warning is also a limiting factor (Etkin et al., 2002) and
some people do not hear or heed the warnings before a tornado strikes. Even if timely warnings are received,
some people become nervous and do not have a clear understanding of how to respond quickly (Dotto et al.,
2010). Preparedness by emergency managers is also not at a sufficient level. To address these issues effectively,
there is a need to improve the awareness and introduce risk mitigation strategies (Durage et al., 2011).
Considering the risk and uncertainties associated with tornados in Canada, McBean (2005) concludes is the
importance of altering Canadian disaster management strategies to account for greater risk of tornado impact
in future. Although the tornado hazard potential cannot be reduced, actions can be taken to mitigate the overall
impact by reducing the vulnerability and increasing the capacity to cope up with tornado disasters. Despite
various barriers to implement mitigation approaches in disaster management (Henstra and McBean, 2005),
Canada is gradually shifting from the ways governments have approached the disaster problem historically by
using response and recovery methods to mitigation strategies (Emergency Management Act, 2007, c.15).
Mitigating the impacts of tornadoes is becoming a major consideration for weather services and disaster
management authorities in tornado prone regions in Canada.
(1) Tornadoes in the Canadian prairies
The Prairie region especially is susceptible to severe summer thunderstorms. Meteorological conditions that
produce severe thunderstorms can arise in any part of the Canadian prairies (Paul, 1982). A higher frequency
of tornado occurrences can be observed in the June, July and August months that have significant summer
rainfall associated with severe thunderstorms.
Alberta is a province in the Canadian Prairies located on the fringe of tornado alley in North America. In the
recent past Alberta has experienced two major events in Edmonton and Pine Lake, which are among the
FRXQWU\¶VWRSWHQGHDGOLHVWWRUQDGRHV&DOJDU\LVDFLW\LQSouthern Alberta, located bordering the foothills of
the Rocky mountain range and relatively close to tornado alley. Calgary has not experienced major tornado
disasters in its history. However, given that Edmonton and Pine Lake regions are further North than the City of
Calgary, the probability of a similar tornado affecting Calgary is not insignificant (Durage et al., 2011). The
Calgary Emergency Management Agency (CEMA), the local level partner in emergency management, has
－ 458 －
Top
PAPERS
been concerned about the tornado issue and is looking into ways to mitigate the impact of future tornadoes.
How local residents in Calgary will receive tornado warnings and how residents as well as emergency services
should react to them are major issues being considered. In this research, we focus on developing the Canada-Alberta-Calgary-Household tornado warning and communication network to analyze issues associated
with tornado disaster mitigation.
3. TORNADO PREDICTION, DETECTION AND WARNING
Development of tornadoes is a complex process and these localized events are hard to detect and forecast
(Murphy et al., 2005 and Cao and Cai, 2011). There is no accepted methodology for predicting tornadoes
precisely. Doppler radars provide information on wind speeds that can be used to detect rotations in order to
infer tornado activities and their approximate locations. Doppler radars detect mesocyclones that provides
tornado vortex signatures. Satellite images and numerical weather prediction models are also used to analyze
severe weather information and detect tornado activities. A warning can be issued with a lead-time of around
10 minutes if the tornado is within the coverage of a Doppler radar installation (MSC, 2003). Outside of the
Doppler radar coverage area, warnings are issued based on eyewitness reports of funnel clouds or tornadoes in
the area.
(1) Environment Canada ±Storm Prediction Centres
Issuing timely watches and warning bulletins can help reduce the destruction due to tornadoes. Warnings,
watches and special statements for severe weather provide public and emergency services with the level of
preparedness required to manage a actual or pending severe weather emergency. Environment Canada (EC) is
the official source of weather warnings in Canada. It serves as a supporting agency to Public Safety Canada
with responsibilities relating directly to the management of severe weather. Through the Storm Prediction
Centres (SPC), EC monitors weather conditions and provides weather forecasts and severe weather warnings.
There are five SPCs in Canada, which are strategically located to FRYHUWKHZKROHFRXQWU\³6LQFHWRrnado sightings have been URXWLQHO\DUFKLYHGE\63&V´&DRDQG&DL7KHUHDUH³SXEOLFIRUHFDVWUHJLRQV´
which consist of groups of municipalities for the purpose of issuing warnings. These regions also can be
sub-GLYLGHGLQWR³VXPPHUVHYHUHZHDWKHUZDUQLQJUHJLRQV´:DWFKHV and warnings are issued for the relevant
region only. Generally, warnings have to be issued for a large area although impacts are localized.
Prairie and Arctic Storm Prediction Centre (PASPC) is the responsible authority for providing round-the-clock
forecast support to the Canadian Prairie Provinces and Arctic region. By continuously monitoring thunderstorms, PASPC issues bulletins according to the severity of weather. Within a storm, numerous bulletins can
be in effect based on the storm monitoring results. When there is a severe weather warning in effect, meteorologists look for conditions that are favourable for the development of tornadoes. Especially the thunderstorms
and associated supercells are closely monitored and tornado watches are issued for unusually strong supercells
so that people in the region can be on alert about tornadoes. Tornado warnings are issued when it is likely that
a tornado would develop soon in the area, when a tornado is occurring in a nearby area and may soon move into
the area, or when a tornado is already occurring in the area. In many cases, watches and warnings are preceded
by bulletins issued for severe weather watches and warnings. Sometimes the sudden appearance of a tornado or
report of a tornado leads to a bypass of the watch stage and the issuance of a warning.
(2) Spotter network
The storm spotters are strong partners in the process of tornado warning and communication. They provide
reports of tornado sightings. CANWARN (Canadian Weather Amateur Radio Network) is the spotter network
in Canada that consists of personnel trained to recognize severe weather. These spotters report sighting of
tornadoes to local weather stations. $FFRUGLQJWRWKH&HQWUDO$OEHUWD$UPDWXUH5DGLR&OXE³&$1:$51LV
not about storm chasing, it is about putting trained eyes at the local level to confirm what is happening under
severe weather and communicating that information to the Meteorological ServicHRI&DQDGD´ (CANWARN,
2011).
In addition to systematic monitoring and detection of tornadoes, people can identify incoming tornadoes
through environmental clues such as a dark or greenish sky, large hail, thunder and lightning, funnel clouds
and rumbling sounds. With these clues, people can be alerted if severe weather is likely to produce tornadoes.
－ 459 －
Top
PAPERS
4. WARNING COMMUNICATION
Communication of tornado warnings should be a rapid process that will require giving information to the
public as soon as possible. As the warning lead-time is very low, HYHQDPLQXWH¶VGHOD\LQWKHLQIRUPDWLRQIORZ
can bring severe impacts. The warning communication system is multi-modal, in order to disseminate warnings rapidly and efficiently.
(1) Broadcasting media
(&KDVVHYHUDORSWLRQVWREURDGFDVWWRUQDGRZDUQLQJVWRWKHSXEOLF,WV³:HDWKHUDGLR´VHUYLFHVHQGVRXWDOHUWV
to the relevant area notifying that a warning is being issued. In addition, radio and television networks, mobile
phone alerts, EC website, private meteorological companies as well as social media broadcast tornado information directly to the public. When there is a tornado warning, local radio and television stations have the
responsibility to air the warning immediately by interrupting regular programming. Private meteorological
companies send out tornado watches and warnings messages obtained from the EC. EC can also access the
province-wide Alberta emergency alert (AEA) system to warn the public in the Province of Alberta.
(2) Alberta emergency alert
The Alberta Emergency Management Agency (AEMA) is the provincial partner responsible and accountable
for emergency management under the Government of Alberta. It has launched a digital public warning system
called Alberta Emergency Alert (AEA) since June 2011 to alert the public to hazards, emergencies or disasters
in the Province. This is the upgraded version of the Emergency Public Warning System (EPWS) which was
established by the Government as a result of the major F-4 tornado in the Edmonton area in 1987. There are
two types of alerts that can be sent to the public, namely; Critical Alert and Information Alert. Critical Alerts
are sent when there is an imminent life threatening danger. Information Alerts provide less critical information
to the public to help them to prepare for an emergency.
EC is an authorized user of the AEA system and PASPC can issue alerts to give tornado warning or watch
LQIRUPDWLRQ³7RUQDGR:DUQLQJ´LVDFULWLFDODOHUWZKHUHDV³7RUQDGR:DWFK´FDQEHD&ULWLFDO$OHUWRUDQ
Information Alert depending on the context. Authorized Provincial and municipal level emergency management officials also can activate the AEA to broadcast warning messages quickly to the public. The AEA disseminates these alerts through the internet, RSS feed, radio, television as well as social media. Turning to
social media such as Facebook and Twitter to disseminate alerts provides a new mobile version of the warning
communication through internet-enabled smart phones. People on the roads can also receive these alerts so that
they can be warned about imminent dangers. Other than radio broadcasts this is the only way in which road
users can be given official alerts and warnings. AEA has made a step forward in designating a warning area in
their alerts, to reduce the location uncertainty about the threat area (Durage et al., 2011).
(3) Calgary Emergency Management Agency (CEMA)
In Calgary, CEMA receives tornado warning information through various ways such as EC, AEA and directly
from the public. When there is an imminent danger of a tornado or a funnel cloud appearing in the Calgary area,
residents can inform the CEMA. Authorized AEA users in the CEMA can evaluate that information and activate the AEA to alert the public in the affected area. Upon receiving this information, CEMA informs other
emergency respondents such as the local police stations and the Emergency Medical Service (EMS) and activates its action plan to respond to the emergency. Further, CEMA guides the public to take emergency preparedness measures and to move to safer locations in a timely manner.
(4) 911 and Police
Emergency Services play a major role in ensuring the safety of the public during disaster situations. They
provide warning and cautioning information to the public to protect their lives and properties. When an
emergency call about tornado sighting in the locality is received by the 911 public safety communication
system, the police receive the message immediately. Upon receiving timely information, emergency services
can assist with information sharing with the public on roads, traffic control and neighboring security. As a
responsible authority for public safety, the police also give sighting information to the local emergency
management officials when a tornado is reported in the locality.
－ 460 －
Top
PAPERS
(5) Self-warning
Though there are various warning communication methods, people cannot entirely depend on official warnings. Sometimes, the relevant agencies are unable to issue warnings until the tornado touches down. The best
warning is based on what people can see for themselves. People should remain alert to severe weather watches
and warnings as well as signs of approaching tornadoes in order to seek shelter if threatening conditions exist.
The above discussion of the role and responsibilities of each level of government and other collaborating
partners in tornado detection, warning and communication process provides the basis to develop a network
showing the sequence of activities, their interrelationships and the time consumption of activities.
5. ACTIVITY NETWORK DEVELOPMENT
Data required for developing the activity network (Durage et al., 2012) representing the tornado detection,
decision-making, and communication was collected by means of discussions with EC, CEMA and AEMA
officials. A series of discussions and brainstorming sessions at the CEMA provided useful information about
their interaction with EC and AEMA who are the collaborating partners at the Federal and Provincial levels
respectively. Discussions with the EC warning coordination meteorologist in Calgary provided information
about the EC involvement and its interaction with the Provincial and local level partners in communicating a
tornado threat to the public. The sequence of the activities was determined and a Canada-Alberta-Calgary-Household tornado detection, decision-making, warning and communication network was
developed (Figure 1). The activities are subjected to a wide variety of fluctuations and interruptions. Therefore,
activity durations become subject to random variations. Time distribution data were collected through a
workshop conducted with participation from officials from CEMA, EMS, EC and the AEMA. Time distribution of each activity was collected via a consensus based on original personal values of participants represented as minimum, maximum, mode and mean (Table 1). It was assumed in this study that activity durations
follow Triangular distributions. Triangular distribution has been widely used in network modeling in construction management applications (Chau, 1995, Lee and Shi, 2004). In the absence of detailed data sets, it can
effectively be used to describe the variation. Time durations were defined by minimum (fastest), maximum
(slowest) and mode (most likely) response times. Further research is required to obtain probability distributions that better represent various activity durations. In the network, the activity name is shown in the upper
part of the box and the collaborating partner of that activity and the duration is shown at the bottom of the box.
(1) Network Modeling Approach
Modeling the sequence of activities throughout the process from detection to warning communication was
carried out using the network modeling approach. Such an approach for tsunami mitigation network analysis
has been suggested by Fernando et al (2008), and further developed in Ruwanpura et al (2009), Wickramaratne (2010) and Wickramaratne et al (2012).There are vital differences between tsunami and tornado disasters
with respect to factors such as origin, nature, duration, risk and uncertainties, warning lead times, and evacuation strategies. Although the approach for network modeling and simulations are similar, the output results
are expected to be widely different (Durage et al., 2011).
The activity network was modeled in the DSSS template of the Simphony Legacy software. The DSSS template developed by Moussa et al (2007) provided an ideal platform to model the network using various tools
that represent interrelationships of activities. In this network, we used the Finish to Start (FS) activity relaWLRQVKLSZLWKQRWLPHODJIURPDQ\DFWLYLW\WRLWVVXFFHVVRU7KH³25´UHODWLRQVKLSZKLFKUHSUHVHQWVWKHUealization of any of the preceding activities to UHDOL]HVXFFHHGLQJDFWLYLW\DQG³$1'´UHODWLRQVKLSWKDWUHTXLUHV
realization of all preceding activities for a succeeding activity to be realized were used as logical relationships.
Monte Carlo Simulation within the DSSS template facilitates analyzing the system model by taking inputs in
the form of random variates. It also gives the output result as a statistical distribution. The DSSS template has
D PRGHOLQJ HOHPHQW FDOOHG ³+DPPRFN´ WKDW FDQ EH XVHG WR DQDO\]H D VSHFLILF SRUWLRQ RI WKH QHWZRUN
Placement of hammocks covering portions of the network gives time consumption for that portion only. The
tornado warning and communication network was simulated with 1000 runs. The main output of the simulation is the visualized Cumulative Probability Function (CDF) as shown in the Figure 2.
－ 461 －
Top
Fig.1
Canada-Alberta-Calgary-Household tornado detection, warning and communication network
(Local information paths are shown in green colour.)
－ 462 －
PAPERS
Top
Table 1
Time duration estimates (in minutes)
Activity
Minimum
Mode
Maximum
SPC
Severe thunderstorm watch issued
1
2
4
Recognize severe thunderstorm potential
5
25
30
Severe Thunderstorm Warning issued
1
2
4
Check for the possibility for tornadoes
5
15
20
Tornado watch issued
1
2
4
Activate spotter network
2
3
5
Obtain ground truth information
5
10
15
Obtain Doppler radar information
5
30
60
Recognize tornado vortex signatures
2
3
5
Recognition of tornadoes
1
10
20
Tornado warning issued
1
2
4
Activate Alberta Emergency Alert
1
1.5
2
1.5
2.5
10
Receive tornado warning
0.5
1
2
Activate AENS
0.5
0.75
3
Receive SPC tornado warnings
1
5
60
Receive local tornado information
3
5
10
Activate AEA and issue instructions
2
2.5
5
Check the sky
5
15
30
Recognize tornadoes
2
3
5
Information sharing
0.5
0.75
5
911 communication
0.5
0.75
5
1
3
5
Check the sky
5
15
30
Recognize tornadoes
2
3
5
911 public safety communication
0.5
0.75
5
Police receive information
0.5
1.5
3
Emergency Preparedness
1
8
20
Disseminate through radio, TV, Social media
1
2
5
Weather updates/mobile text alerts
1
1.5
2
Disseminate through Weather Radio
AEMA
CEMA
Public
Public receive warning
Emergency Services
Media / Private Meteorological Companies
－ 463 －
PAPERS
Top
PAPERS
(2)Simulation Output Results
The CDF curve gives probability estimates of a successful completion of detection, warning and warning
dissemination in a given time.
Fig.2
CDF curve for tornado detection, warning and communication
Based on the simulation results, cumulative probabilities associated with time consumption can be recognized.
According to the CDF curve, there is a 50% chance that tornado detection, warning and communication can be
completed within 25 minutes or less. The maximum time predicted through simulation is about 37 minutes.
According to this simulation, the earliest a tornado detection, warning and communication can be completed is
in 14 minutes from the triggering point of severe weather that lead to a tornado occurrence. This time is much
less than the total lead-time of around 1hr that can be calculated approximately as severe thunderstorm warning
lead time plus tornado warning lead time targeted by the SPC authorities. Simulation results show that, with
the present tornado detection, warning and communication system the possibility of achieving this target is
very low. Improving the warning communication system can bring the curve leftward to achieve the desired
lead-time.
Based on the simulation results, delay points as well as faster links in the information flow can be recognized
and suggestions can be provided to improve its quality and the timeliness.The simulation results have shown
that the recognition of tornadoes by the SPC takes approximately 43 minutes from the triggering point of
severe weather. The highest time consumption within this period is taken for radar, satellite data observation to
detect rotations. Further, verification from different sources at the pre-warning stage also adds more time to the
detection and warning process. This time consumption is even higher than the maximum time consumption for
the overall process (37 minutes) that is shown in Fig 2. Public seeks the earliest possible warning information
coming from various sources. In this regard, instead of using delayed warnings coming from the SPC, simulation has chosen local level information paths (Fig 1) that are quicker than the systematic warning by the SPC.
Thus, the path in the activity network through the SPC process is not the shortest path.
At the local level, if people keep watchful eyes on severe weather development, they can detect possible tornadoes and inform the 911 public safety communication system. This local level detection process takes 25
minutes on average from the triggering point of severe weather development to the 911 calling stage. Activation of the 911 system and warning communication to the public takes 6.6 minutes on average (Fig 3). Having
such fast links improve the local level detection process that provides ground level information to the forecasters, as well as to the emergency managers. Presently, this local level severe weather spotting is not very
active in the Calgary area. It is important to strengthen the local level detection by volunteers or spotter net-
－ 464 －
Top
PAPERS
works. Strengthening of the local level detection also encourage the maximum utilization of the AEA system
for tornado emergencies. However, it is import to ensure that reliable information is coming for immediate
activation of the AEA.
Fig.3
CDF curve of time consumption between activation of 911 and warning communication to the public
This simulation is based on the time consumption taken as triangular probability distribution. Although, triangular distribution is used in many applications to simulate activity networks, it is an approximate distribution
based on a three-point estimate of the endpoints. The most suitable distribution or the best-fit curve to represent the time variation in each activity needs to be determined through a trial and error process. Our future
work will focus on that issue to improve the model and results.
6. CONCLUSION
This paper has presented an analysis of the tornado warning and communication system in Calgary, Canada. It
has provided a detailed discussion from tornado detection to the warning receiving point, highlighting roles
and responsibilities of collaborating partners at different levels. The network synthesizes the connectivity of
different collaborating partners in tornado detection, warning and warning communication. This provides
information to the local emergency management agency to identify various ways of communicating tornado
warnings to the public. Attention can be paid to strengthen the faster links of the information flow. From this
analysis, it is likely that the systematic ways of providing warnings to the public are not always desirable. Of
the various warning communication links identified, public surveillance to recognize environmental clues
could play a major role in tornado disaster mitigation.
ACKNOWLEDGEMENT: The authors wish to acknowledge the assistance of the Calgary Emergency
Management Agency and in particular its Director Bruce Burrell in conducting this research. This paper is an
improved and updated version of Reference 9 which was presented and distributed at a WFEO Panel Session.
REFERENCES
1)
2)
Brotzge, J. and Erickson, S. : NWS Tornado Warnings with Zero or Negative Lead Times, Weather and Forecasting, Vol. 24, pp.
140-154, 2009.
Cao, Z. and Cai, H. :Tornado Frequency and its Large-Scale Environments over Ontario, Canada, The Open Atmospheric Science
Journal, Vol. 2, pp. 256-260, 2008.
－ 465 －
Top
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
14)
15)
16)
17)
18)
19)
20)
21)
22)
23)
24)
25)
26)
27)
28)
29)
30)
31)
32)
33)
34)
35)
PAPERS
Cao, Z., and Cai, H. : Detection of Tornado Frequency Trend Over Ontario, Canada, The Open Atmospheric Science Journal,
Vol.5, pp. 27-31,2011.
CANWARN, Central Alberta Armature Radio Club, Available at http://www.caarc.ca/canwarn , Accessed on 4th August 2011.
Chau, K.W. : The Validity of the Triangular Distribution Assumption in Monte Carlo Simulation of Construction Costs, Construction Management and Economics, Vol.13, No.1, pp. 15-21,1995.
Comstock, R.D. and Archer, P. : Planning + Practice = Preparedness: A case study in injury prevention, Work: A Journal of
Prevention, Assessment and Rehabilitation, Vol. 23, pp. 199-204,2004.
Dore, M.H.I. : Forecasting the Conditional Probabilities of Natural Disasters in Canada as a Guide for Disaster Preparedness,
Natural Hazards, Vol. 28, pp. 249±269,2003.
Dotto, L. et al. : ³&DQDGLDQVDWULVN2XUH[SRVXUHWRQDWXUDOKD]DUGV´Canadian Assessment of Natural Hazards Project, paper
series ± number 48, Institute for Catastrophic Loss Reduction, Ontario, Canada, 2010.
Durage, S.W., Ruwanpura, J.Y., Wirasinghe, S.C. : Preliminary Analysis of the Decision-Making and Communication Network
for Tornado Warning and Evacuation in Canada, WFEO Committee on Disaster Risk Management Panel Session, World Engineers' Convention 2011, Geneva, Switzerland, pp. 50 -60, September 2011.
Durage, S.W., Wirasinghe, S.C. , Ruwanpura, J.Y. (2012). Comparison of the Canadian and U.S. Tornado Detection and Warning
Systems, Natural Hazards, Available online at http://www.springerlink.com/content/nqt6775768275w66/
EC,
³:KDW
LV
:HDWKHUDGLR"´
(QYLURQPHQW
&DQDGD
:HEVLWH
Available
at
http://ec.gc.ca/meteo-weather/default.asp?lang=En&n=792F2D20-1, Accessed on 12th April 2010.
EC, Public Weather Warnings for Canada, Available at, http://www.weatheroffice.gc.ca/warnings/warnings_e.html, Accessed on
13th April 2010.
Edwards, R., and Lemon, L.R. : ³Proactive or Reactive? The Severe Storm Threat to Large Event Venues´Preprints, 21st Conf.
Severe Local Storms, San Antonio TX, 2002.
Emergency Management Act. S.C.2007, c.15 Minister of Justice, 2007, Available online at http://laws.justice.gc.ca, Accessed on
4th August 2011.
Etkin, D.A. : Beyond the Year 2000, More Tornadoes in Western Canada? Implications from the Historical Record, Natural
Hazards, vol. 12 pp. 19-27,1995.
Etkin, D., Brun, S.E., Shabbar, A., and Joe, P. : Tornado Climatology Of Canada Revisited: Tornado Activity during Different
Phases of ENSO, International Journal of Climatology, Vo.21, pp. 915-938, 2001.
Etkin, D.A., Brun, S.E., Dogra,P.: ³$7RUQDGR6FHQDULRIRU%DUULH2QWDULR´Paper Series ± No. 20, Institute for Catastrophic
Loss Reduction,Ontario, Canada, 2002.
)HUQDQGR+-%UDXQ$*DODSSDWWL55XZDQSXUD-<DQG:LUDVLQJKH6&³Tsunamis: manifestation and afterPDWK´In: M. Gad-el-Hak, ed. Large-scale disasters: prediction, control and mitigation. Cambridge University Press, pp. 258±292.
Fujita, T.T. : Tornadoes around the World, Weatherwise, Vol. 56, pp.56-62, 78-83, 1973.
Goliger, A.M., Milford, R.V. : A Review of Worldwide Occurrence of Tornadoes, Journal of Wind Engineering and Industrial
Aerodynamics, Vol 74-76, pp. 111-121,1998.
Henstra, D. and McBean, G.A. : Canadian Disaster Management Policy: Moving Toward a Paradigm Shift? Canadian Public
Policy, Vol. 31, No. 3, pp. 303-318 2005.
Lee, D.E. & Shi, J.J. :³6WDWLVWLFDODQDO\VHVIRUVLPXODWLQJVFKHGXOHQHWZRUNV´Proceedings of the 2004 Winter Simulation Conference, WSC, pp.i-XI, 2004.
NSSL , ³7RUQDGR%DVLFV´ 2009, Available at http://www.nssl.noaa.gov/primer/tornado, Accessed on 13th April 2011.
Murphy, B., Falkiner, L., McBean, G., Dolan, H., Kovacs, P. : ³(QKDQFLQJ/RFDO/HYHO(PHUJHQF\0DQDJHPHQW The Influence
RI'LVDVWHU([SHULHQFHDQGWKH5ROHRI+RXVHKROGVDQG1HLJKERXUKRRGV´Institute for Catastrophic loss Reduction, ICLR Research, Paper Series ± No. 43, Canada, 2005.
McBean, G.A. : Risk Mitigation Strategies for Tornadoes in the Context of Climate Change and Development, Mitigation and
Adaptation Strategies for Global Change, Vol.10, pp.357-366,2005.
Moussa, M. : Development of Decision Support System (DSS) Simulation Tool for Risk Analysis, MSc Thesis, Department of
Civil Engineering, University of Calgary, Canada, pp. 129-140,2007.
MSC : Summer severe weather bulletins in Alberta - Watches and warnings, Meteorological Service of Canada, 2003.
NOAA : ³7RUQDGRHV1DWXUH¶V0RVW9LROHQW6WRUPV´$3UHSDUHGQHVVJXLGHLQFOXGLQJVDIHW\LQIormation for schools, National
Oceanic and Atmospheric Administration, USA, 1995.
NSSL : ³&RQYHFWLYH-scale Warn-on-)RUHFDVW 7KH 6HYHUH :HDWKHU )RUHFDVW ,PSURYHPHQWV 3URMHFW 3ODQ´ Warn-on-Forecast
Science Advisory Board, National Severe Storms Laboratory, National Oceanic and Atmospheric Administration, USA, 2010.
Paul, A.H. : The Thunderstorm Hazard on the Canadian Prairies, Geoforum, Vol . 13, No . 4, pp . 275-288, 1982.
Ravindra, M.K. : ³6WDWH-of-the-Art and Current Research Activities in extreme Winds Relating to Design and evaluation of NuFOHDU3RZHU3ODQWV´,Q7KHTornado: Its Structure, Dynamics, Prediction, and Hazards, Geophysical Monograph 79, American
Geophysical Union, pp. 389 ± 397,1993.
Simmons, K.M. and Sutter, D. : Improvements in Tornado Warnings and Tornado Causalities, International Journal of Mass
Emergencies and Disasters, Vol. 24, No. 3, pp. 351-369,2006.
Ruwanpura, J., Wickaramaratne, S., Braun, A., Wirasinghe, S. C. : Planning and modeling for mitigation of tsunami impacts, Civil
Engineering and Environmental Systems, Vol. 26, No. 2, pp.195-209, 2009.
Wickramaratne, S. : ³'HVLJQDQG$QDO\VLVRI7VXQDPL:DUQLQJDQG(YDFXDWLRQ6\VWHPV´, Ph.D. Thesis, Department of Civil
Engineering, University of Calgary, Calgary, Canada, 2010.
:LFNUDPDUDWQH65XZDQSXUD-:LUDVLQJKH6&³'HFLVLRQ$QDO\VLVIRUD7VXQDPL'HWHFWLRQ6\VWHP ± Case Study: Sri
/DQND´&LYLO(QJLQHHULQJDQG(QYLURQPHQWDO6\VWHPV-4, 2011, 353-373
－ 466 －