26
BAMOS
Jun 2020
Damage
Indicator
Damage Indicator Descriptor
Maximum Degree
of Damage
Expected 3‐second Wind
Gust Speed (km/h)
Enhanced Fujita Scale
intensity rating
DI1 One‐ and two‐family residence (FR12) 4 156 EF1
DI2 One‐ and two‐family residence (FR12) 2 127 EF0
DI3 One‐ and two‐family residence (FR12) 4 156 EF1
DI4 One‐ and two‐family residence (FR12) 4 156 EF1
DI5 One‐ and two‐family residence (FR12) 4 156 EF1
DI6 Softwood Trees (TS) 3 127 EF0
DI7 Hardwood Trees (TH) 2 119 EF0
DI8 One‐ and two‐family residence (FR12) 2 127 EF0
DI9 Hardwood Trees (TH) 4 172 EF1
DI10 Hardwood Trees (TH) 4 172 EF1
Table 4: Summary of EF‐Scale intensity ratings and expected 3‐second wind gust speed for each
of the 10 Damage Indicators assessed during the damage assessment.
Conclusion
The rating of a tornado event should ideally represent an
estimate of the highest wind speed that occurred during the
life cycle of the tornado, but it is acknowledged that wind speed
intensity can vary significantly along the length and across the
width of the tornado damage path, particularly given the storm
motion. In accordance with the recommended approach for
assigning an EF‐scale rating to a tornado event by applying the
highest rated DI, given that there were six DIs that provided
supportive evidence of similar damage intensity in close
proximity to each other, the damage assessment suggested an
EF‐scale intensity rating of EF1 with maximum 3‐second wind
gust speeds of 138–178 km/h.
References
AS/NZS 1170.2, 2011. Structural design actions, Part 2: Wind
actions, Australian/New Zealand Standard
McDonald, J. and Mehta, K. C., 2006. A Recommendation for an
Enhanced Fujita Scale (EF‐Scale), Revision 2. Wind Science and
Engineering Research Center, Texas Tech University, Lubbock,
TX, 111 pp.
Yang, T., Nadimpalli, K. and Cechet, R.P., 2014. Local wind
assessment in Australia: computation methodology for wind
multipliers, Record 2014/33, Geoscience Australia, Canberra.
http://dx.doi.org/10.11636/Record.2014.033
Acknowledgements
The State Emergency Service South Barwon branch for their
hospitality and keenness to assist the Bureau of Meteorology
with the damage assessment, access to affected areas, and
Requests for Assistance data.
The Metropolitan Fire Brigade for the access and use of drone
aerial photography that assisted with the damage assessments.
Daniel Hayward, storm researcher and amateur meteorologist,
for his willingness to provide information including
supplementary observations and photographic evidence.
The residents of Waurn Ponds and Mount Duneed who,
despite experiencing the frightening event that left damage
to their properties, were welcoming, allowed access to their
properties, and were incredibly helpful in providing the Bureau
of Meteorology information that greatly assisted and made this
damage assessment possible.