BAMOS
Jun 2020
25
Figure 4: Google Earth aerial view of the location of damage
indicator 9 (blue marker), along with photographic evidence of the
damage inflicted (insets).
Figure 5: Google Earth aerial view of the location of damage
indicator 10 (blue marker), along with photographic evidence of
the damage inflicted (insets).
Daniel Hayward from an under‐development housing estate
along Boundary Road, Mount Duneed (Figure 5) which
was consistent with those presented in the media from the
same location. A large amount of debris emanating from
house construction sites to the immediate north was strewn
throughout the trees and vegetation, including larger and
heavier items such as air conditioning units, whitegoods,
and fencing. Some debris was evident to have been wrapped
around tree branches and trunks. A few trees were snapped
at the trunks including those of reasonable girth, along with
branches aloft.
Based on the Degree of Damage descriptors in Table 3, DOD 4
“trunks snapped” is satisfied suggesting a 3‐second wind gust
speed range of 150–216 km/h with an ‘expected’ wind gust
speed of 172 km/h.
There also appeared to be some evidence of debarking as well
as local debarking associated with debris scars which would
qualify for DOD 5 “trees debarked with only stubs of largest
branches remaining” being partially satisfied and pushing
the tornado intensity into the EF2 range. Some of the trees
appeared to have smooth textured mottled bark which makes
the identification of debarking difficult and reliant upon the
comparison between possible debarked trees with debris
impact scars and non‐debarked trees. Given these difficulties,
the reliance upon secondary information, and only one damage
indicator suggesting such intensity, the tornado intensity rating
for this damage indicator remained within the upper bounds of
the EF1 intensity rating but noting the possibility of extending
into the EF2 intensity rating. Consequently, the ‘expected’ wind
gust speed for these two damage indicators within, and thus
the tornado intensity rating based upon the observed damage
being, an EF1 rating from Table 1 with estimated 3‐second wind
gust speeds of 138–178 km/h.
DOD Damage Description Expected 3‐second
Wind Gust Speed
(km/h)
Lower Bound
3‐second Wind
Gust Speed (km/h)
Upper Bound
3‐second Wind Gust
Speed (km/h)
1 Small limbs broken (up to 2.5 cm diameter) 97 77 116
2 Large branches broken (2.5–7.6 cm diameter) 119 98 142
3 Trees uprooted 151 122 190
4 Trunks snapped 172 150 216
5 Trees debarked with only stubs of largest branches remaining 230 198 269
Table 3: Degree of Damage (DOD) categories and descriptors for the 'Hardwood Trees (TH)' Damage
Indicator and associated 3‐second estimated wind gust speeds adapted from McDonald and Mehta
(2004) and converted to metric units.