@article {bnh-6801, title = {Improved predictions of severe weather to reduce community impact}, number = {556}, year = {2020}, month = {03/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

The project has completed the second year of its refresh and is progressing with some challenges. The first 3{\textonehalf} years featured a strong focus on developing underpinning science in some important areas, notably the transport of embers by bushfire plumes, and understanding the origin of the moisture when pyrocumulus clouds form {\textendash} is it from the atmosphere, or from the fuel? We also conducted significant case studies, including an ensemble-based study of a severe east coast low, an analysis of the meteorology of the State Mine Fire of October 2013, and a study into tropical cyclone secondary eyewall formation.

This second phase of the project pivots towards utilization. We will not neglect investigations into the underpinning science, or case studies, but we are looking to turn our previous discoveries and knowledge gained into useful products.

The first of these is a new thermodynamic tool for predicting the potential for pyrocumulonimbus (pyroCb) formation, the Pyrocumulonimbus Firepower Threshold, or PFT. This parameter depends on the atmospheric state, both the wind strength within the boundary layer and the full thermodynamic profile and aims to predict the minimum fire power (in GW) that is necessary to trigger deep convection. In favourable conditions, a fire of a few GW suffices, and at unfavourable times, 1000 GW would be insufficient. We have found that there is substantial variability in the atmospheric favourability in time and space, and that observed pyroCb often form during a narrow window of opportunity. We are presently preparing for a major utilization exercise, a near-real time trial of the tool over the coming summer. We expect that the results from this trial will help to finalize the development of the tool, and ready it for operations.

Our case study of the tornado outbreak in South Australia that triggered events which cut power to the entire state showed that the tornado cluster was predictable by modern high-resolution numerical weather prediction (NWP) {\textendash} indeed, the deterministic model predicted the precise location of one of the observed tornadoes. Encouraged by this success, we ran a 6-member ensemble simulation of the event, which showed that while the probability of tornadoes was well over 50\%, the level and location of the activity was less certain. To assist with analysis of this event, we also developed a novel diagnostic of tornadic precursors in NWP systems. A journal article is almost ready for submission on this work.

A second case study is analyzing the Tathra bushfire on the south coast of New South Wales, which led to the destruction of over 60 houses. Although occurring in strong northwesterly winds in the lee of the ranges, mountain wave activity appears to have been modest at the time of the greatest fire activity and probably not the major cause of the disaster. Rather, the extreme fire behavior appears to have been driven by strong, very unsteady and fluctuating winds, caused by roll-like circulations in the flow off the ranges, with the interaction between this flow and a later wind change also of interest. The weak role of mountain waves in this event illustrates the value of performing detailed case studies, as at first glance, several of the ingredients for a mountain wave event were present, and indeed active earlier in the day.

Unfortunately, our development of a parameterization of long-range ember transport has made little progress this year, due to the unanticipated difficulty of the task and the illness of a staff member. We plan to resume work on that shortly.

In recognition of the delays on the ember transport parameterization, and also of new opportunities that have arisen in pyrocumulus prediction, we have negotiated an altered project schedule with the BNHCRC.

}, keywords = {community impact, predictions, Severe Weather}, issn = {556}, author = {Jeffrey Kepert and KJ Tory and Dragana Zovko-Rajak and David Wilke and Serena Schroeter} } @conference {bnh-6511, title = {A case study of South Australia{\textquoteright}s severe thunderstorm and tornado outbreak }, booktitle = {AFAC19 powered by INTERSCHUTZ - Bushfire and Natural Hazards CRC Research Forum}, year = {2019}, month = {12/2019}, publisher = {Australian Institute for Disaster Resilience}, organization = {Australian Institute for Disaster Resilience}, address = {Melbourne}, abstract = {

On September 28, 2016 one of the most significant thunderstorm outbreaks recorded in South Australia impacted central and eastern parts of the state. Multiple supercell thunderstorms were embedded in a Quasi-Linear Convective System aligned with a strong cold front that was associated with an intense low-pressure system. The storms produced at least seven tornadoes, destructive wind gusts, large hail and intense rainfall. Transmission lines were brought down in four different locations, which contributed to a state-wide power outage.

Accurate prediction and understanding of tornadoes and other hazards associated with severe thunderstorms is very important, for timely preparation and announcement of warnings. By conducting high-resolution simulations, this study aims to offer a better understanding of the meteorology of the South Australian thunderstorm and tornado outbreak. It also contributes to improving knowledge of how to best predict similar severe weather events, which in turn enables better risk management and preparedness for such events. Updraft
helicity, a severe storm surrogate that indicates the potential for updraft rotation in simulated storms, is used to investigate the ability of the model to predict supercell and tornado likelihood.

Download the full non-peer reviewed research proceedings\ from the Bushfire and Natural Hazards CRC Research Forumhere.

}, keywords = {modelling, risk management, Severe Weather, thunderstorm, tornado}, url = {https://knowledge.aidr.org.au/resources/australian-journal-of-emergency-management-monograph-series/}, author = {Dragana Zovko-Rajak and KJ Tory and Jeffrey Kepert} } @article {bnh-6311, title = {Community benefits of roof upgrades}, number = {528}, year = {2019}, month = {12/2019}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Legacy houses (Houses built Pre-1982) are at risk of damage from wind loads due to the often inadequate roof hold down provided by connection details. Improving wind resistance through replacing roof connections or retrofitting the existing structure can greatly improve building performance and community safety. The Queensland Government Household Resilience Program (HRP) provides funding to help eligible home owners improve the resilience of their homes against cyclones. This program developed with advice from the Cyclone Testing Station is managed by the Queensland Department of Housing \& Public Works (QDPWH) and commenced in late 2018.

}, keywords = {community resilience, cyclones, Emergency management, engineering, resilience, roof, Severe Weather}, issn = {528}, author = {Korah Parackal and John Ginger and David Henderson and Martin Wehner} } @article {bnh-5432, title = {Impact-Based Forecasting for the Coastal Zone: East Coast Lows- Annual Report 2017/2018}, number = {463}, year = {2019}, month = {03/2019}, pages = {1-28}, type = {Report}, keywords = {Built Environment, Forecasting, Severe Weather}, issn = {463}, author = {Harald Richter and Craig Arthur and Serena Schroeter and Martin Wehner and Jane Sexton and Beth Ebert and Mark Dunford and Jeffrey Kepert and Shoni Maguire and Russell Hay and Mark Edwards} }