End User representatives
This project is using high-resolution modelling, together with a range of meteorological data, to better understand and predict important meteorological natural hazards, including fire weather, tropical cyclones, severe thunderstorms and heavy rainfall. The outcomes from the project will contribute to reducing the impact and cost of these hazards on people, infrastructure, the economy and the environment.
Specific case studies undertaken include the New South Wales Blue Mountains bushfires of 2013; ember transport by fire plumes; pyrocumulus cloud simulation and prediction, and the NSW April 2015 East Coast Low.
The study has been developing understanding of how fire embers generated during bushfires can be lifted into the atmosphere and carried by winds ahead of a fire front, potentially starting new fires downwind. The team has undertaken simulations for ember transport for a wide range of wind speeds and ember fall speeds. It is important to consider a range of fall speeds, since different types of embers have different densities and aerodynamic properties which affect how far they are carried.
Plume modelling has also been utilised to study pyrocumulonimbus clouds (PyroCb). Intense fire plumes in suitably moist environments can lead to PyroCb development, with the possibility of strong downbursts which can exacerbate already extreme fire conditions. A survey of current understanding and forecast techniques has been completed, and the team will be working towards developing improved techniques.
Blue Mountains bushfire
A detailed case study of the Blue Mountains fires of October 2013 was undertaken, focusing on 17 October when some 200 houses were destroyed. Analysis uncovered a weather phenomenon known as mountain waves which contributed to the severe fire behaviour. Mountain waves are atmospheric oscillations that occur due to air flowing over hills or mountains. They can arise in several different ways, some more predictable than others. Often they cause strong downslope winds on the lee slope of the hill or mountain.
April 2015 East Coast Low
Collectively, the ensemble weather simulations accurately predicted the position and intensity of the low, the strong winds and the rainfall. The differences between them give insight as to the forecast uncertainty, the overall envelope of areas at some risk, and the areas at highest risk. The ensemble also enables insight into the processes that lead to the rapid intensification of these systems. The team is continuing to learn from ensemble simulations about predictability of East Coast Lows and how to use this information to benefit both forecasters and the emergency services.
Specific outcomes of this project will:
- Improve the scientific understanding of severe weather phenomena in Australia.
- Improve the knowledge of how to best predict these phenomena, including model configuration and interpretation.
- Contribute to the post-event analysis and lessons learned of selected severe events that occur during the course of the project.
- Inform the development of numerical weather prediction systems specifically for severe weather.
To improve our understanding of and ability to predict severe weather, including for bush fires, tropical cyclones, severe thunderstorms and heavy rainfall, through the use of high-resolution modelling in conjunction with available observations.
The Bureau of Meteorology seeks Australian collaborators to participate in a new 10-year international high impact weather project to develop improved hazard prediction capabilities. Its aims align on an international level with those of the Bushfire and Natural Hazards CRC.
High resolution simulations over the Blue Mountains Region on 17 October 2013 show several interesting meteorological features.
Large-eddy simulations of bushfire plumes are combined with firebrand trajectory calculations to estimate the effects of in-plume turbulence on firebrand transport. In-plume turbulence substantially lengthens the maximum spotting distance AND increases the lateral and longitudinal spread of firebrand landing positions.
Pyrocumulonimbus clouds have been linked to highly dangerous fire behaviour.
In favourable atmospheric conditions, large hot fires can produce pyrocumulus cloud: deep convective columns resembling conventional thunderstorms. These in turn may generate strong surface winds, dangerous downbursts and lightning strikes that may enhance fire spread rates and fire intensity, cause sudden changes in fire direction, and ignite additional fires.
Between 20-23 April 2015 the eastern coast of Australia was affected by a low-pressure system, known as an east coast low, which brought flooding, damaging winds and coastal erosion. This study utilises ensemble simulations to get a better understanding of the dynamics of this event, as well as its predictability. This is important for both forecasters and emergency services.
|Resilience to clustered disaster events on the coast - storm surge||Dr Scott Nichol||Geoscience Australia|
|Fire spread prediction across fuel types||Dr Khalid Moinuddin||Victoria University|
|Improving land dryness measures and forecasts||Dr Imtiaz Dharssi||Bureau of Meteorology|
|Improved predictions of severe weather to reduce community impact||Dr Jeff Kepert||Bureau of Meteorology|