Issue 54 march 2010 Cold-frontal bushfire winds and computer forecast models SUMMARY This photo was taken This research has developed a new model from a Firebird 303 JetRanger helicopter to better forecast cold fronts – and outcome over Lawloit, Victoria, that will help better protect communities and just after a recent firefighters. The work was completed through wildfire was hit by extensive study that has led to a better the downburst from a understanding of the complex phenomenon thunderstorm passing of cold fronts. This research has focused on by to the south. The downburst from the understanding two things. Firstly, the physical thunderstorm turned processes that cause cold-frontal wind the northerly flank changes to be what they are – why sometimes into a headfire - with they are abrupt, why sometimes more gradual, the typical pattern why some have sustained strong winds after from a line of fire of the change (Ash Wednesday 1983) and some about 5/6 headfire and 1/6 backing do not (Black Friday 1939). Secondly, how fire. The change in to verify forecasts of wind change timing at fire behaviour was observation sites and from computer forecast very dramatic, and models. increased risks to ground crews who BACKGROUND were positioned to Wind change matters to fire managers. It can the north of the fire. change bushfire activity in a moment, shifting Photo supplied by the flank of the fire to the fire front, suddenly Steve Grant, DSE Fire Management Officer. putting firefighters and communities at risk. A change in wind can also change the rate of fire spread, increase the quantity, distance and direction of downstream spotting, and change the safety status of residents and townships in a flash. There have been several notable ABOUT THIS PROJECT disasters associated with wind changes, Project A2.1: Fire Weather – Fire Danger is part including: of Bushfire CRC Program A: Safe Prevention, • the Mann Gulch Fire in Montana in 1949 Preparation and Suppression • the Ash Wednesday fires across south- Author: Dr Graham Mills (right) is a Bushfire CRC eastern Australia in 1983 Project Leader and Senior Researcher at the Bureau of Meteorology • the 1994 South Canyon fire in Colorado that killed 14 firefighters Acknowledgments: The research team includes Dr Graham Mills (project leader), Xin-Mei Huang • the 1998 Linton bushfires in Victoria, (Bushfire CRC researcher 2004-06), Yimin Ma where five volunteer firefighters (Bushfire CRC researcher 2007-09), and project perished in their vehicle after being collaborator Kevin Parkyn (Head, Severe Weather caught out by a sudden wind change Forecast Section, Victoria). • the fires in Ku-ring-gai Chase For more information about this research, visit the National Park in 2000 that led to Research page at www.bushfirecrc.com or contact the deaths of four National Parks Dr Graham Mills at [email protected] and Wildlife Service staff and the serious injury of three others when

© Bushfire CRC Ltd 2010 1 Figure 1: A wind change forecast chart.

a routine hazard reduction burn time that, as far as possible, match the Applying the model went wrong changes interpreted by the meteorologist’s Very high resolution computer model • the 2005 fires on the Eyre Peninsula verification. This turned out to be a forecasts (mesoscale numerical weather in South Australia that killed nine challenge, as wind changes differ widely in prediction (NWP) models) have been members of the public caught out their intensity, even on the same day. The developed at the Bureau of Meteorology and by sudden changes in the bushfire research developed a Wind Change Rate provide vital guidance to forecasters. behaviour Index (WCRI), which represents the rate of These models predict the wind speed and change of wind direction with time. • the recent Black Saturday fires in direction, temperature, humidity, and Victoria in February 2009 However, because a wind change is more pressure at every gridpoint (a regular lattice • the deaths of several Spanish firefighters significant as the wind speed becomes approximately every five kilometres) every in July 2009. stronger, the wind speed is included in the hour. If these forecasts are considered as a BUSHFIRE CRC RESEARCH calculation of the WCRI. As wind speeds can time series of observations, then a WCRI can be strong before and after the change, and as be calculated at every gridpoint every hour. Verifying wind change forecast charts there is often a lull at the change time, these This has two applications: Due to the importance of wind change on fire decisions were highly complex. By fine tuning • The time of maximum wind change can behaviour, the Bureau of Meteorology offices the algorithm it was able to estimate times in several Australian states have for many be estimated at a gridpoint closest to that compared favourably with the times an observation site and the numerical seasons issued Wind Change Forecast charts estimated by the experienced meteorologists. (Figure 1). Since 2000 the Bureau’s Victorian forecasts of wind change time verified. Regional Forecast Centre has manually One of the by-products of this algorithm is • A spatial field of WCRI can be verified its wind change forecast charts at that not only is a time of maximum wind generated, and animated in time to selected stations at the end of the fire season. change produced, but the algorithm also provide a powerful visual display of the This verification requires an experienced estimates a change start time and a change wind change and the way it develops, as meteorologist who uses the time series of end time, which suggests that the concept of a it is forecast to move across a region. observations from the verification location, wind change period may have some merit. Such a spatial field of WCRI is illustrated in together with a series of detailed spatial When subjective estimates from experienced Figures 2A and 2B, which show a simulation analyses (‘weather maps’) to estimate a single meteorologists and objective times from the of the cool change on Ash Wednesday 1983. wind change time, which is then compared algorithm were compared, it showed that In these panels the barbs show the direction with the forecasts. This process is demanding over four Victorian fire seasons the subjective and speed of the 10m wind, while the shading and time-consuming. and objective times were within half an hour shows the WCRI, with increasingly dark It was the aim of this research project on greater than 60 percent of occasions, and colours indicating a stronger wind change to develop algorithms to automate this within 2.5 hours on greater than 85 percent of in terms of change in direction and higher process – from the sequence of half-hourly occasions. The subjective time was within the speeds. The first panel shows the simulation observations at a site on a ‘wind change objective wind change period on greater than for 4pm EDST (3:30pm CDST), with the day’, to determine a single wind change 95 percent of occasions. frontal wind change approaching Adelaide,

2 Figure 2A & 2B: Ash Wednesday cool change simulation, according to the Wind Change Rate Index. and just beginning to intensify along the RESEARCH OUTCOMES/ADOPTION western Victorian coastline. The second panel end user statement The project team has run the software at the shows the situation five hours later with a “Sudden wind changes and associated end of the past two fire seasons (2007-08 and much more intense change approaching increase in bushfire behaviour has 2008-09) and provided objective verification Melbourne. data to the Victorian Regional Forecast contributed to the deaths or serious Centre. These have been used in its end-of- When forecasters use NWP model guidance long-term injury to those living in season forecast verification. they have to decide whether to “go” with the bushfire prone environments as well guidance, or whether to make some allowance as firefighters. The scientific research The spatial WCRI forecasts have been made for possible error. Knowing the biases and available to forecasters since the 2006-07 fire undertaken in this project provides the error characteristics of the model forecasts season, and form important part of the fire scientists and fire managers with an helps this decision. The verifications of this weather guidance. The project has received research show that the issued forecasts are understanding of this form of complex enthusiastic endorsement of this form of largely unbiased with time (neither too slow weather phenomena influencing fire forecast guidance and the product has been nor too fast on average), and that more than behaviour. The research developed a included in the Bureau’s new Graphical 60 percent are within 2.5 hours, for forecast Wind Change Rate Index (WCRI). The Forecast Editor system that was implemented lead times between nine and 36 hours. accurate forecasting of wind changes in the Victorian Regional Forecast Centre in late 2008. Cool changes and bad fire days together with the WCRI will provide A further aspect of the study was to fire managers with critical information A software package has been developed that understand how cool changes in disastrous for the planning and execution of will allow the verification of the fire weather fire event days differentiate from cool the most appropriate strategy and forecaster’s wind change forecast to be run by the Bureau’s regional offices. This package, changes on more regular fire weather days. tactical resourcing for firefighter and which runs on the Bureau’s workstations, The re-examination of the Ash Wednesday community safety.” fire event revealed that a characteristic of the takes a tabulated set of forecast wind change most extreme days, and those on which the – Russell Rees, Chief Officer, Country times at a set of observing stations, extracts majority of bushfire deaths in south-eastern Fire Authority (Victoria) observational data at those stations from the Australia in the past 45 years have occurred, Bureau’s archives, extracts numerical weather prediction model data from another archive, is the strength of the front at around 1.5 km A diagnostic tool that allows the strength and computer verification statistics for both above the land surface. Many of summertime of any front to be put in historical context the official forecasts and for the corresponding cool changes are relatively shallow, but those has been developed by this project. This such as that of Ash Wednesday, the day of numerical forecasts. It takes less than an hour is illustrated in Figure 3, which shows a the Hobart fires in 1967, the Streatham fires to install and set up. A user’s guide is being scatterplot of twice-daily summertime values in western Victoria, 1977, the fires on Lower finalised. at 1.5 km of temperature gradient and highest Eyre Peninsula in South Australia in 2005, This study has provided a better temperature in a box over south-eastern and the Victorian Black Saturday fires in understanding on how fronts intensify on Australia over 46 years. The major events such February 2009 are characterised by strong the Victorian coastline and then surge along temperature gradients and high temperatures as Ash Wednesday (1983), Black Saturday the coast. This understanding has been at 1.5 km elevation ahead of the front. This (2009), and Hobart (1967) are highlighted, included in training sessions for US fire indicates a deep strong front that tends to and indicate the meteorological rarity and the weather forecasters, and also in an Advanced have strong winds both before and after the significance of these events – they lie in the Forecaster Workshop attended by forecasters wind change. outer fringes of the total distribution. from all states.

3 Background briefings on emerging issues for fire managers from AFAC and Bushfire CRC. 3 Issue 46: Fires drive major shifts in CO2 Fire Notes: index emissions from sub-alpine woodlands and Download at www.bushfirecrc.com/publications/fire_note.html grasslands. Summary of a scientific paper currently in press for the journal Global Issue 1: Using chemicals in firefighting Issue 27: Community vulnerability tested in Change Biology. operations. 2003 bushfires. Josh Whittaker’s PhD research Issue 47: Plants and fire: survival in Issue 2: The use of prescribed fire in bushfire on communities and the 2003 alpine fires. the bush. This research investigates the control. Issue 28: Fire and Cattle: Impacts on High composition of plants with different fire Issue 3: Smoke and the Control of Bushfires. Country. HighFire project. response traits across a mountainous region of Issue 4: Climate change and its impact on Issue 29: Driving the Prepardeness Message south-eastern Australia, and the role fire plays the management of bushfire. Home. Tim Prior’s PhD research. in these patterns. Issue 5: Seasonal bushfire assessment 2006- Issue 30: Bushfire smoke research – progress Issue 48: Historical patterns of bushfire in 2007. report. Impacts on firefighters and ecological southern Western Australia. Understanding Issue 6: Shifting risk and responsibilities – issues. historical variation in bushfire patterns in the balancing exercise. Issue 31: Remote sensing. Remote sensing of southern Western Australia, to provide a Issue 7: The stay and defend your property forest canopies to quantify burn severity. baseline for future fire regime comparison. or go early policy. Issue 32: Fire Management of the High Issue 49: Forest Flammability – How fire Issue 8: Guidance for people in vehicles Country: A Critical Review of the Science. works and what it means for fuel control. during a bushfires. Issue 33: Planning and Evaluating Forest Flammability is a next-generation fire Issue 9: Understanding communities – Community Safety Programs. behaviour model that reveals the complex links Living with Bushfire: The Thuringowa Issue 34: Seasonal Bushfire Outlook - between fire behaviour and forest ecology. bushfire case study. northern Australia 2009-10. Issue 50: Effectiveness and efficiency of Issue 10: An integrated approach to bushfire Issue 35: Competing Demands for aerial fire fighting in Australia. Bushfire management. Volunteers. Family versus volunteer CRC research examining the practical Issue 11: Recruiting young fire service emergency service work. effectiveness and economic efficiency of aerial volunteers. firefighting in Australia. Issue 36 : Aboriginal Wetland Burning in Issue 12: Firefighter’s exposure to air toxics Kakadu. Burning for biodiversity through Issue 51: Assessing Grassland Curing by during prescribed burns. traditional fire management. Satellite. To improve the assessment of Issue 13: Tree decline in the absence of fire. grassland curing in Australia and NZ, this Issue 37: Eucalypt Decline in the Absence Issue 14: Seasonal bushfire assessment 2007- research developed an improved algorithm of Fire. A study on the premature decline of 2008. . using Moderate Resolution Imaging eucaplyt forests. Issue 15: Bushfire community education Spectroradiometer satellite data. Issue 38: Assessing Aerial Suppression Drop programs. Issue 52: Bushfire Safety for People with Effectiveness. Evaluation of Air Suppression Issue 16: Billo Road Plantation Fire. Special Needs. This study looked at how Techniques and Guidelines. Issue 17: Trends in bushfire arson. households with special needs prepared for Issue 39: Southern Seasonal Bushfire Issue 18: Fuel Moisture and fuel dynamics in and met the challenge of a fire event, and Assessment 2009-10. Summary of fire woodland and heathland vegetation. how community education programs could potential outlook. Issue 19: Measuring responses to fire improve their preparedness. Issue 40: Exploring the Bushfire Experience regimes in northern Australia. Issue 53: Determining grassland fire danger From a Domestic Perspective. A case study Issue 20: Awareness of bushfire risk. with plant models. This project addresses of the Wangary fire. Tamborine Mountain Case Study, the rate of natural die-off in common Issue 41: Investigating perceived teamwork Understanding Communities. grass species and provides a way to adapt effectiveness in Incident Management Issue 21: Bushfire Smoke and Public Health. agricultural modelling to predict curing rates Teams. Enhancing Emergency Incident A collation of publicly available information across temperate grasslands. Management Team Effectiveness and on health issues related to bushfire smoke. Organisational Learning. Issue 22: Keeping your recruits – boosting Fire Note is published jointly by the volunteer retention. Summary report of two Issue 42: Observing Teamwork in Bushfire Cooperative Research Centre studies. Emergency Management. This research (Bushfire CRC) and the Australasian project focused on understanding Issue 23: Recruiting and retaining women Fire and Emergency Service Authorities information flows and incident management fire service volunteers. A summary report Council (AFAC). of four studies on female participation as team effectiveness. Bushfire Cooperative Research Centre volunteers. Issue 43: Fitness For Duty: Legislative Level 5/340 Albert Street, East Issue 24: Seasonal bushfire outlook – and Scientific Considerations. Project D.1 Melbourne VIC 3002 National 2008-09. Australian fire season Firefighter Health, Safety and Well-being on Telephone: 03 9412 9600 outlook 2008-09: summary. the Fireground. www.bushfirecrc.com Issue 25: Climate change and its impact on Issue 44: How Human Factors Drive Australasian Fire and Emergency Service the management of bushfire (updated). An Decisions At Fire Ground Level. Project Authorities Council update of Fire Note 4 with an emphasis on D2.3 Safe Behaviour and Decision Making. Level 5/340 Albert Street, East research directions. Issue 45: Organising For High Reliability Melbourne VIC 3002 Issue 26: Burning under young eucalypts. In Emergency Management: An Empirical Telephone: 03 9418 2388 Phil Lacy’s PhD research on fuel management Link. Project D5, Information Flow and www.afac.com.au in eucalyptus plantations. Incident Management Team.

4 Background briefings on emerging issues for fire managers from AFAC and Bushfire CRC.