Forecasts and Warnings Bureau of Meteorology Western Australia Introduction Implementation - October 2012. The Bureau of Meteorology is implementing a new forecasting system aimed at expanding and improving services to the Western Australian public. The system allows the Bureau's forecasters to develop 7 day forecasts graphically, by "painting" the forecasts on their screen. Forecasters then save the information into a database which provides detail of the weather every 6km in a grid across the state. The information stored in this database is then used to automatically generate text forecasts thereby enabling the Bureau to produce 7 day forecasts for many more locations than before. The new system allows forecasters to input their local knowledge and account for important small scale phenomena not simulated in automated systems and thereby provide the best possible forecast for the community.

GFDI Sensitivity to wind speed and curing Difficulty measuring low humidity

GFDI Strong gradients

Current Fire Weather Policy Agreed by fire agencies and BoM Max FDR/FDI = highest FDI: 6am-midnight For at least one hour Covering at least 10% of the subdistrict

Fire Weather Service Fire Weather Forecasts - Summary The summary page contains key forecast information for each fire weather sub-district. District GFDI – is the representative peak FDI in the district. 10% of the district has a maximum FDI higher than this value. Think of it as the 90th percentile value. Forest Fire Danger Index (FFDI) may be introduced in the future for sub-districts which include forested areas. This will be determined through consultation with FESA and DEC.

Fire Weather Service Fire Weather Forecasts – District Weather Elements

Fire Weather Service Fire Weather Forecasts – Detailed District Forecast Significant GFDI thresholds based on the thresholds for Very High (32), Severe (50), Extreme (75) and Catastrophic (100) Fire Danger Ratings (Indices) in Western Australia.

Fire Weather Service Fire Weather Warnings Fire Weather Warnings will be issued at any time of the year, for any sub-district where the Fire Danger Rating is assessed as Severe, Extreme or Catastrophic. This will highlight dangerous fire weather conditions that occur outside the typical fire season.

4 day outlook GFDI (left) and FFDI (right) A series of static images similar to the one on the slide above may be provided to fire agencies on the registered users web page. The number of images, layout and design are yet to be finalised. The example above shows the spatial variation of maximum grassland fire danger index over Western Australia. These static images must be used in conjunction with official fire weather forecasts and warnings.

FWS Forecasting Limitations: Hides forecast uncertainty. May encourage false confidence in an exact solution. i.e. Creates a false expectation that the FDI value at a specific point is exactly what will happen. McArthur meters are very sensitive at higher values. On “blow up” days small changes in weather result in big changes to GFDI.

Fire Danger Index Uncertainty Any forecast FDI value should be considered as a central value within a spread of FDI values, which reflect the inherent precision of the input variables.

Fire Danger Index Uncertainty The table below provides an example of the spread of GFDI associated with selected values of GFDI, based on a temperature of 40oC and a relative humidity of 8% and precision levels of the input variables of: Temperature + / - 1 degree Celsius Relative humidity + / - 2 percent Wind speed + / - 3 km/h Scenario T = 40 oC +/- 1 oC RH = 8 % +/- 2 % Wind +/- 3 km/h Central GFDI value GFDI range (Fuel Load - 4.5 tonnes/ha) 50 40 – 65 75 55 – 100 100 80 – 130 150 120 -190

Fire Weather Service Spot Fire Forecasts Short Term Spot Fire Forecasts A short term (12 hour) forecast will be provided upon request for bushfires and prescribed burns. There is the option for an 18 or 24 hour forecast. 3 hourly forecast time steps of fire weather elements will be provided in tabular form. An outlook for the following 2 days will also be provided.

Fire Weather Service Spot Fire Forecasts Long Term Spot Fire Forecasts The Spot Fire Forecast (4 day) is for planning, not for tactical decision making. 0900 and 1500 forecast of fire weather elements will be provided in tabular form for 4 days. Curing taken from the sub-district value. This can be changed on request to match local conditions. 4-day spot forecasts are not updated/amended. They are only valid at time of issue.

Fire Weather Service Spot Fire Forecast Request A copy of the final version will be placed on the FESA/DEC registered user web page around the time of the NexGenFWS implementation. We strongly encourage the fire agencies to provide weather observations from the fire site. This will assist in ground truthing model guidance and will improve the quality of the spot fire forecast.

Fire Weather Service Spot Fire Forecast Short Term Fuel Type will change to Not Required. Only GFDI will be provided, at this stage, as agreed to by FESA and DEC. Once an incident is over, BoM would appreciate being notified (through the fire weather forecaster or SOCMET). Spot Fire Forecasts are continually monitored (and are updated if amendment criteria are met) by BoM and/or SOCMET.

NexGenFWS Fire Weather Service Spot Fire Forecast Long Term This forecast is for longer term planning purposes and will not be closely monitored.

Further Information Bureau of Meteorology web site: http://www.bom.gov.au FESA/DPaW Registered User Web Page - http://reg.bom.gov.au/reguser/ Bureau of Meteorology – Severe Weather Section sevwx_wa@bom.gov.au, 9263 2222.