Fire escalation by downslope winds

One of the most challenging situations in fire management is when relatively benign weather conditions are expected, but a severe fire eventuates. These situations can result in significant loss of property or even life. Identifying the cause of such incorrect expectations can help to prevent them from recurring in the future.

Hazard Note 24 investigates the meteorology of several recent cases where unexpectedly severe fire behaviour has occurred. In the three bushfires discussed, a weather phenomenon known as mountain waves has contributed to the severe fire behaviour (the State Mine fire, New South Wales, 2013, the Margaret River fire, Western Australia, 2011 and the Aberfeldy fire, Victoria, 2013). Mountain waves are atmospheric oscillations which 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. If a fire is present, it may become unexpectedly severe as a result.

This research has investigated the meteorology of several recent cases where unexpectedly severe fire behaviour has occurred. In the three bushfires discussed, mountain wave activity seems to be at least part of the cause.

Download the Hazard Note at www.bnhcrc.com.au/hazardnotes/24