Sunday, January 10, 2016

Town of Yarloop destroyed in #Waroonafire #bushfire maelstrom

The Waroona bushfire South of Perth was started by lightning strike last Wednesday. It rapidly grew to be an uncontained uncontrollable fire of such size, ferocity and intensity that it produced pyrocumulus clouds creating it's own local convective weather.

On Thursday evening the bushfire raged through Yarloop, devestating the town and destroying 131 buildings. Most homes were lost, but also the pub, the post office, the hospital and primary school. Even the fire station didn't escape destruction. The remains of two people have been found in the burnt out wreckage of buildings.

On late Saturday afternoon the towns of Harvey, Cookernup, Wokalup and surrounding areas were threatened. Fire fighters fought the flames overnight to stop these towns under seige by the blaze.

By Sunday more than 72,657 hectares had been burnt, with the fire perimeter is in excess of 226km. Some 143 properties including 128 houses and other structures including sheds, caravans and community buildings have been confirmed lost. There are over 250 firefighters and support staff responding to the fire, using more than 50 appliances including 38 heavy machines. Local fire fighters have been joined by 68 personnel from New South Wales including 60 firefighters, 5 paramedic and 3 management support staff who flew in on Saturday evening and will assist local crews. The NSW fireys will provide some welcome respite for local firefighters.

Bushfires can impact infrastructure. The Waroona fire was heading southwest towards Myalup and may reach Binningup. At Binningup there is a Desalination plant which is a major source of potable water supply for both Perth and Bunbury. Electricity transmission has also been cut by the fire resulting in thousands of people losing power.

The two highways heading south from Perth were closed due to the bushfire which has caused some panic buying of petrol in some SW towns. A very long inland detour has been put in place around the fire affected area.

While bushfires are a product of local fire weather conditions, they are projected to be more frequent and intense due to climate change according to a February 2015 Climate Council report regarding the bushfire threat in Western Australia.

Fire generating own local weather system

Photo: Mandy Loveland/twitter

The Waroona fire is so large and intense it has generated it's own thunderstorm weather system resulting in dry lightning strikes and unpredictable wind vortices. Wikipedia describes the phenomena in the formation of Pyrocumulus and Pyrocumulonimbus clouds that we see with this fire.

Similar weather generating fires include the Grampians Bushfire in January 2014 (ABC report) and the particularly destructive Canberra Firestorm of 2003. (See Fromm et al (2006) in Geophysical Research letters: Violent pyro-convective storm devastates Australia's capital and pollutes the stratosphere) The Canberra Fire generated a very rare fire tornado, the only recorded example known to have ever exceeded F3 wind speeds on the Fujita scale.

An analysis of the 2007 Kangaroo Island Bushfires (South Australia) by Peace et al (2011) (PDF) concluded that:

"... vertical atmospheric dynamics and feedback processes frequently and significantly impact bushfires and prescribed burns in Australia. This repeatedly manifests as fire behaviour that would not be anticipated by consideration of the surface weather elements temperature, relative humidity and wind alone. In light of this evidence it is clear that Australian fire weather forecasting should place greater emphasis on vertical atmospheric profiles, convergence zones, dry air entrainment and low level stability."

In the Fromm et al (2010) paper in the American meteorological Society Bulletin on the Untold Story of Pyrocumulonimbus, it describes that injection of wildfire ash particles into the lower stratosphere is more common than previously thought and may have climate consequences: "When fires initiate or intensify towering thunderstorms, they can inject aerosols into the lower stratosphere that were once thought to originate only from volcanic plumes".

Sandra Stonehouse and her husband run a wildlife refuge in Yarloop and also have many valuable vintage cars and collectibles. They decided to stay and defend their house and sheds from the bushfire. They worked overnight and successfuly defended their property. But many of their neighbours made a decision to evacuate and their houses were destroyed by the fire. Hear her story at this ABC report.

Just to give you some temperature background during this fire, John Relf reported that for PERTH METRO, The mean min temp so far this month (1st to 8th January 2016) is 21.6°C (+3.5°C above the January average of 18.1°C). The min temp of 25.6°C recorded overnight was Perth Metro's hottest night since the 29.7°C on 12th January 2012. Perth Metro last recorded rainfall was over a month previous on 7th December (1.0 mm).

On 7th January Perth's maximum temperature was 43.0°C at Perth Airport, and 41.9 °C for Perth.

For Bunbury, the mean max temp so far this month (1st to 6th January 2015) is 33.8°C (+4.0°C above the January average of 29.8°C).

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