[LINK] Bush Fire Speeds (was Re: home emergencies)

[Roger Clarke]

My memory is of people referring to the speed of the fire-storm (i.e. 
the peak, as it hit) as being 200kph, comprising a nor'-wester of 
about 100kph plus the effect of the running, mixed eucalyptus-oil / 
mature-radiata-oil explosion.

The story was that fully-grown (1 metre girth) trees at the top of 
Doyle Terrace were snapped at half-height as the front was driven by 
the topography into a tight circle.

There's nothing specific in this otherwise excellent resource, 
although the animated map gives a frightening clue:
http://en.wikipedia.org/wiki/2003_Canberra_bushfires

The Coroner's Report is at:
http://www.courts.act.gov.au/BushfireInquiry/The_Canberra_Firestorm_Report/The_Canberra_Firestorm_Report.htm

The events of the day are recounted in s.5.14 starting on p.310 of 
the complete Vol. 1 (2.5MB):
http://www.courts.act.gov.au/BushfireInquiry/The_Canberra_Firestorm_Report/The%20Canberra%20Firestorm%20(VOL%20I).pdf

[After doing pretty well in making the document available, they 
botched it by blocking copying!  Tom, where are you?!]

The forecast was 40 degrees, with 35-40kph winds gusting to 55-60kph 
on the ridges (p. 321).

At 13:45, the wind at Tidbinbilla (10km west) was 35-60 with gusts 
over 70, and at Gibraltar Homestead (nearby) a tornado-strength 
whirlwind destroyed a cottage and blew in the windows of a utility 
(p. 347).

At around 13:40 the wind speed in Canberra lifted from 35 to 55 (p. 349).

In one location in the NW, the wind strength in the tornado was 
estimated to be in excess of 200kph and snapped off trees two or 
three metres above the ground (p. 350).

The main fire was moving at 20kph [that's the speed of the winner of 
the Sydney Olympics Marathon, which was won in record time], the 
fastest documented rate of spread of a forest fire to that writer's 
knowledge.  Even in grassland it was running at 11kph [a decent jog] 
(p. 350-351).

__________________________________________________________________________

At 10:48 +1100 20/2/09, Sylvano wrote:
>On Fri, February 20, 2009 9:41 am, Danny Yee wrote:
>>  Ash Nallawalla wrote:
>>>  > Mr Ropar, sobbing at times, said it took just two minutes for the
>>>  > flames to travel 20km, roar up the Sherwin Ranges and explode over the
>>>  > top.
>>>
>>>  Which was calculated by Karl to be 600 km/h.
>>
>>  Is that completely impossible?  With a crown fire spreading by radiant
>>  heat, I don't see why the wind speed is necessarily a limitation.
>
>Most things I've found, mention speeds of 5 to 10 km/h
>
>According to the CSIRO bushfire safety tips fact sheet 2008
>http://www.publish.csiro.au/samples/Essential%20Bushfire%20Tips%20sample.pdf
>
>Fastest known fire front speeds:
>- Grass Fires: 22km/h
>- Forest Fires: 15km/h
>
>But of course that's different to travelling embers, which the fact sheet
>says that from eucalypt fires they can travel up to 8km or more, depending
>on convection patterns.
>
>Sylvano
>--
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-- 
Roger Clarke                                 http://www.rogerclarke.com/

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