


Eucalyptus species trees have resins and oils in their leaves and wood that makes them burn very intensely. The combination of this, with the high fuel loading that occurs in the moister areas of Victoria and New South Wales, and the occasional extreme summer desert heat-waves, gives these areas the dubious distinction of having the greatest potential fire danger in the entire World.
When I arrived in Sydney to start my work assignment in mid-December, I was told by the staff there, that a slow season was expected, because it was not an "El-Nino" year, http://en.wikipedia.org/wiki/El_nino. And, sure enough, the last two weeks of December (equivalent of course to June in the northern hemisphere), were fairly cool and moist in New South Wales and Victoria. But, during January, short-term warm spells became more frequent and warmer, and I had to issue many Fire Weather Warnings during the first three weeks, when I was working there. My last day in Sydney, 1/24/09, was in fact, extremely hot, 40C (104F) or so, with gusty west winds blowing the hot continental desert air from west of the Blue Mountains, east over the city. So hot for me, that my personal warning lights were flashing, i.e., even with only minimal exertion, I was overheating.
Why did this happen, and what can be learned from this tragedy?
These graphics show the departure from average of maximum temperatures during the two stages of the heat wave.
27-31 January, and...
the hottest day ever recorded at many sites in Victoria, 07 February.

The presence of a slow-moving high pressure system in the Tasman Sea, combined with an active monsoon trough, provided the conditions for dry hot air of tropical origin to be directed over the southern parts of the continent. On Saturday strong northerly winds, ahead of an approaching cooler south-westerly change, brought this hot air to southern Victoria. The combination of strong and gusty winds, low humidity and record high temperatures led to extreme fire conditions ahead of the change, while the change in wind direction exacerbated the dangers in fire behaviour.
The day was mostly sunny throughout Victoria, although some mid-level cloud did affect the southwest coast. The most extreme weather conditions were observed in the afternoon shortly ahead of the wind change. Maximum temperatures were up to 23 degrees (Celsius!) above the February average, and for many centres it was the hottest day on record. Melbourne city recorded 46.4°C, its highest maximum temperature since records began. Other places in the Port Phillip region recorded even higher temperatures including Avalon, which recorded 47.9°C. Victoria’s highest official recorded temperature on Saturday was 48.8°C (120 F) at Hopetoun in the Mallee region.

Wind gusts to 115 km/h were reported at Mt William and Mt Gellibrand, while gusts over 90 km/h were recorded at a number of sites including Port Fairy, Aireys Inlet, Kilmore Gap, Dunns Hill and Mt Hotham. After the change wind speeds in excess of 50 km/h continued to be observed for some hours."
What was it like for those who were trapped, or decided to try and save their home? The following is an eyewitness account:
"They warn you it comes fast. But the word fast doesn't come anywhere near describing it. It comes at you like a runaway train. One minute you are preparing, the next you are fighting for your home. Then you are fighting for your life. But it is not minutes that come between. It'

For 25 years we had lived on our hilltop in St Andrews, in the hills northeast of Melbourne. You prepare like they tell you every summer. You clear. You slash. You prime your fire pump. For 25 years fires were something that you watched in the distance. Until Saturday. We had been watching the massive plume of smoke in the distance from the fire near Kilmore all afternoon; secure in the knowledge it was too far away to pose a danger. Then suddenly there is smoke and flames across the valley, about a kilometre to the northwest, being driven towards you by the wind.
I feel the radiant heat burning the back of my hand. The CFA training comes back again. Radiant heat kills. The three of us are inside the car. I turn the key. It starts. We turn on the airconditioning and I reverse a little further away from the burning building. The flames are wrapped around the full fuel tank of the other car and I worry about it exploding. We watch our home - our lives, everything we own - blazing fiercely just metres away. The heat builds. We try to drive down our driveway, but fallen branches block the way. I reverse back towards the house, but my wife warns me sheets of red-hot roofing metal are blowing towards us. I drive back down, pushing the car through the branches. Further down the 400m drive, the flames have passed. But at the bottom, trees are burning. We sit in the open, motor running and air-conditioner turned on full. Behind us our home is aflame. We calmly watch from our hilltop, trapped in the sanctuary of our car, as first the house of one neighbour, then another, then another go up in flames. One takes an agonisingly slow time to go, as the flames take a tenuous grip at one end and work their way slowly along the roof. Another at the bottom of our hill, more than 100 years old and made of imported North American timber, explodes quickly in a plume of dark smoke. All the while the car is being buffeted and battered by a galeforce wind and bombarded by a hail of blackened material. They sound like rocks hitting the car. The house of our nearest neighbour, David, who owns a vineyard, has so far escaped. But a portable office attached to one wall is billowing smoke. I leave the safety of the car and cross the fence. Where is the CFA, he frantically asks. With the CFA's help, perhaps he can save his house. I tell him we had already rung 000, before our own house burnt. Too man

I walk back towards our own house in a forlorn hope that by some miracle our missing dog may have survived in some unburned corner of the building. Our home, everything we were, is a burning, twisted, blackened jumble. Through a gap in the back brick wall that used to be our bedroom window I see blackened mattress springs. Our missing dog Gizmo, Bobby our grumpy cockatoo, Zena the rescued galah that spoke Greek and imitated my whistle to call the dogs, our free-flying budgie nicknamed Lucky because he escaped a previous bushfire, are all gone. Killed in the inferno that almost claimed us as well. I return to the car and spot the flashing lights of a CFA tanker through the blackened trees across the road. We drive down the freeway, I pull clear more fallen branches and we reach the main road. I walk across the road to the tanker and tell them if they are quick they might help David save his house. I still don't know if they did. We stop at a police checkpoint down the hill. They ask us where we've come from and what's happening up the road. I tell them there's no longer anything up the road. We stop at the local CFA station in St Andrews. Two figures sit hunched, covered by wet towels for their serious burns. More neighbours. We hear that one old friend is missing. A nurse wraps wet towels around superficial burns on my wife's leg and my hand. We drive to my brother's house, which fate had spared, on the other side of town. The thought occurs to me - where do you start when you've lost everything? It doesn't matter. We escaped with our lives. Just. So many others didn't."
Gary Hughes is a senior reporter for The Australian
So, to sum up what happened in February, 2009 in Victoria, ten years of drought conditions, combined with an unprecedented heat wave, led to Australia's worst ever natural disaster, in terms of fatalities.
This area of California had been in a record-breaking drought that winter/spring; almost no rain fell in March, which is usually the last wet month of their winter-rainfall season. Very little occurred also in April and May (it gets drier there by May normally anyway), such that by June, fire danger indices were at record high levels. This, combined with a weather day when exceedingly dry air aloft was mixed down to the surface under strong high pressure ridging, combined with terrain interactions, led to the extreme fire behaviour, manifesting as a rotating plume, or firewhirl. It was highly fortunate that there were no fatalities.
Many veteran wildfire specialists I have spoken with have told me that they are seeing more intense fire behaviour throughout the western U.S., than say, 20 to 30 years ago. Fires are burning more intensely, and more often, through the night. This is due to the long-term droughts the western U.S. has been experiencing, killing large swaths of forest stands, combined with warmer summer temperatures caused by stronger high pressure systems (which also contain very dry air).

When forecasting weather, meteorologists assess temperatures, humidities, and winds at different standard levels of the atmosphere, which are measured twice-daily world-wide by radiosonde balloons. This data is input to the Numerical Weather Prediction models, which model the atmosphere through hundreds of quantitative descriptors of physical processes, using trillions of calculations per second, on supercomputers. These models generate forecast charts out to ten days of various levels in the atmosphere (though only the first 3-5 days of course are usually very accurate). One of these standard levels that is assessed is 850 millibars (mb). The main parameter assessed is the height at which the pressure equals 850 mb, which is a function of temperature. The warmer the airmass, the higher that height is, and the colder, the lower it is. This level is usually around 1450-1550 metres (4600-5100) feet here in Alaska.
The most active several days during the record-breaking 2004 Alaska fire season were during a northeast-wind event in late June and early July. 850 mb temperatures at this time were around 16C (61F). Remember, this is at 1500 metres. When air is forced to descend, as it does during high-pressure ridging episodes like the northeast wind-event of late June/early July 2004, it warms at 10 degrees C per 1000 metres. Thus, if the 16C air at 1500 metres descends to near sea level (much of the Alaska interior is at elevations of only 60-250 metres msl), it would theoretically warm to 31C (88F). Factor in solar heating of the ground, and you can add a degree or two. Temperatures weren't quite that warm on those days in 2004, because thick smoke blown out ahead of the fires shaded the region, and kept temperatures 3-6C cooler.

What does this mean for interior Alaska? Well, if we currently could experience a 20C temperature at 850 mb during an extreme warm spell/high pressure ridging episode, in 2050, that would likely be 23C, or more, in a similar event. That would translate to lower-elevation temperatures in the mid 30s to low 40s C (mid 90s to mid 100s F)! In addition, if the average may-august summer temperatures around Fairbanks warm from the current 13C or so, to 16C, the health of the spruce forests will be compromised. White and black spruce in the Alaska boreal forests shut down their growth when average growing-season temperatures reach 16C, and become vulnerable to insect predation and disease mortality. So, with temperatures in the 30s to low 40s C, and large swaths of dead and dying spruce trees, in another 2004-like drought year, I think it would be safe to say that unprecedented fire behaviour would occur. It's not a matter of if, but when this will occur.