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Coastal heathland next to homes at Evans Head, northern New South Wales, burns with ferocious intensity on September 9. This particular heath hadn't burned for 20 years before a firebug took advantage of very dry conditions and a heavy fuel load in the bush. Images © Jamie Brown/weather-wise.com In the line of fire A play-by play account of how dry and volatile September 13, 2000 Four days after burning heathland came within a stone’s throw of the northern New South Wales’ coastal township of Evans Head, smoke continues to billow above the scrub. The fire burnt out hundreds of hectares, a relatively small fire on the scale of Australian wildfires, but heathland burns hotter and more savagely than anywhere else on the planet. The rosy glow in the sky on the fire’s first night and the choking smoke in the days that followed proved that point. The blaze was started on purpose, the cruel joke of some firebug - the vast majority of fires this season were lit on purpose, or were created by accident. According to local fire control officer Boyd Townsend, volunteer fire crews responded to the call quickly and tried in vain to stop the front of the fire advancing south into national park bordering the town. Crews tried to douse flames by running hoses over burnt country and around the flanks of the fire, to fight the very front of the main blaze. But within an hour flames were burning into the tree tops - crowning - leaping over a gravel road and into a heathland swamp. Shifting winds During the day, a north-east seabreeze blew the fire at ground level southwards into remote parkland - a 30km stretch of protected coastal heath, one of the largest areas in the State. But the billowing smoke also told another story of the wind. As the clouds of burning ash rose, its direction curved around from billowing to the south, to blowing eastwards - out to sea indicating a westerly air stream just above the influence of the localised, coastal seabreeze. Wicked westerlies For the preceding two weeks westerly winds blew unabated. They fanned hundreds of fires from the central coast of NSW to Queensland’s Fraser Coast and west onto the Great Dividing Range What firefighters in Evans Head were to find out, was how a small shift in wind can bring about big changes to a fire fighting plan. "We expected a change later in the night - about 10pm," recalled Townsend. "We had hoped to burn into the park to the south and isolate the fire from the township. Our plan would have been successful, but at dusk the wind changed quickly from north east to west." As the seabreeze died, the prevailing westerly came down to ground level and the fire reversed direction. It tore through dry heathland swamp with a speed which impressed even the most experienced of bush fire fighters. "It was only a very light wind, but the dryness of the ground fuel was amazing," said Townsend. "Even hollows in that swampy ground that would normally have been filled with water were dry." Within three hours, flames had crossed to the south of town and were approaching the Pacific Ocean, or ‘the great eastern firebreak’, as some old hands call it. Backburning gets perilously
close to homes during the recent Backburning saves homes For local fire brigades time was running out. Once the wind shifted and blew the fire towards town, they began backburning to save houses from destruction. The front of the main blaze was much too hot and traveling too quickly to battle head on. The best firefighters could do was burn out the fire’s flanks, and steer it away from settlement. The fire that followed was awesome. Flames in the dry heath shot more than 15 metres skyward. There were layers of flame, with tongues of different fronts advancing separately from other tongues. The fire itself reflected as an orange glow from the clouds of smoke above it. It was awesome and terrifying all at the same time. Fire forecast Once a fire operation swings into gear, one of the tools planners rely on is the detailed weather forecast issued by the Bureau of Meteorology specifically for localised fire events. In this case, fire fighters relayed data from weather stations at Evans Head directly to the bureau, which responded with a detailed forecast for the next 24 hours - including temperatures, dewpoints, wind speed and direction. The forecast called for a change in wind direction from west to south-east, signaling the arrival of a large high pressure cell, centred over the NSW Central Coast, and circulating winds anti-clockwise onto the north coast of NSW. In fact, a weak front crossed the coast close to midnight, at the very height of the fire, and its short-lived rush of westerly air further fanned the flames - at the time burning dangerously close to homes on the south side of the town. Firefighters lit more backburns to protect the area, as the main front of the fire crossed roads to burn into heathland that hadn’t seen flames for 20 years. Winds the next day did, in fact, swing around to the south east. In many places the fire was forced onto already burnt country and quickly lost intensity - although it would continue to smoulder for another day. Elsewhere, the new winds allowed fire to creep into unburnt areas, and over successive days, as the wind shifted from south-east, back to west, to north-east and again from the south-east - only stronger - plumes of smoke swung in circles. Fire crews backburned within the national park to keep it contained and on the second night lit up 14 km of dry eucalypt forest to the south in a bid to keep the wildfire within the most remote portion of the park. Firefighting took to the air with three helicopters water-bombing the now inaccessible fire front. The plan worked, although it will be days yet before the last of the fires are out and years before some of the most ravaged heath returns to bloom in the spring again. Flashing emergency lights on top of a Fire Brigade truck reflect on the camera lens as the glow of backburning lights up the sky. Did you know? A seabreeze is a local effect along the coast, caused by warmer air over land rising during the heat of the day and sucking cooler air in off the water. At night, during stable conditions (under the influence of a high pressure cell, for instance) the reverse happens. The land cool and the relative warmth of the water causes air to rise, sucking cooler land wind out to sea. © weather-wise.com 2000 |