Unusual spiraling wind vortices made Black Saturday fire danger worse
Submitted by astone on Mon, 08/13/2012 - 09:49
Extreme temperatures and strong winds during Victoria’s Black Saturday bushfires on February 7, 2009, where 173 people died, created rolling bands of wind that made the fire danger highly variable according to new research.
In a world first, researchers used a detailed weather forecasting model to produce high-resolution simulations of weather patterns on the day.
“Fire fighters reported extraordinary behaviour from the Black Saturday bushfires,” Centre of Excellence Chief Investigator and study author Dr Todd Lane said.
“Our research revealed that the extremely hot daytime temperatures and strong winds generated a series of long horizontal rolling wind vortices which created bands of fast and slow wind around 5-10 kilometres apart. “
As the vortices moved through they generated marked differences in wind speeds, humidity and temperature over relatively short distances, which may have caused the fires to behave very differently at locations relatively close to each other.
“The extreme temperatures meant the wind vortices were stronger and spaced much further apart than usual for this type of phenomenon, which created stark changes in conditions as each one rolled through,” said team member Prof Michael Reeder.
“We also documented for the first time the generation of an atmosphere wave, known technically as an undular bore, which was produced by and ahead of a late evening cool change and reinvigorated the fire around Beechworth after sunset.”
Centre of Excellence researchers used a weather forecasting model with a resolution down to 400 x 400 sqm to investigate the day’s conditions. The skill of the model was verified by comparing its results to actual weather conditions on the day.
The study is the first of its kind to produce such detailed, high-resolution simulations of weather patterns on the day and it is expected to provide insights for future fire management and warning systems.
“As improved computing power continues to become available for climate and weather forecasting models in the future, this kind of analysis should be useful for operational forecasting on days of fire danger,” said Ms Chermelle Engel an author of the study from The University of Melbourne
“The ultimate goal of this research is to provide a better guide for public warning systems and fire fighting resources now and into the future,” Dr Lane said.
The work was funded by the Australian Research Council and is published online in the Quarterly Journal of the Royal Meteorological Society.
For more information, images of the weather patterns or to arrange and interview with Dr Todd Lane or Professor Michael Reeder contact Media Manager Alvin Stone: