Weather News

Forrestdale blaze ignites amid sweltering heat and gusty winds, but no fire ban was declared

By Irena Ceranic, Friday February 8, 2019 - 21:56 EDT
ABC image
The Forrestdale blaze was fanned by strong and hot easterly winds. - ABC

The Forrestdale bushfire in Perth's south this week was sparked on a day when temperatures above 35 degrees Celsius were forecast, along with hot, easterly wind gusts of up to 80 kilometres per hour.

That may sound like the ideal scenario for a catastrophic blaze to take hold, yet a total fire ban was not declared.

The Department of Fire and Emergency Services (DFES) issues the bans on days when fires are most likely to threaten lives and property due to extreme weather conditions or when firefighting resources are already stretched.

Fire bans are intended to stop people from lighting any fires in the open air, including for cooking and camping, or doing anything that may start a fire such as welding and grinding.

Why wasn't a total fire ban declared on Thursday?

Before declaring a ban, DFES considers factors including:
The weather forecast
The firefighting capability
The number of days since it last rained, and
The amount of vegetation in the area

DFES Superintendent of state co-ordination Danny Mosconi said bans were issued in consultation with the Bureau of Meteorology.

"We look at what the fire danger rating is for the day, we look at what the forecast temperature is, what the wind speed is and what the humidity is," he said.

"Yesterday for example, while the temperatures were quite high they weren't simultaneously accompanied by dangerous fire weather conditions such as low humidity."

The Bureau of Meteorology's six fire danger ratings in order of severity from highest to lowest are:
very high

"There are a number of fire danger indices and it is worked out with a mathematical formula," Superintendent Mosconi said.

"[On Thursday] it actually only just went into that very high range, and that was only in one part of the metropolitan area, the rest was actually a fair bit lower."

The last time a total fire ban was declared in the Perth metropolitan area was on February 1, when the danger was rated at severe.

The factors need to align

Superintendent Mosconi said a total fire ban also required the high temperatures, gusty winds and low humidity to align at the same time, but on Thursday the strongest winds were forecast when the temperature was dropping, while humidity was moderate for most of the day.

"It was still reasonably humid for a summer day … humidity of 15 per cent or lower, that's when we really get concerned," he said.

Superintendent Mosconi said total fire bans had a far-reaching impact across the community, but safety was paramount

"If there's a total fire ban imposed, people aren't able to use cookers, pizza ovens and solid wood fuels," he said.

"Some industry works are also banned such as welding, soldering, grinding, gas cutting, using incinerators, those sorts of things.

"It does have an impact on the community and on industry, so we have to weigh all that up.

"Obviously community safety comes first, but we do have some fairly rigid triggers that we look at before declaring a total fire ban.

"It is always easy to look at things in hindsight. We try to prepare as best we can."

People who ignore total fire bans faces fines of up to $25,000 and 12-month jail terms.

Local governments, DFES, the Department of Biodiversity, Conservation and Attractions and WA Police can also issue $1,000 on-the-spot-fines.

Current total fire bans can be found here:


© ABC 2019

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