Former NSW Rural Fire Service commissioner Shane Fitzsimmons says bushfire conditions over the summer exceeded their worst case scenarios and wreaked unprecedented destruction and damage on NSW.
However the scale of the response was also unparalleled, with 200,000 firefighting shifts over the season.
"It was an extraordinary and unprecedented season in so many ways," Mr Fitzsimmons told the Royal Commission into National Natural Disaster Arrangements on Wednesday.
"Obviously the indications were for above normal, but no one had the capacity to forecast and predict the extent and the scale to which weather and fire behaviour played out with the stretching of fire literally from the Queensland border all the way through to the Victorian border along the Great Dividing Range."
Mr Fitzsimmons, who now heads Resilience NSW, laid bare the extraordinary conditions firefighters grappled with during the Black Summer fires.
Due to the drought, firefighters saw fire behavior and spread that defied the predictions some of the country's leading experts.
"We did see unprecedented fire danger ratings materialise in a number of areas, particularly our most populated centres around places like the Hunter, the great Sydney and the inner Shoalhaven regions. We saw 17 fires concurrently at the emergency warning level in November, which we simply haven't seen before," Mr Fitzsimmons said.
"What we also identified through the season, because of the volatility and flammability of the fuels due to the moisture depletion and the very dry atmospheres, we saw fire behaviour, fire spread exceeding the latest available modelling and scientific procedures, techniques as well as some of the best qualified fire science behavioural experts we have available in the country.
"On a number of occasions, fire behaviour and fire spread exceeded well and truly the worst case scenario and we saw fire behaviour at 2, 3 or 4 in the morning, the likes of which you might normally expect at 2, 3 or 4 in the afternoon where traditional conditions are at their worst."
The fire season was longer than normal without any "meaningful interruption from weather", Mr Fitzsimmons said.
"Traditionally there would be some break or some reprieve in the weather with frontal activity, shower activity, some rainfall," Mr Fitzsimmons said.
"As a matter of fact where we did see frontal activity or movements across the state, we saw significant dry lightning, dry lightning storms and considerable new ignitions at any one time."
Current NSW Rural Fire Service Commissioner Rob Rogers said the effect of hazard reduction burning "dissipates" in the conditions seen over the summer.
"We saw a lot of these fires burning through areas that were only burnt or hazard reduced in recent years," Commissioner Rogers said.
"But when the conditions weren't up at that upper end of the rating area, then obviously hazard reduction and other mitigants are much more effective when it comes to suppression options and slowing fire behaviour and fire intensity down."
Mr Fitzsimmons also said there was an "unprecedented toll for NSW when it came to damage, destruction, despair and tragedy".
Nearly 2500 homes were destroyed in NSW and 26 people died.
What was also unprecedented was the scale of the firefighting response, Mr Fitzsimmons said.
There were 200,000 firefighting shifts across 12,000 fires.
Around 6500 interstate and overseas firefighters were also deployed on the fire grounds.
The large air tankers flew more than 1700 missions, dumping 24 million litres of suppressant across the fireground.
Commissioner Rogers said interstate resources were deployed to the areas where fires posed the biggest threat to life.
States sent their resources elsewhere even if they had their own fires to deal with based on where the biggest risk lay.
"Where we've got a shared threat, there's very much that discussion across the incident management teams and indeed at the state levels to ensure that we're think about who has got the biggest threat to life and property at that time irrespective of which state they happen to live in," Commissioner Rogers said.
However Commissioner Mark Binskin took issue with Mr Fitzsimmons' consistent use of the word "unprecedented".
"You've used the word 'unprecedented' for a number of times, and that's the reason we're here, because it's no longer unprecedented," Commissioner Binskin said.
"That's the reason the Royal Commission is looking at the higher level jurisdiction, the cooperation and how we use these resources nationally to respond to future natural disasters."
