Softwood, winds

Where a fire goes after it’s underway is sometimes easy to figure, and sometimes not so much.

The Tantallon fire spread quickly after it started Sunday afternoon, fueled by high winds, softwood trees, and a wind that it generated on its own.

On Monday, the fire was being held at 788 hectares, but shifting and increasing winds meant that its expected path was going to see it pushing south later Monday, the Department of Natural Resources and Renewables said.

Department spokesman Dave Steeves said at noon Monday that forward growth was minimal overnight “but we are expecting that to change this afternoon as the relative humidity drops. The winds are high again today, too. We have winds gusting 35 to 45 km / h and the fire behavior we’ve seen to date is leading us to believe there is going to be some (extensive) fire behaviour this afternoon.”

He said the fire is expected to move generally south until Tuesday night, when the weather shifts again.

On top of the wind and low humidity, the fire also creates its own winds that can spread the blaze.

“When fires get to a certain size they do because of the excessive heating and cooling of the air within the fire, there is a possibility for that to happen,” he said. “Any time you get any kind of extreme fire behavior, spread rates are extreme.”

He said safety is paramount for firefighters on the ground, and “if things are getting to the point that it’s dangerous for our crews to be out there, we’ll move them off the line.”

He said flying embers can also cause the fire to spread, even as water bombers continue to drop thousands of gallons at the head of the fire.

“Any time you get erratic fire behavior, spot fires are an issue, and especially now where we haven’t had any precipitation for a really extended period of time. Those forest fuels are really, really dry. The embers fly up into the atmosphere, and as they cool, they fall down ahead the main body of the fire and create spot fires that are a serious safety issue for our guys and girls on the line.”

Other factors that contribute to the extreme fire spread are the makeup of the forest and the level of development.

“We have a majority of mixed wood forest, but it has a high percentage of softwood, and softwood is quite a volatile forest fuel because of the resins and oils and things along those lines. Any time you get into softwood stands versus hardwoods, you’re going to get increased spread rates. This wind and fuel type is not going to help us.”

And on top of that were the homes in the subdivisions, with their vinyl siding, asphalt shingles, vehicles and size.

“That’s a definite, definite concern,” Steeves said. “My counterparts at Halifax Fire have been doing their very best to be proactive with the structure side of things. We’ve been working arm in arm to do our very best to get a handle on this, but unfortunately right now we are still at zero per cent contained. We just have to keep our nose to the grindstone.”