Combo of weather factors leading to more intense wildfires on Maui

10 August 2023 , 22:14

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The wreckage from the wildfires in Maui (Image: AP Photo/Rick Bowmer)

The wildfires ravaging the Hawaiian island of Maui may have been caused by the perfect storm — literally, says a meteorologist.

Vast swaths of flame broke out on Tuesday on the resort island, which is one of several that comprise the American state.

Thousands of residents and tourists were evacuated, and horror scenes erupted as various people jumped into the ocean to avoid the scorching brush fires.

The death toll is already at 36, and that number is expected to rise as search crews peruse the destroyed areas around the fires in the hopes of discovering survivors, said Adam Weintraub, communication director for the Hawaii Emergency Management Agency.

Front Street in Lahaina burns in the wildfires (AP)

Dozens are dead after the fires broke out on Tuesday (AP)

"These were large and fast-moving fires, and it’s only recently that we’ve started to get our arms around them and contain them," he said. "So, we’re hoping for the best, but we’re prepared for the worst."

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But what caused the fires?

That remains to be seen, but the weather certainly didn't help things along, said National Weather Service meteorologist Ian Morrison, who is based in the capitol city of Honolulu on the nearby island of O'ahu.

"In Hawaii, we have what are called trade winds, which are caused by high pressure to the north," he said. "Usually, those trade winds are anywhere from 10 to 20 mph (16 to 32 kmh)."

"They bring rainfall to the eastern part of the islands, and it's usually pretty dry across the west and southwest parts of the islands," he added. The northwest of Maui is where the fires broke out.

Hurricane Dora was also a contributing factor to the Maui wildfires

The trade winds are generally caused by high pressure systems to the north of the islands. But what's unusual about the current situation is that Hurricane Dora, a Category 4, is also ripping through the seas to the south of the island.

The juxtaposition of the high pressure system to the north and the extreme low pressure system carrying Hurricane Dora is strengthening the trade winds and essentially creating a wind tunnel on Maui, Morrison said. Gusts of up to 80 mph (129 kmh) have been battering the island.

"With the low pressure to the south and high pressure to the north, it puts the island in the accelerating wind band between those two features," he said. "We have very strong winds because of those two features."

It's also very dry on Maui — the relative humidity has been around 30% or slightly higher, and Morrison said the threshold for a fire alert is 45% RH.

A map shows where the worst areas of fires on Maui are (FIRMS/NASA)

The vegetation is therefore very dry, and that makes it easily flammable.

"If you get some type of fire started, then it’s going to burn with those dry fuels, and the wind is going to pick it up very quickly," Morrison explained.

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"It was the combination of [these] not-so-unusual events," he added. The high pressure to the north isn't unusual, and neither are hurricanes to the south — but they generally don't occur at the same time and while a drought is occurring, too.

So, the NWS issued a red flag warning stating that the conditions were ripe for fire. Residents were encouraged to burn items in metal barrels covered by weighted metal covers, if burning was allowed, and urged to monitor all fires and extinguish them with water, ensuring everything is cold to the touch by the time they leave it.

Red flag warnings can't predict where fires will start — they just note that there is an increased risk for them, Morrison said.

It may take rain for the flames to die down on Maui (County of Maui /AFP via Getty Im)

To put out the fires, which have already damaged or destroyed 271 structures in the historic town of Lahaina and nearby, Morrison said rain is likely necessary.

The problem is that side of the island rarely gets any rain.

"Right now, it looks like we’re moving back into our trade wind weather routine," Morrison said, "and while that will bring showers to the windward areas, it’s not going to really bring too much rainfall to those areas of the fire."

The humidity would also need to rise, which would help saturate the flora that's providing fuel for the flames, and the winds would need to die down.

But rain is the main thing that could mitigate the situation, he said.

President Joe Biden said the government will be providing "all available federal assets" to help combat the fires. The Coast Guard, Navy and the Marines are deploying helicopters to fight the flames, too.

In the meantime, the Hawaii Convention Center in Honolulu is expected to accommodate up to 4,000 people displaced by the blaze, including thousands of tourists — many of whom got stranded at the airport after flights were canceled.

Jeremiah Hassel