Drought in Hawaii is fueling rare concerns over November bushfires


You don’t often expect to hear “Hawaii” and “fire danger” in the same sentence, but bushfire concerns have been very real in the Aloha State in recent days. An ongoing drought is dehydrating the landscape, with significant effects on agriculture and ecosystems.

More than half of Hawaii is currently experiencing abnormally dry conditions, with 30% facing moderate or worse drought. That’s according to the federal government’s Drought Monitor, which provides detailed synopses of the intensity and impacts of droughts across the United States each week.

More than 80% of the US is facing worrying drought conditions

The Drought Monitor even warns that, in the few isolated locations entrenched in extreme drought conditions, “wild asses move into populated areas” and “trees are dry and dropping leaves.” This further exacerbates the risk of wildfires, something the local National Weather Service office in Honolulu is increasingly concerned about.

“A combination of high winds, low relative humidity and warm temperatures can contribute to extreme fire behavior,” he cautioned on Monday, after issuing a red flag warning. These warnings do not predict fires, but rather communicate that any sparks can quickly turn into raging infernos.

The red alert in effect on Monday was the first in Hawaii in November since 2012.

Red flag warnings are most commonly issued in the late summer months of August and September, when the landscape tends to become moisture starved after the summer dry season.

According to the Hawaii Wildfire Management Organization, “0.5 percent of Hawaii’s total land area burns each year, equal to or more than the percentage burned of any other U.S. state.”

Autumn rains usually end the summer dry season, but this year they have been unreliable. Only 0.09 inches of rain has fallen in Honolulu so far in November, about an inch and a half less than average, and October has received only half of normal rainfall.

Since the beginning of the year, Honolulu has gained 9.8 inches, compared to a 13.6 average; while representing a 28 percent shortfall, it’s nowhere near as bad as it was in 1998, when just 3.34 inches had fallen in mid to late November.

Temperatures are also at their highest during late summer, which means the greatest amount of evaporation. This dries out the landscape, with rapid desiccation ensuing in late July and early October. The drought peaked in early September of this year when 94% of the state was affected.

The rainfall deficit “goes back to the last rainy season,” said John Bravender, meteorologist for alert coordination at the National Weather Service in Honolulu. “We had a very wet December that wiped out all the drought, then January, everything dried out.”

A series of quiet hurricane seasons in the Pacific, balanced by an intense Atlantic, limited the amount of moisture that flowed north to Hawaii during the summer.

Much of Hawaii remained in a drought until the end of October, when the beneficial rains arrived. But since then the dry weather has returned.

“In the wake of rains that eased the drought, Hawaii got a little drier in a mostly trade wind regime,” wrote the Drought Monitor. “As a result, no further improvement was seen in Hawaii after 9 consecutive weeks with reduced drought cover.”

Lack of rainfall this year has led to low relative humidity, sometimes dipping below 45%. While 45 percent is humid by California standards, it is quite dry on a tropical island chain like Hawaii located about 20 degrees north latitude. Over the past few days, a strong high pressure system rotating clockwise north of the archipelago has swirled dry air southward, also causing gusts of wind.

In addition to the obvious bushfire risk issues, the ongoing drought is also having impacts on agriculture and ecosystems. In August, about 8 percent of Maui was listed as experiencing “exceptional” drought, the highest level.

SFGate.com, an online news publisher in San Francisco, reported that lack of rain and past pineapple growing practices in the mountains of western Maui have made it more difficult to retain and conserve water, affecting catchment levels and the breeders.

On Molokai and Maui, wild deer have encroached on farmland and competed with livestock for resources, in part due to drought conditions. Donkeys also roam the populated areas.

“Despite ongoing efforts, the axis deer population has grown to an estimated 60,000 or more, which cannot be sustained by the environment in Maui County,” read a proclamation from Hawaii Governor David Ige (D ) released on November 18. fifth consecutive proclamation related to the deer crisis, with special measures in effect until 17 January.

“This includes fencing axis deer, culling deer to sustainable levels, clearing vegetation along fence lines, and erecting and/or reinforcing fence lines to keep axis deer off roadways, airports, and runways.” , says the document.

Winter forecasts from the Climate Prediction Center’s National Weather Service call for a gradual improvement in the state’s drought conditions.

“We’re hoping for some improvements,” Bravender said. “The wild card is where the above-normal rainfall will occur. Especially with La Niña models, there is more uncertainty. If it is a stronger event, then it tends to have more trade winds, which would concentrate more precipitation on the windward parts of the islands. If it’s weaker, we could see the trade winds break down, as is typical during the winter, and get more precipitation on the leeward sides. Right now it’s the leeward sides that really need it.

Hawaii joins much of the Lower 48 which is also currently experiencing a significant drought. The Drought Monitor’s Nov. 15 update showed that 82 percent of the contiguous United States is dealing with abnormally dry or drought conditions, close to the highest percentage on record (85 percent Nov. 1 of this year ).

A July study in the Journal of Climate found that drought conditions in Hawaii, which have prevailed for much of the past decade, are among the most severe on record. However, it has been unable to link the drought to long-term climate change, as computer models evaluating its drivers have been unable to detect a human influence.

“[N]Not every event has an apparent and simple “root cause”: Natural weather mechanisms have proven powerful in producing extreme events and trends over considerable periods,” the National Oceanic and Atmospheric Administration’s climate program office wrote in a news release. .

The US government’s fourth National Climate Assessment, released in 2018, warned that rising temperatures in the future will increase the risk of extreme drought and flooding in Pacific Island communities.

Jason Samenow contributed to this report.

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