Lack of Trade Winds Shift Vog Over E. Hawaiʻi

An unwanted guest recently returned to East Hawaiʻi. And while residents were definitely aware of its visit, fortunately, a pause in the eruption within Halema‘uma‘u crater at the summit of Kīlauea volcano has provided a reprieve from its effects.

Vog, the hazy mixture of sulfur dioxide gas and aerosols, which can affect broad areas downwind of volcanic eruptions, moved back into the air — and lungs — of the Big Island for several days the first week of the new year and early last week.

“Driving home after work, I was like, what is this?” said Melisa Boteilho, who lives in Panaʻewa. “At first, I thought it was smoke, and then I was like, nope. Then you can see that hue, yeah, like when you shine the light.”

She hadn’t seen the vog that thick for years.

Nichol Nishiyama, who lives up Kaumana in Hilo, agreed, saying it’s been at least a couple of years since she noticed that much of the volcanic fog in the air and its recent visit is the most she’s seen since Kīlauea started erupting again in September.

“To the point where it made for really, really pretty sunsets and really, really pretty sunrises, but super, super heavy, where it looked like Waimea fog, but it was actually vog,” said Nishiyama. “So, like, when you drove around in the early mornings or late at night, you could see it in the streetlights.”

According to the Hawaiian Volcano Observatory, vog typically has a greater impact on the south and west sides of the Big Island during eruptive periods because volcanic gasses are carried downwind. The general trade wind direction is to the southeast of Kīlauea summit, but slack or non-trade winds can shift the location of the vog. Trade winds typically move from east to west.

Nishiyama said wintertime is typically when the Hilo side of the island experiences voggy conditions during an eruption because the wind shifts. For about half of January so far, winds have come generally from a southerly direction or the southeast, according to the National Weather Service in Honolulu.

Average wind speeds most of the month also haven’t gotten above 9 mph in Hilo, according to NWS data. The highest wind speed NWS recorded this month in Hilo was 21 mph on Jan. 3. Since then, winds haven’t reached more than 17 mph.

Light and non-trade winds mean vog was able to once again infiltrate the skies above East Hawaiʻi before the most recent pause in the Halema’uma’u crater eruption.

The size of an eruptive event also plays a part in how much sulfur dioxide and other particles are being pumped into the air.

“There are always some volcanic gasses emitted during volcanic eruptions,” according to HVO. “Large-scale eruptions, such as the 2018 lower East Rift Zone eruption, do emit larger quantities of volcanic gas than smaller eruptions, such as the current summit eruption.”

HVO reported the most recent sulfur dioxide emission rate for Kīlauea was measured at about 300 tonnes per day on Jan. 11, which was during a pause in the eruption. The previous measurement was about 3,300 tonnes per day on Jan. 6, while lava was erupting into the summit lava lake. In the past month, according to data on the HVO website, the highest average sulfur dioxide emission rate was measured at nearly 5,000 tonnes per day at one point during the last week of December.

About a month ago, the summit eruption began going through cycles of eruption and pauses that generally last one to several days. The eruption began another pause on Jan. 15.

“Because the current eruption has gone through cycles of eruption and pauses, the amount of volcanic gasses being emitted has varied substantially,” according to HVO. “This means that there can also be variable vog conditions downwind depending on the eruptive activity; less vog downwind during eruption pauses and more vog downwind while lava is erupting.”

The observatory mainly monitors volcanic gasses near eruption sites, where gas concentrations are higher and easier to detect with its instruments. The Hawaiʻi Interagency Vog Information Dashboard — a joint effort by the state Department of Health, U.S. Geological Survey, Hawaiʻi County Civil Defense, County of Hawaiʻi, National Park Service, National Oceanic and Atmospheric Administration, U.S. Department of Agriculture and the Center for the Study of Active Volcanoes — has compiled information and data related to vog and its impacts.

“On this site, you can find vog and wind forecasts, air quality data and space-based data and images that shows current conditions,” according to HVO. “This site will give you information on real-time and historic air quality data.”

Residents and visitors can check Kīlauea summit webcam images or read HVO’s daily updates to check whether the eruption is active or paused. They can also visit the Vog Information Dashboard to view vog and wind forecasts.
High levels of volcanic air pollution can be hazardous, especially to people with underlying respiratory conditions.

“Short-term symptoms can include eye, nose, throat and/or skin irritation, coughing, shortness of breath and other symptoms,” according to HVO. “If someone is experiencing negative effects associated with vog, the best thing to do is to leave the impacted area or stay indoors.”

Nishiyama and Boteilho felt some of those effects. And with the ongoing surge in COVID cases because of the Omicron variant, the vog has also led to some thinking their symptoms are signs of something worse.

Boteilho, who experienced some of the symptoms of vog exposure, including a dry throat, said she “got a little freaked out” because she thought it might have been COVID, but she tested negative. She also was glad East Hawaiʻi got a little bit of rain last week, which she said helped clear out some of the vog — at least for a little while.

Nishiyama said the vog has many people confused when it comes to COVID.

“You feel a little bit like congested, you feel sluggish,” she said. “You feel almost like it’s the coming on of symptoms of being sick, which has a lot of people freaking out because they think they have COVID — and they don’t.”

She has a friend who took about five COVID tests since the first week of January because she keeps thinking she is COVID-positive and she’s scared since she works with the public. So her friend keeps testing even though it was just the vog.

“So it does definitely affect you,” Nishiyama said. “It makes you, like, really, really tired, just kind of like bogged down.”

“It is important for residents and visitors to be aware of any volcanic hazards, including vog, from Hawaiian volcanoes,” said HVO. “The best way to stay up to date on current volcanic activity and unrest is by visiting the Hawaiian Volcano Observatory website.”