Categorized | Featured, Sci-Tech, Volcano

Volcano Watch: Online tools help Hawaii breathe easier during trade wind time-outs

Visitors to Wailoa River State Park walk along the shore as vog blankets Hilo in the background. Kona winds pushed the vog from Kilauea Eastward. Hawaii 24/7 File Photo

Visitors to Wailoa River State Park walk along the shore as vog blankets Hilo in the background. Kona winds pushed the vog from Kilauea Eastward. Hawaii 24/7 File Photo

(Volcano Watch is a weekly article written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.)

We are currently sandwiched between the Halloween and Thanksgiving holidays as the inexorable march of time brings the winter festivals ever closer. For Hawai‘i, this period also signals the time of year when interruptions in the trade winds become more common.

After 3 decades of eruptive activity on Kīlauea’s east rift, and 5 years of simultaneous summit eruption, island residents have become familiar with the importance of wind conditions in determining the geographical fate of Kīlauea’s noxious gas and particle emissions. Volcanic pollution from Kīlauea, commonly referred to as vog, impacts some part of the Island of Hawai‘i most days.

Big Island SO2

Big Island SO2

In a story familiar to most Hawai‘i residents, prevailing trade winds blow the vog plume to the southwest, affecting areas of Ka’ū and much of the leeward side of the island. Population centers in East Hawai‘i, including popular areas of Hawai‘i Volcanoes National Park, are upwind of Kīlauea’s emission sources during trades; thus, they are unaffected by volcanic emissions, and generally have very good air quality. During the winter months, however, when trade winds are absent as much as 50 percent of the time, these areas experience very high concentrations of volcanic gases and particles due to their close proximity to the active vents.

When trade-winds are absent for prolonged periods, vog travels up the island chain; our disgruntled neighbors have come to understand that the appearance of vog in their area is normally due to lack of trade winds, rather than an increase in Kīlauea’s activity.

A number of online tools have been developed to help people in Hawai‘i minimize their exposure to volcanic pollution. The tools provide color-coded alert levels, based on the familiar traffic-light motif, to identify current vog concentrations and forecast future ones. The six-color conditions range from good (green) to hazardous (brown) and are based on human health and environmental studies used by the U.S. Environmental Protection Agency (EPA) to set national air pollution exposure limits.

The components in vog known to affect health are sulfur dioxide (SO2) gas, and tiny respirable particles called PM2.5 (particulate matter with a diameter of 2.5 microns or less, or 1/10 the thickness of a human hair). While both of these pollutants are regulated by the EPA, Hawai‘i’s advisories for volcanic SO2 and PM2.5 have been customized for local conditions. A shorter exposure time interval has been adopted, since variable wind conditions can cause volcanic gas concentrations to change rapidly.

Four websites are particularly useful for helping individuals stay informed on current and future vog conditions in their general area. The Hawaii State Department of Health provides a short-term SO2 advisory with current 15-minute average SO2 concentration data for nine locations ranging from Hilo to Waikoloa ( The National Park Service provides 15-minute average gas and particle data for 9 and 2 sites, respectively, within Hawai‘i Volcanoes National Park. The Park data is used by managers to help limit visitors’ exposure to potentially hazardous areas (

Current PM2.5 conditions and a one-day forecast are provided by the AirNow group, a partnership of Federal, State, and local agencies ( And finally, an interactive map-based forecast model known as VMAP is operated by the University of Hawai‘i at Mānoa. This model provides 60 hours of animated gas and particle data and has proved useful for people planning outdoor activities (

Individual responses to vog vary widely, although people with pre-existing respiratory conditions, such as asthma or chronic respiratory disease, show special sensitivity. Health studies examining the long-term effects of vog are ongoing; however, documented short-term effects include headaches, breathing difficulties, increased susceptibility to respiratory ailments, eye irritation, and sore throat. A multi-agency response team of State and County organizations recommends protective actions during periods of vog. These include staying informed of air quality conditions, staying indoors during periods of heavy vog, drinking plenty of water, and keeping medications handy (

Using online tools for monitoring air quality can help determine whether vog in your area, rather than some other environmental (or holiday) stressor, is affecting your well-being. As the season unfolds, we wish everyone good cheer in using available resources to live harmoniously with these beautiful volcanic islands.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

RSS Weather Alerts

  • An error has occurred, which probably means the feed is down. Try again later.