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

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

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


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

In a story familiar to most residents, prevailing trade winds blow the vog plume to the southwest, affecting areas of Ka‘u and much of the leeward side of the island. Population centers in East Hawaii, including popular areas of Hawaii Volcanoes National Park, are upwind of Kilauea’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 high concentrations of volcanic gases and particles because of 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 Kilauea’s activity.

A number of online tools have been developed to help people in Hawaii 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 to set national air pollution exposure limits.

The components in vog known to affect health are sulfur dioxide 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, Hawaii’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 state Department of Health provides a short-term SO2 advisory with current 15-minute average SO2 concentration data for nine locations around the island ( The National Park Service provides 15-minute average gas and particle data for nine and two sites, respectively, within Hawaii 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 Hawaii at Manoa. 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 multiagency 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.

Kilauea activity update

A lava lake within the Halemaumau Overlook vent produced nighttime glow that was visible via Hawaiian Volcano Observatory’s webcam during the past week. Back-to-back deflation-inflation cycles occurred during the week, and the second was ongoing as of Thursday. The lava lake level fluctuated correspondingly.

On Kilauea’s East Rift Zone, the Kahaualea 2 flow continues to advance slowly into the forest northeast of Puu Oo. It had traveled 4 miles from Puu Oo when mapped on Nov. 7.

There was one felt earthquake in the past week on the island. On Monday at 1:33 p.m., a magnitude-3.3 earthquake occurred 10 miles northwest of Naalehu at a depth of 6 miles.


Visit for Kilauea, Mauna Loa and Hualalai activity updates, recent volcano photos, recent earthquakes and more; call 967-8862 for a Kilauea summary; email questions to

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