VOG Forecast Discussion update for 7:00 AM HST Monday, Aug 14th 2017.


Vog influence will be limited to the southwestern portions of the Island of Hawai'i (Ocean View and Pahala sites) for the rest of the week (Aug 18) as northeasterly trade winds with showers resume.

Current Measured Conditions:

As of 7:00 AM HST on Monday, Aug 14th 2017, Pahala currently reports 0.04 ppm of SO2. For current conditions, please see: http://weather.hawaii.edu/vmap/current/index.cgi.

The Island of Hawai'i Forecast:

Through the end of the week, vog-influenced air will be limited to the Island of Hawai'i to southwestern portions of the island, affecting the Pahala and Ocean View sites.

State-wide Forecast:

The rest of the state (excluding the Island of Hawai'i) unlikely to be affected by vog. Trade winds and showers continue.

Forecast issued by: L. D. Holland

Revisit this page periodically for updates as forecast conditions change.


Visit Steven Businger's Hawaiian Weather Blog for discussions of recent vog episodes.


News and Items of Interest

Vog Climatology

The transport of volcanic aerosols, or volcanic smog (Vog), is primarily controlled by two factors - (1) the wind direction and (2) the height of the tradewind temperature inversion. The winds determine which direction the vog will be transported. Typically the winds in Hawaii are out of the northeast or east, as demonstrated by the graph below. This results in the vog being transported around the southern tip of the Big Island of Hawaii. The winds wrap around the westside of Hawaii and are often found over Kailua-Kona during these periods. When the winds are southerly, or are light, the vog is transported north over the northern end of Hawaii and across the northern islands of Maui, Molokai, Lanai, Oahu, Kauai, and Niihau. Again, from the graph below it can be seen that this will most likely occur during the winter months but can also happen in the spring and autumn. It is least likely to occur in summer (June, July, August) whenthe northeast trade winds are most persistent. The tradewind temperature inversion determines how high the vog can mix in the atmosphere. The trade wind inversion is typically between 2000 meters (6500 feet) and 2500 meters (8200 feet). Since the volcanic emissions are quite hot when they exit the vents the gas and aerosols rise quite rapidly, however, they mix with the surrounding air and cool just as fast. This results in large amounts of vog at higher elevations where it is trapped by the tradewind inversion, which it cannot mix across. Regions downwind of the volcano, be it to the south or north, are thus greatly effected near the base of the tradewind inversion and may experience high concentrations of vog periodically.


Photograph by M. Poland, November 13, 2008, USGS HVO.