Summertime pattern of northeasterly trade winds limit vog influence to the southwestern side of the Big Island (Ocean View and Pahala sites) into next week (June 16 - 21).
As of 9:30AM on Thursday, June 22nd 2017, Ocean View measurements report in at 0.15 ppm SO2 and Pahala at 0.07 ppm SO2. For current conditions, please see: http://weather.hawaii.edu/vmap/current/index.cgi.
Vog influenced air limited to the Island of Hawaii at the Pahala and Ocean View sites into the next week.
Northeasterly trade winds continue to bring improved air quality across the state (June 22 - 27).
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
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.