Vog Forecast Discussion for 4:00 PM HST Wednesday, Nov 21st 2018

Summary:

Emission rates continue to be very low. Trade winds continue through today (11/21). Tomorrow, winds become weaker, then more easterly to southeasterly through Sunday (11/25). Today (11/21), extremely low concentrations of vog may affect areas on the on the island of Hawai'i that include the western and southwestern portions of the island, mostly affecting the Ocean View, Pahala, and Kona sites. Tomorrow (11/22) through Sunday (11/25), easterly to southeasterly winds combined with low emission rates mean extremely low concentration (small amounts) of vog may affect large portions of the state of Hawai'i, including the interior and northern portions of the island of Hawai'i, Maui county, Oahu, and Kauai County.

The primary pollutants in vog are sulfur dioxide gas and fine particulate matter. See the Vog Dashboard for information and protective measures for vog: https://www.ivhhn.org

Current Measured Conditions:

As of 4:00 PM HST on Wednesday, Nov 21st 2018:


For current conditions, please see: http://weather.hawaii.edu/vmap/current/index.cgi.

Island of Hawai'i Forecast:

Emission rates continue to be very low. Trade winds continue through today (11/21). Tomorrow, winds become weaker, then more easterly to southeasterly through Sunday (11/25). Today (11/21), extremely low concentrations of vog may affect areas on the on the island of Hawai'i that include the western and southwestern portions of the island, mostly affecting the Ocean View, Pahala, and Kona sites. Tomorrow (11/22) through Sunday (11/25), easterly to southeasterly winds combined with low emission rates mean extremely low concentration (small amounts) of vog may affect large portions of the state of Hawai'i, including the interior and northern portions of the island of Hawai'i.

The primary pollutants in vog are sulfur dioxide gas and fine particulate matter. See the Vog Dashboard for information and protective measures for vog: http://www.ivhhn.org

State-wide Forecast:

Emission rates continue to be very low. Trade winds limit the area affected by vog to the island of Hawai'i today (11/21). Tomorrow (11/22) through Sunday (11/25), easterly to southeasterly winds combined with low emission rates mean extremely low concentration (small amounts) of vog may affect large portions of the state of Hawai'i, including the interior and northern portions of the island of Hawai'i, Maui county, Oahu, and Kauai County.

The primary pollutants in vog are sulfur dioxide gas and fine particulate matter. See the Vog Dashboard for information and protective measures for vog: http://www.ivhhn.org

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.