Vog Forecast Discussion for 9:00 PM HST Monday, Jan 16th 2021

Summary:

Kilauea summit (Halema'uma'u) is currently erupting with an active lava lake at the summit caldera.

Southeasterly (from the southeast) winds near Halema'uma'u tonight (1/18) return to trade winds tomorrow and Wednesday (1/19-1/20) after a cold front slowly passes over Hawai'i island.

Tonight (1/18) southeasterly winds and clearing skies over the interior of Hawai'i island and the Ka'u district mean the saddle region between Mauna Loa and Mauna Kea and Mauna Kea itself may have some exposure to vog. Vog is not expected to impact any other islands because of precipitation associated with the passing cold front. Tomorrow and Wednesday (1/19-1/20) as trade winds return, vog will impact areas southwest of the Kilauea summit caldera that include the Ka'u district and Kona (west) coast of Hawai'i island.

Air quality will be "Good or Acceptable" based on current emission rates and exposure to PM2.5 and SO2, except for areas near the primary SO2 emission source Kilauea's summit, Halema'uma'u.

The primary pollutants in vog are sulfur dioxide (SO2) gas and fine particulate matter of size 2.5 micrometers or less (PM2.5) that derives from sulfate aerosol (SO4). See the Vog Dashboard for information and protective measures for vog: http://www.ivhhn.org

Current Measured Conditions:

As of 9:00 PM HST Monday, Jan 18th 2020:


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

Island of Hawai'i Forecast:

Kilauea summit (Halema'uma'u) is currently erupting with an active lava lake at the summit caldera.

Tonight (1/18) southeasterly winds and clearing skies over the interior of Hawai'i island and the Ka'u district mean the saddle region between Mauna Loa and Mauna Kea and Mauna Kea itself may have some exposure to vog. Tomorrow and Wednesday (1/19-1/20) as trade winds return, vog will impact areas southwest of the Kilauea summit caldera. Small amounts of vog will impact the western half of the southern coast of Hawai'i island (Ka'u district) that includes Pahala, Na'alehu, Ocean View, and South Point areas. Small amounts of vog will impact the Kona (leeward, west) side of Hawai'i island, as the Hawai'ian lee eddy transports vog onshore to the Kona district.

Air quality will be "Good or Acceptable" based on current emission rates and exposure to PM2.5 and SO2, except for areas within HNVP.

The primary pollutants in vog are sulfur dioxide (SO2) gas and fine particulate matter of size 2.5 micrometers or less (PM2.5) that derives from sulfate aerosol (SO4). See the Vog Dashboard for information and protective measures for vog: http://www.ivhhn.org

State-wide Forecast:

Kilauea summit (Halema'uma'u) is currently erupting with an active lava lake at the summit caldera.

Tonight (1/18) southeasterly winds and clearing skies over the interior of Hawai'i island and the Ka'u district mean the saddle region between Mauna Loa and Mauna Kea and Mauna Kea itself may have some exposure to vog. Vog is not expected to impact any other islands because of precipitation associated with the passing cold front. Tomorrow and Wednesday (1/19-1/20) as trade winds return, vog will impact areas southwest of the Kilauea summit caldera that include the Ka'u district and Kona (west) coast of Hawai'i island.

Air quality will be "Good or Acceptable" based on current emission rates and exposure to PM2.5 and SO2, except for areas near the emission source on the island of Hawai'i.

The primary pollutants in vog are sulfur dioxide (SO2) gas and fine particulate matter of size 2.5 micrometers or less (PM2.5) that derives from sulfate aerosol (SO4). 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.