Notice a slight sulphuric tang to the air when the Tradewinds cease? A tickle in the throat, a runny nose?
It doesn’t happen often – thank goodness – but “vog” is a form of air pollution that results when sulfur dioxide and other gases and particles emitted by an erupting volcano react with oxygen and moisture in the presence of sunlight.
The reason you are feeling vog some 400 miles distant from the actual eruption on the Big Island, is because of the wind pattern.
Accounting for 70% of all winds in Hawaii, trade winds are the most common winds over Hawaiian waters. Tradewinds come from the direction of Alaska -- NE to ENE -- and are Hawaii’s natural air conditioning.
When we don’t have Tradewinds, the wind pattern shifts to a southerly flow. Kona, a resort town on the leeward side of Hawaii's Big Island, is a Hawaiian term for winds that come from the SW or SSW -- the opposite direction of trade winds.
Since the Kilauea volcano on Hawaii’s Big Island began erupting in 1983, Kona winds can bring vog up the island chain. This makes visibility poor and causes eye and respiratory irritation. Headaches, watery eyes, sore throat, breathing difficulties (including inducing asthma attacks) and flu-like symptoms are commonly reported. These effects are especially pronounced in people with respiratory conditions and children.
On the Big Island, the gas plumes of Kilauea rise up from three locations: Halemaʻumaʻu Crater, Puʻu ʻŌʻō vent, and from along the coastline where lava flows from the East Rift zone enter the ocean. The plumes create a blanket of vog that can envelop the island.
Prolonged periods of southerly Kona winds can affect islands across the entire state as well. Lucky we live Kauai! By the time the vog reaches other islands, the sulfur dioxide has largely dissipated, leaving behind ash, smoke, sulfates, and ammonia.
Kona, or vog producing conditions are most prevalent in winter months when cold front move through. These months include October through March.
Plumes of vog from Big Island volcanic eruptions as seen and photographed from the Space Shuttle "Atlantis".
Please see http://www.konaweb.com/vog/index.shtml