Volcanic ash

Volcanic Ash Fine particles of mineral matter from a volcanic eruption which can be dispersed long distances by winds aloft. The chemical composition and abrasiveness of the particles can seriously affect aircraft and also machinery on the ground.

Volcanic Ash- Fine particles of rock powder that originate from a volcano and that may remain suspended in the atmosphere for long periods.
Vort Max- (Short for vorticity maximum), a center, or maximum, in the vorticity field of an airmass.

Volcanic Ash Advisory Centers
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Aviation, Darwin Volcanic Ash Advisory Centre
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VAFTAD stands for Volcanic Ash Forecast Transport and Dispersion Model and is used in conjunction with the numerical forecast models of the National Weather Service to predict the track and dispersion of ash plumes.

VAACVolcanic Ash Advisory CentersVADVelocity Azimuth DisplayVAD Wind ProfileA radar plot of horizontal winds, derived from VAD data, as a function of height above a Doppler Radar.

According to the National Weather Service, some of the obstructions to visibility include blowing and widespread dust, fog (including freezing fog and patchy fog) haze, mist, sand and blowing sand smoke, blowing spray, and volcanic ash.

Volcanic Ash: Very fine particles of powered rock produced by a "Volcanic Explosion"
Volcanic Explosion: A violent explosion of a volacano produced by subterranean heated rock.
VOR: A VHF Omnidirectional Range Navigation System.

Weather satellite images helped in monitoring the volcanic ash cloud from Mount St. Helens and activity from other volcanoes such as Mount Etna. Smoke from fires in the western United States such as Colorado and Utah have also been monitored.

Above 24,000 feet, the AWC provides warnings of dangerous wind shear, thunderstorms, turbulence, icing and volcanic ash for the Northern Hemisphere from the middle of the Pacific Ocean eastward to the middle of the Atlantic Ocean.

In the atmosphere water vapor starts to condense on microscopic particles suspended in the air: dust, soot, volcanic ash, salt spray, etc. These are called cloud-condensation-nuclei.

Examples are haze, dust, smoke, fog or ice fog, spray or mist, drifting or blowing snow, duststorms or sandstorms, dust whirls or sand whirls, and volcanic ash. Potentially, all hydrometeors and lithometeors may be obscuring phenomena.

penetrate to this layer, they remain there for very long periods, hence the concern regarding such substances due to both the actions of mankind (e.g. CFC's) and those of natural processes (e.g. volcanic ash).

See also: Water, Surface, Snow, Atmosphere, Weather