After more than 400 years of no volcanic activity, the Indonesian volcano Mount Sinabug has recently awakened with a vengeance. Volcanic activity started in January and proceeded well into February 2014. Sinabug began to spew lava and incredible amounts of ash into the atmosphere that the locals haven't seen in years.
Natural disasters such as volcanic eruptions are an incredible force of nature. A recent video from Sinabug has led scientists and meteorologists wondering if an event such as volcanic tornado is possible.
Video/Dr. Richard Roscoe [www.photovolcanica.com] Jan. 14, 2014
Eruptions, and thus volcanic plumes, have been known to spawn waterspouts and dust devils, but are they also capable of creating what appears in the video as volcanic miniature tornadoes?
"The exact process of tornado formation is not well understood, but it appears that there
are three main ingredients: buoyant updraft, rainy downdraft and a mesocyclone," Dr. Pinaki Chakraborty, Associate Professor of the Fluid Mechanics Unit, Okinawa Institute of Science and Technology, Japan.
Tornadoes are also often associated with supercell thunderstorms where updrafts and rainy downfalls are necessary components.
"The mesocyclone is the 'mother vortex' that, ultimately, conspiring with items one and two above [updrafts and downfalls], spawns tornadoes farther from the column," Chakraborty said.
The takeaway from the video is that volcanic tornadoes aren't such a far-fetched idea but also highly unlikely and not very comparable to the average tornado, Chakraborty said.
These so-called volcanic tornadoes are built from the ground up and tornadoes are built adversely. Despite its backwards construction, the reason spectators see the rotating column of air is because the conditions are perfect and the three tornadic ingredients are there.
"My guess is that the same three processes are active here. The updraft initiated by the air heated near the ground, with the downdraft as the ash falling from the clouds and the mesocyclone may exist in the column of the main plume. But amongst all the dangers from volcanic eruptions, I think volcanic tornadoes are, comparatively speaking, benign," Chakraborty said.
An alternative explanation to what the spinning columns of air in the video might be is that perhaps they are nothing more than glorified dust devils.
A large dust devil or waterspout is all a volcano is capable of producing, not quite something as severe as a tornado Dr. Jeffrey Frame, clinical assistant professor of Atmospheric Sciences at the University of Illinois (Urbana-Champaign) said.
"All it takes for a waterspout or dust devil to form is low circulation over a cumulus cloud," Frame said. Low pressure also aids in this process.
Think of an ice skater as she spins: if the skater wants to spin faster, she pulls her hands close to her sides. If she wants to spin more slowly, she will spread her arms out as far as she can. A tornado works in a similar way.
"Air rushes in at the ground to take the place of the air that was pulled up due to low pressure, just like the ice skater bringing her arms in, and the air spinning faster," AccuWeather Meteorologist Jim Andrews said.
Dust devils are comparable to tornadoes simply in the way that they are both are a weather phenomenon created from a vertically oriented, rotating column of air, Frame said.
With dust devils, the hot updrafts are the main players and have nothing to do with a volcanic mesocyclone, Chakraborty said.
"Notable tornadoes are associated with a supercell thunderstorms which are rotating warm, moist air and a strong change in wind direction to give it height. The family [of volcanic mini tornadoes] in the video might resemble tornadic activity, but it's just ash and gas with similar rotation," Frame said.
The family in the video gets its heat from the pyroclastic flows headed down the mountain that can reach speeds up to 450 mph and the gas can get as hot as 1,800 F. They incinerate anything in their path, and add the necessary heat to form these miniature twisters if the conditions are right.
These miniature volcanic tornadoes seem to be a weather phenomenon that has to have just the right ingredients for the human eye to even bare witness to them.
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