Atmosphere And Weather

Types of Tornadoes

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Tornadoes are vicious weather phenomena that sometimes appear with severe thunderstorms.  There are two types of tornadoes, the type spawned by supercell storms and all others, but there are as many varieties of destruction and wild beauty within those types as imagination allows.

Supercell thunderstorms

“A supercell is an updraft (a rising current of air) that is tilted and rotating.”  There are some constants to consider when one is attempting to identify a storm as a supercell.  These storms can display:  “strong downburst winds, heavy rainfall, moderate-sized hail, and occasional tornadoes.”  (Weather Spotter’s Field Guide, U.S. National Weather Service, June 2011, page 28)

“Supercell thunderstorms, and the tornadoes they sometimes produce, are most common in the central part of the United States.”  Storm formation requires that different types of air fronts collide (warm/cool or wet/dry), and, for supercell formation, that they at some point begin to rotate around one another.  When warm or wet air is nudged higher into the atmosphere, where freezing temperatures are found, positively charged ice crystals may form in the presence of negatively charged water droplets.  This will eventually produce lightning discharges, which is the origin of thunder heard on the ground. 

Supercell thunderstorms, upon visual inspection, may show large, low-hanging wall clouds that appear to be spinning.  These clouds may also structures that look like a barber pole (which indicates the path of wind updrafts), and these updrafts may be traveling near 100 miles per hour.  Observers should never approach such storms closely enough either to be in a possible tornadic debris field or to be able to feel the very strong downdraft; supercell storms can be very dangerous.

Non-supercell events

Two meteorological events that are classed as tornadoes but originate differently are gustnados and landspouts.  Each of these grows from air rotation that starts near the ground.  “Non-supercell tornadoes are circulations that form without a rotating updraft.”  These will likely be less damaging than other varieties of tornado, and they will not last as long.  They are still potential hazards for anyone caught in their circulation; if you are too close to take a steady picture, you are too close for safety.

Measuring the strength of tornadoes

Prior to 2007, the Fujita (F) Scale was utilized to estimate the strength of tornadoes.  This scale, named for Dr. Ted Fujita of the University of Chicago in 1971, used visual assessments of the damage left behind tornado events to determine at what level (F0 – F5) to rank the events.

“The Enhanced Fujita (EF) Scale was devised by a panel of meteorologists and engineers convened by the Wind Science and Engineering Research Center at Texas Tech University.”  Having determined through experience of violent storms and the damage they left behind that Fujita Scale winds were estimated to be too fast at F3 and above, the panel adjusted the scale for the observed evidence.  The EF Scale (EF0 – EF5) is the result, and citizens will hear reports based on this revised scale in weather and news broadcasts.

Dangerous beauty

Tornadoes are phenomena of mysterious beauty that combine the physics of heating and cooling with atmospheric displays of electrical power.  Therefore, they are fascinating for many people, some of whom get too close to the event and are subjected to its destructive power.  Beautiful and mysterious as they can be, tornadoes deserve a measure of respect based on their unpredictability and the amount of misery they yearly inflict on unsuspecting people in communities across the nation.

Keeping safety always first in your mind is a good way to live to see another tornado on a different day.  Out of 100,000 severe weather events per year, the chances are that you won’t have to go out of your way to find something of interest.

More about this author: Jon Dainty Sr.

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