Download A Hitchhiker`s Guide to Tornado Alley

A Hitchhiker's Guide to Tornado Alley
By Ryan Loverick
3/23/2012 7:58:11 AM
The term "Tornado Alley" has become a common term to describe the region in America most
affected by twisters, but a closer look reveals that Tornado Alley is actually composed of four
extreme wind expressways.
The clash of warm, moist air and cooler, dry air coupled with a strong jet stream are the key
ingredients for severe storms capable of producing a tornado. When you have a strong jet
stream from the west or southwest high in the atmosphere and weaker, southern winds at the
surface, you get a twisting motion in the atmosphere. The strength of a tornado depends upon
how much of each ingredient is present as well as the topography of the land.
Long-tracking tornadoes, or the storms most commonly found in box office hits, are the "one
percent" of the extreme weather world, because tornado paths of 25 miles or longer can only
account for one percent of the total amount of recorded twisters. This one percent, however,
creates an estimated 46% of total destruction and 70% of deaths caused my tornadoes in the
United States, reports National Geographic.
Tornado Alley
The most frequently used funnel freeway in America is the Great Plains area, which includes
Iowa, Oklahoma, Nebraska, Kansas and Texas. The geography of these states provides the
perfect recipe for destruction, as the nation's breadbasket contains flat fields as far as the eye
can see. Western winds riding the North American jet stream over the Rocky Mountains have
roughly 500 miles to meet with dry air coming out of the north from Canada. "When looking at
the population of the Plains, it's not surprising that there are so many tornadoes," said Rayno.
"With major cities so spread out, there is a great deal of space for winds to start whipping."
Kansas has had the highest amount of F-5 tornadoes since 1880, the year America started to
keep record of its tornado sightings, and Iowa has had the highest percentage of "violent"
tornadoes, which consist of F4 and F5 twisters.
Dixie Alley
The deadliest tornadoes in America come from Dixie Alley, a region that spans from the
Mississippi Valley to the Tennessee Valley. Here, most tornadoes are violent, long-tracked
storms. There is no other tornado alley in the world quite like Dixie Alley, in that there is a
tornado threat three seasons out of the year.
Warm, moist air comes out of the Gulf of Mexico to clash with the dry air coming from the
deserts of Arizona and the west side of Texas at the center of Dixie Alley, which is where more
lives are lost due to tornadoes than anywhere else in the United States. In the fall, winter and
spring months, the North American jet stream is in prime real estate to get the air churning
enough to create some wicked windstorms. "Normally, people associate tornadoes with the
summer months, but at that period in the year, the jet stream is too far south to create
tornadoes" said Bernie Rayno, Expert Senior Meteorologist. The presence of moist air will enjoy
its starring role over the summer in hurricane season.
Simpson County, Miss., has historically been the most vulnerable to long-tracked storms. The
area places second in the nation for F-3 to F-5 tornadoes, averaging about one every 25 years.
The northern Mississippi and northern Alabama region is also a haven for heavy wind.
Hoosier Alley
Hoosier Alley is the region from southern Michigan to southern Indiana, and from eastern
Illinois to western Ohio, an area that turns into a hotbed for tornadoes from late spring to the
early summer months. This region is the last place a tornado can begin to churn before the
Appalachian Mountains in Pennsylvania and West Virginia muddle the opportunity to generate
enough wind speed to become a tornado. Hoosier Alley is not as active as the first two tornado
hotspots and is at its peak in the spring and early summer months due to location of the North
American jet stream.
Carolina Alley: A Newer "Alley"
Finally, a newer "alley" is starting to be more recognized. This new alley includes the northern
portion of Georgia through the top of South Carolina extending toward the coast into the
northeastern part of North Carolina. This region offers two impacting tornado threats, including
active cold fronts in the spring and passing tropical cyclones in the summer and fall months. The
double threat allows this region to be the fourth most tornado-ridden area in the country.
Since 1990, South Carolina has averaged around 28 tornados per year, and North Carolina has
averaged 16 tornadoes per year. Although the region has not experienced an F5 tornado in
recent years, a strong threat is always on one of the horizons. In 1998, North
Carolina experienced a record 66 tornadoes, and South Carolina's record stands at 54 in 1995.
Tornados can strike anywhere at any given time as long as there is potential for dry air to clash
with a predominant jet stream overhead. Make sure to check the AccuWeather.com Severe
Weather Center when severe weather is a threat.
Name: __________________________
Period: __________
LABEL the tornado alleys in the following United States Map.
http://www.kdheks.gov/hcf/data_consortium/data_consortium_health_indicators/US_states_map.htm
What contributes (causes) tornado alleys to form?
Which tornado alley do you think is the ‘safest’ to live in? Justify your answer.
Which tornado alley do you think is the most dangerous? Justify your answer.
Name: ______________________
Period: _________
Complete the following graphic organizer based on the article
information.
Tornado
Alley
Location
(states)
Air
Mass/Winds
creating the
severe
weather
Seasons/Time
of Year when
the alleys are
most active
Dixie
Alley
Hoosier
Alley
Carolina
Alley