Evening times-Republican. [volume] (Marshalltown, Iowa) 1890-1923, 1920-03-30
Why and Ho.u Of
The Destructive
Wind Tlvisters

Somewhere In Alaska q cold wind
blew up late last week and wandered
southeast over British Columbia into
the United States. In southeastern
Nebraska II blew over a warm, low
lying wind from Arizona and New
Mexico that was starting northeast.
The warm wind tried to rise above
the cold breeze. as was natural, but
the velocities Of the two set I'D a
struggle.
A gyrating, whirling motion was
set up. The aerial whirlpool grew In
Intensity and early Sunday morning
a full fledged tornado swept past
Sioux City. Iowa, headed east. Short
ly after noon Sunday 1t arrived In
the environs Of Chicago, there to
wreak Its havoc, and by evening had
reached Lake Superior.
Sundays tornado was typical OF
that most diminutive yet most vio-
lent and destructive Of storms. 1t is
small storm within what meteorol-
ogists call an eStratroplcal cyclone.
and usually originates from 200 to
500 miles from the center Of the larg-
er disturbance. An extratropical cy-
clone Is simply a vast wind center
marked on weather maps as Tow"
areas.
Marked by Funnel.
The chief characteristic of the tor
nado is the black. funnel shaped
.cnn,,tp ho ha
low hanging masses of dark clouds,
whirlins and dancing as it carries
destruction in it's wake.
1t Is always associated with vio-
lent thunder showers and is usually
accompanied by hail. squall winds,
and excessive thunder and lightning.
1t almost always comes during the
warm months Of the year and the
hottest part OF the day. 1t is usual
ly less than 1000 feet in diameter
and the average speed with which 1t
covers the ground is fifty miles an
hour. resulting in its passing CIV
en- point in a half minute. The whirl-
ing velocity Of a tornado has never
been accurately measured. but II has
pttu nS AASLAh <NN W.
miles an hour.
Tales of the freakish behavior OF
tornadoes are without number. They
have been known to drive straws
thru solid timbers and timbers thru
metal posts and plates. With its
gentle" touch 1t will strip the feath-
ers from a chicken, leaving the bird
otherwise intact, and tie metal post
into knots while carrying 1t mile
or more.
Vacuum Causes Destruction.
Tho whirling motion Of tornado
sets I'D a vacuum or "air hole" with
In itself and It is one theory that the
destruction is wrought when this
core passes over an object. The core
nullifies the air pressure around the
object, such as house. and the AIR
pressure within the house causes II
to burst open just as deep sea nshes
explode when brought to the surface
of the water because of reduced out
side pressure Of the air.
The tornado Sunday was unusual
in that It struck q wooded district,
CRIu6 SO cdil ih ZIG yS~&s $500
Cured near large body OF water.
Tornadoes prefer nat, deforested
areas, such as the Mississippi valley.
and rarely visit territories adjacent
to large lakes. The air above large
body of water Is usually OF q uni
form temperature, tending to prevent
or dissipate storms such as the tor
nado.
The Different Storms.
The weather man" differentiates
between several varieties of storms
which the layman is apt to classify
under the general heads Of tornadoes,
cyclones. or hurricanes. To the
scientist cyclones are either tropical
or extratropical. The tropical cy-
clone Is a storm which originates In
the tropics and is q vast atmosphere
whirl. rotating counter-clockwise in
the northern hemisphere and clock
wise In the southern hemisphere, and
il not dangerous except when the
wind attains a hurricane velocity.
A tropical cyclone, or typhoon as
It Is sometimes called, always is at
tended by torrential downpours o.
rain and may be from 800 to 800
miles In diameter. The winds often
attain a velocity Of more than 100