The Richmond Virginian. (Richmond, Va.) 1910-1920, 1917-09-23
WEATHER BUREAU
DEFINES A TORNADO
0e1ls Oausns and Effects of Wind
snnrms. When They Occnr and
Prosecutions TO be Taken to
Avoid Injury.

YNuprt sa&ecn appears 20 De Parh-
ssiAriy favorable 70 the development
At tornndoas. according 20 the United
0asss weather eursu, which issues
. series OF warnings And definitions
e tewnace conditions
II seys that fcrnadoe~ are usually
SreosdSA by high temperature ana
humid1cy--a weather condition gen
wuyfy said 70 be "sultry." sticky or
sepprs~stvA" Rain may eope Before.
With. or after tornado, or, very
Tqreky. there may be no rain al al.
Ia barometer does not foreteh
snrnadc though Il aqdicates low pres
sures: and tcrnadces} always occur IN
. Tow area
The season In which tornadoes may
- erpertat vsrtes according to the
region They may visit the guH states
In winter, ard as the season advances.
the region Of greatest frequency is IN
the plains states and the MISSISSIPPI
valley, frsm April 10 September m
elusive In this region May Is the
wcrSt month, with April next. East
ct tie Appala chan mountains. now
avss, tornadoee rarely occur until af
car July. Generally they come between
axo and 500 p. NJ, but they may
wpar come at night
What 10 Do.
pereons may sornwhat avoid tor
nAde danger, hy watching the local
stxre and reading the weather maps,
which at least show the conditions
which favor tornado formation. The
lncal sters are heavy, dark clouis
f4rst In TIE Northwest and North.
funnei-shaped cloud Is a sure sign.
though there may be a tornado when
such a cloud is not readily seen. IL
4 rurnal cloud cannot he seen, the
whirhns motion Of the afr may he
known hy peculiar roaring noise,
oAnevhat like the rumble Of distant
thunder or the approach Of heavy
train OF cars.
m idea OF the direction in which Il IS
raevtng. the zone OF safety is at right
angles TO the direction of motion.
Tie southern margin Is usually more
dangerous thar the nothern, and this
should be remembered IN seeking a
place of safety. The width of the
path Of greatest destruction In ordi
nArtly not more than a few hundred
Yards. though this destructive diamet
a nav be from some rods wida 20 a
half mile, or sometimes wider, How
ever, the worst part in comparatively
narrow and relative safety may be had
only q short distance at right angles to
the tine Of the ad"ance of the tornado.
In some OF the plains states there
are so-called cyclone cellars and
where these are not available the
southwest corner OF the cellar Of a
frame building Is the next best place.
Brick buildings are not SO safe, but
the calIar is probably the safest place
in them In the Omaha tornado of
1919 very few brick houses were seri-
nusIy damaged. These are ordinarily
unrcofsd, though sometimes the walls
crum BILE or fall outward
Tornadoes and Cyclones.
Weather men define a tornado as
4 violeat widstorm with rain or hail.
thunder and lighting. In which the
air nasses whirl with great velocity
around a central core while the whole
storm travels across the ountrv in a
narrow path at high speed The
thunder and the whIriing molten have
given rise to two theories of the deri-
vaeion OF the word; as TO whether
II 10. derived from the Spanish 'tro-
nAda" thunder storm. or from the
Latin 'tornare. 70 turn.
A cyclone. in the definition Of the
weather bureau. is not necessarily a
w1ndstorn OF great velocity, but rather
q widespread storm that moves with
ne great, speed, Its wia,h may cover
s~veral states. This cyclone, or area
Of low Observation-Disclosures as low
an the weather map--eives conditions
to tarnsdnes. Many cyclones
never develop a tornado. but a tor
made never develops without the cy-
clone and almost invariably the tor
nAdoex occur in the southeast quarter
of the low area, About 40 cyclones
rAse across the United States sacf
year. moving In q general way from
west TO east They are of great bene-
~ because they induce a movement OF
surface air from the south and south
east. and the rainfall that makes tht
great interior valleys a rich agricul
rural region La dependent upon these
seutheriy. moisture bearing winds
Practically all of the cyclones OF the
warm season give rise at some time
or place TO thunder storms. or hal
ar violent winds. These winds ma.
Be violent enough to cause destrur
ton, but unless they have the whir,
tEy column OF air they are not tor
nadoea IN the East IL is not Away
eAsy to guish the funnel-shspec
cloud, but the lay OF the debris after
q storm will tell whether there hat
been a twisting motion
Tornadoes almost invariably move
50 an exsterly direction and general,
from southwest to northeast, Tn,
average length Of the path Of destruc
ton Ia about twenty-five miles, anc
this path may not be continuous, +
the funnel cloud In not In contact with
the earth during its whole course
Sometimes IT rises and goes for
censiderahl distance before descend
SAg again.