Evening capital and Maryland gazette. (Annapolis, Md.) 1910-1922, 1917-09-25
DEFINES A TORNADO
WHEN THEY OCCUR
Weather Bureau Tells Causes and Eff
fects Of Windstorms Precautions
Taken To Avoid Injury

particularly favorable TO the Develop
ment of tornadoes, according to the
United States Weather Bureau. which
issues a series of warnings and def
nitions of tornado conditions.
II says that tornadoes are usually
preceded by high temperature and hui
midity-a weather condition general
" said to be "sultry," sticky" or
Oppressive Rain may come be-
fore. with, or after tornado, or,
very rarely, there may be no rain at
all. The barometer does not fore
tell tornado though it indicates low
pressures; and tornadoes always oc-
cur in "lowe area.
The season in which tornadoes may
be expected varies according TO the
region. They may visit the Gulf
States in winter, and as the season
advances, the region of greatest fire.
ouency is in the Plains States and
the Mississippi Valley. from April
to September inclusive. In this re-
gion May is the worst month, with
April next East of the Appalachian
Mountains, however, tornadoes rarely
occur until after July. Generally
they come between $50 and 500 p. m,
but they may even come at night.
What To DO.
Persons may somewhat avoid tor
nado danger. by watching the local
signs and reading the weather maps,
which at least show the conditions
Il, 60
local signs are heavy, dark clouds,
first in the Southwest, almost imme-
diately followed by clouds in the
Northwest and North. A funnel
shaped cloud is sure sign, though
there may be a tornado when such
cloud is not readily seen. If fun
mel cloud can not be seen, the whirl-
ing motion of the air may be known
by a peculiar roaring noise, somewhat
like the rumble of distant thunder or
the approach of a heavy train of
cars.
If one can see the cloud and get an
idea of the direction in which it is
moving, the zone of safety is at right
angles to the direction of motion. The
southern margin is usually more dan
gerous than the northern, and this
should be remembered in seeking
place of safety. The width of the
path of greatest destruction is ordi-
narily not more than few hundred
yards, though this destructive dame
ter may be from some rods wide to
half mile, or sometimes wider How
ever, the worst part in comparatively
narrow and relative safety may be
had only short distance at right an
giles to the line of the advance 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 cellar is probably the safest place
in them. In the Omaha tornado of
1913 very few brick houses were
seriously damaged These are ordi-
narily unroofed, though sometimes the
walls crumble or fall outward.
TOrnadoes and Cyclones.
Weather men define tornado as a
violent windstorm with rain or hail,
thunder and lightning, in which the
air. masses whirl with great velocity
around central core while the whole
storm travels across the country in
a narrow path at high speed. The
thunder and the whirling motion have
| given rise to two theories of the de-
rivation of the word; as to whether
it is derived from the Spanish ''tron-
! ada" thunder storm, or from the
Latin "tornare," to turn.
| A cyclone, in the definition of the
Weather Bureau, is not necessarily a
windstorm of great velocity, but
rather widespread storm that moves
with no great speed. Its width may
! cover several States. This cyclone, or
area of low Observation-Disclosures as
low" on the weather map-gives con-
| ditions essential to tornadoes. Many
cyclones never develop a tornado. but
tornado never develope without the
cyclone, and almost invariably the
tornadoes occur in the southeast
/ A-N
cyclones pass across the United
States each. year, moving in gen
eral way from west to east. They are
| of great benefit because they induce
a movement of surface air from the
south and southeast, and the rain
fall that makes the great interior val
leys a rich agricultural region is de-
pendent upon these southerly, mois-
ture-bearing winds.
Practically all of the cyclones OF
the warm season give rise at some
time or place to thunder storms, OF
hail or violent winds. These winds
may be violent enough to cause de-
struction, but unless they have the
whirling column of air they are moi
tornadoes. In the East 1t is not al
ways easy to distinguish the funnel
shaped colud, but the lay of the de
bris after storm will tell whether
there has been a twisting motion.
Tornadoes almost invariably move
in an easterly direction and generally
from southwest to northeast The
average length Of the path of destrue.
ton is about twenty-five miles, and
this path may not be continuous, i
the funnel cloud is not in contact
with the earth during its whole
course. Sometimes it rises and goe:
for considerable distance before de
scending again