The news and herald. (Winnsboro, S.C.) 1877-1900, 1881-06-11
HaIistorms and Waterspouts

Tornadoes. Hai'storms and Waterspouts
The conditions of tOrnadoes depend ra
ther upon vertical relations of Temperature
under which the unstable equilibrium OF
the atmosphere Is liable to be yio)ent],
disturbed by slight local changes of tenn.
perature causing the under strata of air to
burst up through the everything strata. A
cyclone Is usually broad, flat, gyrating
disk OF atmosphere, very many times
greater In width than In altitude; a tornado
may be regarded as column of gyrating
air Ill which the altitude Is several times
greater than it's diameter. The enormous
velocities of the ascending currents in a
tornado appear to be caused by the differ
ences between the gyratOry vclocitics above
and @se very near the carth's surface.
1hc largely prevent the air from
pres fill up the partial vacuum
near er, while the smaller gyratory
yelocitl-.. Lar the earth allow it to rush in
there to supply the draught. The tendcn-
cy OF friction Is constantly to use up the
energy of gyration 80 that the tornado can
not continue very long. The ascending
currents carry up an enormous amount of
aqueous vapor into the upper regions of
the air, where it is condensed and produces
the heavy rains observed in connection
with tornadocs. An ascending current of
90 meters a second, which cannot be un-
usual in tornadoes, would furnish, under
extreme conditions Of air saturation, four
inches of rain IN minute, If it were to
fall directly back. With such an ascend
ing velocity, however, no rain could so fall.
1t would he thrown OUTSIDE the vortex,
giving an immense though lighter fall OF
rain over larger area, especially if the
tornado in its regular progressive motions
should remain stationary or nearly 80 for
several minutes. If the velocity of the
ascending current is not so great that the
water is oil carried up to where the cur
rents are outward from the vortex, and vet
great enough to prevent its falling back,
there may be in the lower part Of the cloud
a vast accumulation of rain, prevented from
falling by the ascending currents and from
being dispersed by the inflowing currents
from all sides toward the vortex. When
the sustaining energy Of the tornado is ex-
hausted by friction or by the weight CT
water accumulated in the cloud. the water
is liable to fall in q mass, causing what is
called a cloud burst. This is especially
liable to occur In mountainous regions, for
contact with mountain must greatly in
terfeve with the gyratory motion of the
tornado and the infowing currents below,
and tend to break up the system at once
and let the whole load of water drop sud-
denly.
When the ascending current carries the
vapor into the region of frost-which is at
lower altitude within the gyratlng funnel
than outside of 1.-THE condensed vapor is
converted into hail. The small hailstones
may then be kept suspended near the base
of the snow cloud and enlarged by the
additions of freezing rain. In this way
compact homogeneous hailstones Of ordi-
nary size are formed. At the height of
Z 1,UOU yards the air has lost more Llluu l,a,r
Its density, yet an ascending velocity of
twenty yards second. which must be no
unusual one in tornadoes, would sustain
even at that altitude hallstones of consider
able size. 1t is not necessary that the
hallstones should remain in the freezing
regittl long time, or remain stationary.
They may be carried from this vortex out
where the ascending current is small, and,
dropping down some distance, may be
carried into the vortex by infowing cur
rents and again thrown up to the region of
frost. The nucleus of large hallstones is
usually compacted snow, A small ball of
snow saturated with water is carried higher
and freezes; and being of less specific
gravity than compact hail it is kept where
1t receives thick coating Of ice from the
unfrozen water dashed against 1t, and after
wards falls to the earth, either at distance
from the vortex where the ascending cur
rents are weak, or near 1t after the uprush
has been sufficiently exhausted. Some.
times, as IN the case of the cloud burst, an
almost incredible amount Of accumulated
hail may fall in short time, when the
energy of the system is suddenly spent.
Tho formation of large hailstones by
concentric layers of clear ice and white
snow, laid on like the coats of an onion,
will be readily understood from the fore
going. AS many as thirteen layers have
been observed in large hailstoncs, showing
that they must have been made of half a
dozen circuits, being succcssively thrown
out Of the frosty vortex above and sucked
IN below by the intiOwing currents, each
time adding to their coatings OF snow and
ice before their final fall to earth.
When the tornado is very small in the
area covered by the gyratory notion,
land spout or water spout is formed, as
it may happen TO occur on land or at sea.
In these the gyratory velocity diminlshcs
with distance from the center. Their de-
structive habits arc sudden and often great,
but the area of violence is small. In the
center of waterspout, as In that of
tornado In tull force, no rain falls or water
descends in any form, though n heavy
shower often falls in the vicinity. On
land dust and light substances are carried
up, and as they arc being collected from
all sides by inflowing currents toward the
vortex below, they assume the form of
cone, which meets the descending spout,
falling apparently from the clouds, and
thus give the whole phenomenon the ap-
pearance Of an hour. glass.
The observed diameters of waterspouts
range between two and two hundred feet
or more, and their heights from thi ty to
fifteen hundred feet. sometimes very much
more but none of these observations can
be regarded as at all exact. With a high
temperature and very low dew point Mr.
Fcrrel calculates that water spout might
reach mile in height, but such conditions
must occur rarely. Waterspouts are often