The Omaha Sunday
How tbe Rising Hot Air Currents Start the Formation of a Thunderstorm. A 1
Cross 8ectlon of a Thunderstorm. (A) Rising Hot Air Currents. (B) De
eending Cold Air Currents. (C) The Storm Collar, a Constriction Which
Produces Violent Winds. (S) The Roll Scud, or Hot Air Driven Upwards
by the Cold Descending Current. (D) Wind Gust. (H) Hall Produced
by Ice Particles Blown Up and Down In the Cloud. (T) Where the
Thunder and Lightning Appear. (R) Rain In the Thunder Cloud (R1)
Rain Produced In Adjacent Cloud.
Science at Last
Penetrates the Mystery
of Cyclones, Tornadoes,
Cloud-Bursts, Thunder
and Lightning, Which
Have Heretofore Been
WHY do we have thunderstorms (
toward the close of a hot Sum- A UZZlljalS?
mer's afternoon?
Many features of this familiar occur- TT JL
rence have not been clear even to sclen- lVJl VSlCITIGS
tlst.s, and Professor William J. Humphreys, J
the well-known meteorologist of the United
States Government, has recently furnished'
Rome interesting information on the sub
ject. The rain of the thunderstorm occurs
because the earth, heated much more rap
Idly than the upper air on a hot Summer's
day, sends a violent current of hot surface
air into the upper region. This current
gathers moisture as It rises, is finally
cooled, and then falls In the form of rain.
Why thunder and lightning accompany
the storm is a more obscure matter, and
is explained by Professor Humphreys by
a description of a recent experiment in
which a minute thunderstorm was pro
duced. Thn exnerlmrnter allowed (Irons
of distilled water to fall through a vertical
Diane oi air ot sunicieui gtrcngui to lnouuce
spray. From this the following facts were
ascertained: 1. The breaking of drops of
water is accompanied by the production
of both negative and positive ions (the
particles of which electricity is composed).
2. Three times as many negative ions as
positive are released.
Now this experiment closely reproduces
the conditions that produce a thunder
storm. Such a storm is characterized by
strong upward currents of hot air. aud
these are strong enough to account for the
breaking up ot all rain drops which would
otherwise fall through them. Hence at
the top of the uprushlng air current of the
storm, 1. e., within the thundercloud, a
rapid electrical separation goes on, the
first result of which is positively charged
rain drops and free negative particles. The
positive charges of the rain drops are con
tinually increased by the successive dlvi
slon and union of the drops. These posi
tively charged drops fall to the earth when
ever the air current becomes weak enough
to permit their passage.
The negative particles are carried up
Into the higher part of the cloud, wher
they unite with the cloud particles and
facilitate their formation into negatively
charged drops. These ultimately fall in
the gentler rain of the storm. The reunion
of the two separated forms of electricity
produces lightning.
Any weather condition In which a layer
oi warm air is beneath a layer of cold air
is likely to give rise to a thunderstorm if
the temperature contrast be strong enough.
Buch a situation is unstable and leads to
the violent moving about of different
strata of the air, which is the essential
feature of a thunderstorm.
The storm may arise from intense local
beatlug of the earth's surface. In which
case it is knows as a local or heat thunder
storm, or from the over-running of one
layer of air by another at a different tem
perature. Thunderstorms may also result
from the under-running, and consequent
uplift, of a saturated layer of air bv a
denser layer.
Non-local types cf thunderstorms are
classified by the wc.ither experts as cy
clonic, tornadic, an'l-cyclonic and border
thunderstorms, ucio.din to their position
with respect to cyclonic and anti-cyclonic
formations In th a-i.io-i.!'ere. A line or
row of tornalic storms extending from a
cyclonic te.it re constitute the well-known
"line snua'.l."
On land thunderstoms occur most fre
quently In the esr!y afternoon and in Sum
mer, and at sea they are most frequent at
nitsht and in Winter. This is because the
relative temperature :t the air as com
pared wlh land aud with water at the two
seasons is reversed. Thunderstorms are
more frequent In warm and wet years than
in cold and dry ones. Heat is the determ
ining factor in producing them, and con
sequently they ore most frequent at the
period of minimum sun spots and least
frequent at times of maximum sun spots.
Professor Humphreys explains the struc
ture of a typical thunderstorm in a very
interesting manner. First we have sir
L
1W
flowing in from all sides, rising, cooling
by expansion, and building up the thun
dercloud. As a result of this process rain
is formed at a considerable altitude where
the air is quite cold in fact, so cold that
hail Is often formed. This cold rain, or a
combination of rain and hall, as it falls to
tho earth, chills the air all the way down
to the ground, partly as a result of its low
temperature at the start, and partly b-L-ause
of ttw evaporation that takes place
during its fall. This cold current of air Is
correspondingly dense and becomes a
strong downward current The frlctlonal
drag of the falling rain is an additional
factor in giving it this downward move
ment. The current plunges down and at the
same time is carried forward by the gen
eral movement of the storm, under-running
and buoying up the warm adjacent air in
front. This current Is a typical thunder
squall, which rushes forward from an ap
proaching thunderstorm, agreeably cooling
the air.
Between the uprising sheet of warm air
and the adjacent descending sheet ot cold
.iir horizontal funnels are formed, in which
the two currents are more or less mixed.
These become visible at a point near the
front lower ed?e cf the main thundercloud,
where the rising air has eo nearly reached
'he rain point that the somewhat lower
temperature produced by the admixture
of the descending cold air is sufficient to
produce a fog-like condensation. This
constitutes what weather experts call a
nail cloud" or "roll scud."
Tiiese are the stages of a thunderstorm
in order: (1) An abrupt fall of tempera
ture, due to the rain-cooled descending
urrent; (2) a sharp rise of barometlc
temperature, which Professor Humphreys
believes to be due to lower temperature,
decreasing humidity and other more ob
scure factors; (3) a violent gust of wind
or thunder squall, already referred to; and
(4) initial heavy rata of the storm.
.The name of "rain gush" is given to a .
sudden acceleration to rainfall immediate
ly fallowing a heavy clap of thunder. The
uxi ...nation is that excessive condensation
In tue thunder cloud leads to a local ex
cess of electrification and electrical dis
charge, sine the latter processes depend
upon the presence and abundance of water
' Ibt SMmmer After mooms
t
How the High Buildings
r
I.
4 t . ,1
a "
Photograph
of a
Thunder
storm
in
Course
of
Formation
Taken
from a
Balloon.
. - h .a t-i
'H.V f v7 .-7.1
lrops Hence excessive condensation or
rain formation really precedes the thunder
slap, but as sound travels faster than rain
falls we hear tbe. thunder before the rain
push reaches us.
When the descending current of rain is
very heavy, the drops being so large and
close together that they form an almost
continuous sheet of water, we have what
is known as "a cloudburst." They usually
occur over very dry sections of country
which have sent an unusually strong hot
air current rushing up into the cold air
region. Cloudbursts are often very de
structive, especially in hilly country, where
the entire fall of water floy suddenly into
the tiearby valley.
Hall, which Is a phenomenon of severe
thunderstorms, consists of roughly con
centric layers of tnow and ice. It can
only be formed In the upper part of a
thunder cloud, where both snowftakes and
excessively cooled water drops sre present.
The nucleus of the hailstone having been
formed in this cold region gets into one of
th upper weaker undrafts of the storm and
fall fo the level of liquid drops, where its
own low temperature enables it to gather
a coating of ice. Presently a more violent
upward puff carries it aloft strain, and it
acquires a coating of snow. This process
may be reneatcd several times, until the
halftone U too heavy to be supported by
ascending currents and falls to earth.
Itpcent photographs of the lightning
flash by scientific observers have done
. much to elucidate the real shape of this
startling l henomennn. It Is now known
that the old, popular and artistic concep
tion of a zig zag streak of lightning is mis
taken, and that the fash has several typi
cal forms, all quite different from this con
ception. The fact is. of course, that a
llghtnin? flash Is so dazzling that the hu
man eye ran not obtain an accurate im
pression of It.
The photographs show that most often
the lightning flash fills itself up gradually,
and consists of several successive dis
charges along the same path. The dis
charge differs from that of an electrical
machine in one important respect the dis
tribution of the charge. In the case of tho
machine this takes place almost wholly
on the surface of the apparatus, while In
that of lightning It is Irregularly dlstrlb-
Copyright, 1013, by the Star Company.
Bee Magazine Page
of Now York and the Narrow Streets Between Them When Superheated
Particularly Violent Thunderstorms.
' ' k ' ' i( .
.. . S , ' ... " . J .
7 v " . . I-. liaitWyyiW. v t ' ' ' "
Remarkable Lightning Effects Photographed During a Thunderstorm
uted throughout the cloud. In both cases,
however, the air must be charged with
particles of one kind of electricity before
the discharge can take place freely. This
condition at times seems to establish It
self gradually.
According to Professor Humphreys's
view the lightning spark, once started,
"Ionizes" the air and makes Its own con
ductor as it goes. A similar condition can
be produced on a photographic plate by
bringing in contact with the film some dis
tance apart two conducting points attached
to the opposite poles of an electrical ma
chine, "lirusb" discharges develop about
each point, but the glow at the negative
pole detaches itself and slowly meanders
across the plate toward the positive point
This explanation furnishes a possible clue
to the cause of "rocket lightning," which
is a flash progressing slowly across the
sky line a sky-rocket and of "ball light
ning." Professor Humphreys has investigated
the question whether lightning is unidirec
tional, i. e., flowing In one direction or
oscillatory. He has come to the conclu
sion that it Is unidirectional, for the fol
lowing reasons: (1) Lightning operates
telegraph instruments; if these discharges
were alternating it would not be so; (2)
at times it reverses the polarity ot dyna
mos; this requires a direct and not a high
frequency alternating discharge; (3) the
oscillograph shows each surge or pulsa
tion, as well as the whole flash, to bs
flowing In one direction.
If the day grows excessively warm and
toward evening the clouds seem to rest on
the western horizon and become grayish
at the base, if the wind dies away and the
atmosphere seems unusually quiet, it is
the best evidence of a coming thunder
storm. Thunderstorms are more dangerous over
waterways than over dry land, because
water is a good conductor ot electricity.
Over a river the lines ot electrical force
are concentrated between tbe low-lyinz
clouds and tbe water, which creates an
electrical disturbance of greater energy
than is observed over the land.
Why Many Go-Carts Are So Bad for Babies
T
'HE choice of a vehicle for the baby
is a matter of great importance.
The folding cart, which may be
taken on the street cars, permits mother
and baby to go out many times when it
would not otherwise be possible. The
great convenience of this cart cannot
be denied, but such cars should be used
only for the purpose for which they are
intended, namely, to cenvey the baby
short distances, and not as pleasure veh
icles, nor should the baby be left to sit
fastened In one of these small carts for
any great length of time.
Some of the go-carts of the present day
are so small., so stiff, and so 111 adapted
to the baby's anatomy that they can
Qreat Britain Rights Keetrvsd
'MM&er
"H ,
. ... ,
A cyclone occurs at an area of low pre I- of one hundred to two hundred miles be
sure that is, where the atmospheric pres- fore it is dissipated.
sure is least, or where the barometer reads The explanation of a tornado is that
the lowest, and is nothing more or less
than a comparative vacuum In tbe atmos
phere, into which the winds from all sides
blow. The system of winds established by
blowing toward the low-pressure centre Is
called the "cyclonic system," for the rea
son that they blow spirally inward and up
ward, with a motion contrary to the direc
tion of movement ot the hands of a watch,
and when nearlng the centre the spiral
motion becomes more pronounced.
The storm centre Is known by sailors as
the "eye of the storm." At the centre of
tbe cyclone the atmosphere for an hour
or two In tbe most extensive storms be
comes clear, the clouds disappear, the
barometer shows a slight rise, and to all
appearances, except to the experienced ob
server, tbe storm is practically over. This
condition changes after the storm centre
passes, when the wind shifts from the
easterly quarter from which It has been
blowing to a westerly one and attains a
greater force.
This peculiar phenomenon Is due to the
ascending current of air at the storm cen
tre being dissipated by a descending cur
rent from higher altitudes, thus prevent
ing the formation of clouds at that point.
The tornado Is the smallest and yet the
most powerful and destructive of all storms.
It is of local origin, limited In width and
length of its path. Its chief characteristic
is a funnel-shaped cloud, which dips to the
earth's surface and has a violent rotary
motion. The upper surrounding sky is
covered with a mass ot black, treacherous
looking clouds. A tornsdo and a cyclone
are very different formations, and are only
alike In that each is a storm of whirling
motion. The cyclone is a wide-area storm,
covering flv hundred to two thousand
miles, with brisk to high winds extending
from its centre to Its outer edge. Tbe
tornado Is only from fifty to a thousand
feet wide and usually travels a distance
hardly be recommended even for tem
porary use. Also, they are so close to
the ground that tbe child is propelled
through only the lower and colder air
currents, which fling an unending stream
of germ laden dust off the street into
his face.
They frequently have no cover with
which to shield the baby from the heat
or cold, or sun or wind, and in cold
weather It Is impossible to keep baby
sufficiently warm In one of them.
The best vehicle for ordinary use about
the borne Is one which Is at least two feet
high. It should have room for the baby,
with the necessary wrappings, in any
position, and a cover that can be readily
adjusted to secure the needed protection.
It should have strong, well balanced
in Summer Cause
, ; ..v-..-'vi .
'V r
n
at Sea.
when an area of low pressure passes over
the country the general circulation of
winds from all sides flows toward Its cen
tre, which brings the colder, dry winds
from the north and west, and the warmer,
moist winds from the south and the east
into the general circulation of air bearing
toward the storm centre.
It Is believed that In this rush of warm
and cold air there must be a point of meet,
ing where there Is a great difference ot
temperature. In tills general case the war
mer current uuderruna the colder layers
of air, and In seeking an outlet forces Its
way through the place of least density,
causing a violent upsetting of the atmos
phere, which results in the formation ot
a funnel-shaped cloud of condensation of
moisture from tbe uprushlng ot warm,
moist air. The greater the difference In
tbe temperature between the warmer and
colder air layers tbe greater will be the
violence of tbe rotary motion which takes
place at the vortex.
A tornado as it advances produces a ter
rible roar, which has been compared to the ,
noise of thousands of trains ot cars pass-'
ing through a tunnel at the same time.
This terriflo noise usually occurs about
fifteen minutes before tbe arrival of the
tornado, and elves warning of its approach.
It Is probably due to friction caused by the
violent rotary motion of tbe tornado fun
nel. No power has ever resisted the force ot
a tornado except a mountain range. To
be within the tornado path is almost cer
tain death. On tbe south side one may
stand within a distance ot five hundred
feet with impunity, but on the north side
It Is almost certain destruction to be with
in a thousand feet The tornado uproots
trees, blows down houses, lifts bridges and
large buildings from their foundations,
blows trains of cars from their tracks and
lifts them several feet In the air before
overturning them.
springs and stand squarely on four
wheels. .A safety strap which fastens
about the baby's waist gives greater pro
tection than the ordinary carriage strap.
Carriage outings are, at best, not an
unmixed advantage to the baby, although
often they afford the only available means
of his getting the out-of-door air. The
lack of exercise and tbe more or less
rigid position maintained for considerable
periods ot time serve to tire the baby.
Also It is no doubt true that a baby sent
out in charge ot another child or ot
some person not altogether competent to
Judge ot his comfort la often neglected.
A more wholesome and natural place for
the baby to take his airing is In the yard
or on the porch, where he can be under
the mother's supervision.