Manchester Democrat. [volume] (Manchester, Iowa) 1875-1930, 1900-01-24

air masses from one point to another |
to restore the equilibrium, is what
we term a storm.
This variability in pressure is prin-
cipally caused by the unequal distri-
button of land and water, and the un-
equal elevation of the land surface.
During the summer the continents
oceans, and low barometer conditions
the winter the continents become in
tensely cold, while the oceans are
more equal in temperature, and this
causes reverse of conditions So we
have greater prevalence of high
pressure on the continents in the win
ter, and on the oceans in summer.
And the fact should be noted that n
high barometer is generally co-inci-
dent with cooler weather. By the
effect of heat the air expands, becomes
lighter, and weighs less in the ba-
rometric scale. So all general storm
movements are preceded by warm
waves, with low pressure and followed
by colder waves of high pressure.
There is another important factor
concerned in the formation and pro-
gress of storms, and that is the vapor
of water. Evaporation and precipi-
tation are constants, and must be prac-
tically equal to maintain the equilib-
rum.
Under the influence of the solar rays
the atmosphere is expanded and takes
up vaporj from the surface Of both sea
and land. This vapor, though form
ing only a very small portion of the
body of thu atmosphere, really possess
es much greater power of absorbing
and radiating heat than the other COM
ponents. We may judge something
of the power and expansibility of va
por by noting its effects when confined
and made to do service in the steam
engine.
Il Some of the most eminent authori-
ties in meteorology tell us that the
chief distributing influences at work
in the atmosphere are the forces called
Il into play by its aqueous vapor. 1t is
y certain that both heat and moisture
! cause the unequal density and varyin g
weight of the atmosphere. And SO it
may be said that storms are born of
heat and feed on moisture.
So we find that humidity, as we'll
as pressure and high temperatures
plays an important part in the devel-
opment of storms. When the watery
vapor is precipated the latent heat is
liberated, and thus contributes an add
ed force in perpetuating storm condi.
lions.
The discovery was made by Benja-
min Franklin in the middle of the
last century, that great storms move
l across the North American continent
. from west to east. In recent years,
: by the aid of the telegraph, we have
! worked out the details Of the science,
? and have learned vastly more concern.
g ing the origin and general character.
{ istics of the storms that traverse our
, country.
Since the establishment of the
weather bureau, under the auspices Of
the government, more progress has
, been made than in all preceding
years. A large portion of the cont.
: nent is covered by stations, fully
t equipped with instruments, where OBJ.
servations are made and recorded anG
d sent to Washington twice day, set
!. ting forth all the essential facts as tc
Q weather conditions in all sections Of
Q the country. These reports are use6
S in making weather maps, as the bash
s of forecasts, or predictions of storm
q movements.
On these maps we note the passing
of continuous procession of "highs'
and Flows" across the continent
S Every day in the year these map
show high and low areas, with storm
Q conditions prevailing in some portion
, of the country. And usually before
, one storm disappears off the eastern
t coast another we'll developed disturb
: ance is crossing the heavy barriers O.
the Rocky Mountains, at some poin
3 along the line north or south. Ere
q quently we note two or more low ba
q rometer storms depicted on the mai
! at the same time.
The storms of this midland region
may be classed as primary and second
airy, or major and minor disturbances
The primary storms are named cy
: clones, which is the generally adopted
n scientific name Of all widely extend
o ed storm movements of rotary char
9 acter. The secondary storms ar
thunder and hail storms, local wine
e squalls, tornadoes (sometimes mis-
Q named cyclones) waterspouts, ant
j sand whirls.
In this valley the weather is affect
h ed BY the passage from west to cas-
J, of or s cyclones, or low pressur
areas, and about an equal number o
S3OACoy VI 411SA PIC6SulS dIGdS
= in each month. They make thei
8 transit in 4 to days,-the waves be
y ing more frequent and rapid in white
e and spring than in summer and fall
+ These cyclones usually assume al
e eliptical form. with their longest di
J. ameters on line southwest to north
Is east, from 500 to 1900 miles in length
J. Occasionally we note vast chasm O
trough of low pressure, extendin,
d from the Gulf to Lake Superior, witt
# considerable disturbance in the large
g part OF the low area. During tn,
passage of cyclone the general cir
J, culation of the wind is rotary, O.
d spirally inward around the storm cen
II ter, or the point where the baromete,
! shows the lowest pressure. The fore,
b or velocity of the wind depends al
}. ways upon the steepness of the gradi
IS ent, or the descent froul the high tt
j. the low area; just as the velocity of
: stream of water depends upon tn,
n steepness of the grade from the higl
to the low level.
e Here we note the cause or philoso
+ ply of all wind movements. Tn,
d wind blows from the high to the low
or from the area of excess to the are,
J. OF deficiency, being propelled by the
Il law of gravitation, like the flowing
v Of stream of water. So all wind!
are caused by decided contrasts or diff
, ferences in the atmospheric pressure
: resulting primarily from different
: temperatures.
The greater number of the cyclones
t which cross its mid-continent region
Q unquestionably have their origin in
the Japan current of the Northern
$ Pacific ocean, where there is an abun.
dant supply Of heat and moisture tc
$ give the initiatory movement to cy.
4 clonic formation. The expanding at
: mosphere and the enormous masses
l Of vapor cause ascending currents, and
9 these form vast eddies which drift
. along under the influence of the east
S ward trend of the upper air.
3 These Northern Pacific cyclones US
a ually strike our continent somewhere
. along the upper Pacific coast, passing
into the interior either through Brit
s ish Columbia, Washington or Oregon.
They are generally heavy laden with
vapor, which is rapidly condensed