Evening star. [volume] (Washington, D.C.) 1854-1972, 1885-01-17

OFFICIAL WEATHER PROPHETS.
How the Observations and Predictions
are Made.
THE COURSE OF STORMS UNIVERSALLY EAST
wARD-wHY NO STORM EVER REACHES Us
FROM THE PACIFIC SLOPE COLD WAVE
THE NORTHWEST THAT BLOWS BOTH HOT AND
c0LD-How TO BECOME AN INDEPENDENT
WEATHER PROPHET
The science of meteorolocy is still In its in
fancy. About fourteen years ago the first
predictions. being then called "proba-
bilities," were made by the signal service In
| order to secure accurate observations taken by
over two hundred observers located in different
parts of the United States. and all taken at ex-
actly the same instant of time. it was decided
| oy Congress to make these observers amenable
to military discipline by enlisting them In the
signal corps of the army. The wisdom of this
measure, it is claimed BY the officers of the
service, is amply proven by the clock work pre-
cision with which each man performs his duty.
Three times daily, ut intervals of eight hours.
is he noting the readings Of his instruments:
FIRST, the weight or elastic force of the atmos-
phere as shown by the barometer: second the
relative humidity or per cent of moisture con-
eter; third. the velocity, ferce and direction of
the WIND, as per anemometer; and lastly the
kind, amount and direction of clouds, and
amount of rainfall For the purpose of breyity
this is reduced to cypher form. and within thirty
minutes from the time the first instrument IL
read the full observation is received by tele-
graph at the office of the chief signal officer in
this city.
HOW THE PREDICTIONS ARE MADE
These observation ofices are distributed over
every section of the country from Florida to
Oregon. They record their observations at ex-
actly the same moment washington time).
Therefore when received at headquarters and
their facts and figures charted upon a map of
the United States, the chart becomes simple
photograph Of the conditions existing in the
atmosphere at that moment. 1t is from this
chart that the predictions for the following day
are made. BY drawing a line connecting all
| stations OF the same barOmetric pressure the
area OF lowest barometer Is easily located
Moist air being lighter than drv the center Of
low barometer becomes the storm center. This
center has no wind direction geographically
the atmosphere moving with a rotary motion
upward and the surrounding air being drawn
towards the center. The winds always blow
from high to low barometer, that is. from
heavy atmospheric pressure toward the point
OF least resistance. moving spirally Inward
toward the storm-center.
The low area is usually several hundred miles
IN extent. When the storm is stationary its
form is nearly circular, but when moving east
ward its sides are depressed until it becomes an
oval, the depression being proportionate with
its velocity. Twenty-four hours is the average
time required Tor storm to trave, from the
Mississippi river to New York and nearly the
same time from New York to Newfoundland
The preparation of these daily weather charts
enable the student to go back fourteen years
and find complete record of every storm that
has occurred during that time: where formed
the direction and velocity with which it travelled
across the country, and all the natural phe-
nomena attendant upon it from its inception to
It's dissipation It is the accuracy of these
records that has enabled the United States to
take the first place among all nations in the
progress made In the science of meteor0lOgy;
and it Is the study of them that enablss the indi-
cation officer of the signal service to detect the
formation of a storm in its ncipiency and to
foretell the path it will travel and give warning
accordingly.
THE COURSE OF STORMS
is universally eastward. No storm of the Pacific
coast ever reaches US. as, in crossing success
svely the several ranges of mountains inter-
vening. the atmosphere is :orced up to such An
elevation that all moisture is condensed by
cold and it descends the eastern slope Of the
Rocky mountains perfectly dry air; indeed 80
void of all humidity that hunters cure fresh
meat in the middle of summer by simply hang
ing 1t on the limbs OF trees, and the region for
hundred miles east of the hills is barren
waste.
Many of our severest storms form In the re-
gion just west of the Mississippi river. pass east
ward of the Atlantic coast, and augmenting in
force as they cross the ocean, continue their
course over Europe until disslpated by encoun-
tering some range OF mountains Between July
and October the United States is usually visited
by from one to three heavy storms, which come
up from the West Indies crossing the extreme
southern states In northeasterly direction and
then following up the coast violent gales always
attend. 1t is claimed that millions of dollars
annually are saved to shipping interests Of the
Atlantic ports by means Of the warnings dis
played by the signal service several hours in adj
vance OF these storms.
COLD WAVE
is an immense river of air flowing from the arc
tic regions southwark through British America.
and entering the United States letween the
Rocky mountains and the great lakes, whence
1t spreads out east and south. 1t ALWAYS comes
from the same direction, and usually takes
about twenty-four hours to travel from Saint
Paul, Mimi, to New York and Washington. AS
the cold waves comes from the northwest it
would be natural to suppose that the warm
waves come from the equatorial regions. But
such is not the case. They also come from the
northwest. When observations become more
general over the entire world, it is presumed
s0Soiihk, ihSohsistCuSy Will ue CA
planned.
INDEPENDENT WEATHER PROPHETS,
Every few years some person suddenly gains
notoriety as weather prophet by predicting
snow or rain several months in advance. They
usually claim that their predictions are based
upon some astronomical influence The claim
that there is any ground for such prediction is
disputed by the best authority. Relying upon
the consistency of climate, which has been estab-
lished by observation, we may predict the gene
raj character of any month in the year with a
fair degree OF accuracy. Observations continued
for an entire century at various places. both in
the United States and Europe. show that the
climate Of country remains precisely the same
from age to age; that one extreme will GER
tainly be cquaiized by another; that the mean
annual rainfall is the same the mean tempera-
ture the same, the mean direction Of wind
the same. and tho mean of the last frost in,
spring and the first in autumn the same II sew
eral months have been unusually warm, or ex-
tremely cold it is not to be supposed that the
climate has changed and that the succeeding
months will be similar In character: but we
should rather anticipate weather of an opposite
description, as we know that all fluctuations of
temperature are soon equaiiZed. In the sane
manner, II the snow and rain tall for the year have
been considerably less than the mean precini-
tation. it Is equally certain that the next wear.
or the succeeding two years, will be propor.
tionately large. 1t Is probably upon this gene
raj law of equalization that our independent
weather DrOpnet denends for any fnrek n ~ ~