The Portland daily press., 1882-02-11
Foretelling the Weather.

[Prof. j. W. Chickering in American Agriculturist
Those who have longest and most carefully
studied and recorded the weather, know best
that beyond two or three days, no predictions
can be made possessing the slightest reliability,
or that should be taken into account in making
our plans. There may be lucky guesses, as
there may be woeful failures in guessing.
Everybody has full liberty to guess what the
weather will be at any time in the future.
But when anybody undertakes to label his
guesses for weeks or months ahead ''predic-
tions," and to issue them as guides for the far
mer, or the traveller, or the clothing dealer,
he, in the language of Shakespeare, "writes
himself down an ass" When he undertakes
to get money for doing this, he shows himself
swindler on level with other quacks
But for one or two or even three days ahead,
the weather may be foretold two-thirds Of the
time with great certainty, the other third with
more or less of doubt. And not only can this
be done by the trained observer at the signal
station, but it may be attempted with good
success by any intelligent person who has nc-
cess to the daily weather maps, or even to the
full daily report. 1t would be great gain to
the community if our daily papers would give
us these reports in full as they are sent out, in
BIeaQ Oh cutting QOWn W luOEd luOiC8-
tions" for their own vicinity, even if they had
to lessen the space given TO horse races, base
ball matches, dog fights and police courts.
The whole theory of foretelling changes in
the weather, with the aid OF the telegraph, Is
based upon the fact that our weather changes
come, as general rule, from the west and not
from the east; that the great waves OF baro-
metric pressure, which we name high and low,
and whose alterations produce our storms,
move across our country from west to east, and
-, fIaO o1f hat
for our weather tomorrow, we look to see
what it is to-day to the west of us, with very
little interest as to what is going on to the east
ward Thus in New England northeast
snow storm is often telegraphed as coming
from the southwest, from New York, or even
from Virginia, or the Carolinas. or even from
farther south.
The pressure of the atmosphere in the tenn
perate zone varies about one pound per square
inch, and Indicated by the barometer varying
from 80 inches Qow) to 81 inches (high) as the
extremes, the ordinary variations being only
about half as great. Now the storm centre is
at or near the place of low barometer, where
the pressure is least, the air from all
sides rushing toward this with . rotary
motion, which in very severe storms is
named a cyclone. Sometimes, however,
the areas of high and low barometer extend in
long lines across the country from north TO
south but moving from west to east, as In
many of our "cold waves" extending some
times from the lakes to the Gulf. The greatest
fall of rain or snow is usually little IN ad-
vance of the storm centre, while the barometer
is falling. When the centre has passed, the
barometer begins to rise, and clearing weather
may be expected, generally with northwest
winds.
These storm centres, or "areas OF low barom-
eter," or slow pressure" oftenest make their
appearance little east of the Rocky Noun
tains, very often in Dakota, and then move
with greater or less rapidity toward the ATTAIN
IL yauarallv 6xIa OcoQSOnalIV storm
centre develops in Texas and moves northeast.
More rarely cyclones make their appearance
in the West Indies and follow along the course
of the gulf stream, the outer edge sometimes
reaching the Atlantic coast, very rarely OK
tending inland.
Out of 100 storm centres noted duriag 1879,
one moved north, three southeast, "A northeast
and 70 nearly due east. Their velocity varies
from 20 to 40 miles per hour, SO that either
storm centres or cold waves travel from the
mountains to the sea in from two to five days,
then passing off upon the ocean, frequently
taking a northeasterly direction after reaching
the coast. Sometimes storm may be detected
from its course, or spend its force midway, or
increase in severity as itmovcs eastward. IL Is
these possibilities, together with the varying
velocity of the wave, which render us depend
ent on the telegraph for its record OF daily or
even hourly progress, and which sometimes
contradict the best founded predictions. But
with all these possibilities Of error, 80 to 80 per
perhaps 70 per cent our reliance may be al
most perfect. AT times, either on land or sea,
a single warning may save property TO an
amount greater than the whole annual expense
of the bureau, to say nothing Of life and COM
fort Our weather, then, in general terms,
comes from the west, and when we read in the
papers that ''an area of low pressure with heavy
rain and severe gales is developing in the up
per Mississippi or upper lake region, the farm
er had better not begin his haying or his harv-
esting, and the traveller had better not set out
by way of the lakes or the ocean until it has
passed by. While if in the fall or winter, you
read that "an area of high pressure with yio-
lent winds and rapidly falling temperature is
prevailing in the same regions, the farmer
had better look to his young stock and make
all snug about cellar and barn, and the traveller
will do we'll to take his heaviest Overcoat.
Bearing in mind these few simple facts, eve
ry farmer or farmers boy who has access to the
daily indications aad reports" or better still,
to the daily weather maps, may become to a
great extent, his own weather prophet for two
or three days ahead and thus neither be taken
in by the guesses of those who make predictions
SO sell, nor fail of the advantage which may
often be gained by a tolerably definite and reli-
able knowledge of what sort of weather is COM
inQ.