Smyrna times., 1886-02-03
Mechanism of Cold Waves.

Mechanism OF U0ld waves
The Washington Weather Bureau
has published "a preliminary study "
of Gold Waves and Their Progress"
prepared by Lieutenant Thomas NJ.
Woodruff. If it sheds little new light
on this interesting subject, it at least
strengthens some existing theories re-
garding the phenomena in question.
One of the most obvious facts in
weather science is that a large rOtatOry
storm, in crossing this continent from
West to East, is closely preceded by a
rise in temperature, and followed by a
fall. Part of this extra warmth is at
tributable to the liberation of latent
heat by the condensation of vapor in
the front half of the storm. But some
portion of it is due to the southerly
winds which, by an invariable law,
prevail in advance of such swirls. Be-
hind the storm the air is dryer, and
hence incapable Of yielding up much,
if any, heat, by manufacturing rain or
snow. Moreover, the prevailing wind
there is from some point of North, and
of course cooler than that in front.
MeteorOlOgists have not settled among
themselves precisely to what extent
these currents are a cause, and to what
extent an effect, Of the atmospheric
gyratiOn around a centre of low bar
Ometer; but their existence is un-
questioned. They come from frigid
British America and the tepid Gulf of
Mexico, and, after meeting, rush up
ward through the vortex of a colossal
aerial whirlpool. Another reason for
the difference in temperature on OppO-
site sides of a storm is that the air
which feeds its front usually comes for
some distance along the earth's surface,
while that which supplies its rear often
comes from higher, colder strata. The
atmosphere, having been heaped up,
hundreds or thousands of miles away
from the storm centre by ascending
currents, begins to settle. From un-
derneath the mass a downpOur and
Outgush result. The winds in the
eastern half of this anti-cyclone are
northerly, and hence colder than those
in the western section. From these
facts one would naturally infer that the
severest cold waves would occur when
a storm of powerful inward suction, as
shown by a very low barometer, is
closely followed by a tract of abnor-
mally high pressure; that they would
be most frequent when such cOmbina-
tiOns happen often; and that Their
route and rate of progress would de.
pend upon the movements of the
storms centre. If, now, we compare
Lieutenant WoOdruff's statistics Ol
great fluctuations in temperature with
the barOmetric data contained in the
monthly weather reviews, we shall
find these inferences strikingly con.
irmed.
His valuable and elaborate table
covers eighty eight of the most promi
nent cold waves which have been felt
in the United States in the first halve:
of 1881, 1882, 1883 and 1884 The worst
of these invariably came between 8
decided cyclOnic storm and a follow
ing anti-cyclOne. The latter always
entered the country from the north
west, usually along the eastern slope
of the Rocky Mountains, but occasion
! ally from the North Pacific coast. i
the storm which, to take a simile from
Wall street, was bulling the tempera-
ture also originated in the Northwest
and came along the Lakes to New York
and New England, the ensuing beai
movement was confined to these dis
tricts. But if the pioneer took a more
sOutherly course, through Tennessee
to the South Atlantic, the bOreal pur
suer followed that path instead
Again, when the storm organized in
! the Rio Grande Valley or came in
from the Gulf of Mexico, and moved
nOrtheastward, a cold blast would
first sweep down the Missouri Valley
to Texas, and Louisiana as "nOr.
! theT," and then extend to the seabOarC
or the Lakes, according to the track Of
the cyclone. When no anti-cyclOnt
followed, or when one was preceded
by no storm, the cold wave was sleight
Generally the huge air-wheel which
heralded an unusually 'cold snap u
was so energetic that no barrier would
materially retard its progress. But
did some obstacle intervene, the polar
billOw would also be delayed, and the
region that it then OVerlaid would suf.
fer more severely than Ony other. The
combined effect of two storms. one
south of tho other, making simulta-
neOus sight drafts on the northern
air reservoir, was clearly apparent
when they merged, as they sometimes
did, on their eastward journey. The
greatest attendant fall in temperatorC
occurred just west or southwest of thu
point of union. Lieutenant Wood
ruff's review does not include Decem.
Der, but of the eighty-eight cold waves
enumerated by him twenty-nine cam,
in January, twenty in February
twenty in March, ten in April, sever
in May and two in June. These fig
ures harmonic with the fact that eye
Ionic storms are severest and most FIRE
! qnent in Winter.
The practical value of this "pre
liminary study" in the light of history
| gained from other sources, is to con
centrate attention, in fOrecasting colo
waves. upon the energy, route anC
speed of low areas whenever they en-
ter the country, and upon the heigh
of the barometer, at such times, il
Western British America.-N. Y
Tribune.