The record-union. [volume] (Sacramento, Calif.) 1891-1903, 1891-05-29
AERIAL GYMNASTICS.
Recent Storms, Their Origin and
Routes of Travel.
Signal Officer Finley Explains About
Cyclonic Movements, Air Cur
rents, Storm Centers, Etc.

Lieutenant John P. Finley, who is in
charge of the Pacific Coast Signal Service,
writes that many inquiries have reached
his office as to the causes which underlie
the peculiar conditions that have pre-
vailed in California and parts of Nevada
and Arizona during the past two weeks,
The subject is an important one, and
should be fairly well understood by those
whose interests are affected.
During the first week of May, he saws.
a cyclonic disturbance of decided energy
prevailed over Oregon, Washington and
British Columbia. Severe gales occurred
off the Washington coast, and unusually
heavy rains were reported as far south as
San Francisco. The area of light rains
extended southwark TO Mexico. The
barometer was decidedly below the nor
NAL in all districts. Before the atmos-
phere could recover it's equilibrium over
southern California, southern Nevada
and Arizona, another storm entered
British Columbia, and again the barom-
eter began TO fall in all districts, at
tended by the development of heavy
clOudiness and cool weather.
There has been a rapid succession of
these cyclonic areas passing eastward
over British Columbia, which continually
affected atmospheric equilibrium over the
southern portion of the Pacific Coast
States, and prevented any attempt at re-
covery. This region is SO far south of the
line OF storm movements, especially at
this season of the year, that weather
fluctuations are very gradual there. Once
under the influence Of a pronounced con-
dition of weather the change from it is
very slow. This is one of the marked
climatic differences between the south
Pacific rpDInn and tho north 60
region.
Within the path of cyclonic movement
across this country, from ocean to ocean,
we find the maximum of meteorological
changes. This region lies between 43o
and $50 north latitude. The area of a
cyclonic disturbance is a region of verti-
cal currents which give rise to high
winds, clouds and precipitation Verti-
cal atmospheric currents prevail over the
south Pacific region not always under the
intiunece of cyclonic action, but from
the effect of the suns heat upon it's vast
arid plains. Devoid of vegetation the earth
becomes excessively heated, and in turn
heats the air resting upon it. Therefore
low barometrlc pressure is a normal con-
dition Of this region, in the summer es-
pecially.
The easterly movement of cycionic dis
turbances over the north Pacific rephDn
intensifies the low atmospheric pressure
OF the south Baclf1c region, because the
two systems of vertical currents are prac-
tically the same, differing slightly as to
their origin. The air from the ocean is
drawn inland where, under the influence
of the vertical currents, its moisture is
condensed by the cold of elevation form
ing clouds, occasional showers, and Civ
ing rise TO low temperatures at the sur
face. If there is a marked increase in the
frequency of cyclonic disturbances pass
ing over the north Pacific region, there
results necessarily an increase in the con-
ditions which give rise TO cool, cloudy,
threatening weather and showers in the
south Pacific region.
For the reasons above given, the
weather of the latter region is particu-
larly dependent upon the movement of
cyclonic disturbances along the northern
boundary of this country. Even after
the cyclonic center reaches eastern Mon
tana and Dakota, it's southwest quadrant
is still connected with the low barometric
pressure in the south Pacific region. Low
barometric pressure and vertical currents
over Nevada will cause westerly winds.
and cool, cloudy weather over Northern
California.
If this condition is prolonged by the
passage of cyclonic disturbances to the
northward, light rains with snow in the
mountains will follow, attended by low
temperatures in the valleys If the YER
teal currents are checked over Nevada
by the presence of an anti-cyclone (high
barometric pressure) then the flow of air
from the ocean and consequent condensa-
ton is prevented. The SUMS heat pro-
duces its full effect in the quiet air. the
ground heats up rapidly, and lack of mo-
ton in the superintendent air tends to
accumulate the heat over such a region.