The National tribune. [volume] (Washington, D.C.) 1877-1917, 1890-12-11
THE WEATHER.
The Progressive Movement Of Cyclones.
BY LIEUT.. J. P. FINLEY, U. s. SIGNAL SERVICE

By LIEUT.. J. p FINLEY, o. S. SIGNAL SERVICE.
fCorrcspondeuce invited suggestions desired
and Information cheeTfully furnished Every ef
fort employed to make this Bureau Of practical use
TO the readers Of THE NATIONAL TRIBUNE. All
communications should be addressed Weather
The NATIONAL TRIBUNE Office. Washington. ID. O. ]
cyclone, as has been previously explained
in this department of THE NATIONAL Tribune
is temperature disturbance in the atmosphere,
covering a region several hundred miles in ex-
tent north and south, and east and west. IL is
not a tornado, although a gyratOry velocity Of
the air is apparent when the storm 10 examined
as a whole.
Ordinary cyclones are never stationary, aud
the directions in which their ceUters move, and
also their yelOcities. vary, not only in different
latitudes and regions Of the globe but in the
same places at different times. In general
their tendency IN lower ATTITUDES is westerly,
and in the middle and higher ATTITUDES easterly.
There are several circumstances which control
to greater or less extent, the progressive
motions Of cyclones. The principle of one Of
these is undoubtedly the general motion OF the
atmosphere in which they exist. not at and
near the earth's surface merely, but at high
attitudes, where the center of energy is. This
carries them along rs a stream Of water carries
along the small whirling eddies which are
formed in it. Tropical cyclones move west
NdIut OF AT icttSL nave q large west component,
because the general motion Of the atmosphere
there up to a considerable altitude is westerly,
while in the higher ATTITUDES cyclones move in
an easteTly direction with much greater We
locities, because there the general motion at
all attitudes Is easterly, and the velocity, es-
pecially at high attitudes, is comparatively
great.
The average direction for the United States,
as determined by LOOmis from an examination
Of "a fNrfw FTv.r
Weather maps Of the Signal Service for three
years comprising 4s5 cases, is y. 81 T.. with
an average velocity of % miles per boar. The
monthly averages indicate an annual inc
quality. For April TO September, inclusive, it
IS n, S2'.5 f. p miles, and for October to
March, inclusive, y. 1926 E. % miles per hour.
Hence the direction is more nearly toward the
east and the velocity greater in Winter than in
Summer.
The rate Of progress OF cyclones over the
North Atlantic Ocean and over Europe seems
10 be much less, and the annual inequality pro-
pOTtionaily less. The average rate over the
United States, as determined from the records
for 10 yesrs-1S72- lS54-is 25.4 miles per hour.
This is the yearly average. For the six Winter
months the average 10 3I.7 miles, and for the
Summer months, 2i.9 miles.
Over the North Atlantic Ocean the average
velocity, as determined from period Of four
years-lS79- Isis $50 miles per hour for the
year. Over Europe, as determined from the
records OF five years-157G- 1S60-the velocity is
1871 miles per hour The increased velocity Of
progression over the United States is probably
duo TO the enormous stretch of land between
the two oceans, and its peculiar topography,
which permits the uninterrupted flow north
ward Of great masses of warm, moist air from
the Gulf and Gulf Stream, thus greatly develop
ing the intensity of all cyclonic centers Of dis
turbance The food Ofa storm is heat and moist
ure, and where il is not supplied in abundant
quantities the storm soon dies out. In Europe
the country is not only extremely broken, but
there IS no permanent source of heat and moist
ure 20 the southwark.
The cyclones which come into the United
States from the Pacific Ocean are developed
from the heat and moisture of the Japan cur
rent. After these storms have passed over the
Rocky Mountains they are very much reduced
in force and were il not for the vigOr and new
life they receive from the heat and moisture Of
the Gulfand Gulf Stream, they would disappear
after entering the Mississippi Valley. This
condition Of things would tend to make the
country east Of the Rocky Mountains q desert
and destroy its great productiveness.