The Roanoke times. [volume] (Roanoke, Va.) 1890-1895, 1891-06-09
CYCLONES AND ToRNApoEs.
The limo and Conditions Most Favorable
to Them.


to Them.
Lieutenant John P. Finley, of the
United States Signal Service, has writ
ten very interesting article on the
origin and development of cyclones and
tornadoes-the former being the typical
general storm and the latter the typical
local storm. He shows that while cy-
clones may develop within the United
States, they usually enter this country
from adjacent regions. The places of
entry are the North Pacific coast (Ore-
gon and Washington), North Dakota
and the Gulf coast. From each of these
quarters the cyclones approach with po-
culiar characteristics Those entering
the country over North Dakota arc most
frequently accompanied by tornadoes-
To understand the relation of the
tornado to the cyclone we must con-
slider the cyclonic disturbances as di-
vIded into quadrants by two lines at
right angles, one running north and
south and the other east and west. The
northwest quadrant is distinguished by
great humidity. high winds and heavy
cloud formations, especially in the
southern portion, together with pre-
tains the maximum of heat and moist
ure; 1t is the region of all classes of
local storms. especially of the tornado.
The southwest quadrant is marked by
clearing weather and diminished hui
Nudity, while the northwest has the
minimum of heat and moisture, with
brisk. cold winds. The southeast quad
rant bcing the recipient of heat and
and moisture, generates the cyclone,
and the most violent disturbance of the
equilibrium being in this quadrant, and
within limited area, the ccntripctal
force becomes much greater and the
formation of the tornado cnsucs.
The questions which naturally occur
arc: What places are best adapted to
the development of tOrnadoes and what
is the time when conditions are most
favorable to them? Lieutenant Finley
points out that tornadocs are found in
regions where warm, moist air begins
to flow underneath Il colder and DRYER
upper stratum that comes from another
direction. This condition is followed
shortly by an inversion of the air in the
upper and lower Strata, the first visible
effect of the coming storm being the
appearance in the west and northwest
of Il heavy. portcntous bnnk OF clouds,
followed suddenly by a violent com
motion on the face of the dense black
mass, and by the rushing of adjacent
clouds toward the center of the dis
turbance, especially from the southeast,
east and northeast; as to time the sum
mcr season is most favorable for lorna
does, when the interior of the continent
IS warming and the air of tn. lower
strata is drawn from lower attitudes far
up In the northern portions of the coun-
try on the eastern side of the Rocky
Mountains the iSOthemal curve being
DETECTED very decidedly toward the
north.
Lieutenant Finlcy's summary of the
results of his Investigations seem to
cover every thing that can he learned on
the subject. Briefly, the most import
ant of them are rs follows: Tornadocs
generally accompany Il low pressure
area: the progressive motion of the tor
nadO is TO the northeast and the lorna
do, with scarcely an exception, occurs
in the afternoon, just after the hottest
part of the day. The tornado season in
cludes March, April. May. June, July.
August and September, the months of
greatest freqncnce being April May,
June and July. From careful inves-
tigation there is every reason to believe
that these storms were as frequent and
violent 200 years ago rs they are now,
and there appears tn he no cause for
any unusual change in their annual
frequency for like period to come.
tornado, Lieutenant Finley can, unfor-
tunately, say little, except that the
south side of the tornado's path is the
dangerous portion and the north side is
the safe one. II the clouds be moving
to the northeast then the line of escape
Is to the northwest; if to the east, then
to the north. To one who stands facinr
the advancing cloud in the direct line of
its approach, the safe side is always to
the right. No structure that rises above
the earth, however built, can wholly
resist the violence of the tornado, and.
therefore, no building is safe, either as
property or as a refuge 20 protect life.
From a business point of view, there
fore, as affecting the questions of life
and property, the tornado must bc con-
sidcrcd us IL natural agency for dcstruc-
ton. To Inc carefully watched and con-
tinunlly provided against. Philadelphia
Record.
CARRIAGE PEOPLE.
a Concern Tint Was Run IN 3, SfrIctIv