Evening star. [volume] (Washington, D.C.) 1854-1972, 1895-08-31

DofiuHs up III the h1gn as 1t runs down,
iesds any vortex or whirl that may have
peen started along its edge, and thus
continues to supply 1t for the many days
that these violent storms orc obsaryad ~
last
Some students have claimed that the
tendency of the warm, moist dodrum air
10 rise I'D Is the first cause of producing
these cyclones. But there is one very diff
can be established. Air will rise by con-
vection only when the difference of tenn
perature is considerable between the ris-
ing column of air and the adjacent
gions; Yet in hurricanes this difference of
temperature Is not observed.
How the WhfrIins Vortex Begins.
Now, on examining the maps for the
isobars. it is almost always seen that the
lower isobar, marking out the edge of
the great ocean high, has a loop or sort
OF pocket, by the bending down of the
line, and in this the whirl begins. In the
autumn, as the sun is moving southwark,
the impulse of the air is to follow it, and
It may we'll be that the smooth isobar
lines stretch out fingers toward the equa-
tor, into the doldrum calm, making a pock-
e. OF lower pressure. and that herein the
whirling vortex begins it's course. Its
future, dependent, as has been said, upon
the performance of the high area in open
ing up a passage near the American coast,
Is merely the sucking in of the air from
the nigh area, practically regardless of
temperature, the rain also being a Sc
oadary phenomenon.
The Approach of the Cyclone.
AS to the hurricane itself when once set
In motion, we have more definite informa-
tion. The approach CT a hurricane is usu-
ally indicated by a long swell on the
ocean, propagated to great distances and
forewarning the observer by two or three
days faint rise III the barometer is in
dicated before the gradual fall that may
become very pronounced at the center; fine
Wisps of cirrus clouds are first seen which
surround the center to the distance of 200
miles, the air is calm and sultry, but this
IS gradually supplanted by gentle breeze
and later the wind increases to gale, the
clouds become matted the rough, rain
falls and the windsraue gusty and danger
GUS as the vortex core comes on. Here IS
the 1ndescribable tempest, dealing destruc-
ton, impressing the tmaginati ton with its
wild exhibition of the forces of nature, the
mas hes of lightning. the torrents of rain,
the cooler air ali the elements In an up-
roar, which indicate the close approach of
the center. In the midst of this turmoil
there Is a sudden pause. the winds almost
cease, the sky clears. the air is cool the
waves, however, rage in great turbulence
This is the eye of the storm, the core of
the vortex and is, perhaps twenty miles
IN diameter one-fortieth of the whole cy-
clone The respite is brief and is soon fol-
lowed by the abrupt renewal of the violent
wind and rain, but now coming from the
opposite direction. and the storm passes off
other in the reverse order.
How the Vortex Discharges
By the laws of vortex motion the winds
approach the center in spirals, the circular
and the centrifugal movements increasing
every moment. At the core, in the walls
of the columnar vortex, the air circles
about the calm central part, gradually ris-
Ing upward to the cloud stratum, Just
above the in1owing disk. Here the air
flows out suddenly On all sides, the circu-
lar motion decreasing. cooling by eXpan-
sion, causing great thin sheet of rain,
two or three hundred miles from the CEN
ter. At this distance the vortex sheet
turns up suddenly, not down, usually
stated, and discharges the expended
tex matter into the high upper currents of
the atmosphere. If one holds a saucer of
ordinary shape up and looks at it from
! the under side. it will not give a very in
correct idea of the general shape of this
thin vortex sheet as it turns up and dis
! charges at the edges. Over the whole
detSide OF IT. is the rain cloud, in the CEN
ter the ring core and the calm part
| The feeding wind lines are more nearly
| parallel to the ground than the upper disf
charge lines, but they all form a simple
| colunlnar vortex of unusual configura ton.
The clear sky at the center is as If hole
were pierced in the saucer. through which
the undisturbed air above alone was visible.
There is probably no feature of nature
more interesting to study than hurricane,
however sentiment may be affected by the
experience of one at work
Twenty-FOur Septembers.
The following data, compiled from the
weather bureau records, cover the period
of twenty-four years for the month of
September and Should prove of value and
| interest in anticipating the more important
meteorological elements, and the range
within which such variations may be ex-
pected to keep for the coming month
Mean or normal temperature, 6S degrees.
an average of n degrees.
The coolest month was that of 1871, with
an average of 81 degrees.
The highest temperature was 1O4 degrees
on It'll, 1881.
The lowest temperature was SO degrees
on 26th, 1879.
Average precipitation for the month, 3.62
inches.
Average number of days with .01 of an
inch or more, o.
The greatest monthly precipitation was
1881 inches, in 1876
The least monthly precipitation was OIL
irch, in 1884.
The grea test amount of precipitation re-
corded in any "a consecutive hours was 5.66
inches, on 18th and 18th, 1874
Average number of clear days, IL; partly
cloudy days, IL; cloudy days. 8.
The prevailing winds have been from
the south.
The highest velocity of wind was SO
miles, from the northwest, on Goth, 1882.