The Indianapolis journal., 1903-07-05

most commonly Indicated Dy the Slhsie
word rain or snow as the case may be.
Thus. Rain tonight And when used in
this form il is expected that the rain will
continue several hours. In any other sea-
son of the year any one of the following
terms viz: Local rain,' showers thun-
derstorms' may be used. Local rains and
showers are almost identical in meaning.
The word thunderstorm Of course carries
its own significance. Any one OF these
terms indicates that the rain will not be
general over the whole State or district.
The most marked feature of the precipita-
ton in the warm season as compared with
the cold is its unequal distribution over
relatively small areas. A shower cloud
may form and pass over several counties or
it may dissipate within five miles of its
origin. Indeed L may say that ii is only in
exceptional cases that general and contin-
uous rains occur in some part of State
every day in the year. But the science of
meteorology is not yet far enough advanced
TO determine the path of the local shower
and the exact time for its occurrence.
Forecasts of local rains, showers or
thunderstorms indicate that the conditions
are favorable for the occurrence of precip-
itation in the district and for the given
period
MEANING OF CLEARING"
Clearing is word. frequently used
which carries a broader meaning than the
work itself signifies. that is TO say. the
occurrence of precipitation in the early part
of the period. Thus. Clearing tonight
would indicate that rain or snow. which
ever might be falling at the beginning of
<l,, ~fol eh lx her ffar
and that the weather would be clear dur
ing the greater part of the time
Clouds are formed from the moisture
that is always in the air in varying quanti
ties, even over the desert. Like the air
itself, the moisture that is within 1t is in
visible so long as it remains in the form of
gas. When a mass of air is cooled by any
means whatever a portion Of its water
vapor is condensed and becomes visible,
mist or cloud is formed. familiar Illus
tration of cloud formation in nature is
afforded when a current of warm moist air
strikes a cold mountain. The colder sur
face of the mountain condenses some of
the moisture that is in the air, forming
a cloud which frequently obscures the top
of the mountain and floats away in the
prevailing winds.
This simple phenomenon indicates to an
observer the leeward side of the noun
tain that a warm, moist current of air. with
probably rain or snow, is approaching. In
some parts of the world the formation Of a
cloud cap on a mountain is not an indica-
ton of precipitation, yet in majority Of
cases it is believed to be a reliable prognos-
tic of falling weather. In general the for
nation of clouds after a clear spell is the
first sign of coming rain. Unfortunately
there is no definite interval between the time
for the first appearance of clouds and the
occurrence Of rain. Rain may not fall for
several days after the first appearance of
Clouds and, on the other hand. it may be-
gin within two or three hours after the first
cloud makes its appearance.
"An increase in the amount of moisture in
the air is indicated in various ways. 1t is
specially noticeable to the senses when
coupled with high temperature. Man does
not need a thermometer to tell him that the
air is oppressively warm. nor a hygrometer
to tell him that there is an unusual amount
Of moisture present.
IAN increase in the amount of moisture in
the air is a sign of a change from fair to
foul weather, both winter and summer. In
the colder months an increase in the tenn
perature Of the air above the average for
the season, coupled with an increase in
moisture, is a sign of rain or snow within
twenty-four or forty-eight hours. In the
summer an increase Of temperature alone
is not always sign Of rain.
But these are not always infallible rules
The old proverb, All signs fail in dry
weather. is as true to-day as when first
formulated"