The daily sentinel., 1914-01-22
UNCLE SAM GIVES DATA SHOWING
HOW WEATHER FORECASTS ARE MADE


Washington, ID. c., Jan. 22-
Many people have an idea that there
is Something mysterious and occult
about the work of the weather bu-
reau in forecasting the coming of
storms, frosts and floods. Not a few
think that the observers must ne
cessarily get their data by reading
the planets, the stars and the moon
As matter of fact the forecaster
of the bureau foretells the coming
of disturbances in businesslike
way. very similar to that in which a
man who has ordered a shipment of
goods would estimate the date of its
arrival.
SuppoSe business man had order
ed carload of pineapples from the
Hawaiian Islands. He would know
the average time it would take the
steamer to make the trip to the Pa
cific port, the average time for un-
leading and loading into refrigerator
cars. and the average number of days
to be allowed these cars for their
trip across the continent to New
York. His estimate, however, would
be subject to error because the
steamship might be delayed by fog,
or the cars might meet with an ac-
cident.
Storms, like pineapples, as rule
do not originate in the United States.
They come to us, some from the Phil
| ippines, Japan, Siberia, Alaska, Can
ada or the Gulf of Mexico The
weather bureau gets cable, telegra-
phic or wireless notice of a foreign
storm. Station after station, or yes
sci after vessel reports the storms ar
rival in its neighborhood, so that the
general direction and rate of pro-
gress can be determined very early.
In fact. the arrival of some storms
can be foretold ten days in advance.
The forecasters watch for the re-
gion of low barometer which is the
storm center around which the winds
blow. This whirl or eddy moves bod
| lily forward with the general east
ward drift of about $50 miles a day
In our ATTITUDES. AS the lines of
equal pressure tisobars) around the
lew center crowd closer together, the
winds attending the storm increase
| ir force. The forecaster determines
the direction of movement of the
storm and its velocity.
When weather disturbances are
reported, the forecasters know from
experience about how long it takes
them to reach our Pacific coast, and
then how long after they will reach
the Atlantic coast. For example, if
a storm coming from Siberia drifts
eastward around the north pole and
re-appears in Alaska, it should ap-
pear in Washington and Oregon in
about two days; should get to the
Great Lakes in six days and to the
| Atlantic coast in seven or eight days.
| ITnaNnpptnI
storms or divert them from the
straight track just as u refrigerator
car may be thrown off it's schedule
OF be shipped by accident on a wrong
road. Some of these storms deplete
| themselves by running into regions
of high barometer which are of great
er magnitude and extent than the
storm itself. Some of them, how
ever, travel completely around the
world.
To keep tab on cold waves that
come into the United States from
Canada and Alaska, the weather bu-
reau studies the Canadian weather
reports. England sends reports from
Iceland, the British Islands and con-
tinental Europe, and daily reports
come from st. Petersburg on the con-
d;tions in Russia and Siberia.
in tracing the track of a storm is
applied in determining the arrival
OF frosts.
Flood forecasts are made in much
the same way. Information as to the
amount of rainfall at the headwaters
of streams that cause floods are COW
cred by telegraphic reports sent by
local observers. AS this rain reaches
the main channel, the height of the
water in the channel is determined
by successive gaging stations. Past
records establish how much height,
say Of 20 feet at Dubuque, Iowa, will
produce at Davenport, another sta
tion so miles down the Mississippi.
| This plan is followed all the way
down the river, and at each point full
allowance is made for the effects of
water from tributaries, and from ad-
ditional and local rainfall. As a re-
suit of these observations in the re-
cent flood, the people of Cairo had
warning a week or ten days in ad-
vance. The Pittsburgh district can
be given only 12 to "a hours notice,
because a flood is upon them within
"a hours after a heavy rain storm.