The Washington times., 1914-05-03

laboratory.
In this article the daily task {
ProfS. H. {. FraHkenfeM and E. +
Bowie is followed, and Charles
Marpin, chief of the bureau, or
lines the progress made in weathe
prognoSticdtion.
By J. R. HILDEBRAND.
Fair and cooler tonight, moderate
northwest winds" you read in your
paper.
And you shape your plans accord
fngly unless you are one of that
narrowing circle of cynics who will
have their little, joke at the expense
OF the weather man.
But how did the forecaster know?
he did not look out of the window
and guess. Neither is he afflicted
with any insignificant rheumatic
twinges, nor does he possess an Of
ilcial razor strop which registers the
state of the atmosphere. Nor yet
does he lay claim to any of the oc-
cult powers Of the gifted Uncle
Horace" johnson, OF Haddam, Conn,
whose word. weather wise, is law
with scores of his neighbors.
Weather prediction is an exact
science. And If there yet is an av-
erage from 10 to 12 per cent of er-
rors in the predictions, as now is
J the case. it is because the science
is so complex that even an expert
rannot always solve the problems, as
various and unexpected as those of
a baseball game.
Perhaps chess game would be
better comparison. For a board. the
forecaster uses a map of the north
ern hemisphere. And that cold
wave over in Siberia, that low pres
sure area off Halifax, that high
wind at Dawson, and the high tenn
perature off Galveston, each has
course of movement as definite as
the chess players pawn, or bishop.
or castle.
II the forecaster figures the ag-
gTegate result Of these moves cor
rectly. he wins the game for that
day, and predicts the weather ac-
curately. II he overlooks a wind or
q group of clouds he is apt to lose.
Get Data by Telegraph.
How, then, does the forecaster
know about the coming weather?
By telegraph and mathematics.
Six or eight operators are stationed
at the United States Weather Bu-
Tesu, at Twenty-fourth and VI
streets, receiving daily reports from
more than 900 weather stations
throughout the country. Thcsc sta
LIONS do not vouchsafe opinions.
They state facts covering rainfall,
i"mpcrature. barometric pressure
wind dill ection, wind velocity, cloud
conditions in respect to amount,
character. and directions; high tenn
perature. low temperature. vapnr
pressure and the state Of rivers
All of which one might susp~,.,
would make a lengthy telegram. Not
At all Unless some special CondI-
ton arises, this report is made with
In ten words: usually it takes but six
pr seven. by the use of a simple
@ode. Thus the telegraph tolls on
these twice daily reports are kept
Gown to 5000 month. The entire
monthly telegraph bill of the DEPART
rnent is about 81, 600. So that any
words saved mean a considerable
aggregate saving
As fast rs these bulletins come
N the forecaster or his assistants in
dicate the conditions described in lit
tie circles scattered all over a rnap
II the United States Look AT one
= these maps and besides the 200 or
more circles. representing reports
from each of the stations, there will
hc series OF free and easy curves
= red and blue lines. The red lines
indicate equal pressure areas. the
.luc lines indicate equal temDera-
iure. These lines play an important
Iart in the days forecast.
II the red lines are far apart
comparative calm will prevail. II
strong wind may be expected. while
" they are twenty-five miles apart
gale may be predicted The action
or air In motion is much like that of
water. And the closeness of equal
pressure lines means that the air
VIII De forced. with a rapidity en-
rendering a high wind. TO seek an
other level
Two Maps Made Daily.
Two sets OF reports are received
daily. and a map is made from each.
From comparison of these reports
the course and progress of storms
and periods of clear weather can be
seen at a glance.
The significance of the high and
low pressure areas may need cx-
iIiahailOn. These terms are used 10
describe the weight or pressure Of
the atmosphere. The barometer. at
sea level. is 30 under normal condf-
iions. As soon as il registers even
fraction more than thirty the
pressure becomes "high.' and If It
drops 10 less the pressure becomes
low"
The fact that these highs" and
lows" travel eastward across the
country forms the keystone Of the
science of weather prognosticatiou.
This fact arises from the shane of
the earth and the tendency OF hot
air To rise. AS explained in re-
cent bulletin Of the bureau. The
tropical sun in the regions along the
Equator heats great masses of air.
which rise and drift toward the
North and South Poles As the
arth r"voiycs from west 10 east.
ibes" masses are carried al"n@ with
Il AT the same speed. But the
Equator rcNolves much faster than
u" poles. which are pra ctirally STA
ii"nary, in the sam" way that the
i'm Of a wheel reVOl rs faster than
its hub. Therefore, these masses Of |
air revolving al the same rate az the /
begin. as they approach