The morning news. [volume] (Savannah, Ga.) 1887-1900, 1891-09-28
HOW TO STUDY THE WEATHER.
signal Observer Smyth Explains the
Mysteries of Weather Map.

signal observer Smyth Explains the
Mysteries of a Weather Map.
Signal Observer Smyth of the weather
bureau is anxious that the weather maps
which are Issued every morning from the
signal Office should be properly understood.
especially by the business men and others
most interested in the prevailing weather
conditions throughout the country.
The weather maps are posted every day
in the cotton exchange, the board of trade
tbenewspaper offices aud other public places
To the uninitiated weather map is a queer
labyrinth Of dotted lines, curves, figures
and hieroglyphics, and one who has meyer
studied a map would find it very difficult to
extract any information as TO the prevail
ing weather from 1t.
Some of the members Of the cotton ex-
change understand the meaning of the diff
ferent lines on the map, with their CORE
spending figures, and can form a pretty
correct idea as TO the weather conditions
from short study of the map. The ma
iority, however, pay little attention to the
maps.
The preparation of a weather map Is the
most scientific work which the observer has
20 perform and in which the competent
observer takes great deal of pride. Sig
nal Observer Smyth says that at New Or
leans and other cotton stations where be
has been the cotton men, after having the
map once explained to them, found no
difficulty in interpreting it for themselves,
and some OF them could even make pretty
fair forecasts of what tho weather was
likely to be for the next twenty>four hours
Such knowledge affords every man the op-
portunlty of doing his own guessing at the
weather. On this line Mr.. Smyth speaks as
follows:
ITO understand the atmospheric changes
1t is necessary to give attention to the map
maoo up each day from observations taken
at S a. m, 10Th meridian time, at
all stations in the United States, showing
the.pressure barometer readings, tempera-
ture of the air, velocity and direction of
the wind, the state of the weather. Ga the
right-hand side of the map is a column
giving the rainfall, in inches, during the
preceding twenty-four hours. Areas of
equal pressure are indicated by unbroken
lines called isobars. The dotted lines are
lines of equal temperatures and are called
isotherms.
tine normal pressure of the air at sea-
level Is about thirty inches, but at an alti-
tude of 4,S6l feet it only measures about
twenty-five inches, consequently a correc-
ton is applied to the actual reading of
the barometer for the elevation above sea-
level, so that the varying air pressure may
be intelligently compared.
station on the map are reduced air pressures
in inches. The next figures are tempera-
lures, and the last figures, if any. indicate
the wind velocity. The terms high and
low indicate areas of high and
low pressure. and the figures at the
terminal of the isobars encircling the terms
show the hight to tenths of inches The
figures found at the terminal of the iso-
therms dotted lines) show the temperature
for every 100.
THE tendency of the wind is always
from region Of high barometer toward a
region of low barometer, and the force of
the wind is generally proportional to the
nearness of the isobars. The common ten
dency Of these areas is eastward. The rain
area is generally found in advance OF the
center of a low.
General storms are more frequent and
better defined during the late fall, winter
and early spring tthe cold wave season.,
while local disturbances are peculiar to the
warm season.