Aberdeen herald. [volume] (Aberdeen, Chehalis County, W.T.) 1886-1917, 1891-03-26
SOME FACTS ABOUT WEATHER
FORECASTS.

SIGNAL SERVICE UNITED STATES ARMY,
DIVISION OF THE PACIFIC,
SAN Francisco, March IS, 1891.
BULLETIN No. 5.
The branch office of the National
weather service, Division of the Pacific,
was opened ut San Francisco, March 1,
1885, and is the only office of its kind in
the country outside of the central Office
at Washington D. G. 1t was established
for the purpose Of providing, in the most
direct and practical manner, an opportu-
nifty for the people of the Pacific coast to
receive all the benefits that may be de-
rived from the work of the signal service.
The main object was to prepare and dis
tribute through the press and by tele-
graph, weather forecasts for the Pacific
coast states, and warn vessels of the APP
proach of storms dangerous to shipping
off the coast. Also to make special fore
casts of rain, frosts, floods and local
storms. Such work had been carried on
at the central Office in Washington many
years for the eastern portion of the
United States, and it was believed that
the time had come for the organization
Of Pacific coast weather service, with
headquarters at the metropolis of the
coast, and at place centrally located
for the convenient receipt and distribu-
ton of telegraphic reports. To properly
apply the weather forecasts to difnite
areas Of country, the Pacific coast was
divided into three districts, designated
officially as follows: North Pacific re-
gion, embracing western Oregon and
western Washington; Middle Pacific re-
gion, embracing the western portion of
California north of parallel 81 degrees
north, or an east and west line cutting
the northern edge Of the Bay Of Monte
rey; South Pacific region, embracing
the western portion of California south
Of parallel 81 degrees north. On May
l, 1885, an order was issued from WASH
ington changing the districts to state
areas, and thereafter the weather fore
casts were made for the following re-
gions: Washington, embracing the en-
tire state; Oregon, embracing the entire
state Northern California, embracing
that portion Of the state north Of the
latitude of SO degrees, or an east and
west line passing through the central
portion Of Lake Tulare; Southern Cali
fornia, embracing that portion of the
state south of the latitude of SO degrees.
There have been several changes in the
hours at which the forecasts have been
prepared for issue, dependent upon the
hours of meteorological observation and
the convenience Of the press. Observa-
tons are now throughout the United
States at a. m. and at p. M, seventy
fifth meridian time, which corresponds
to a. m. and p. M, Pacific time. The
weather forecasts are issued from the San
Francisco Office about $3.50 a. m. and
$50 p. m, daily. An earlier hour can
not be selected because of the want of
telgraphic facilities in concentrating the
reports at San Francisco from all parts
of the Pacific coast states. The language
of the forecasts must largely conform to
the official instructions issued from the
central office at Washington.
Forecasts Of higher or lower tempera-
ture are made each morning with refer
ence to the expected minimum tempera-
ture of the following morning, and each
evening with reference to the maximum
temperature expected on the following
afternoon. The forecasts of stationary
temperature indicate change Of four
degrees or less from March to October
inclusive, and six degrees or less for the
remaining months OF the year. In the
cast of higher or lower temperature
change Of one degree or more is sufficient
to verify the forecast. A cold wave, in
general terms, is defined to be fall in
over an extensive area of
twenty degrees in twenty-four hours, or
twenty-eight degrees in forty-eight hours,
and to the freezing point or below
Warnings of cold waves are issued when
it is expected that the area affected will
exceed 100000 square miles in extent,
and in we'll defined cases for lesser
area. Forecasts of fair weather mean an
entire absence Of rainfall, but not neces-
sarily an absence of clouds. Forecasts
are usually made for a period of twenty
four hours, but whenever the meteorlog-
ical conditions are SO decided as to dom
mate the present and are expected to
materially modify coming weather over
any extensive part of the country, fore
casts may be made for periods Of 36, 4S
and " hours. Generally speaking it is
more difficult to forecast accurately the
weather of summer than that of winter,