The times., 1901-06-09
FORECASTINGTHEWEARH
Phrases Used by Official Students
of the Elements.

Cloudy skies DO Not Always Give
Certain Promises of RHin-W ind
Not SO Prophetic rs VapOr Com
dTtIons-Lnnd and Ocean Breezes.
In the Year Book which the Depart
ment Of Agriculture has Just issued, Al
fred J. Henry. professor of meteorology,
has an interesting paper on weather fore
casts, entitled "Amplification of Weather
Forecasts" The purpose of this paper
he says is TO promote the understand
ing of Government weather forecasts and
to encourage the making of local prediC-
tions by persons whose working hours
are spent for the most part i'm the open
air The time at the disposal OF the fore
cast official of the Weather Bureau at the
central office in Washington City for the
purpose of forecasting probable weather
changes, cold waves, and severe storms
is about thirty minutes in the morning
and forty minutes at night. 1t is impos-
sible in :his short time to do more than
express tae character of the anticipated
changes for each district east of the
Rocky Mountains in any but the most
general terms. The local or State fore
cast official, on the other hand. is con-
cerned with but a single district. He is
at liberty to amplify the national fore
cast or to put forth a statement of his
own. in which the anticipated changes
may be given in as much detail as the
conditions seem to justify.
Persons who use the forecasts constant
ly should cultivate the habit Of carefully
noting the weather changes in their re-
spective localities. especially the sequence
in which changes occur. for it is only by
acquiring a knowledge Of local weather
signs that they can use Government fore
casts to the best advantage.
DAILY WEATHER FORECASTS AND THEIR
TECHNOLOGY.
The Weather Bureau issues from its
Washington Office two forecasts daily, at
about ID a. m. and 10 p. m, respectively,
The observa tions on which the forecasts
are based are made at a. m. and p. M,
Eastern standard time. The morning
forecast covers a period Of twenty-four
hours. beginning at p. m. of the day on
which the forecast is issued.
The first twelve hours Of the period is
always referred TO as tonight the sec /
ond is given the name of the day to
which it may refer. Thus, Fair tonight
and Tuesday would be the form of
forecast issued at 20 a. m. Monday. To
night" in this case would begin at p.
II. Monday. and run until s a. m. Tues |
day. while Tuesday would end at p. m.
Of that day. not midnight. as some might
suppose. The forecast made at 10 p m.
is for period of forty-eight hours A
forecast made on Monday night would
take the form, Partly cloudy Tuesday !
and "Wednesday" This forecast, it viii !
be observed. does not apply To the night /
Of either Tuesday or Wednesday.
Fair weather. that is. the absence Of !
rain or snow, is indicated by several |
terms. The first of these is the word it |
self. It may be used singly or be pre- |
ceded 10y the word generally "Geuer- !
ally fair" as used by the forecaster, is |
less positive than fair alone. 1t sig |
uites that the probability Of fair weather |
over the whole district, and for the en- |
tire period is not so great as when fair
alone is used. Partly cloudy" is another |
expression that is used when the iadica- /
ti1us favor cloud, but no precipitation. |
Threatening Is used when. in the judg- |
ment Of the forecasteT, the weather viii |
be overcast and gloomy. with the appear |
ance Of rain or snow 81 any moment yet /
a measurable amount Of precipitation is /
not anticipated.
A forecast Of rain or snow may be ex- /
pressed in various ways In the late fail. |
early spring, and the winter season it is |
most commonly indicated by the single /
word rain" or snow" as the case may |
be thus. Rain tonight" And when used
in this form it is expected that the rain
viii continue for several hours IN other
seasons Of the year any one Of the fol-
lowing teri :, viz, local rain show