The Portland daily press., 1891-11-13
THE WEATHER BUREAU.
An Interesting communication
From the Chief observer

| Tho fouowins communication from Mr..
d lanes weather. bureau observer In
por,,and will be read with much interest:
o.s, ~, THE U. s. WEATHER BuREAu.l
OFfloN PoRTIAND, ME-, Nov H. 1891
| an those who are interested In meteor1logy
or the work of the Weather Bureau as admin,
istered by the Department OF Agriculture are
Cordially invited to call at the Weather R,ireau
once on the fourth floor of the First National
Bank building. Among the books In the libra
ry furnished oy the government. are sciantifc
and professional papers which are yerv intarast
ing, also rainfall and temperature charfs
weather maps and records which would be Of
great value TO any one desiring informatinn in
regard to the ciimatology of any sectinr on ~
cinity where observations have been carried on
Particnlar attention is invited TO the daily
weatneF charts a issued from this office as being
They are posted in many public pIaces fnrn
isned TO the city schools and mailed to institn-
eSes sssr Weggtb 5ar9Sgnont the state The
ulpute THESE charts as. widely as possible in
order that The intelligent part Of every commnn.
i lcy may utlize them by making special and
taken from the report of the chief ofithis hnresn
is given for the benefit of all:
lnese maps not only contain the forecasts
prepared IN washington and the local forecasts
put also the data on which the forecasts are
based, so that they may be studied and person
al conclusions drawn by every one engaged in
weather; and this includes all classes of peopIe'
The data embodied In the maps are fhe ar
pressure, the temperature at s o'clock a. m.
7bth meridian time, the minimum Temperament
wind direction and velocity, the Character al
the weather at the hour of observation and the
amount OF rain or snow. AS soon as the
Qines connecting places or embracing sections
OF equal air pressure) are drawn for each tenth
OF an inch; isotherms dotted lines connecting
are drawn for each ten degrees; the Section az
sections of country having the highest or low.
est air pressure are marked, respectively,
nigh, aid low, The former is antl-cyclonic
words, the area covered by high pressure of
air usually has clear and cool, or cold weather.
whereas the reverse is the case in advance OF
and surrounding an area of low pressure where
rain or snow and cloudiness, with a Compare
lively high temperature prevail. The drift of
the atmosphere being from west to east, the
cnarting o. these cycionic and anticyclonic
glauce their respective centres and the direc.
ton in which they are heading, graphically
portrayed by the curvature of the several un-
broken lines, and by the arrow showing the
wind direction, the air flowing into the low
with spiral inward motion, contrary to the
movements OF the hands of a watch, and out OF
nigh with the hands of a watch.
After little study on the part of the intelli-
gent observer it is evident that the nearer the
areas of high and low pressure are to each
pressure. the more rapid will be the flow Of air
from the greater to the lesser pressure. The
lsOtherms temperature lines) vary according
to the isobars. IL a low pressure area is ad-
vancing eastward over the middle ATTITUDES
and high pressure area is moving
eastward from the far West or Northwest
the isotherms will assume toward the perpen-
dicular; If the conditions are static 4. e., that
there is but little variation In the pressure, the
isotherms will appear in nearly horizontal DO
sition. according TO the latitude. Cold waves,
weather and temperature changes, the prOba-
bility OF thunder storms or other severe local
storms are easily located by giving the daily
weather maps moments STUDY. The several
laws OF storms will gradually unveil themselves
to the mind of the student OF the map, and the
apparently unintelligible mass OF lines and fig
ures OF day becomes the guide for business
transactions of any character. That severe To-
cal storms occur In the southeast quadrant of
low pressure area; that the wind will back from
the southwest to northwest II a low area pres
sure moves south of given place, or shifts
from southeast to northwest as the storm
moves north OF the place; that the temperature
rises In advance OF storm, and falls after it
has passed; that storms generally move in the
direction OF the greatest RAINFALL or snowfall
or where the air is most humid, are all facts
evolved by study of the maps"
The maps issued at Portland contain an ex.
PLANTATION OF the meteorological features affect
Ing this district. E. p JONES.
observer Weather Bureau.