NEW YORK, FEBRUARY 22, 1908. 
WEEKLY, $1.00 PER YEAR. 
Vol. LXVII. 
FORECASTING WEATHER CHANGES 
Some Principles of Meteorology. 
1’lease state in your paper what value can be placed 
upon aneroid barometers for the use of farmers. In other 
words, have they a practical value for farmers or others 
in foretelling weather changes and storms? The weather 
reports in the daily papers do not prove of much practical 
use, and if you can confidently recommend the use of a 
barometer and furnish hints in regard to it we think it 
would he gladly welcomed by your numerous constituents. 
N. c. v. 
I he barometer of any type, including aneroids, if 
in good work-ing condition, is a useful adjunct in 
forecasting weather changes when used with under¬ 
standing. It must be remembered, however, that it is 
the manner in which the barometer is changing; that 
is, whether it is rising, falling or remaining nearly 
stationary, rather than the particular reading at any 
time or place, which is significant. A gradually fall¬ 
ing barometer is usually associated with an approach¬ 
ing storm, and the barometer usually rises again after 
the storm center has passed the 
locality, while it becomes more or 
less stationary while the center is 
passing, and may again become 
stationary after it has entirely 
passed and fair weather conditions 
are restored, and also, if another 
storm may be closely following 
the one just passed. An aneroid 
barometer which makes a contin¬ 
uous record of the changes of 
pressure would be very much more 
serviceable on the farm, because 
then the eye can see at a glance 
and without trouble of keeping a 
record, not only what is, but what 
has been taking place. Such in¬ 
struments are made, the record 
sheet driven by clockwork, and 
they are in fact a combined 
barometer and clock, requiring 
winding and the record sheet 
changing once a week. 
But without the aid of a barom¬ 
eter, and with a little knowledge 
of the underlying principles gov¬ 
erning ordinary storms, and some 
experience, it is possible for any 
farmer or farmer’s boy or girl to 
pass a good judgment upon what 
the weather changes in the next 12 
to 24 hours are likely to be, the 
judgment being based largely on 
changes in the direction of the 
wind and the appearance of the 
sky. A class of three young men once kept a careful 
record of daily forecasts for 24 hours in advance made 
dui ing a month, and of the observed weather changes 
as they did actually occur, predicting the changes 
which would take place in the direction of the wind, 
changes in temperature, the position and course the 
storm center was taking, indicating the direction from 
them, whether or not precipitation would occur and 
whether or not a cold wave would follow the storm, 
the observations being made in the Winter. At the 
end of the month a comparison of their records with 
the observed facts and with the weather charts of 
the local Weather Bureau, showed that for the three 
men their predictions were verified to the extent of be¬ 
tween 76 and 7!) per cent. Because this is possible, 
and is so valuable to the farmer, and especially be¬ 
cause it forms so valuable an exercise for the prac¬ 
tical training for children in rural schools, a diagram 
is here given, and a few general statements made 
which, with a little study and patience, will enable any¬ 
one to form a fairly good judgment regarding 
prospective changes in the weather 12 to 24 hours in 
advance. We do not of course mean to say that pre¬ 
dictions can be made without failures, because this is 
not possible with the Weather Bureau with all of its 
appliances and skill, but an opinion is readily formed 
which is very much more likely to be correct and far 
safer to follow than a mere guess. A good barometer 
would be helpful in making these judgments, but ex¬ 
cellent results can be secured without it because the 
changes in the direction of the wind, which result from 
changes in the barometer, are capable of being inter¬ 
preted exactly as a barometer would be read. More¬ 
over, the observations on the wind and the sky give 
much fuller needed information for prediction than 
the barometer alone. 
PRINCIPLES OF STORM MOVEMENT.—1. 
Storms in and passing across the United States gen¬ 
erally travel from some westerly toward some easterly 
point, the course varying at times between a direction 
from the northwest to the south of east to directions 
from the southwest to the northeast, the prevailing di¬ 
rection being a little north of east after they have 
crossed the Mississippi River. 
2. The storms cover a more or less'circular area, 
as represented ideally in the illustration, with the 
lowest barometer toward the center, marked “low” 
on the weather charts. They arc never true circles 
in area but the principles underlying their move¬ 
ment can be most simply stated by such a representa¬ 
tion, which they tend to take. 
3. They vary in diameter from 1,000 to 1,500 or 
more miles. 
4. They travel usually with a mean velocity of from 
26 to 30 miles per hour; rarely they become stationary 
for a time and sometimes travel with much higher 
velocities. 
5. The wind always blows obliquely around and 
toward the low center, in the general direction repre¬ 
sented by the arrows within the circles in Fig. 63. 
6. Rain or snow usually falls at some distance in 
front of the storm center, generally in the eastern half 
of the storm area, as expressed by shading and words 
in the illustration. 
7. If the storm travels so as to bring the dotted 
area marked “generally cloudy, rain or snow” over the 
observer the rainfall or snowfall will be more or less 
steady and continuous, or it may be simply generally 
cloudy. 
8. But if the storm center passes far enough to one 
side to bring the area marked “showers, rain or snow” 
over the place, if precipitation occurs it will be local, 
in the form of thunder showers in the Summer and 
snow flurries covering small areas in the Winter. 
9. As.thc storm center passes beyond the observer 
the region of “sky clearing” and then that marked 
“fair” arc in turn brought over the observer. 
'I he large, long arrow reaching through the dia¬ 
gram represents the direction of progress of the storm 
area. The solid black arrows within the circles repre¬ 
sent the surface winds which would be observed, the 
thin arrows outside the circles represent the normal 
prevailing winds when the place is 
not under the influence of a storm 
center and when the sky would be 
generally clear and the weather fair. 
10. During cold weather the front 
or stormy side of these low areas 
are associated with rising tempera¬ 
ture because in Winter it can neither 
rain or snow without the temperature 
of the air being raised, the condensa¬ 
tion of moisture tending to warm the 
air. On the contrary the rear side 
of the storm area is usually one of 
falling temperature because a clear 
sky in Winter allows the heat to 
escape rapidly because the cold upper 
air is falling to the surface there 
and because it is traveling from the 
north and colder region toward the 
area, importing cold with it. 
11. With the wind blowing contin¬ 
uously in toward the low or storm 
center there must be some escape for 
it and this is more or less directly 
upward and outward from the cen¬ 
ter, above the surface clouds. 
PRINCIPLES OF FORECAST¬ 
ING.—For the sake of clearness of 
conception regarding the nature and 
movement of storms across the 
United States, which is essential in 
forecasting, we use an illustration 
which, while like the diagram chosen, 
is a long way from representing the 
facts in detail, is nevertheless so 
close to the truth in fundamental principles and gen¬ 
eral character of phenomena concerned that it will 
serve the purpose better than the more complex storm 
itself. We use in illustration the method which will 
be adopted (?) in the far-away future of American 
agriculture to cause it to rain whenever it is wanted, 
wherever it is needed and as much only as is de¬ 
sired. This time cannot come until science has made 
us masters of the unlimited energy of space and we 
are able to concentrate and transform at any point 
desired quantities as rapidly as we wish. Perhaps it 
cannot come until we have established intimate com¬ 
munication and thorough acquaintance with the people 
whom some astronomers feel they have seen through 
their telescopes, aided by their imagination, managing 
the fertile belts along the gigantic irrigating ditches 
on the planet Mars, which are supposed to distribute 
the waters melting from the ice-caps first south and 
then north as Summer and Winter shift places, one 
side and the other of its equator. 
Imagine a sufficiently large train of cars on a prop- 
