Evening journal. [volume] (Wilmington, Del.) 1888-1932, 1901-08-07
W BN TO EXPECT
WARM WEATHER
W. A. Eddy Lays Down Rules
for FOrOtelling Its Ap-
prOaCh

William A. Eddy, the Bayonne. n.
Y. kite flyer, has formulated the follow
ing rules for forecasting the breaking
up OF hot waves:
1T is a well-known fact, which will
be at once admitted by the Weather
Bureau officials, that the correctness of
ltheir predictions rarely exceeds 80 per
cent, and is apt to fall below So per
cent. Even this is very valuable, but
many OF the ten or fifteen failures in a
hundred may occur at a time when peo-
pie are dying by the hundreds from the
excessive heat. The discouraging pre-
diction OF no relief is in itself killing
Viewing these facts. / began a series
of elaborate measurement of the cloud
velOcities, the light OF the sky. the dim
ness due to mist of distant hills and
the humidity at a. m. daily, especially
during hot waves The humidity Of
the air, as a precursor of local storms.
has not been sufficiently considered by
many fOrecasters, and the cloud veloc-
i ity measurements have been almost
overlooked. and so fer as / know the
measurements of the light of the sky
have not been even thought OF.
j My investigations have been carried
on for several years, including meas
urements of the moisture of the upper
air by means of kite-sustained wet and
4 dry bulb thermometers A cold wave
aloft, especially i'm Summer, instantly
causes a great increase in the speed
with which clouds move, and such cool
/ air begins 20 affect the hot earth within
from twenty-four to forty-eight hours
latter the increased velocity of the cloud
J in observed. The fact that the entire
lake region from Chicago to New York.
N q thousand miles in length. may cool
\ within few hours shows that the re-
a lief comes from the upper air, and with
3 lincalculable suddenness. Following are
some Of the facts which each man can
use to forecast weather for himself dur
r ing hot waves, and good for about
. twelve hours in advance.
mo clouds whatever, with dry air at
the earth, after the second or third day
of a hot wave, with an a. m. tempera-
p ture of about so degrees, indicates, as
] a rule, no relief within twenty-fom
{ hours.
D Immense masses Of very thin white
lclouds, covering about half or two
Lnliuo III lnt Chef nAb oNAAA tNAAAANNA+-t
q plenty of sunlight and heat, indicates
probably. thunderstorms that day ant
a break in the heat within about two
days. This will be followed by thun
derstorms the following day with I
$ still further break in the heat.
1.-THE final cooling of about 10 de
grees is preceded during most of tn
= day of the breakup by high whit
clouds, not of the thunderhead type
- but stratihed and covering more thai
~ three-Quarters Of the sky.
a The thunderheads, high white pin
- nacles Of cloud, are of two types. tn
d first type, known as heat clouds. ar
N small in size, looking like puffs c
= steam, and may melt in the intens
N heat without causing a shower. Will
~ they indicate a thunderstorm tendenel
: yet such a storm may not occur neare
"a than a hundred miles. The true thur
"a derheads. which result in such storm
NJ nearby. are narrow at the top, hay
no some stratihcation at their bases an
~ are from ten to fifteen degrees
NJ width. They form all around the hor
zon and not in small detached patch'
like the heat clouds
IF AFTER several days of a hot wa
~ the humidity is above 20 per cent. al
IA the light of the sky has progressive
decreased during forty-eight hours, o'
{. ing to haze, even If the sky is clear
" shower clouds as late as 2 p. m, the
thunderstorms are practically certa
le and have occurred at or near suns
,es in all the hot waves which 1 have so 4
examined.
on, while the measured light Of the s.
p indicates the approach of shower co
= ditions taken with the humidity, yet
us chief use is to indicate cloud bursts a
N floods before a drop of rain has J
he fallen The light Of the sky probal
nd. deceives the unaided eye more than
a, cloud velocities, the delicate decline
the light being too gradual for the
ST. to measure. have made several hi
ia. dred observations which show that
ty- light OF the sky exactly correspoI
nee with the rainfall measured by
Weather Bureau during the time q
cred and fer a region eight miles
mo diameter.
al "The only instruments necessary
r a. wet and dry bulb thermometers, IA
ng- lened back to back and whirled witt
af- cord a foot long, a clOud-timer "
.ide cross wires, a measuring rod with
- candle OF stearic acid wax, and a pi
of paper with translucent spot in
When the paper is held at a cert
VI distance from the candle the vel
Id glare of tho canfYla fades ont af a I