The sun., 1901-07-28
HOT WAVE WEATHER MGNs.
william A. Eddys Rules for Forsteliins the
Coming Of Relief.

William A. Eddy. the Bayonne kite flyer,
has formulated the following rules for fore
casting the breaking up OF hot waves;
1T Is a well-known fact. which will be at
once admitted by the Weather Bureau oficials.
that the correctness OF their predictions
rarely exceeds 90 per cent and Ia apt to
fall below as per cent Even this Is very
valuable but many Of tho ten or fifteen fail
ures in q hundred may occur at a time when
people are dying by the hundreds from the
excessive heat. Tho discouraging predic-
ton OF no relief is In itself killing.
Viewing these facts. I began a series OF
elaborate measurement OF the cloud veloci-
ties, the light Of the sky. the dimness due
to mist Of distant hills. and the humidity at
= A. NJ daily. especially during hot waves
The humidity OF the air a. n precursor Of
local storms. has not been sufficiently con-
sidered by many forecasters. and the cloud
velocity measurements have been almost
completely overlooked. and 80 far as l know
the measurements Of the light OF the sky
have not been even thought Of
MY investi ga tions have been carried on
for several years. including measurements
OF the moisture Of the upper air by means
Of kite-sustained wet and dry bulb ther-
summer, Instantly causes a great increase In
the speed with which clouds move. and such
cool air begins 70 affect the hot earth within
from twenty-four TO forty-eight hours after
the increased velocity Of the cloud is observed.
The fact that the entire Lake region from
Chicago 10 New York, a thousand miles In
length, may cool within Few hours shows
that the relief comes from the upper, air.
and with incslculabie suddenness Follow
can use to forecast weather for himself during
hot waves. and good for about twelve hours
no clouds whatever. with dry air at the
earth. after the second or third day Of hot
wave, with an 3 A. NJ. temperature OF about
so degrees. indicates. as a rule no relief within
~immense masses Of very thin white clouds.
covering about half or two-thirds Of the sky,
but still admitting, plenty Of sunlight and heat,
indicates probably, thunde erstorms that day
and break In the heat within about two days.
This will be followed by thunderstorms the
following day with still further break in
The final cooling OF about 10 degrees is
preceded during most of the day of the break
up by high white clouds, not OF the thunder
head hsd type DHs ~ be ana more
The thunderheads. high white pinnacles
OF cloud. are Of two types The first type.
ing like puns Of steam. and may melt IN the
intense heat without causing shower. While
they indicate a thunderstorm tendency. yet
such storm may not occur nearer than
hundred miles. The true thnnderheads.
which result in such storms nearby. are mar
row at the top, have some stratihcation at
their bases and are from ten 70 hfteen de-
Rrees In width. Ihey form all around the
horizon and not in small detached patches
like the heat clouds
II after several days OF hot wave the
humidity Is above 10 per cent and the light
OF the sky has progressively decreased during
forty-eight hours owing TO haze. even II the
sky IL clear Of shower clouds "a la 10 as /? y NJ,
then thunderstorms are practically certain
and have occurred az or near sunset In all the
While the measured light OF the sky indi-
Gates the approach Of shower conditions
taken with the humidity. vet It's chief use IL