New-York tribune., 1891-09-23
THAT MONTHLY WEATHER CYCLE.

The tendency of the weather for 1891 here
abouts to repeat itself in cycles Of between twenty
seven and twenty-eight days was noted IN Inc
Tribnne q few weeks ago; and at that time IL was
remarked that if this persisted for another month
cool weather might be looked for about August "a
and warm weather September As. The date tor
the cool spell should have been made at least three
days later than it was, inasmuch as the previous
temperature minimum fell on July 81. August oV
proved to be the coldest day in this city since
midsummer; so that here was repetition Within
two or three days of the prescribed time Inc
warnest day inside of the next fortnight was
September 4, although there was no such pro-
lon0ed and extreme heat as in the interval TO
which it corresponded, namely, August S-l2. mus
in point of time, though not in degree. there was
q repetition Of the temperature unuui@uoh' pic
yiously observed.
But besides the alternate hot and cold spells
already discussed, careful study OF the tempera-
ture curves for the last eight ten months shows
that there has been in nearly every 27 or 29-day
cycle a second warm wave and second cold one
recurring rather regularly. The schedule roughly
adhered 70 most of the time has run like this ::
First what may for convenience be called the
major warm wave; second the minor cold wave.
usualIv eliminating from four 10 six days later
then the minor warm wave, with its crest about
twelve days behind that of the first one; finally
the major cold spell its severest day coming SIX
teen or eighteen days after the principal warmth !;
leaving about ten or eleven days before the next
cIimav of heat. The earliest Of the two cold
waves in any civen series has not invariably been
the slighter; but generally it was. Nor has the
6rst hot wave of the two always been the chief
A notable exception is found in the present month.
The temperature rise of September 4, CORE
sponded. in time, to the major heat stage {;
hrt il was brief and trihing compared
with that of September 1922, two warm
waves with only triaing break between
them. the whole being more fully developed than
most of the warm spells holding the same relative
position in the series. TO illustrate the general
senuence. let us take for starting point August
10 not only the central day of that famous hot
period August S-12, but itself hotter than any
| dov for weeks before and weeks after. 1t corrc-
spouded 10 July 10, June l6 and dates of other
heat maxima an average distance Of twenty y-seven
or t,yenty-eight days apart This was followed
bv minor cold spell, August 1919, its central
| dav bciuC August II heat again, August 2l-2s,
central day being August "a; short, sharp cold
wave August 80, with slow rise in temperature
| thereafter The heat of September 4, the next
! sta ring point. was only twenty-five days from
| August 10, and may be considered two or three
4
days ahead of time; on September we had the
| lowest fall Of the mercury since midsummer, but
| it was only a brief chill; September 1920
marks the central point of the warm period
September l7-22, though not the hottest point; I;
and now the major" cold wave, due late this
week. would complete the system. II the mini
| mum of July be considered as having been on
time. then that Of July 81 was a day late that
of August 80 two or three days behind, and the
closing member Of the current series would be due
| about Thursday, the cath, or Friday.
The recurrence Of these weather features is not
marked by machine-like precision; both in time
and intensity there is more or less deviation from
the average But for several months IL has at
| least resembled the efforts of a candlc-fame 70
| maintain o perpendicular in slightly troubled
air: Obvious. but little unsteady. What Pro-
! temor Hermann Fritz has said about the in
auences which In our latitudes must to some ex-
tent mask this monthly manifestation has already
| been cited In The Tribune.
| Those influences, the irregularities observed Ill
the undulations described in these columns and
tbe fact that in some years this periodiciw Ii
scarcely apparent. are only q few Of the reasons