The morning call., 1892-07-28
TALK ABOUT THE WEATHER.
What Causes the Heavy Mist-N0thiDE
Unusual in This Months Cold.


The weather is npTeT-failing theme for
.=s.7 Tsa-set.'sI. IEtssa people who are intro
duced to each other should find it difficult to
start a conversation the weather forms
ready subject on which both can express an
opinion without in any way treading upon
each others corns.
The extreme GOODNESS of the weather dur
Ing the present month, and more particu-
larry the disagreeable mist of Monday and
Tuesday last, has been a good deal talked
about. The assertion has been freely made
that this July has been marked by unusu-
ally unfav0rable weather. To ascertain the
truth or falsity OF such an assertion the
opinion Of experts was obtained yesterday
by reporter of THE CALL
Thomas Tennent, the Yell-kn0wn chro-
nometer and instrument maker of Caljfor-
MIA street, said he had kept a record Of the
weather in San Francisco since lS49 Al
though be could not 60 into the matter SCI
entificallY, that being the province of the
chief Of the Weather Bureau. he could say
that there was nothing unusual in regard to
the weather of this month.
Now" continued Mr.. Tennent, "here
are my records. We viii take tie month 6f
July every 10 years, beginning in 1852. On
the Stb, 9th, 10th, 18TH and 2Ist we had
heavy mist, amounting to drZZle. In July,
1862. on the 26th we had mist. In July,
1872, on the 10th we had heavy mist in the
morning, almost equivalent to rain: on the
18th and 18th we had it morning and even
ing; on the 18th in the evening, and on the
24th early In the day. In July. 1882 on the
Ist and 4th there was heavy mist in the
evening; on the 22d and 31st in the morn
Ing So, you see, there is nothing unusual
IN The heavy mist Monday and yesterday.
I'VE Will take July, 1855. On the 9Th,
7th and 8th we had mist and drZziing rain ;
on the 25th mist in the evening; 26th, heavy
mist morning and evening; 9th, mist in the
morning. July, 1886, on the 10th we had
rain with heavy thunder and lightning from
5 10 A. NJ; on the oath. mist. July. 1887.
on the 9th and 2Sth we had mist People
are liable TO forget the kind of weather a
few years back, but these records tell the
truth every time"
Lieutenant Finley Of the Weather Bureau
said: we are always subject to this sort
OF weather In the latter part Of July, Au-
gust and September. 1t is caused by very
low Darometrc pressure over Nevada and
Utan, ana a nigh barOmetric pressure off
the California coast Under those clrcum-
stances the air blows in from the ocean and
continues just as long as that distribution
OF atmospheric pressure continues. In
other words. we would have what is popu-
larly known here as trade winds, or west
eriy winds. although strictly speaking they
are not trade winds.
This weather is not unusual at this time
OF the year We have had for the past
week heavy westerly winds blowing at tn G
rate of from 20 10 % miles per hour The
result is that air is brought over US here
from a long distance out at sea- Sew
eral hundred miles from here we have the
Japan current Of warm air. These con-
tinued heavy westerly winds bring this hot
air IN contact with the cold air from the
Alaskan current off our coast, and this
warm air By this contact Is condensed and
fog and mist follow.
owing to the low barometer over Ne
Vada the circulation is from the ocean in
ward. instead Of from the land TO the ocean.
1t might be asked, why does the barometer
fall so low there? The answer is that it
has always been caused by a succession of
storms passing eastward from the ocean
over the British provinces. which keeps the
barometer low over the interior There is
the appearance of another Of these storms
coming, and we will likely have more of
this weather yet"