The Kennewick courier-reporter. [volume] (Kennewick, Wash.) 1914-1938, 1916-02-10
EXPLAINS ORIGIN
OF THE CHINOOK
Walla Walla Weather Observer
Gives Facts Regarding the
Familiar Warm Wind

nave hNeu III Iue NOrtnWeSC year
who are not familiar with the well
come, but sometimes disastrous wind
known as the Chinook. There are
fewer people, however, who know what
Chinook really is. The two popular
but erroneous beliefs are that the
Chinook is wind warmed up by blow
ing over the waters of the Japan cur
rent or that it gathers its warmth
from the warmer regions of the south.
Writing in the Walla Walla Union
C. c. Carrot, observer of the weather
bureau explodes these two misbeliefs
and says:
"Winds are the result of natures
attempt to equalize the atmospheric
distribution. The familiar "highs"
and slows" of the daily weather may
outline the regions where the pres
sure is high THAT is, where the air is
dense) and where the pressure is low
(air less dense). A circulation is set
up between these regions, the air of
course moving from the region where
it is .piled up" to where it is de-
pressed. There is a constant pro-
cession of these atmospheric forma-
tions passing across the United States
following the drift of the atmosphere
in these ATTITUDES. When a low is
passing north of this valley and a
high is located over the great plateau
region to the south there is an inter-
change of air from south to north
over this section. When the gradient
is steep, that is when the ''highs" and
slows" are most pronounced in char
acter, the wind blows hardest. Most
of the lows pass north of this region,
which accounts for our prevailing
southerly winds. Whenever there is
a high area covering the plateau re-
gion and low north of us chinook
winds may occur. When the highs and
lows bear a favorable relation in di-
rection to each other, chinooks will be
most apt to occur. In this connection,
/ will say that the Weather Bureau
forecasters seldom attempt to speci-
fically forecast a chinook, as there is
great uncertainty as to their time of
occurrence in any particular locality.
"The air in passing from the region
south to that north of US is forced to
rise over mountain chains. 1t ex-
pands, and cools at the rate of 1.6 de-
grees Fahrenheit, per 800 feet of as
cent. This cooling by expansion causes
it to reach its dew point, it becomes
cloudy and yields more or less copious
precipitation. The changing of the
vapor to water drops causes latent
heat to be liberated and thus prevents
the further cooling of the ascending
air at so rapid rate as 1.6 degree per
800 feet. The rate may be cut to half
that amount, so the cooling after pre-
cipitation sets in is small. After the
top of the mountains is reached the
air begins its descent upon the other
side. 1t is now compressed as it
makes its way to lower levels, and the
rate of increase of temperature re-
sulting from the compression is the
same as that of its decrease upon ris-
ing, 1.6 per 800 feet. But this rate
continues during the whole of its des-
cent. AS a result it may reach the
other side 20 or more degrees warmer
.kan before it started to ascend. II
has also become very dry, as much
moisture was removed by precipita-
ton.
1T is hard to fully explain a chinook
without using technical language.
These facts should be kept in
mind. The air in chinook
does not derive its added heat
from an outside source 1t comes
from within itself by compression.
Heat is not substance-it is a form
of energy. Some Of the energy (la-
tent heat) that was necessary in main
tanning the larger bulk of the air is no
longer needed in that form when the
air is compressed into smaller bulk.
and it becomes sensible heat, that is,
makes the air warmer. This is known
as dynamic heating of air. When air
is warmed its relative humidity is
thereby decreased, that is, it becomes
dryer. The masses of air within a
chinook are warmed and dried by
compression when descending noun
tain slope after they have been cooled
to lesser degree in the ascent on
the other side.
"The first signs of chinook exhibit
themselves on the mountain tops
where a peculiar blue haze is first
seen. Later horizontal streamers Of
clouds unfurl along the SUBMITS af-
fording a fairly sure indication of the
opprooch of tho oir From roUionS of