Evening star., 1940-10-12
Of Stars, Men
And Atoms
Notebook Of Science Progress
In Field, Laboratory
And Study
Bu Thomas r. Henry.

By Thomas r. Henry.
Senegal, the French colony whose
capital at the westernmost tip Of Africa
might be the jumping of place for
transatlantic bombing planes, is cra-
die Of hurricanes, particularly the one
that wrecked New England two years ago.
This devastating storm has been traced
backward for u days to slight local
disturbance in the Bilma Oasis at the
western edge of the Sahara Desert by
the French meteorologist, Henry Hubert,
it is reported by DR.. Charles F. Brooks OF
Harvard University in the current issue
of the journal Of the American Geo.
graphical Society. For the first time one
of the annual West Indian hurricanes
has been tracked to its lair and mech
anism discovered which may be the first
cause of many Of them.
Every three or four days during the
late summer and early fall Hubert re-
ported, westward moving area of fall
ing pressure is shown by barometers
passing over the Western Sahara and
Senegal. When this remains within nor
NAL limits it causes no disturbance. On
September 4, 1888, observations at the
Bilma Oasis, duly recorded on the Sene-
gal weather maps, showed that this wave
of low pressure was considerably greater
than usual.
Bilma at that time was an important
station, because 1t lay on the caravan
route between Tripoli and Lake Chad
and observations there gave evidence of
the kind of weather to be expected in
the desert. 1t lies on the edge OF
semi-permanent area of low pressure
known to the French meteorologists as
the Tamanrasset Low, name that
promises to be Of increasing Importance
in predictions of American weather.
For four days the French weather
maps studied by Hubert show there was
a fairly regular westward advance Of the
loW-pressure area across Senegal. 1t was,
as he expressed it, IAN excrescence on the
regular low"
Then, somewhere near the fateful city
of Dakar, it broke away as separate
depression with a strong cyclonic, or
dull-ClOGhN4St, CIIIu4dlAOIl VI OIL oAOOll0
its edges. Over the Azores there is
permanent high-pressure area, we'll
known to meteorologists. Out of this
high on September 7 there seems to
have been strong flow of the northerly
trade winds exceptionally close to the
earth. The heavy winds and the low
pressure out of the Sahara ran into
each other and set up the whirling cir
culation
Senegal itself suffered from strong, dry
winds on September 8, which did no spe-
cial damage, and the infant cyclone
passed over Dakar on its long voyage Of
death and destruction across the Allan
tic. On the 10th it was reported passing
over the Cape Verde Islands. There all
record of it would have been lost had 1t
rot been for observations of a French
ship halfway across the Atlantic three
days later. On September IA there were
reports of it from the French island of
Martinique. When these observations
are plotted on the map they leave little
doubt as to the identity of the cyclone.
The great smash against the New Eng
land coast came on the 18th and resulted
in some of the most extensive storm dam
age yet known in the United States.
Until quite recently the hurricanes ex-
pected every autumn have first been
picked up by weather observers some-
where in the West Indies. They have
realized that they must have originated
further to the east. This is the first one
that has been traced step by step from
its start.
The general late summer setup in the
Senegal area, it is pointed out in the
report, is such as tends to produce cy-
clones although it evidently is matter
of luck whether or not they gather
enough strength to cross the Atlantic.
The Azores High and the Tamanrasset
Low are always there, essentially balanc-
ing each other. Disturbances in this
balance account for local weather. Su-
perimposed on these practically perma-
nent centers are waves Of low and high
pressure of considerable amplitude which
pass back and forth and frequently run
into each other.
When this happens, it Is pointed out in
the report, circulation centers are set up
and extended, bringing diverse air masses
into direct conflict. When this happens
a cyclone is formed. American houses
may be blown down few days later.
The practical applications OF the
French meteorologists findings must be
delayed until after the war. At present
no weather reports are received from
that part of the world. When the service
is resumed the day-by-day conditions in
Senegal during the early fall may tip
off American meteorologists of possible
hurricanes as much as 10 days in ad-
vance. With stations scattered across
the ocean to keep track of the passage
of such cyclones the observations promise
to be of great value to peacetime trans
Atlantic aviators.
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