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THE
HURRICANE GUIDE:
BEING
AN ATTEMPT TO CONNECT THE
ROTATORY GALE OR REVOLVING STORM
WITH
ATMOSPHERIC WAVES.
INCLUDING INSTRUCTIONS FOR OBSERVING THE PHÆNOMENA OF THE WAVES AND
STORMS;
WITH
PRACTICAL DIRECTIONS FOR AVOIDING THE CENTRES OF THE LATTER.
BY
WILLIAM RADCLIFF BIRT.
LONDON: JOHN MURRAY, ALBEMARLE STREET.
_PUBLISHER TO THE ADMIRALTY._
1850.
PRINTED BY W. CLOWES AND SONS, STAMFORD STREET.
PREFACE.
In introducing the following pages to the notice of the Public, it is
the Author's wish to exhibit in as clear a light as our present
researches on the subjects treated of will allow, the connexion between
one of the most terrific phænomena with which our globe is visited, and
a phænomenon which, although but little known, appears to be intimately
connected with revolving storms. How far he has succeeded, either in
this particular object or in endeavouring to render the essential
phænomena of storms familiar to the seaman, is left for the Public to
determine. Should any advantage be found to result from the study of the
Atmospheric Waves, as explained and recommended in this little work, or
the seaman be induced by its perusal to attend more closely to the
observations of those instruments that are calculated to warn him of his
danger, an object will be attained strikingly illustrative of the
Baconian aphorism, "Knowledge is Power."
_Bethnal Green_, April 19, 1849.
CONTENTS.
PAGE
CHAP. I.--PHÆNOMENA OF REVOLVING STORMS 7
" II.--PHÆNOMENA OF ATMOSPHERIC WAVES 13
" III.--OBSERVATIONS 18
SECT. I.--Instruments 19
" II.--Times of Observation 28
" III.--Localities for Additional Observations 31
" IV.--Storms, Hurricanes, and Typhoons 43
" V.--Seasons for Extra Observations 48
" IV.--PRACTICAL DIRECTIONS FOR AVOIDING THE CENTRES
OF STORMS 52
NOTICE.
In the pocket accompanying this work are two rings of stiff cardboard,
on which will be found all the information contained in figures 1 and 2.
When they are laid flatly upon a chart, the continuity of the lines on
the chart is not materially interfered with, while the idea of a body of
air rotating in the direction indicated by the arrows is conspicuously
presented to the mind. These rings are more particularly referred to on
page 52.
THE
HURRICANE GUIDE.
CHAPTER I.
PHÆNOMENA OF REVOLVING STORMS.
It is the object of the following pages to exhibit, so far as
observation may enable us, and in as brief a manner as possible, the
connexion, if any, that exists between those terrific meteorological
phænomena known as "revolving storms," and those more extensive and
occult but not less important phænomena, "atmospheric waves."
To the great body of our seamen, whether in her Majesty's or the
mercantile service, the subject can present none other than the most
interesting features. The laws that govern the transmission of large
bodies of air from one part of the oceanic surface to another, either in
a state of rapid rotation or presenting a more or less rectilineal
direction, must at all times form an important matter of inquiry, and
bear very materially on the successful prosecution of the occupation of
the voyager.
In order to place the subjects above alluded to in such a point of view
that the connexion between them may be readily seen, it will be
important to notice the principal phænomena presented by each. Without
going over the ground so well occupied by those able writers on the
subject of storms--Redfield, Reid, Piddington, and Thom--it will be
quite sufficient for our present purpose simply to notice the essential
phænomena of revolving storms as manifested by the barometer and vane.
The usual indications of a storm in connexion with these instruments are
the _falling_ of the barometer and the _freshening_ of the wind, and it
is generally considered that a _rapid_ fall of the mercury in the
hurricane regions invariably precedes the setting in of a storm.
There are three classes of phænomena that present themselves to an
observer, according as he is situated _on_ the line or axis of
translation, or _in_ either the right or left hand semicircle of the
storm. These will be rendered very apparent by a little attention to the
annexed engraving, fig. 1.
[Illustration: Compass rose]
In this figure the arrow-head is supposed to be directed true north, and
the hurricane--as is the case in the American storms north of the 30th
parallel--to be moving towards the N.E. on the line N.E.--S.W. If the
ship take the hurricane with the wind S.E.,--the letters within the two
larger circles indicating _the direction of the wind in the storm_
according to the rotation as shown by the circle of arrow-heads, and
which it is to be particularly noted is in the northern hemisphere
_contrary to the direction in which the hands of a watch move_: in the
southern hemisphere the rotation is reversed--the only phænomena
presented by the storm are as follows:--The wind continues to blow from
the S.E., increasing considerably in force with the barometer falling to
a very great extent until the centre of the storm reaches the ship, when
the fury of the winds is hushed, and a lull or calm takes place,
generally for about half an hour, after which the wind springs up mostly
with increased violence, but from the opposite quarter N.W., the
barometer begins to rise, and as the storm passes off, the force of the
wind abates.
The point to which we wish particularly to direct attention in connexion
with this exposition of the phænomena attending the transmission of a
storm is this:--If the observer so place himself at the commencement
that the wind passes _from his left hand towards his right_, his face
will be directed towards the centre of the storm; and the wind
undergoing no change in direction, but only in force, will acquaint him
with this important fact that the _centre_ is not only gradually but
surely approaching him: in other words, in the case before us, when he
finds the wind from the S.E., and he places himself with his face to the
S.W. he is looking towards the centre, and the wind rushes past him
_from his left to his right hand_. Now the connexion of the barometer
with this phase of the storm is _falling with the wind from left to
right, the observer facing the centre while the first half is
transiting_.[1] During the latter half these conditions are reversed,
the observer still keeping his position, his face directed to the S.W.,
the barometer _rises_ with a N.W. wind, which rushes past him _from his
right to his left hand_ with a decreasing force. We have therefore _a
rising barometer with the wind from right to left during the latter half
of the storm, the observer having his back to the centre_.
The above _general_ enunciations of the barometric and anemonal
phænomena of a rotating storm hold good with regard to the _northern_
hemisphere, whatever may be the direction in which the hurricanes
advance. This may be placed in a clearer light, as well as the remaining
classes of phænomena shown, by consulting the following tables,
constructed for the basin of the Northern Atlantic, and comparing them
with fig. 1. In this basin, with lower latitudes than 25°, the usual
paths of the hurricanes are towards the north-west, in higher latitudes
than 30° towards the north-east. The tables exhibit the veering of the
wind with the movements of the barometer, according as the ship is
situated in the right or left hand semicircle of the hurricane. It must
here be understood that the right and left hand semicircles are
determined by the observer so placing himself that his face is directed
towards the quarter to which the hurricane is advancing.
LOWER LATITUDES.
NORTHERN HEMISPHERE.
Axis line, wind N.E., barometer falling, first half of storm.
Axis line, wind S.W., barometer rising, last half of storm.
RIGHT-HAND SEMICIRCLE.
Wind E.N.E., E., E.S.E., S.E., barometer falling, storm increasing.
Wind S.S.W., S., S.S.E., S.E., barometer rising, storm passing off.
LEFT-HAND SEMICIRCLE.
Wind N.N.E., N., N.N.W., N.W., barometer falling, storm increasing.
Wind W.S.W., W., W.N.W., N.W., barometer rising, storm passing off.
HIGHER LATITUDES.
NORTHERN HEMISPHERE.[2]
Axis line, wind S.E., barometer falling, first half of storm.
Axis line, wind N.W., barometer rising, last half of storm.
RIGHT-HAND SEMICIRCLE.
Wind S.S.E., S., S.S.W., S.W., barometer falling, storm increasing.
Wind W.N.W., W., W.S.W., S.W., barometer rising, storm passing off.
LEFT-HAND SEMICIRCLE.
Wind E.S.E., E., E.N.E., N.E., barometer falling, storm increasing.
Wind N.N.W., N., N.N.E., N.E., barometer rising, storm passing off.
N.B. The directions of the hurricane winds are so arranged as to show
the points of commencement and termination. Thus in the lower latitudes
a storm commencing at E.N.E. passes off at S.S.W. after the wind has
veered E., E.S.E., S.E., S.S.E., and S., being in the order of the
letters in the upper line and contrary to their order in the lower. One
commencing at E.S.E. passes off at S.S.E. right-hand semicircle. In the
higher latitudes a ship taking the storm at E.N.E. will be in the
left-hand semicircle, and the hurricane will pass off at N.N.E. These
changes are rendered very apparent by moving the hurricane circle in the
direction in which the storm is expected to proceed.
Fig. 2 represents the whirl and hurricane winds in the south.
[Illustration: Fig. 2]