conditions within the area from 25° to 50° north latitude, 50° to 85°
west longitude, at 7 A.M., 75th meridian time, March 11th, 12th, 13th
and 14th respectively. Data for land stations have been taken from the
daily weather maps published by the U. S. Signal Service, and the set
of tri-daily maps covering the period of the great storm has been
invaluable for reference throughout this discussion. Marine data are
from reports of marine meteorology made to this office by masters of
vessels, and not only from vessels within the area charted, but from
many others just beyond its limits. The refined and accurate
observations taken with standard instruments at the same moment of
absolute time all over the United States by the skilled observers of
the Signal Service, together with those contributed to the Hydrographic
Office by the voluntary co-operation of masters of vessels of every
nationality, and taken with instruments compared with standards at the
Branch Hydrographic Offices immediately upon arrival in port, make it
safe to say that never have the data been so complete and reliable for
such a discussion at such an early date.
It will not be out of place briefly to refer to certain principles of
meteorology that are essential to a clear understanding of what
follows. The general atmospheric movement in these latitudes is from
west to east, and by far the greater proportion of all the areas of low
barometer, or centers of more or less perfectly developed wind systems,
that traverse the United States, move along paths which cross the Great
Lakes, and thence reach out over the Gulf of St. Lawrence across the
Atlantic toward Iceland and northern Europe. Another very
characteristic storm path may also be referred to in this connection,
the curved track along which West Indian hurricanes travel up the
coast. The atmospheric movement in the tropics is, generally speaking,
westward, but a hurricane starting on a westward track soon curves off
to the northwest and north, and then getting into the general eastward
trend of the temperate zone, falls into line and moves off to the
northeast, circling about the western limits of the area of high
barometer which so persistently overhangs the Azores and a great
elliptical area to the southwestward. The circulation of the wind about
these areas of low barometer, and the corresponding changes of
temperature, are indicated graphically on the map: the isobars, or
lines of equal barometric pressure, are, as a rule, somewhat circular
in form, and the winds blow about and away from an area of "high" in a
direction _with the hands of a watch_ (in nautical parlance, "with the
sun"), toward and about "low" with an opposite rotary motion, or
against the hands of a watch; in front of a "low" there will therefore
be, in extra tropical latitudes, warm southeasterly winds, and behind
it cold northwesterly winds, the resulting changes of temperature being
shown by the isotherms, or lines of equal temperature. Moreover, in a
cyclonic system of this kind the westerly winds are generally far
stronger than the easterly winds, the motion of the whole system from
west to east increasing the apparent force of the former and decreasing
that of the latter. Upon reaching the coast, such areas of low
barometer, or storm systems, almost invariably develop a great increase
of energy, largely due to the moisture in the atmosphere overhanging
the ocean, which, when the air is chilled by contact with the cold dry
air rushing in from the "high," is precipitated and becomes visible in
the form of clouds, with rain or snow. The latent heat liberated by the
condensation of this aqueous vapor plays a most important part in the
continuance of the storm's energy and, indeed, in its increase of
energy: the warm light air flowing in towards the central area of the
storm rises rapidly into regions where the pressure is less, that is,
where the thickness and consequently the weight of the superincumbent
atmosphere is less; it therefore rapidly expands, and such expansion
would result in a much more rapid cooling, and a corresponding decrease
in its tendency to rise still higher, were it not for the latent heat
liberated by the condensation of the moisture which it contains. Thus
the forces that are conspiring to increase the energy of the storm are
powerfully assisted by the presence and condensation of aqueous vapor,
and the increasing updraught and rarefaction are at once marked by the
decreasing barometric pressure at the center. For example, a storm was
central over the Great Lakes on Jan. 25th, with lowest barometer 29.7;
the following day it was central off Nantucket, barometer 29.2; and on
the 27th and 28th, over the Gulf of St. Lawrence, with barometer below
28.6. But such instances are so common as to make it the rule, and not
the exception. As stated above, the isobars about an area of low
barometer are somewhat circular in form; more strictly speaking, they
are somewhat oval or elliptical in shape, and the more elongated the
north and south axis of this ellipse, the greater the resulting changes
of temperature, because, as it moves along its broad path toward the
Atlantic, the indraught, or suction, is felt in front far down toward
the tropics, and in rear far to the northward, beyond the territorial
limits of the United States.
Similarly with regard to the general movement of areas of high
barometer, certain laws of motion have been clearly established by
means of studies of the daily international charts; instead of a motion
toward east-northeast, these areas when north of the 40th parallel,
have in general a motion towards east-southeast, and as a rule move
more rapidly and with greater momentum than "lows," so that they may be
said to have the right of way, when the tracks of two such systems
converge or intersect. These laws, or at least that relating to the
Great Lake storm track, as it may be called, soon become evident to
anyone who watches the weather map from day to day, upon which are
charted the systems of low and high barometer as they follow one
another across the continent, bringing each its characteristic weather.
MARCH 11TH, 7 A.M.
The first of the accompanying weather charts indicates graphically the
meteorological conditions over the wide area charted, comprising about
3,000,000 square miles, of which one-third is land and two-thirds
water. Over the land there is a long line, or trough, of low barometer,
extending from the west coast of Florida up past the eastern shore of
Lake Huron, and far northward toward the southern limits of Hudson Bay.
In front of this advancing line the prevailing winds are southeasterly,
and the warm moist air drawn up from southern latitudes spreads a warm
wave along the coast, with generally cloudy weather and heavy rains,
especially south of Hatteras; the Signal Service observer at Pensacola,
for example, reports the heavy rain-fall of 4.05 inches on the 10th.
About midway of this trough of low barometer there is a long narrow
region of light variable winds; of rapid changes in meteorological
conditions; calms, shifts of wind, intervals of clearing weather; then
overcast again, with cooler and fresh northwesterly winds, increasing
to a gale. The front line of this advancing battalion of cold
northwesterly winds is more than a thousand miles in length, and covers
the whole breadth of the United States: its right flank is on the Gulf,
its left rests on the Great Lakes, or even farther north; the
temperature falls rapidly at its approach, with frost far south into
Louisiana and Mississippi, and heavy snow in central Kentucky and
eastern Tennessee. The long swaying line is advancing toward the coast
at the rate of about 600 miles a day, followed by a ridge of high
barometer reaching from Texas to Dakota and Manitoba. At points along
the trough the barometer ranges from 29.70, a hundred miles north of
Toronto, to 29.86 at Pittsburg, 29.88 at Augusta, and 29.94 at Cedar
Keys. Along the ridge the barometer is very high; 30.7 to the northward
about Lake Winnipeg, 30.6 in Wyoming, 30.7 in Indian Territory, and
30.5 south of the Rio Grande. The difference of pressure from trough to
ridge is thus measured by about an inch of mercury in the barometer.
Moreover, the chart shows that there is another ridge of high barometer
in advance, curving down off the coast from northern Newfoundland,
where the pressure is 30.6, toward Santo Domingo, where the pressure is
30.3, and passing midway between Hatteras and Bermuda. Farther to the
eastward the concentric isobars show the presence of a storm which
originated about Bermuda on the 9th, and is moving off toward Europe
where, in a few days, it may cause northwesterly gales with snow to the
northward of its track, and southeasterly gales with rain to the
southward. Storm reports from various vessels show that this storm was
of hurricane violence, with heavy squalls and high seas, but it need
not be referred to in this connection further than to say that it sent
back a long rolling swell from northeast, felt all along the Atlantic
sea-board the morning of the 11th, and quite distinct from that caused
by the freshening gale from the southeast.
METEOROLOGICAL CONDITIONS OFF THE COAST.
While this trough of low barometer, with all its attendant phenomena,
is advancing rapidly eastward toward the Atlantic, and the cold wave in
its train is spreading over towns, counties and states--crossing the
Great Lakes, moving up the Ohio valley, and extending far south over
the Gulf of Mexico--we may pause for a moment to consider a factor
which is to play a most important part in the warfare of the elements
so soon to rage with destructive violence between Hatteras and Block
Island, and finally to disturb the weather of the entire North Atlantic
north of the 20th parallel.
The great warm ocean current called the Gulf Stream has, to most
people, a more or less vague, mythical existence. The words sound
familiar, but the thing itself is only an abstract idea; it lacks
reality, for want of any personal experience or knowledge of its
characteristic effects. To the navigator of the North Atlantic it is a
reality; it has a concrete, definite existence; it is an element which
enters into the calculations of his every-day life--sometimes as a
friend, to help him on his course, sometimes as an enemy, to endanger,
harass, and delay. Briefly, the warm waters of the tropics are carried
slowly and steadily westward by the broad equatorial drift-current, and
banked up in the Caribbean Sea and Gulf of Mexico, there to constitute
the head or source of the Gulf Stream, by which the greater portion is
drained off through the straits of Florida in a comparatively narrow
and swiftly moving stream. This great movement goes on unceasingly,
subject, however, to certain variations which the changing seasons
bring with them. As the sun advances northward in the spring, the
southeast trades creep up toward and across the equator, the volume of
that portion of the equatorial current which is diverted to the
northward of Cape San Roque is gradually increased, and this increase
is soon felt far to the westward, in the Yucatan and Florida straits.
Figures fail utterly to give even an approximate idea of the amount of
heat thus conveyed from the tropics to the north temperate zone by the
ceaseless pulsations of this mighty engine of oceanic circulation. To
put it in some tangible shape for the mind to grasp, however, suppose
we consider the amount of energy, in the form of heat, that would be
liberated were this great volume of water reduced in temperature to the
freezing point. Suppose, again, that we convert the number of
heat-units thus obtained into units of work, so many foot-pounds, and
thence ascertain the corresponding horse-power, in order to compare it
with something with which we are familiar. Considering only the portion
of the Gulf Stream that flows between Cape Florida and the Great Bahama
bank, we find from the latest and most reliable data, collected by the
U. S. Coast and Geodetic Survey, that the area of cross section is
10.97 square miles (geographic or sea miles, of 6,086 feet each); mean
velocity, at this time of the year, 1.305 miles per hour; mean
temperature, 71° F. These figures for mean velocity and temperature
from surface to bottom are, it will be noticed, far below those for the
surface current alone, where the velocity is often as great as five
knots an hour, and the temperature as high as 80°. The indicated
horse-power of a great ocean steamship--"La Bourgogne," "Werra,"
"Umbria" and "City of New York," for example--is from 9,000 to 16,000;
that of some modern vessels of war is still greater; the "Vulcan," now
building for the British Government, is 20,000, and the "Sardegna," for
the Italian Government, 22,800. Again, if we convert into its
equivalent horse-power the potential energy of the 270,000 cubic feet
of water per second that rush down the rapids of Niagara and make their
headlong plunge of 160 feet over the American and Horse-shoe falls, we
get the enormous sum of 5,847,000. The Gulf Stream, however, is every
hour carrying north through the straits of Florida fourteen and
three-tenths cubic miles of water (more than three thousand times the
volume of Niagara), equivalent, considering the amount of heat it
contains from 71° to 32° F., to _three trillion and sixty-three
billion_ horse-power, or more than five hundred thousand times as much
as all of these combined; indeed, considering only the amount of heat
from 71° to 50°, it is still two hundred and seventy-five thousand
times as great.
Sweeping northward toward Hatteras with its widening torrent, its
volume still further increased by new supplies drawn in from the
Bahamas and the northern coast of Cuba, its color a liquid ultramarine
like the dark blue of the Mediterranean, or of some deep mountain lake,
it then spreads northeastward toward the Grand banks of Newfoundland,
and with decreasing velocity and lower temperature gradually merges
into the general easterly drift that sets toward the shores of Europe
about the 40th parallel.
The cold inshore current must also be considered, because it is to
great contrasts of temperature that the violence of storms is very
largely due. East of Newfoundland the Labrador current flows southward,
and during the spring and summer months carries gigantic icebergs and
masses of field-ice into the tracks of transatlantic steamships. Upon
meeting the Gulf Stream, a portion of this cold current underruns it,
and continues on its course at the bottom of the sea; another portion
is deflected to the southwest, and flows, counter to the Gulf Stream,
along the coast as far south as Hatteras.
The broad features of these great ocean currents have thus been briefly
outlined, and, although they are subject to considerable variation as
to temperature, velocity, and limits, in response to the varying forces
that act upon them, this general view must suffice for the present
purpose.
Now to consider for a moment some of the phenomena resulting from the
presence and relative positions of these ocean currents, so far as such
phenomena bear upon the great storm now under consideration. With the
Pilot Chart of the North Atlantic Ocean for March there was issued a
Supplement descriptive of water-spouts off the Atlantic coast of the
United States during January and February. Additional interest and
importance have been given to the facts, there grouped together and
published, by their evident bearing upon the conditions that gave rise
to the tremendous increase of violence attendant upon the approach of
this trough of low barometer toward the coast. In it were given
descriptions, in greater or less detail, of as many as forty
water-spouts reported by masters of vessels during these two months, at
various positions off the coast, from the northern coast of Cuba to the
Grand banks; and since that Supplement was published many other similar
reports have been received. Moreover, it was pointed out that the
conditions that gave rise to such remarkable and dangerous phenomena
are due to the interaction between the warm moist air overhanging the
Gulf stream and the cold dry air brought over it by northwesterly winds
from the coast, and from over the cold inshore current, and the greater
the differences of temperature and moisture, the greater the resulting
energy of action. Reports were also quoted showing that the Gulf Stream
was beginning to re-assert itself after a period of comparative
quiescence during the winter months, and with increasing strength and
volume was approaching its northern limits, as the sun moved north in
declination.
Such, then, were the meteorological conditions off the coast, awaiting
the attack of the advance guard of this long line of cold northwesterly
gales,--conditions still further intensified by the freshening gale
that sprung up from the southeast at its approach, drawing
re-enforcements of warm, moist ocean air from far down within the
tropics. The energy developed when storm systems of only ordinary
character and severity reach the Atlantic on their eastward march
toward northern Europe is well-known, and need not be referred to
further: let us now return to the consideration of this storm which is
advancing toward the coast at the rate of about 600 miles a day, in the
form of a great arched squall whose front is more than a thousand miles
in length, and which is followed, far down the line, by northwesterly
gales and temperatures below the freezing point.
THE NIGHT OF THE 11TH-12TH.
Sunday afternoon, at 3 o'clock, the line of the storm center, or
trough, extended in a curved line, convex to the east, from Lake
Ontario down through New York State and Pennsylvania, along about the
middle of Chesapeake Bay to Norfolk, across North Carolina to Point
Lookout, and thence down through eastern Florida to Key West.
Northeasterly, easterly, and southeasterly gales were therefore felt
all along the coast from the Gulf of St. Lawrence to the Florida Keys,
except in the bight between Lookout and Cañaveral, where the barometer
had already reached and passed its lowest point and the wind was
northwest, with much cooler weather. Reference to the Barometer Diagram
shows pretty clearly that the trough passed Norfolk a short time before
it reached Hatteras, where the lowest reading was undoubtedly lower,
the evening of the 11th, than it was at Norfolk.
By 10 P.M. the line has advanced as far east as the 74th meridian.
Telegraphic reports are soon all in from signal stations along the
coast. The barometer is rising at Hatteras and Norfolk and still
falling at Atlantic City, New York, and Block Island, but there is
little or no indication of the fury of the storm off shore along the
74th meridian, from the 30th to the 40th parallel, where the cold
northwesterly gale is sweeping over the great warm ocean current,
carrying air at a temperature below the freezing point over water above
75° Fahrenheit, and where the barometer is falling more and more
rapidly, the gale becoming a storm, and the storm a hurricane. Nor are
there any indications that the area of high barometer about
Newfoundland is slowing down, blocking the advance of the rapidly
increasing storm, and about to hold the center of the line in check to
the westward of Nantucket for days, which seem like weeks, while a
terrific northwest gale plays havoc along the coast from Montauk Point
to Hatteras, and until the right flank of the line has swung around to
the eastward far enough to cut off the supply of warm moist air pouring
in from the southeast. Long before midnight the welcome "good night"
message has flashed along the wires to all the signal stations from the
Atlantic to the Pacific slope, whilst at sea, aboard scores of vessels,
from the little fishing-schooner and pilot-boat to the great
transatlantic liner, a life-or-death struggle with the elements is
being waged, with heroism none the less real because it is in
self-defence, and none the less admirable because it cannot always
avert disaster.
The accompanying Track Chart gives the tracks of as many vessels as can
be shown without confusion, and illustrates very clearly where data for
this discussion are most complete, as well as where additional
information is specially needed. Thus it is here plainly evident that
vessels are always most numerous to the eastward of New York (along the
transatlantic route), and to the southward, off the coast. To the
southeastward, however, about the Bermudas, there is a large area from
which comparatively few reports have been received, although additional
data will doubtless be obtained from outward-bound sailing vessels,
upon their return. Of all the days in the week, Saturday, in
particular, is the day on which the greatest number of vessels sail
from New York. The 10th of March, for instance, as many as eight
transatlantic liners got under way. Out in mid-ocean there were plowing
their way toward our coast, to encounter the storm west of the 50th
meridian, one steamship bound for Halifax, five for Boston, nineteen
for New York, one for Philadelphia, one for Baltimore, and two for New
Orleans. Northward bound, off the coast, were six more, not to mention
here the many sailing vessels engaged in the coasting or foreign trade,
whose sails whiten the waters of our coasts.
Of all the steamships that sailed from New York on the 10th, those
bound south, with hardly a single exception, encountered the storm in
all its fury, off the coast. Eastward-bound vessels escaped its
greatest violence, although all met with strong head winds and heavy
seas, and, had the storm not delayed between Block Island and Nantucket
on the 12th and 13th, would have been overtaken by it off the Grand
banks. Without quoting in detail the reports received, let us see what
they indicate regarding the general character of the storm during the
night, preparatory to our consideration of the weather chart for 7 A.M.
March 12th. To do so, be it remembered, is a very different task from
that which is involved in the study and comparison of observations
taken with standard instruments at fixed stations ashore. Here our
stations are constantly changing their positions; different observers
read the instruments at different hours; the instruments themselves
vary greatly in quality, and while some of them may have been compared
with standards very recently, there are others whose errors are only
approximately known. Moreover, when a vessel is pitching and rolling in
a storm at sea, in imminent danger of foundering, it is, of course,
impossible to set the vernier of the barometer scale and read off the
height of the mercury with very great precision. It will thus be
readily understood that the many hundreds of observations carefully
taken and recorded for the Hydrographic Office by masters of vessels
are necessarily more or less discordant, although the results obtained
rest on the averages of so many reports that the probable error is
always very small. An exhaustive study of reports from vessels at
various positions along the coast, from the Straits of Florida to Sandy
Hook, together with the records of the coast stations of the U. S.
Signal Service, indicates a continuous eastward movement of the trough
of low barometer during the night, accompanied by a rapid deepening of
the depression. All along the coast we have the same sequence of
phenomena, in greater or less intensity, according to the latitude of
the vessel, as we noticed here in Washington that Sunday afternoon,
when the warm southeasterly wind, with rain, died out, and after a
short pause a cold northwesterly gale swept through the city, piling up
the snow in heavy drifts, with trains belated or blockaded, and
telegraphic communication cut off almost entirely with the outer world.
It was a wild, stormy night ashore, but it was ten-fold more so off the
coast, where the lights at Hatteras, Currituck, Assateague, Barnegat,
and Sandy Hook mark the outline of one of the most dangerous coasts the
navigator has to guard against. To bring the scene vividly before the
mind would require far more time than I have at my disposal, and I can
only regret that I cannot quote a few reports to give some idea of the
violence of the storm.