The Philosophy of the Weather Part 17

[Ill.u.s.tration: Fig. 17.]

In relation to this, I observe, 1st. _About one-half of our N. E. storms, including some of the most severe ones, not only set in N. E., but continue in that quarter without veering at all, during the entire period that the storm cloud is over us_; usually for twenty-four hours; not unfrequently for forty-eight hours, sometimes for seventy-two or more hours. This every one can observe for himself, and it can not, of course, be reconciled with his theory.

2d. N. E. storms, whether they set in from that quarter in the commencement, or veer to it afterward, when they do "change" round, more frequently veer by the S. to the S. W. in clearing off, than back through the N. into the N. W. The former, in accordance with his theory, they can not do, as the reader can see by pa.s.sing the left side of the card over his place of residence on the map from S. W. to N. E.

3d. N. E. storms often pa.s.s off without hauling by S. or backing by N., and with or without a clearing off shower, the _wind s.h.i.+fting and coming out suddenly at S. W._ This they could not do in accordance with his theory, as slipping the card will show.

4th. From June to February it is _exceedingly uncommon_ for a N. E. storm to back into the N. W. They do so more frequently from February to May, especially about the time of the vernal equinox and after; and then, because the focus of precipitation and storm intensity of the extra tropical zone of rains is S. of 42 east of the Alleghanies. His theory requires them to back by N. into N. W. _in all cases, when they set in N.

E._

5th. When they do back from the N. E. into the N. W., it rarely indeed continues to storm after the wind leaves the point of N. E. by N., and generally, if it does continue stormy, _the wind is light_, and not a gale, how violent soever the gale from the eastward may have been.

Usually, by the time the wind gets N. W., it has cleared off. This, Mr.

Redfield, as we shall see, evades by embracing the N. W. fair wind as a part of the same gale. According to my observation, therefore, a _very large proportion_ of the _N. E. storms_, and they are a majority of the most violent ones of our climate east of the Alleghanies, do not _commence, continue_, or _veer_ in accordance with his theory, but the _reverse_; and so long as this is so, I can not receive his theory as true.

6th. S. E. storms do not always, or indeed often, conform to the requirements of his card. When they set in violently at S. E., and continue so for hours without veering, the axis of the storm should be over us, and the wind should change _suddenly_ to N. W. This did not occur in the storm of Sept. 3, 1821, nor does it often, if ever, occur in the summer or early gales of the autumnal months. In the later storms of autumn, and as often in those which are very gentle as any, and in the winter months when S. E. gales are rare, it does sometimes so change after the storm cloud has pa.s.sed. But in the winter months, as in the storm investigated by Professor Loomis, the storms are frequently long from S.

E. to N. W., and the S. E. wind blows nearly in coincidence with its long axis, for a thousand or fifteen hundred miles, till the barometric minimum is pa.s.sed, and the inducing and attracting force of this part of the storm cloud is spent, and then the N. W. wind follows; sometimes blowing in under the storm cloud, turning the rain to snow; but oftener following the storm within a few hours, or the next day. The storm of Professor Loomis, when over Texas, was not probably more than four or five hundred miles in length. As it curved more, and pa.s.sed north and east, it extended laterally, its center traveling with most rapidity, and when it reached the eastern coast was about fifteen hundred miles long, and not more than six hundred broad. Along the eastern part of that storm, except when by its more rapid progress the front projected much further eastward over New England than its previously existing line, the S. E. winds blew. When it bulged out, so to speak, by reason of the increased progress of the center, the wind veered to the N. E. The center of the storm pa.s.sed near St. Louis and south of Quebec, as the _fall of rain_, the _bulging_ of the _rapidly-moving center_, and the _line of subsequent cold_, attest. It is utterly impossible for any unbiased mind to look at the description of that storm, and attribute to it a rotary character. With all the data before him, Mr. Redfield himself has not attempted it directly.[8]

The September storm of 1821 was more violent in character than any which have since occurred. My recollection of it is as distinct as if it occurred yesterday. Peculiar circ.u.mstances, not important in this connection, fixed my attention upon the weather during that day and night.

There were cirro-stratus clouds pa.s.sing all day, from about S. W. to N.

E., thickening toward night with fresh S. S. W. wind and flocculent scud, such as I have since seen at the setting-in of S. E. autumnal gales. In the evening the wind (in the immediate neighborhood of Hartford, Ct.), veered to S. E., the cloud floated low, it became very dark, and the wind blew a most violent gale. The trees were falling about the house where I then resided, the windows were burst in, and I was up and observant. When the cloud pa.s.sed off to the east, it was suddenly light, and almost calm.

The western edge of the storm cloud was as perpendicular as a steep mountain side, and was enormously elevated, and very black. I have sometimes seen the western side of a summer thunder cloud, which had drawn a violent gust along beneath it, as elevated and perpendicular, but never a storm cloud. No cloud of that _depth_, or _intensity_ as exhibited by its peculiar blackness, ever floated or will float so near the earth, without inducing a devastating current beneath. After it had pa.s.sed the ridges east of the Connecticut valley, its top could be seen for a long and unusual period over the elevated ranges.

Now that storm was but an _intense portion_ of an extensive stratus-rain cloud. Such portions frequently exist, and Mr. Redfield admits the fact.

Another like portion, in the same storm, pa.s.sed over Norfolk, Virginia, and the adjacent section, where the wind was N. E., and veered round by N.

W. to S. W. Baltimore, and some vessels at sea, were between the two intense portions of the storm, and were not affected by either. Its northern limit was bounded by a line, drawn from some point not far north of Trenton, New Jersey, north-eastward, and north of Worcester, Ma.s.sachusetts. I was about forty miles south of its northern limit, and north of its center. During that day, and the next, there was wind from S. W. to S. E., inclusive, including the gale, and _from no other quarter_. It did not at any time veer to the W. or N. W. After the pa.s.sage of the storm-cloud, the wind was very light. When this intense portion of the storm pa.s.sed over the valley of the Connecticut, its longest axis was from S. S. E. to N. N. W., and the _wind was S. E. the whole length of it_. In its pa.s.sage from the longitude of Trenton to Boston, there was N.

W. wind at one point, and but one, and that was in the iron region, at the N. W. corner of Connecticut, at the northern limit of the intense cloud, and owing, doubtless, to some local cause. The direction of the wind in that storm was in accordance with what is generally true of our storms.

The wind on the front of the storm depends upon its shape. If the storm is long in proportion to its width (and no other _violent_ autumnal or winter storm has been investigated, to my knowledge), the wind blows axially, or obliquely, on its front. Thus, if long from S. E. to N. W., the wind on its front will blow from the S. E. So, if the storm is long from S. W. to N. E., and has a south-eastern lateral extension, with an easterly progression, the wind will blow axially in the center, and obliquely at the edges. Instances might be multiplied, but I refer to one of recent date and striking character. All of us remember the drought of 1854. It ended in drenching rain on the 9th of September. This rain fell from a belt, half showery and half stormy in character, which had a S. E. lateral extension.

The evening of the previous day there was some lightning visible at the north, and the usual S. S. W. afternoon wind _continued fresh after nightfall_. The next day we had a brisk wind from the same quarter, and, after noon, the clouds appeared to pile up in the far north, seeming very elevated. They continued to do so, extending southerly during the afternoon, _with a high wind from S. S. W._, the c.u.mulus clouds moving E.

N. E. At 5 P.M., gentlemen who left New York at 3 P.M., reported that a dispatch had been received from Albany, dated 1 P.M., stating that it was raining very heavily there. About 7 P.M., the belt reached us, and it rained heavily from that time till morning. Not far from 8 P.M., and during the heaviest rain, the wind s.h.i.+fted from the S. S. W. to N. E., and blew fresh and cold from that quarter during the night, and till the belt had pa.s.sed south, and then from N. E. by N., cool, with heavy scud, during the forenoon, veering gradually to the N. N. E., and dying away. After the rain ceased, the northern edge of the belt was distinctly visible in the S. and S. E., its stratus-cloud moving E. N. E., and its scud to the westward.

The front of that storm did not pa.s.s over us. It was long and narrow. The wind blew somewhat obliquely inward, along its southern border, to the eastward, and, in like manner, to the westward, on its northern border, but from the N. E. axially along its central portions.

In the last instance, the wind changed from S. W. to N. E. This, too, is impossible, according to Mr. Redfield's theory. Similar instances, in summer, and early autumn, are not uncommon. But I shall recur to this in connection with the different _cla.s.ses_ of storms.

Again, the manner in which these S. E. winds co-exist with the N. E., and become the prevailing wind, toward the close of the storm, is instructive, and inconsistent with the theory of Mr. Redfield. In the West Indies, the first effect of the storm is to increase the N. E. trade; the wind then becomes baffling, but settles in the N. W. or N. N. W., _in direct opposition to the admitted progress of the storm_. At this point, or at S.

W., it blows with most force. Sometimes it veers gradually, and sometimes falls calm, and comes out from the S. W., blowing violently. It ends by veering to the S. E., following gently the course of the storm. Thus, Mr.

Edwards, in the third volume of his History of Jamaica, as herein before cited, "_all hurricanes begin from the north, veer back to W. N. W., W., and S. S. W., and when they get round to S. E. the foul weather breaks up_."

A short, sudden gale, resembling those of our summer thunder-showers, is sometimes met with from the S. E.; but the violent hurricanes of any considerable continuance are, in almost every case, as just stated.

Now, there is, in our lat.i.tudes, an obvious law on the subject, and it is this:--If the storm is not disproportionately long, northerly and southerly, there is a general tendency to induce and attract a surface current, in opposition to the course of the storm on its front, and especially its north front. At the same time, there is a tendency to induce a lateral current on its side, particularly the southerly side, and sometimes its south front: that the latter current is, in the first part of the storm, above the former; in the middle and latter part, it becomes the prevailing current at the surface, and the wind changes accordingly, with or without a calm--that this lateral change sometimes takes place on either side, but usually occurs on the side where the water is warmest, or there is, for other and local reasons, a _greater susceptibility in the atmosphere to inductive and attractive influence_. Thus, our N. E. storms very frequently have a southerly current also, drawn from the ocean, south of us, which forms the middle current, and, in the middle and latter part of it, becomes the prevailing one. _I have seen more than a hundred such instances, clearly and distinctly marked._ Since I have been writing this chapter, January 29th, 1855, such an instance has occurred. On Sunday, the 28th, the cirro-stratus were all day pa.s.sing from the S. W. to N. E., and gradually thickening with light air from the E. N. E., in the afternoon.

During the evening the wind set in _violently_ from the N. E., with a deluging rain. During the night, and after a brief calm, it changed suddenly to the southward, and blew in like manner. This morning the storm was gone, and with it, six inches of hard, frozen icy snow; the trade was clear, with the exception of here and there a broken, melting piece of stratus, but scud were still running from the southward, and the wind has been from the south, veering to S. W., all day, with suns.h.i.+ne. As I have before remarked, this middle current is always present, in this locality, in stratus storms, when there is a heavy fall of rain or snow, although, when the latter happens, the middle current is sometimes from the northward; if it be from the southward, it turns the snow first into very large flakes, and then to rain in our part of the storm.

Doubtless, the same thing occurs every where. In the West Indies, and especially over the Leeward Islands, the middle current is most commonly from the stream of warm water which runs off to the westward into the Caribbean Sea; as the S. W. moonsoon is from the same current below the Cape de Verdes. The S. W. winds, which come from those south polar waters, in the West Indies, appear to be the most violent. But it may be on either or both sides.

The hurricane cloud of the West Indies moves confessedly N. W. in most instances, and undoubtedly it does in all. There is an immutable law that requires it. The seeming exceptions are not such; they are but instances imperfectly investigated. Now, a circular storm moving N. W. can set in N.

W. only on the left front, and _can not change to S. W. on that side of the axis_. Nor can the wind blow at the axis from N. W. at all. It should be N. E. in first half, and S. W. in last half. Strange as it may seem, the axis of a West India hurricane in conformity with Mr. Redfield's theory, and a N. W. progression, has never been found, with perhaps a single exception, in any one of which I have seen a description. On the west coast of Europe, the gale is commonly from the Atlantic, either following under the storm from the S. W., or blowing in diagonally from the W. or N. W.; the N. E. wind of western Europe being a cold, dry wind, which there is reason to believe has been around the Siberian pole and is returning, as the cold northerly winds of the North Pacific have around the North American magnetic pole. "If the N. E. winds always prevailed,"

says Kamtz, speaking of Berlin, "even at a considerable height it would never rain." This was based on an observation of showers, and not fully reliable. But the dry and cool character of the N. E. wind of western Europe is unquestionable. The S. E. wind is also a storm wind, but owing to the character of the surface from which it is attracted, it is not as violent as the westerly winds are.

Such, too, is the general course and character of the side wind in the southern hemisphere. There gales are less frequent, the magnetic intensity is less, the counter-trades are less; it is not in "the order of Providence" that as much rain shall fall there. Nevertheless, gales occur, although rarely, if ever, with equal violence. About New Holland, where storms are pursuing a S. E. course, they have the wind N. E., corresponding to our S. E., veering from thence, _by the north_, to the westward, clearing off from S. W., with a rising barometer, as ours do from N. W.

In the Bay of Bengal, the Indian Ocean, and the Arabian Sea, there is more irregularity.

But the law of progress and lateral winds can be distinctly traced as _present_ and prevailing, notwithstanding the irregularities. Our limits do not permit an a.n.a.lysis. In the celebrated case of the Charles Heddle, there was much evidence to show that she was driven across the front of the storm by one lateral wind, and back by another. (Diagram of Colonel Reid, p. 206.)

The waters of the Indian Ocean are hot and confined. Storms there are often composed of detached ma.s.ses, move slower--sometimes not more than three or four miles an hour--and they curve over the ocean, where it is hotter than in any similar lat.i.tude. Yet, notwithstanding all peculiarities and irregularities, the law we have been considering is probably the _prevailing_ law there.

No man knows better the existence of these different currents than Mr.

Redfield. Doubtless it has escaped his attention that the upper of two, after the pa.s.sage of a considerable proportion of the storm, becomes the lower, and causes a seeming change of the same wind.

In a series of elaborate articles, substantially reviewing the whole subject, published in the American Journal of Science, for 1846, he says:

"In nearly all great storms which are accompanied with rain, there appear two distinct cla.s.ses of clouds, one of which, comprising the storm scuds in the active portion of the gale, has already been noticed. Above this is an extended stratum of stratus cloud, which is found moving with the general or local current of the lower atmosphere which overlies the storm. It covers not only the area of rain, but often extends greatly beyond this limit, over a part of the dry portion of the storm, partly in a broken or detached state. This stratus cloud is often concealed from view by the nimbus, and scud clouds in the rainy portion of the storm, but by careful observations, may be sufficiently noticed to determine the general uniformity of its specific course, and, approximately, its general elevation.

"The more usual course of this extended cloud stratum, in the United States, is from some point in the horizon between S. S. W. and W. S.

W. Its course and velocity do not appear influenced in any perceptible degree by the activity or direction of the storm-wind which prevails beneath it. On the posterior or dry side of the gale, it often disappears before the arrival of the newly condensed c.u.muli and c.u.mulo-stratus which not unfrequently float in the colder winds, on this side of the gale."

"The general height of the great stratus cloud which covers a storm, in those parts of the United States which are near the Atlantic, can not differ greatly from one mile; and perhaps is oftener below than above this elevation. This estimate, which is founded on much observation and comparison, appears to comprise, at the least, the limit or thickness of the proper storm-wind, which const.i.tutes the revolving gale.

"It is not supposed, however, that this disk-like stratum of revolving wind is of equal height or thickness throughout its extent, nor that it always reaches near to the main canopy of stratus cloud.

It is probably higher in the more central portions of the gale than near its borders, in the low lat.i.tudes, than in the higher, and may thin out entirely at the extremes, except in those directions where it coincides with an ordinary current. Moreover, in large portions of its area, there may be, and often is, more than one storm-wind overlying another, and severally pertaining to contiguous storms. In the present case, we see, from the observations of Professor Snell and Mr. Herrick, at Amherst, Ma.s.sachusetts, and at Hamden, Maine (115 and 135 b.), that the true storm wind, at those places, was super-imposed on another wind; and various facts and observations may be adduced to show that brisk winds, of great horizontal extent, are often limited, vertically to a very thin sheet or stratum."

Much of the foregoing is graphically described, and unquestionably true.

But it may well be asked how he, or others, distinguish which of two or more currents (for there are frequently three, and sometimes four visible), are the true currents of the storm, and which interlopers from another storm? Is the true one always the upper one, and why? If the upper one, why is the interloper at the surface noted and quoted to prove what a storm is? How does he know what proportions of the winds he has recorded to show the revolving motion of gales, were the true storm winds of the particular storm? or, that every one of them was not an interloping wind on which the true storm wind was superimposed?

These inquiries are pertinent, for obviously, unless some rule for distinguis.h.i.+ng between the currents is given, and there be evidence of direct observation to show that the surface wind, whose direction is noted, is the true wind of the storm, and that the _latter_ is not _superimposed_, no reliance can be placed upon logs, or newspaper accounts, or registers. There is another element besides direction, viz.: superimposition, a determination of which _is_ essential to _truth_. It will be difficult for Mr. Redfield to say that a determination of that element has been made, with certainty, in a single storm he has investigated; and in relation to the convergence of storms, and blending, and superimposition of their winds, I think he is mistaken.

Mr. Redfield is right in saying (American Journal of Science, vol. ii., new series, p. 321) that "too much reliance may be placed upon mere observations of the surface winds in meteorological inquiries," and yet _they_ only have thus far been regarded, and he has proved gyration in no other way. I have frequently, with a vane in sight, asked intelligent men how the wind was, and been amused and instructed by their inability to state it correctly. Mr. Redfield, in his inquiries, often found two reports of the weather at the _same time_, from the _same place_, materially different; and I have known, from my own observation, newspapers and meteorological registers to be several points out of the way; and this, because the vanes are influenced by local elevations, and change several points, and very often; because few know the exact points of the compa.s.s in their own localities, and because entire accuracy has not been deemed essential. For these reasons, newspaper and telegraphic reports are not always reliable; and therefore, and because, also, storm-winds are easterly and fair winds westerly, and the former veer from east around to west, on one or both sides in many cases, there are few storms which can not be represented as whirlwinds, by a proper _selection_ of _reports_, a corresponding _location_ of the _center_, and an _extension_ of the lines of supposed gyration, so as to include the _preceding_ winds, the actual winds of the storm, and the _lateral_, and _succeeding_ fair weather ones.

But, again, Mr. Redfield is right in saying there is, in such cases, "an extended stratum of stratus cloud," and it is always present. But why does he say this _covers the storm_? Is it distinct from it, and if so, what is it doing there? What power placed it there, and for what purpose? Has this extended stratum of cloud, which forms the canopy of a vast chamber--five hundred to one thousand miles in diameter, and less than two miles in vertical depth, while the earth forms the floor--any agency in producing the whirl that is supposed to be going on within it, and if so, what? Has the earth any agency, and if so, what? If neither the ceiling nor floor of the chamber have any agency in producing it, what does? Are we to consider the _storm-scud_ as possessing the power, and as waltzing around the aerial chamber, carrying the air with them in a hurricane-dance of devastation? _What, in short, is the power, and how is it exerted?_

To these questions, Mr. Redfield's essays furnish no comprehensive answer.

There is an intimation that the cause of storms will be, at some future day, developed. One attempt, and but one, has thus far been made, and that I quote entire:

"We have seen that the two Cuba storms, as well as the Mexican northers, have appeared to come from the contiguous border of the Pacific Ocean.

"Now, are there any peculiarities in the winds and aerial currents of those regions, which may serve to induce or support a leftwise rotation in extensive portions of the lower atmosphere, while moving on, or near the earth's surface? I apprehend there are such peculiarities, which have an extensive, constant, and powerful influence. First, we find on the eastern portion of the Pacific, from upper California to near the Bay of Panama, an almost constant prevalence of north-westerly winds at the earth's surface. Next, we have an equally constant wind from the southern and south-western quarter, which, having swept the western coast of South America, _extends across the equator to the vicinity of Panama_, thus meeting, and commonly over-sliding the above-mentioned westerly winds, and tending to a deflection or rotation of the same, from right to left.

As this influence may thus become extended to the Caribbean or Honduras Sea, we have, next, the upper or S. E. trade of this sea, which is here frequently a surface-wind, and must tend to aid and quicken the gyrative movement, ascribed to the two previous winds; and lastly we have the N. E. or lower trade, from the tropic, which, coinciding with the northern front of the gyration, serves still further to promote the revolving movement which may thus result from the partial coalescence of these great winds of Central America, and the contiguous seas.

"Thus, while a great storm is, in part, on the Pacific Ocean, its N.

E. wind may be felt in great force on that side of the continent, through the great gorges or depressions near the bays of Papagayo or Tehuantepec, as noticed by Humboldt, Captain Basil Hall, and others, the elevations which there separate the two seas being but inconsiderable; and, when the gyration is once perfected, the whole ma.s.s will gradually a.s.sume the movement of the predominant current, which is generally the higher one, and will move off with it, integrally, as we see in the cases of the vortices, which are successively found in particular portions of a stream, where subject to disturbing influences."

The a.n.a.logy between this and the theory of Professor Dove, cited above, and prior, in point of time, is obvious. They are substantially alike in principle, with different locations. They differ also in this, Professor Dove appears to think something more than over-sliding necessary, and a.s.signs the duty of crowding the upper current down in to the lower, to make an _encounter_, to a lateral overflow from Africa. Mr. Redfield seems to think there may be a tendency to deflection when they "over-slide" each other. They are both closet hypotheses, the poetry of meteorology, with something more than poetical license as to facts.

In the first place, _no such concurring winds exist in the same locality at the same time_. When the inter-tropical belt of rains is over Central America and Southern Mexico, a S. W. monsoon blows in under it, but it usurps the place of all other surface winds; and, when the belt is absent, that portion of the eastern Pacific is most remarkably calm, or is covered by the N. E. trades. Secondly, the _trade-winds every where pursue their appointed course without "tendency to deflection" by the meeting, or "over-sliding," or "breaking in," or "encounter,"_ of other winds. The great laws of circulation do not admit of any such _confusion_. And, lastly, _no storm ever came over the eastern United States from that quarter_. The unchangeable laws of atmospheric circulation forbid it.