Intensified Trade-wind Belt.—Another very important fact (established by Meldrum, at Mauritius) may be stated thus: When a hurricane is moving along the equatorial limits of a trade-wind region, there is a belt of intensified trades to windward of its track: not until the barometer has fallen about six-tenths of an inch it is safe to assume that, because the trade-wind increases in force and remains steady in direction, you are on the track of the storm. By attempting too early to cross its track, running free as soon as the wind begins to freshen, you are liable to plunge directly into the vortex of the hurricane.
General Information.—Hurricanes are especially liable to be encountered from July to October, inclusive, in the tropics (north of the 10th parallel), the Gulf of Mexico, and Gulf Stream region. Earliest indications: Barometer above the normal, with cool, very clear, pleasant weather; a long, low, ocean swell from the direction of the distant storm; light, feathery cirrus clouds, radiating from a point on the horizon where a whitish arc indicates the bearing of the center. Unmistakable signs: Falling barometer; halos about the sun and moon; increasing ocean swell; hot, moist weather, with light variable winds; deep red and violet tints at dawn and sunset; a heavy, mountainous cloud bank on the distant horizon; barometer falling more rapidly, with passing rain squalls.
Brief Rules for Action.—If the squalls freshen without any shift of wind, you are on the storm track: run off with the wind on the starboard quarter and keep your compass course (see caution in paragraph entitled "Intensified Trade-wind Belt"). If the wind shift to the right, you are to the right of the storm track: put the ship on the starboard tack and make as much headway as possible, until obliged to lie-to. If the wind shift to the left, you are to the left of the storm track: bring the wind on the starboard quarter and keep your compass course; if obliged to lie-to, do so on the port tack. In scudding, always keep the wind well on the starboard quarter, in order to run out of the storm. Always lie-to on the coming-up tack. Use oil to prevent heavy seas from breaking on board.
The next plate,
THE HURRICANE OF NOVEMBER 25, 1888,
is a very instructive illustration of an actual hurricane, and one of the most severe on record off our Atlantic coast. The spiral lines have been added to bring out conspicuously the wind-circulation, and several features will at once attract attention: the elongated shape of the storm, along a north and south line (the direction of motion); the wide region where there is a southeasterly gale (exactly analogous to the belt of intensified trades); the long sweep of northeasterly winds along the coast; and the marked variation from a strictly circular whirl. The right-hand side is the dangerous semicircle, and it is here that the navigator is called upon to decide whether he shall dare make the attempt to run before the wind and cross the track of the storm; the left-hand side is the navigable semicircle,—not very navigable in this particular case, we may well believe, with no sea-room to the westward, a fearful N NE. gale, and a terrific sea. This is a case where every resource of seamanship and navigation may fail to save a ship, as the loss of the steamship "Samana" and a dozen other strong vessels, with all on board, bears sad testimony. Let me quote a few lines from a thrilling report by Captain Drew, of the American ship "Sea Witch" (this vessel's position is plotted on the chart about lat. 32° N., long. 75° W.): "Nov. 24: Hurricane from NE.; our position a perilous one, the ship rolling heavily and filling the decks with water; an awful gale, the worst we have ever had,—how will it end? At 3 P.M., the sun out a moment through the thick sky. Nov. 25: Still blowing a hurricane, with awful squalls of rain; the seventh day of the gale. No side-lights can burn; the binnacle-light goes out as fast as we can light it. One blast from the north blew our brand-new lower-maintopsail away like brown paper. We performed the critical manoeuver of wearing ship, which saved the vessel: we were foundering." Verily, this was "out of the jaws of death," and probably there were few more sincere thanksgiving services than those held on board this vessel on Nov. 29th, 1888, as recorded in her log. One other report may be referred to here, as it is of especial interest. It is from the British steamship "Effective," whose position is plotted about half way between Bermuda and New York. At this time the wind was S SE., force 8, and the storm center was moving directly toward her. We learn from Captain Crosby's report that by noon, local time, the wind was strong from south; at 4:30 P.M., a hard gale from east, moderating until midnight, barometer falling very rapidly. Nov. 26th, very heavy gale from NE., ship heading bow to sea; noon, wind east, barometer 28.60; 5 P.M., wind N NE., 28.20; 10 P.M., SW.; midnight, W., 28.20. This report illustrates the experience of a vessel close to the line of sudden shift of wind from SE. to N NE., and sustains very well the spiral lines drawn on the chart, just where there is an absence of data on the chart itself.
THE HURRICANE SEASON.—June may be fairly said to be the first of the five hurricane months in the North Atlantic, and the above diagram is presented in order to call special attention to the Law of Storms, especially to certain important modifications of the old laws. The spiral lines indicate the general wind-circulation in this particular hurricane, and the complete data presented on the Chart must convince any one that conclusions based upon such evidence must be worthy of the most careful consideration. This hurricane was one of the most severe on record off our Atlantic coast, and, though much larger than a hurricane in the tropics, similar evidence can be presented to show that the 8-point rule is seldom a safe guide for obtaining the bearing of the center; a 10-point or even a 12-point rule is generally better, although the 8-point rule is fairly correct if applied to the direction of the low clouds, rather than the wind. The long sweep of NE'ly winds along the coast, when there is a hurricane below Hatteras, is a very characteristic and important feature. With a NE'ly wind off Block Island, for instance, it should not be assumed that the center bears SE.: the Chart shows that it may be almost due south. There is likewise a wide region where the wind is from the SE., and a vessel running before this steady SE. wind would plunge deeper and deeper into the hurricane. Similarly in the trades, to windward of the track of a hurricane: not until the barometer has fallen about 6-tenths of an inch is it safe to assume that, because the trade-wind increases in force and remains steady in direction, you are on the track of the storm; by attempting too early to cross its track, running free as soon as the wind begins to freshen, you are liable to plunge directly into the vortex.
Lack of space does not allow of further details, and I must go on to the next plate,
THE ST. THOMAS-HATTERAS HURRICANE OF SEPT. 3–12, 1889.