National Geographic : 1890 Jul
WEST INDIAN HURRICANES, AND OTHER NORTH ATLANTIC STORMS. From the Pilot Chart of the North Atlantic Ocean, August, 1889, with Additional Paragraphs. Explanation.--These diagrams are for practical use in West Indian hurricanes. The upper one will also answer for ordinary storms along the trans atlantic route. The small arrows fly with the wind, the direction being stated at the end of each dotted line; the long arrow on each diagram is the STORM TRACK, that is, the probable path of the cyclone through the belt of latitude to which the diagram applies. Use of the Diagrams.-When a falling barometer, freshening rain squalls, &c., indicate a hurricane, select the proper diagram (according to the MONTH and LATITUDE), plot your position upon it by means of the direction of the wind, and thus ascertain the approximate bearing of the E .N. E E JUNE and OCTOBER, storm center. The probable storm track is indicated by the long arrow. If the wind shift, plot N.E/ . .S.E lat. 23° to 55° your position by means of the new wind-direction nearer the center if the wind has freshened S. ." JULY and SEPT., and the barometer has fallen). In this way you can readily observe every change of position N.N.' ' /t. 29 to 55. relative to the storm center, and decide what action to take, according to the character of your S "/. . AUG , vessel, the lay of the land, &c. These storms vary greatly in size, but are smallest and most violent S. ' . AUGUST, in the tropics, where the cloud ring averages about 500 miles in diameter and the region of stormy - " 1.,'-- "\ \". .. . \ lat. 33° to 55°. winds 300 miles, or even less. You can therefore only roughly estimate the DISTANCE of the cen N.N.w ..." . .. y. it. .s STORM TRACK, ter, although its BEARING can be obtained from the diagrams with a high degree of probability. S// N NE. to E NE. There is also considerable variation in the direction of motion and the velocity of the storm along EN'. " Motion f o' its track, but the general tendency is as stated herewith. S /sw Motion of storm Cyclonic Circulation.-One of the most important indications that an approaching storm W / center along track, is of hurricane violence is the marked cyclonic circulation of the wind. lower and upper clouds, /--S.w 20 to 30 miles per etc. This may be easily appreciated by remembering that a cyclone of any great intensity is an W 4w hour. ascending spiral whirl, with a rotary motion (in the Northern Hemisphere) against the hands of a watch, as shown on the diagrams The surface wind, therefore, blows spirally inward (not N EN. circularly, except very near the center); the next upper current (carrying the low scud and rain /. JUNE and OCTOBER, clouds), in almost an exact circle about the center; the next higher current (the high cumulus), in i-- - °. an outward spiral-and so on, up to the highest cirrus clouds, which radiate directly outward. SSE lat. 200 to 230. The angle of divergence between the successive currents is almost exactly two points of the com 'N . . ,.." JULY and SEPT., pass. Ordinarily, with a surface wind from N., for instance, the low clouds come from N., also; i. r on the edge of a hurricane, however, they come from N NE., invariably. In rear of a hurricane, N.N.W\;..\ H SE tat. 270 to 290 the wind blows more nearly inward; with a SE. wind, for instance, the center will bear about . .. .. : AUGUST, W., the low clouds coming from S SE. itwo points to the right of the wind), etc. Great activity ." t. . 80 to 33. of movement of the upper clouds, while the storm is still distant, indicates that the hurricane is of N .at. 80° to 33. great violence. If the cirrus plumes that radiate from the distant storm are faint and opalescent '. t\S.S . E STORM TRACK, in tint, fading gradually behind a slowly thickening haze or veil, the approaching storm is an old - 'N NW. toN NE one, of large area; if of snowy whiteness, projected against a clear blue sky, it is a young J I W. to NNE. cyclone of small area but great intensity. "-- i \ Motion of storm Intensified Trade-wind Belt. - Another very important fact (established by Meldrum, at w- center along tr , Mauritius) may be stated thus: When a hurricane is moving along the equatorial limits of a 10 mleser along rac, trade-wind region, there is a belt of intensified trades to windward of its track: not until the 5 to 0 milesper hour. barometer has fallen about six-tenths of an inch it is safe to assume that, because the trade S/S.SW wind increases in force and remains steady in direction, you are on the track of the storm. By sw -_ attempting too early to cross its track, running free as soon as the wind begins to freshen, you .ENE TJUNE and OCTOBER, are liable to plunge directly into the vortex of the hurricane. . GJU eneral Information.-Hurricanes are especially liable to be encountered from July to Octo S lat . 100 to 200. her, inclusive, in the tropics (north of the 10th parallel), the Gulf of Mexico. and Gulf Stream /- ... /-Z~ 6 s JULY and SEPT., region. Earliest indications: Barometer above the normal, with cool, very clear, pleasant N'/ ' lat. 100 to 27. 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 . \. AUGUST center. Unmistakable signs: Falling barometer; halos about the sun and moon; increasing NNW\ .. . ,at. t0 to 30*. ocean swell; hot, moist weather, with light variable winds; deep red and violet tints at dawn \ .... STORM TRACK, and sunset; a heavy, mountainous cloud bank on the distant horizon; barometer falling more w\\ ,'1... .. W.byN. rapidly, with passing rain squalls. So ". * s.s.E Brief Rules for Action.-If the squalls freshen without any shift of wind, you are on the S. storm track: run off with the wind on the starboard quarter and keep your compass course w. ' . Motion of storm (see caution in paragraph entitled " Intensified Trade-wind Belt"). If the wind shift to the right, ' "/ I/ ' ' center along you are to the right of the storm track: put the ship on the starboard tack and make as much t // I track, about 17 headway as possible, until obliged to lie-to. If the wind shift to the left, you are to the left of the 'sw /ss.w miles per hour. 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, [Edition of July, 1890.] 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.