Great Disasters and Horrors in the World's History

by Allen Howard Godbey

The accompanying diagram illustrates the fact that the wind blows from all directions toward the center of the storm. As the storm revolves, the wind would come apparently from the south for any one on the eastern edge of the cyclone of the northern hemisphere. Hence, in the case of a storm of large diameter, people in Richmond or Washington may often be surprised by an apparent northeast gale, which reaches them before it strikes New York or Boston. At the center of the storm is absolute calm. So if a cyclone pass centrally over any point in the northern hemisphere, a person at that place will find the wind blowing violently from the southeast: then after an interval of calm, it will blow with equal violence from the northwest. This will be the case if the path of the storm has already turned to the northeast, so that its northeast quarter may be called its front. If on the northwest course, however, the apparently alternate winds would be from the northeast and southwest. So one in the path of a southern cyclone would find the winds proceeding from the same quarters; for though it revolves in the opposite direction, its front or path is also in the opposite direction; so in either hemisphere, the southeast or the northeast wind will be the first felt by one directly in the track of the storm.

ROTATION OF STORMS.

Another result of the path of a cyclone is that the direction of its center from the stand-point of any observer is readily known. A glance at the diagram shows at once that if any one within the storm area of a cyclone of the northern hemisphere stands with his back to the wind, the storm center, where the barometer is lowest, is invariably on his left: but if he stand with his back to the wind of a southern cyclone, the storm center is always on his right. Hence, if a vessel be overtaken by a cyclone, the captain at once may know how to pass beyond its range, by shaping his course at right angles to that of the wind. Thus, if in a northern cyclone, he must sail to the right, supposing his back is to the wind: in the southern hemisphere, he would sail to the left.

As an example of the expansion of the storm area in its journey, may be mentioned the West India hurricane of 1839, which had, in the Antilles, a diameter of three hundred miles, which increased to five hundred at the Bermudas, and eight hundred on the parallel of 50° north latitude.

To draw again upon the illustration of the spinning top, it will be observed that the curvilinear motion is extremely slow in comparison with that of rotation, but increases as the rotation decreases. The same law applies to the movement of cyclones. The slowest motion forward is usually near the apex of the curve: and the progress on the ocean is much slower than on the land. Traveling over the latter, the irregularities of surface act in the case of the storm just as a rough surface does in the case of the top. The motion may be accelerated, but its regularity is lessened. So while at sea the parabolic path of the storm is almost absolutely perfect, but on reaching the land its motion is more rapid, and less regular, conforming somewhat to the configuration of the surface.

To illustrate, take the great cyclone of August 16th to 22nd, 1888. This started off Point Jupiter, Florida, with a rainfall of 2.2 inches in twelve hours, while the rotary velocity of the wind was sixty miles per hour. Its path across the Gulf of Mexico was a perfect semi-parabola, curving northward into western Louisiana; but rapid as was the rotary velocity, three and a half days were required for the journey across the gulf. Meanwhile, it was rapidly widening: for within a few hours of its reaching land, its eastern edge was assailing Mobile, Alabama, with a south wind of fifty-five miles an hour. Almost at the same time the western half was flooding Memphis and Vicksburg with an enormous rainfall—almost four inches in twelve hours, at Memphis. By the morning of August 21st, thirty-six hours after reaching land, it was central over middle Tennessee and Kentucky; heavy rains fell over the entire region. But by this time its eastern edge was in collision with the Appalachian chain; while a heavy local rain at the northern extremity of that chain created an additional diversion in a new area of low barometer. So it left the hitherto parabolic route, and shot away nearly at a tangent along the western Appalachian slope, passing from Tennessee to Newfoundland in thirty-six hours, thus moving nearly three times as rapidly as in the Gulf: while its violence, or rotary speed, was vastly lessened.