Tropical cyclone

“ Once within the area of the dense, low clouds, one should observe their direction of movement, which is almost exactly along the isobars, with the center of the storm being 90° from the direction of cloud movement (left of direction of movement in the Northern Hemisphere, and right in the Southern Hemisphere) . The winds are probably the best guide to the direction of the center of a tropical cyclone. The circulation is cyclonic, but because of the steep pressure gradient near the center, the winds there blow with greater violence and are more nearly circular than in extratropical cyclones. ”

“ High Winds and Flooding The high winds of a tropical cyclone inflict widespread damage when such a storm leaves the ocean and crosses land. Aids to navigation may be blown out of position or destroyed. Craft in harbors, often lifted by the storm surge, break moorings or drag anchor and are blown ashore and against obstructions. Ashore, trees are blown over, houses are damaged, power lines are blown down, etc. The greatest damage usually occurs in the dangerous semicircle a short distance from the center, where the strongest winds occur. ”

“ Wind gusts, which are usually 30 to 50 percent higher than sustained winds, add significantly to the destructiveness of the tropical cyclone. Many tropical cyclones that reach hurricane intensity develop winds of more than 90 knots sometime during their lives, but few develop winds of more than 130 knots. ”

“ In special regions only, and at special seasons, is the regular sequence of weather temporarily interrupted by an occasional tropical cyclone. These cyclones—the hurricanes of the West Indies and the typhoons of the China seas belong to the group—although infrequent, are notable features of the climate of the areas in which they occur. The devastation produced by one such storm often affects the economic condition of the people in the district of its occurrence for years. ”

“ On the average, six cyclonic storms form each year. These include two storms that generate winds of 48 knots or greater. Another 10 tropical cyclones never develop beyond tropical depressions. The Bay of Bengal is the area of highest incidence. However, it is not unusual for a storm to move across southern India and reintensify in the Arabian Sea. This is particularly true during October, the month of highest incidence during the tropical cyclone season. It is also during this period that torrential rains from these storms, dumped over already rain-soaked areas, cause disastrous floods. ”

“ THE TAIL-END OF THE WEST INDIAN HURRICANE.
On September 18 a tropical cyclone was central near these islands. The storm set in Monday morning, September 17, and was raging with increased severity the next day. Heavy cyclone rollers were sweeping in upon the coast and a strong northeast gale was blowing.
All of the telegraph wires were blown down.
Southeast rollers began to wash the shores Sunday, but the barometer continued high. During the night, however, it commenced falling, showing 29.91 inches. At 7 o’clock in the morning the wind was rising. ”

“ Torrential rains can occur when a storm moves against a mountain range; this is common in the Philippines and Japan, where even weak tropical depressions produce considerable rainfall. A 24-hour total of 46 inches was recorded in the Philippines during a typhoon in 1911. As hurricane Camille crossed southern Virginia’s Blue Ridge Mountains in August of 1969, there was nearly 30 inches of rain in about 8 hours. This caused some of the most disastrous floods in the state’s history.
Flooding is an extremely destructive by-product of the tropical cyclone’s torrential rains. ”

“ The responsibility for issuing gale and storm warnings for the Indian Ocean, Arabian Sea, Bay of Bengal, Western Pacific, and South Pacific rests with many countries. In general, warnings of approaching tropical cyclones will include the following information: storm type, central pressure given in hPa, wind speed observed within the storm, storm location, speed and direction of movement, the extent of the affected area, visibility, and the state of the sea, as well as any other pertinent information received. ”

“ The influence of wind on water-level is most remarkable in heavy storms on the flat coasts of the North Sea and Baltic, when the rise may amount to very many feet. In the region of tropical hurricanes the converging wind system of a circular storm causes a heaping up of water capable of devastating the low coral islands of the Pacific. On the 1st of November 1876 a cyclone acting in this way submerged a great area of the level plain of the Ganges delta to a depth of 46 ft. ”

“ In the West Indies, and in other tropical regions, these tornadoes are of frequent occurrence, and the damage is often fearful, whole towns being completely swept away. In the East Indies, and on the coast of India, these storms are known as Cyclones, because of their rotary motion—the Greek word Ruklos, from which "Cyclone" is derived, meaning "a whirl". A cyclone frequently extends across a great belt, and is from fifty to five hundred miles in width. ”

“ The depression turned toward the north on 18 June and north-northeast the next day as it moved around the western periphery of a mid-level ridge over Mexico and ahead of an unusually deep trough approaching California. By the evening of 18 June, the system was on the verge of becoming a tropical storm, but convection associated with the system weakened early the next day. Visible satellite images indicated that the low-level circulation became elongated and ill-defined on 19 June as the low approached southwestern Mexico. ”

“ If the eye of the storm passes over the vessel, the winds suddenly drop to a breeze as the wall of the eye passes. The rain stops, and the skies clear sufficiently to permit the Sun or stars to shine through holes in the comparatively thin cloud cover. Visibility improves. Mountainous seas approach from all sides in complete confusion. The barometer reaches its lowest point, which may be 11⁄2 or 2 inches below normal in fully developed tropical cyclones. ”

“ The hurricane does not originate in the circumpolar drift, but is a cyclonic whirl developed on the periphery of the great North Atlantic anti-cyclone. It is a tropical intruder, the only general storm disturbance the tropical circulation gives us. It is no new type, but simply one of the two great eddies known to the general atmospheric circulation the world over. ”

“ However, in tropical cyclones, strong winds rarely persist for a sufficiently long time or over a large enough area to permit enormous wave heights to develop. The direction and speed of the wind changes more rapidly in tropical cyclones than in extratropical storms. Thus, the maximum duration and fetch for any wind condition is often less in tropical cyclones than in extratropical storms, and the waves accompanying any given local wind conditions are generally not so high as those expected, with similar local wind conditions, in the high-latitude storms. ”

“ Hurricanes heading northwestward from the Caribbean and curving to follow the coastline, sweep over the Cape, which juts into the ocean at the point where the northward-moving storms still retain great force. In winter, big extratropical cyclones passing eastward across the region of the Great Lakes tend to produce small companions or secondaries in the southeastern states and some of them develop gales of hurricane force by the time they reach Hatteras. Here the cold air masses of the continent, guided by storm winds, are thrown against the warm, moist air from the Gulf Stream. ”

“ In every case the cyclone moves with the prevailing wind along its track.
Unfortunately, we know very little about the rate at which these storms advance, some of them moving at the extraordinary speed of fifty or sixty miles an hour, as for instance that of March 12, 1877; while others, like the West India hurricanes, do not attain one fourth of that rapidity of translation. It is remarkable that the rate of progress bears no relation to the intensity of the storm, the slow-moving tropical hurricanes being infinitely more violent than many of our rapidly-moving disturbances ”

“ Thus, storms range in scale from tornadoes and thunderstorms, through tropical cyclones, to widespread extra tropical cyclones. From a local and special interest viewpoint, a storm is a transient occurrence identified by its most destructive or spectacular aspect. Examples are rain storms, wind storms, hail storms, snow storms, etc. Notable special cases are blizzards, ice storms, sandstorms, and dust storms. 3. A term once used by seamen for what is now called VIOLENT STORM on the Beaufort wind scale.
storm center. The area of lowest atmospheric pressure of a cyclone. ”

“ Activity is widespread in January and February, and it is in these months that tropical cyclones are most likely to affect Fiji, Samoa, and the other eastern islands. Tropical cyclones usually form in the waters from 105°E to 160°W, between 5° and 20°S. Storms affecting northern and western Australia often develop in the Timor or Arafura Sea, while those that affect the east coast form in the Coral Sea. ”

“ Definitions Tropical cyclones are classified by form and intensity as they increase in size.
A tropical disturbance is a discrete system of apparently organized convection, generally 100 to 300 miles in diameter, having a nonfrontal migratory character, and having maintained its identity for 24 hours or more. It may or may not be associated with a detectable disturbance of the wind field. It has no strong winds and no closed isobars i.e., isobars that completely enclose the low. ”

“ While yet in the band of easterly trade-winds the storm will invariably work its way or be propagated toward the most humid region, unless mechanically borne in another direction by the great atmospheric current in which it is often embedded as an eddy in a river. The cyclone-tracks over all the oceans lie in the central bands of the great ocean-currents of high temperature and great evaporation, and the band of cyclonic violence is often beautifully coterminous with the sharply-marked edge of the Gulf Stream. ”

“ Those aboard the schooner peered anxiously over the storm swept waters for a sight of the motor craft, but they saw nothing. They shouted and called, but only the wind howled back at them.
Then, with a suddenness that was appalling, they seemed to be flung into the midst of a hurricane. The wind lashed the sea to fury, and the Mary Ellen spun around like some gigantic top.
"We're in the vortex!" cried Jack Jepson. "We're in the vortex of a cyclone! All hands look to themselves!" ”

“ The searching north-east wind had scarcely diminished in its parching fierceness, and in hot suffocating gusts swept fitfully over the broad glittering expanse of water and salt whereon the moon shone brightly—each deadly puff succeeded by the stillness that foretells a tropical hurricane—an absolute absence even of the smallest ruffling of the close atmosphere. ”

“ Those terrifying outbursts which now and then cause so much destruction in our own country seem to be the concentration of the prodigious force of an immense ocean cyclone within a small space, which renders them resistless.
A writer in the N. Y. Herald gives some interesting facts regarding these scourges of the air. While the cyclone, as we have shown, may have a diameter of hundreds of miles, the track of a tornado is often limited to a few hundred feet, and rarely has the width of half a mile. ”

“ At any moment an overhanging wall might crash into the street and then it would be empty.
No one can hope to wholly describe a typhoon, that great wind, which is to the cyclone of the American plains what the tornado is to a little whirlwind adrift down a dusty road. Slaughter as well as destruction marks its path, for the typhoon is made up of flames and floods as it is of winds, and what escapes death or ruin from its cyclonic breath is devoured by its fires or swept away by its torrents. No one hopes in a typhoon, and men flee but a little way from it. ”

“ The hurricane of the West Indies, which is really born in the heated waters of the South Atlantic, and which as a rule curves when it reaches the Yucatan Channel and follows the course of the Gulf Stream, decreases in intensity as it travels further north, broadens in diameter, and becomes the cyclone of the North Atlantic. ”

“ So far as anyone knows, the most furious of the typhoons of the Pacific are no bigger or more violent than the worst of the huge hurricanes of the Atlantic and the West Indies. They belong to the same death-dealing breed of storms, but the typhoons come from the bigger ocean; they sweep majestically across these vast waters toward the world’s largest continent; and to the south and southeast lies a longer stretch of hot tropical seas than anywhere else on earth. ”

“ The storm once engendered, no matter in what part of the world, may be stationary or progressive. There are well-authenticated instances of almost stationary cyclones and almost stationary typhoons, of which latter will be remembered the famous gale of the ship Charles Heddle—an Indiaman, carried round and round the storm-centre for five days—which progressed not more than ninety miles a day. Indeed, we may, as has been said, regard every wet-monsoon region as a stationary and semi-perennial cyclone. Such a meteor has been shown to resemble an eddy moving in the current of a rapid river. ”

“ THE DEVIL ON AN EXCURSION. I wonder how many boys and girls have ever witnessed a cyclone—a great big hurricane of wind and rain, of lightning and thunder, that just knocks down all the trees and takes the roofs off all the houses.
It is a terrible thing, the cyclone is!
The other day one came to our town. We could look up into the sky and see coming, from afar, a great big black cloud that looked for all the world like a balloon—a great big balloon, ever so large. The wind was blowing at a rapid rate, the dust flying, and everybody was frightened. ”