storms.
14
Appendix A.
THE LAW OF STORMS IN THE EASTERN SEAS.
INTRODUCTION.
15
334
The earliest signs of a typhoon are clouds of the cirrus type-looking like fine hair, feathers or all pale white tufts of wool-travelling from the east or thereabout, their direction backing towards he north, a slight rise in the barometer, clear and dry but hot weather, calms or very light winds. cirrus come from W, they prove that there is no typhoon. If they come from the S, then there be a typhoon more than 600 miles to the southward. This fine weather lasts for days and the
The first clmpter of the following paper treats of the law of storins and was first publishedence of a typhoon at a great distance is a cause of fine weather all round and contributes therefore. Hongkong in September, 1886. It was read before the British Mercantile Marine Officers' Assoc the safety of ships at sen, a fact that is not sufficiently appreciated by mariners. tion on the 17th May, 1893. It is now reprinted with later additions. The second chapter treats s The cirrus clouds, which frequently assume fantastic shapes, make their appearance within 1,500 the management of ships in typhoons, and was originally included in the pamphlet on the law ailes of the centre of a typhoon. They show that water-vapour has risen about 6 miles in the
It was read as a separate lecture before the Shipmasters' Society, London, on the 1mosphere through the air rising near the centre. January, 1896, and is now reprinted with a few additions. The third chapter was printed in les of the centre, and the men of the twenty-four hours' temperature rises in Hongkong above The barometer is generally rising beyond 600 Government Gazette.
The fourth and fifth chapters, on different classes of typhoons and on wie deg. Halos round the sun and the moon, phosphorescence of the water and also glorious sunsets typhoons in the southern part of the China Sea, appeared in "Zeitschrift für Meteorologie" in 1891th grand twilight rays, appear to be frequently noticed before typhoons.
Plate I illustrates the different classes of typhoons enumerated in § 4. Figure 1 shows how Cirrus radiate from various directions but when there is a typhoon, and the radiation is very wind blows in a typhoon as determined by aid of observations made at the Hongkong Observatory dar stinct, it is usually from the same direction as the bearing of the centre. the 18*4-87 inclusive. Figure 2 shows a typhoon in the Formosa Channel on the 21st and 2 An increasing swell in the sea is noticed from 300 to 600 miles from the centre, or farther off,
years August. 1884.
The height of the barometer is noted near the isobars. The arrows fly with the wit this depends greatly upon the situation of the nearest land, and particularly upon whether land whose force is given in numbers. The large arrow shows the direction in which the whole listu tervenes between the observer and the typhoon centre. The swell arises from the heavy seas that ance was progressing. Figure 3 shows a typhoon that was lying a little N of Formosa on the Lompany a typhoon, and form the real danger to ships, which are usually well fit to stand the force July, 1890.
The number of feathers on the arrows indicates half the wind-force, eg, 5 feathers me the wind without too serious damage. As the velocity of waves in the sea is much greater than the force 10. Figure 4 shows a typhoon in the China Sea on the 15th November, 1891. Figure 3 que elocity of the centre, the swell is frequently of great help in forecasting a typhoon, but it appears that the 20th November, 1891, that was moving towards SW. Figure 6 one on the 13th November, 18he bearing of the centre is not well determined from the swell; besides the swell would indicate
$L-THE TYPHOONS IN THE EASTERN SEAS.
here the typhoon was at a certain time previous when the waves that caused the swell were raised the wind. For instance, N of Formosu, i. e.. between the E coast of China and SW Japan there It appears that typhoons in the China Sea originate in elongated slight depressions, which times lie across the Philippines as well as the China Sea, but usually exist only over the sea extende usually a heavy E to SE swell, when a typhoon centre is approaching from SE or E, and the s sometimes far into the Pacific. To the north of them it blows inoderate NE breezes and south of the here gets very high when the centre is yet at a great distance. somewhat less strongly from the SW. The NE breezes reach generally only as far as northern Fordication of a typhoon, except near rocky land, where cross swell may be caused by reflection of the in summer, but in autumn the NE (and farther north the NW) mons on blows much farther norrect swell. The cross swell arises from the heavy confused cross sets raised by strong winds from
ifferent directions round the centre. Sometimes the SW breezes to the south of the axis of the depression are stronger than the NE bread
Within 600 miles of the centre the sky is often half overcast with cumulus, above which cirro- to the north of it, and extend apparently down to the equator and are probably a continuation ofth
S and SW of and SE trade. To the E of these depressions in the Philippines there are light S and SE breezes.mulus is seen, the sky being frequently paled by high and faint cirro-stratus.
They may also occur to Amam it probably blows from the N. In summer these depressions begin with rising pressure in teyond 200 miles of the centre, thunderstorms and cumulo-stratus are seen. interior of China or in Japan. In autumn it seems the pressure rises slightly near the equator and Wand E of and as close as 250 miles to the centre, but there they are rare, at least during the NE onsoon. In fact, the belief of the Chinese that where there is a thunderstorm there will be no winds extend gradually northward over the China Sen. In January and February depressions dayphoon appears to be well founded. If thunder and lightning should appear to the N of the centre, During the rest of the year they occur about once a month on au average. During the sale or no rain falls at the time. The old accounts of typhoons are probably sometimes to be explained months and in autumn they frequently give rise to a typhoon or a small circular depression.
smere thunderstormis, while on the other hand during a typhoon the uoise of the wind and waves might easily be mistaken for thunder.
occur.
SOI
trough-like depression then ceases to exist. In spring they do not alter into typhoons bat ces
exist owing to the NE monsoon filling them and spreading to the southward.
he
A heavy cross swell is a certain.
Then the
Within
On approaching nearer than 500 miles to the centre, the cloudiness increases, and the mercury The depressions have their major axes lying E and W, or ENE and WSW. Their average lati from June to September is 17° N, later more southerly, and in November perhaps 10° N. They do is to fall slowly (seldom as much as a tenth of an inch in 24 hours) in the parotueter.
fr becomes oppressive, a slight haze is observed during the morning hours, and the sky presents a The barometer is read little more th appear to move at all, and they may be traced for 3 or 4 days.
hreatening and vaporous appearance. The weather is then most unhealthy and depressing. Many a tenth of an inch lower in the axis than along the coasts all round them. Along these consts lig
In such depressions the weather is squally and wat,eople find it impossible to get any sleep owing to the very high night temperature. All sorts of veriniu, winds circulate against the hands of a watch. the wind variable, frequently in heavy squalls with great downpour of rain, but thunder is selling stakes, spiders, beetles, and typhoon flies (dragon flies), are unusually active.
Within 300 miles (or in different typhoons between 200 and 400 miles) of the centre there is a heard. It appears that in such squalls S wind happens to extend itself northwards and N wind sout wards, and revolving storms are thereby generated. If this occurs in the middle of the China Say cross sea, which therefore gets up some time before, and lasts longer than the wind.
50 miles in front of the centre the sky becomes overcast, and the temperature falls in consequence, is likely to give rise to a typhoon. Of course, it more often happens that a circular storm origie
Within 200 miles of the centre the temperature falls quickly, owing to the heavy roll-cumulus near the E and W end of the elongated depression as the winds there already revolve as in a ro
ith which the sky is densely overcast.
About this distance, just in front of the centre, the air storm except to the W or E of the centre forming, so that the N or respectively squalls needs comes sometimes abnormally dry, and the sky at the same time presents a peculiar black and
small typhoons
minous appearance. gain ground on one side, but in such cases only minor circalar depressions or very
And meantime the wind has risen and blows generally with the force of a strong originated.
When the trough stretches from south of Hainan through the Bashee Channel right out in Pacific to the south of Japan and the NE and SW winds on either side of it are fresh or strong, conditions have often been mistaken for two typhoons, one in the China Sea and one to the southsually a mountainous cross seat Japan, before ever any typhoon was formed.
rising to a moderate gale in the squalls. But this depends also upon the bearing of the centre, he wind being usually strongest in the right-hand semi-circle. Within 200 miles of the centre there Within 200 miles to the N, and within 150 miles in front of and to the S of the centre, heavy begins to fall, and within 60 miles (or from 60 to 150 miles) it pouts dow of the centre, heavy
The heavy rain is, of course, not the cause of the phenomena, for the rain itself is caused by then rising in the axis of these depressions, also the water vapour condensing gives out heat and thus inture near the centre in Hongkong is often about 78° and over the China Sea 76, pres. The first instance makes the mercury rise in the barometer before a squall, but there cannot be any do a temperature as high as 83° has been registered, but that is very he whil that the quantity of water-vapour condensed to form perhaps 10 inches of rain per day, and pressure is thus abstracted from the barometric pressure of the air, causes the permanency depressions. It is different with the rainfall in the SW monsoon. That is spread over a large and does not give rise to a low pressure in one spot surrounded by higher pressures.
of
The dimensions of different typhoons vary inch and near land the strong winds are often so regularly distributed than in a place near the centre less wind may actually be experienced than at me distance farther away from it.
The approach of the centre is judged by the fall of the mercury the barometer and by the increase in the strength of the squalls.
No conclusions can be drawn with certainty from the reading of the barometer concerning the The readings differ in different typhoons occurring during the same month
stance of the centre.
It is rather difficult to say whether a depression in the China Sea, when its existence has le ascertained, is a typhoon or only a minor disturbance, but if the following signs are observed as now to be explained, then it is certain to be a typhoon. A minor depression gives signs less "
marked and more confused.
are also different in different months (Owing to the annual variation in monthly mean pressure). aking the mean of several typhoous I obtained at 40 miles 29.20, ar 50 miles 29.30, at 100 miles
9.40, and at 200 miles 29.50.