Sessional_Paper_1898 — Page 118

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In 1884 I suggested the division of typhoons into four classes (Comp. "Observations and Researches made at the Hongkong Observatory in 1884," app. M) but the final arrangement of sub- classes could not then be effected:

In

Ib

originate in the China Sea (most frequently near 18° to 20° N and 113° to 116° E) north of 15° N and enter, or at least approach the mainland to the W of Hongkong. 10 p.c. of all the typhoons registered belong to this class. They prevail from the middle of June till the end of September.

Ia ẞ originate in the Pacific and enter the China Sea north of 15° N and enter, or at least approach the mainland to the W of Hongkong. 12 p.c. of the typhoons belong to this class. They prevail from the beginning of July till the middle of October. originate in the Pacific and enter the China Sea north of 15° N, move SW and disappear

Only one or two cases of this kind have ever been registered (late in the year). originate in the China Sea and move N, but describle vastly different paths, moving in various directions between W, round by N, to ENE. Sometimes they recurve after entering the mainland. They occur from June till the end of September, but they are most common at the beginning of the typhoon season (4 p.c.).

Ic

Id

at sea.

originate in the China Sea, where they recurve, and sometimes move into the Pacific passing near South Formosa. They occur from May till September incl. (2 p.c.). Typhoons of classes In and Ic (26 p.c. of all typhoons) are frequently felt in Hongkong.

CLASS II.

Ia

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IIc

Ild

originate in the Pacific, enter the China Sea north of 15° N, and enter China to the E of Hongkong. There they pass (IIa1) N, or (Ha2) W. They occur in July, August, and September (2 p.c).

originate in the Pacific and move into the Formosa Channel. They occur from June to September incl., and are most common in August and September (7 p.c.).

originate in the Pacific, pass N of Formosa, and enter China. They occur from June till September, with a distinct maximum in July (3 p.c.).

originate in a high latitude in July and August and move W-ward into China (4 p.c.).

With the exception of Ila, which sometimes cause fierce SW gales in Hongkong, typhoons of Class II are not dangerous to this Colony.

CLASS III.

These typhoons originate and rage mainly in the Pacific,

enter the coast of Luzon but recurve (usually before the centre enters the China Sea). They prevail in October and November (1p.c.).

IIIa

IIIb

IIIe

enter the coast of Formosa but recurve, usually in October (1 p.c.). move N and enter Korea in July, August and September (4 p.c.).

recurve in the Pacific and enter Japan between June and October incl. frequent in August and September (15 p.c).

They are most

IIId

IIIe

remain in the Pacific. They occur from May till December incl. Their

Their average latitude decreases on the whole with the altitude of the midday-sun. 10 p.c. of all the typhoons registered belong to this class, but there must be many that are not met by ships and therefore not registered. Their prevalence may be estimated at 12 p.c.).

CLASS IV.

IVa originate in the China Sea south of 15° N and move towards Hainan and Annam. They occur from May till December incl., but are rarely encountered in August (8 p.c.). In November they often originate in about 11° N and 116° E.

IVa B originate in the Pacific and enter the China Sea south of 15° N. They are less common than those originating in the China Sea, as the long passage across the southern Philip- pines tends to break them up. They occur at the beginning and end of the typhoon season (3 p.c.).

IVb

IVe

IVd

enter the China Sea after crossing the Philippines in a low latitude, and then move SW and disappear at sea. They occur from the beginning of September till the beginning of December, but are most common in November (4 p.c).

recurve in the China Sea and re-enter the Pacific. They occur at the beginning and end of the typhoon season but mostly in May (4 p.c.).

occur in the Gulf of Siam in April and December (1 p.c.).

The accompanying plate illustrates the average paths of these different kinds of typhoons. The average rate of progress in 24 hours is also marked, but it must be remembered that individual typhoons move in very irregular orbits, whose vagaries have disappeared from the average paths. Also they travel at very different rates. It is presumably as useful to the travelling public, and the freight-carrying public to know where and when typhoons prevail, as to the weather-forecaster, who in default of precise . observations reaching him by wire, must forecast according to such paths as these.