SUPPLEMENT TO THE HONGKONG GOVT GAZETTE OF 2ND OCT., 1886.
GOVERNMENT NOTIFICATION.-No. 392.
The following report from the Director of the Observatory on the Typhoons of 1884 and 1 published for general information.
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By Command,
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Colonial Secretary's Office, Hongkong. 2nd October, 1886.
FREDERICK STEWART
Acting Colonial Sea
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REPORT ON THE TYPHOONS OF 1884 AND 1885.
(With six plates).
Typhoons as a rule originate E or SE of the Philippines in the trough of low pressure betwe wo high pressure areas in the North Pacific and in Australia, which region is characterised by his urface temperature.
Their origin is not quite understood but appears to be connected with an abnormally high temper nd humidity in some place in comparison wi... the neighbourhood. The hot air expands and a ver such a place and the heat Aberated by the consequent condensation of aqueous vapour enal rise still further. The air rising to a higher level in the atmosphere causes there an incre pressure, in consequence of which the upper air is set in motion towards the circumference of the question. Thus a decrease of pressure near the surface of the earth in the hot and damp reg ffected, and the surrounding air is impelled towards it. This motion of the air at the earth's Into the area is of course contemporaneous with the escape of the air above out of the same area, further increased by the greater pressure at the surface of the earth in the surrounding area can the outflow of air above. Thus it is seen that whenever a limited area is hotter and damper thi neighbourhood, the wind must commence to blow straight in towards its centre, or rather in eac from high towards low pressure in a direction vertical towards the isobar. But air in motion is orthern hemisphere deflected towards the right owing to the rotation of the earth except whe ry near the equator, and in consequence we have not traced typhoons nearer to the equato bout nine degrees. It is however possible that they may originate nearer than that to the equ urricanes have been encountered at a lower latitude. But at the equator the surrounding a nuing to blow straight towards a barometric depression would soon fill it up. Owing flection towards the right the wind is caused to move in a curved path in towards the centre
trifugal force, in consequence developed, still further deflects it from the centre of the low pr so the friction between the wind and the surface of the earth or the more or less disturb face retards the entrance of air into the central depression, while the upper air, subject ction escapes from the upper high-pressure area. Thus we see that once a cyclonal motion iss
ends, to increase and to spread outwards.
Of course it is not thereby implied that a typhoon may not originate within an extensive pressure round which the air has already a gyratory motion inwards. But that such a cond sufficient to originate a typhoon is frequently instanced in the China Sea, when the wind ald thern coast of China is E, in Tonquin N, over the Philippines S and lower down in the Chi without being followed by a typhoon. That a typhoon may follow on similar circumstance
additional conditions are fulfilled, is instanced in case of Typhoon VI of 1885. But that a typhoon in the beginning of its existence rather spreads from the centre outward everse, is made probable both by the similarity between a typhoon in a very low latitude waterspout (Comp. e. g. Typhoon IV of 1885) and by the subsequent expansion of the typh progress. There is however the important difference between a typhoon and a tornado,
is taller than it is broad, while the height of the former does certainly not reach four mil its horizontal diameter may exceed a thousand miles. Moreover there is dow, and it is rather unlikely, that the centre with the lowest pressure at any level abo ce of the earth is situated vertically above the lowest pressure at the earth's surface or eve ght line with the lowest pressure above and below its level, so that we are not entitled to a is in a typhoon.
The enormous energy exhibited by a typhoon must be traced to the radiation of the sun, the central area and effects the evaporation of water, to which the great humidity is due. y is partly spent in overcoming friction between air and sea-surface and also between layer ng in different directions, but mainly in overcoming the former, and in raising quantities energy is partly recuperated by the heat generated through friction, by the condensation of a ur, and by the descent of air in the surrounding area. Whether part of the energy is draw
momentum of the earth is not known for certain.
The high pressures surrounding the cyclone in a typhoon are plainly traced on our weather although imperfect with regard to isobars, generally show the barometer to be rising from about 1000 miles in front and to the right and left side of the cyclone, which rise is as panied by clear and dry but hot weather and light winds of variable direction. It is muc
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