Annam Coast.
Gulf of Tongking to Swatow.
540
Table No. 5.-Gale Signals.
One Symbol at yard-arm.
IT T+
Formosan Channel.
Formosa
to
Yangtze to Gulf of
Sea
North
Yangtze.
Shantung Pechili and Promontory. Yalu Gulf.
of Japan.
of Hokkaido.
East Coast of
South
Japan.
of Kiushu.
It is important that seamen should realise that the position of the centre of the typhoon as signalled is the position according to the data possessed by the Observatory at the time of the issue of the warning. That data may be as much as 12 hours old. Thus, if the time signal indicates that the warning was issued This morning," it may be that the position corresponds to data concerning yesterday afternoon.
(6
If the sigual "Deepening" is made, it indicates that there is reason to believe that the barometric gradient and, consequently, the intensity of the typhoon are increasing.
If the signal "Exceptional velocity" is made, it indicates that there is reason to believe that the rate of progression is 25 per cent, or more greater than the average rate.
If the signal "Position uncertain" is made, it indicates that the data possessed is unreliable and that the position signalled is a mere probability.
The several tracks which a typhoon may follow in the several months are very varied, and the velocity of progression is liable to be erratic. It is not safe to count on a typhoon maintaining a velocity indicated by previous positions of its centre. The volocity is liable to increase very suddenly. Seamen are recommended to study from available sources the tracks and average velocities for the month and locality concerned. In the absence of more exact information the following table of velocities in knots for the several latitudes may be useful.
BEFORE RECURVING.
AFTER RECURVING,
LATITUDE.
Ordinary Limite.
Mean.
Exceptional Velocity as sigualled,
Maximum Ordinary recorded. Limits,
Mean.
Exceptional Velocity as signalled.
Maximum recorded.
to 15
5 to 12
9
I I
22
15°
وو
20
25
30°
35
70°
45° 50°
25°
30°
» 35° 400
20°
5 "
14
IO
J
24
"J
7 "
16
5 to 17
10.
13
22
I 1
19
14
17
23
17
21
7
27
13
I
30
15
11
1523
18
23
10
39
11 36
47
20
25
16
42
IZ
45°
22
36.
2 I
26
50
17
36
21
26
48
12 36
2 I
26
52
12
37
ZI
26
49
Seamen should realise that, whatever may be the probability of a certain velocity in a given case, there is always the possibility that it may be greatly exceeded. The safest guide is to make allowance for extreme velocity.
TYPHOON SIGNAL.
DEPRESSION SIGNAL.
Time
Latitude
Direction
9
Time
Latitude
Direction
Longitude Radius, etc.
A severe typhoon within 30 miles of lat. 26° N., long. 120° E., travelling N.E. Warning issued this morning.
Longitude
Radius, etc.
A continental depression in lat. 56° N., long. 109° E., travelling E.S.E. Warning issued yesterday morning.
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