41
429
It should be remarked that the above are average results as pressure decreased near the centre till it struck the coast of Formosa.
The average angles between the direction of the wind and the radius are shown in the following table. The first column shows the bearing from the centre. The first line the distances in miles between which the angles were obtained :-
0-50
50-100
100-150
150-250
>250
NNE
59°
48°
36°
+420
+29°
ENE
60
67
79
27
ESE
54
46
66
78
SSE
68
78
42
SSW
67
66
+18
WSW
50
31
22
+ 9
-
3
WNW
59
31
50
5
NNW
49
60
40
+61
-83 +88
Mean.......
53
49
44
39
6
The
A negative angle indicates anti-cyclonic motion. It is seen that at a great distance from the centre the wind blew nearly straight towards it, while near the centre the wind direction was 59° away from the centre. On an average it was 69° in front of the centre and 22° behind the centre. diagram shows clearly that the wind was blowing almost straight into the typhoon behind the centre. This was known to be the case with typhoons passing Hongkong and moving westward. It is now proved also for typhoons moving eastward. On an average (within 250 miles) the wind formed an angle of 45° with the radius. But in the right hand semi-circle the angle was nearly a point greater than in the left hand semi-circle. All these results bear out FERREL's opinion, that it is the prevailing wind that causes the typhoon to proceed, and that the wind direction round the centre is the result of a combination of the cyclonic motion and the motion of the centre. Therefore the incurvature is more uniform round the centre for strong winds than farther from the centre where the winds are light.
The forces of the wind in different directions and distances from the centre are shown in the following table :--
Miles.
NNE
ENE
ESE
SSE
SSW
WSW
WNW
NNW
30
10
10
10
10
10
75
6
9
7
7
*
125
5
над
5
6
200
3
5
5
This shows that the wind was strongest in the right hand semi-circle, where the cyclonic and progressive motion acted in approximately the same direction, and the amount of the difference between the wind velocities agrees near enough with the speed of the centre.
The wind force in a typhoon in the Formosa Channel whose centre usually makes westward is strongest to the N of the centre i, e. in the right hand, the dangerous semi-circle. In this typhoon the strongest wind was to the S as the centre moved eastward.
It was densely overcast within from 200 to 250 miles of the centre. Rain commenced to the N of the centre within 200 miles, to the E within 250 miles, to the S within 150 miles, and to the W within 180 miles. Heavy cross seas were logged within 200 miles of the centre on all sides of it, so that the sea got up before the wind rose to a fresh breeze, thus giving early warning on board the vessels at sea. A gradient of 0.01 inch in 15 nautical miles corresponded to force 4, 0.02 to force 6, 0.03 to force 7, 0.04 to force 8, 0.06 to force 9, 0.15 to force 10, 0.25 to force 11 or 12. The steepest gradient 0.30 in 15 miles occurred at Fisher Island between 2 p. and 3.30 p. on the 21st July accompanied by full typhoon force. It is evident that the wind forces were to a great extent under- estimated, as frequently happens when a beginner observes in a typhoon for the first time. However many of the observers were old hands, and it must be remembered that the wind blows in tremendous squalls in a typhoon along tracks on both sides of which the wind is not felt so much. The compara- tively low forces recorded may therefore be due to chance at least to some extent.
At
During the afternoon and evening of the 22nd the wind gradually decreased in force in Southern Formosa and the barometer continued rising. The weather at S Cape and Takow was squally and showery and lightning was noted during the evening. At Anping the weather had improved greatly, towards evening the sky having cleared. At S Cape at 9 p. the wind was from W by N force 3 barometer 29.49. At Takow NNW 3 barometer 29.52. At Anping NE 4 barometer 29.48. Fisher Island N 4 barometer 29.51 and fine weather. On the SE coast light SE airs and breezes chiefly prevailed, the weather being fine and the barometer still rising. In Northern Formosa there were light NE breezes, fine weather and the barometer was rising, at Tamsui 29.58, at Takow 29.54. At the lighthouse stations at the Northern entrance to the channel the wind was from NNE and NE gentle to moderate breezes with fine weather and rising barometer. Some vessels at the time in that part of the channel experienced the same wind and weather.
The typhoon had apparently moved to the Eastward since noon of July 22nd.
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