Vòi rồng hay lốc xoáy là một cột khí xoáy dữ dội, hút từ bề mặt đất lên đám mây đối lưu, tạo thành hình phễu hoặc hình xoáy lủng lẳng từ một đám mây trông giống như cái vòi.
Có 2 loại vòi rồng chính: Vòi rồng thời tiết tốt và vòi rồng trong cơn dông.
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| Theo Chỉ số Rủi ro Thiên tai Toàn cầu 2018, Việt Nam là một trong 10 nước phải chịu tác động nhiều nhất của các sự kiện thời tiết cực đoan gây tổn thất. |
Beaufort Number
|
Description used by HKO
|
General Description
|
Wind Speed
|
TC strength
|
Land conditions
|
Sea
conditions |
Wave Height
|
Image
| |||
knots
|
km/h
|
m/s
|
m
|
ft
| |||||||
0
|
Calm
(無風) |
Calm
|
0
|
0-1
|
0-0.2
|
(N/A)
|
Calm. Smoke rises vertically.
|
Flat.
|
0
|
0
|  |
1
|
Light
(輕微) |
Light air
|
1-3
|
2-6
|
0.3-1.5
|
Wind motion visible in smoke.
|
Ripples without crests.
|
0.1
|
0.33
| | |
2
|
Light breeze
|
4-6
|
7-11
|
1.6-3.3
|
Wind felt on exposed skin. Leaves rustle.
|
Small wavelets. Crests of glassy appearance, not breaking.
|
0.2
|
0.66
|  | ||
3
|
Moderate
(和緩) |
Gentle breeze
|
7-10
|
12-19
|
3.4-5.4
|
Leaves and smaller twigs in constant motion.
|
Large wavelets. Crests begin to break; scattered whitecaps.
|
0.6
|
2
|  | |
4
|
Moderate breeze
|
11-15
|
20-29
|
5.5-7.9
|
Dust and loose paper raised. Small branches begin to move.
|
Small waves.
|
1
|
3.3
|  | ||
5
|
Fresh
(清勁) |
Fresh breeze
|
16-21
|
30-39
|
8.0-10.7
|
LPA
|
Smaller trees sway.
|
Moderate (1.2 m) longer waves. Some foam and spray.
|
2
|
6.6
|  |
6
|
Strong
(強風) |
Strong breeze
|
22-27
|
40-50
|
10.8-13.8
|
TD
|
Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult.
|
Large waves with foam crests and some spray.
|
3
|
9.9
|  |
7
|
Near gale
|
28-33
|
51-62
|
13.9-17.1
|
Whole trees in motion. Effort needed to walk against the wind.
|
Sea heaps up and foam begins to streak.
|
4
|
13.1
|  | ||
8
|
Gale
(烈風) |
Gale
|
34-40
|
63-75
|
17.2-20.7
|
TS
|
Twigs broken from trees. Cars veer on road.
|
Moderately high waves with breaking crests forming spindrift. Streaks of foam.
|
5.5
|
18
|  |
9
|
Severe gale
|
41-47
|
76-87
|
20.8-24.4
|
Light structure damage.
|
High waves (2.75 m) with dense foam. Wave crests start to roll over. Considerable spray.
|
7
|
23
|  | ||
10
|
Storm
(暴風) |
Storm
|
48-55
|
88-103
|
24.5-28.4
|
STS
|
Trees uprooted. Considerable structural damage.
|
Very high waves. The sea surface is white and there is considerable tumbling. Visibility is reduced.
|
9
|
29.5
|  |
11
|
Violent storm
|
56-63
|
104-117
|
28.5-32.5
|
Widespread structural damage.
|
Exceptionally high waves.
|
11.5
|
37.7
|  | ||
12
|
Hurricane
(颶風) |
Hurricane
|
64-71/ 64+
|
118-132/ 118+
|
32.6-36.6/ 32.6+
|
TY CAT. 1
|
Considerable and widespread damage to structures.
|
Huge waves. Air filled with foam and spray. Sea completely white with driving spray. Visibility greatly reduced.
|
14+
|
46+
|  |
13
|
(Not used by HKO)
|
(Not used except Taiwan and China)
|
72-80
|
133-149
|
36.7-41.3
|
Not generally seen on land. Catastrophic damage otherwise.
| |||||
14
|
81-89
|
150-166
|
41.4-46.1
|
TY CAT. 2
| |||||||
15
|
90-99
|
167-183
|
46.2-50.8
| ||||||||
16
|
100-108
|
184-201
|
50.9-55.8
|
TY CAT. 3 & above
| |||||||
17
|
109+
|
202+
|
55.9+
| ||||||||
