2.02 Wind-Speed Estimation Over Land In Bangladesh According To The Beaufort Scale

No. Name

Indication

 Wind speed (at 33 feet) M.P.H.
0. Calm Smoke rises vertically Less than-I
1. Light air Wind direction shown by smoke drift, but not by wind-vane. 1-3
2. Light breeze Wind felt on face. Leaves rustle,  wind-vane moves. 4-7
3. Gentle breeze Leaves and small twigs in constant motion. Light flag extended. 8-12
4. Moderate breeze Dust and loose paper raised 13-18
5. Fresh breeze Small leafy trees sway. Small waves on water. Surfaces form crests. 19-24
6. Strong breeze Large branches sway. Telephone wires whistle. Difficult to use umbrella. 25-31
7. Moderate gale Whole trees sway. Difficult to walk against the wind. 32-38
8. Fresh gale Twigs broken off trees. Wind impedes progress when walking 39-46
 
9. Strong gale Branches broken off trees. Slight structural damage to buildings (chimneys, roof slates) 47-54
10. Whole gale Trees uprooted. Considerable structural damage to buildings. 55-63
11. Storm Widespread damage to trees and properties. 64-75
12. Hurricane Widespread damage to trees and properties Above 75
       
In Bangladesh, wind  speed of hurricane force occurs in cyclones and tornadoes. Wind speeds in line-squalls  (nor-westers) are generally of forces 6-8, occasionally 9-10. Source: Meterological Department