What is Beaufort Scale?

Beaufort number: 0

Description: Calm

Wind speed (km/h): <>

Wave Height (metres): 0

Sea Conditions: Flat

Land conditions: Calm. Smoke rises vertically.

Beaufort number: 1

Description: Light air

Wind speed (km/h): 1.1 - 5.5

Wave Height (metres): 0 - 0.2

Sea Conditions: Ripples without crests.

Land conditions: Wind motion visible in smoke.

Beaufort number: 2

Description: Light breeze

Wind speed (km/h): 5.6 - 11

Wave Height (metres): 0.2 - 0.5

Sea Conditions: Small wavelets. Crests of glassy appearance, not breaking.

Land conditions: Wind felt on exposed skin. Leaves rustle.

Beaufort number: 3

Description: Gentle breeze

Wind speed (km/h): 12 - 19

Wave Height (metres): 0.5 - 1

Sea Conditions: Large wavelets. Crests begin to break; scattered whitecaps.

Land conditions: Leaves and smaller twigs in constant motion.

Beaufort number: 4

Description: Moderate breeze

Wind speed (km/h): 20 - 28

Wave Height (metres): 1 - 2

Sea Conditions: Small waves with breaking crests. Fairly frequent white horses.

Land conditions: Dust and loose paper raised. Small branches begin to move.

Beaufort number: 5

Description: Fresh breeze

Wind speed (km/h): 29 - 38

Wave Height (metres): 2 - 3

Sea Conditions: Moderate waves of some length. Many white horses. Small amounts of spray.

Land conditions: Branches of a moderate size move. Small trees begin to sway.

Beaufort number: 6

Description: Strong breeze

Wind speed (km/h): 39 - 49

Wave Height (metres): 3 - 4

Sea Conditions: Long waves begin to form. White foam crests are very frequent. Some airborne spray is present.

Land conditions: Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic garbage cans tip over.

Beaufort number: 7

Description: High wind, Moderate gale, Near gale

Wind speed (km/h): 50 - 61

Wave Height (metres): 4 - 5.5

Sea Conditions: Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction. Moderate amounts of airborne spray.

Land conditions: Whole trees in motion. Effort needed to walk against the wind. Swaying of skyscrapers may be felt, especially by people on upper floors.

Beaufort number: 8

Description: Gale, Fresh gale

Wind speed (km/h): 62 - 74

Wave Height (metres): 5.5 - 7.5

Sea Conditions: Moderately high waves with breaking crests forming spindrift. Well-marked streaks of foam are blown along wind direction.

Considerable airborne spray.

Land conditions: Some twigs broken from trees. Cars veer on road. Progress on foot is seriously impeded.

Beaufort number: 9

Description: Strong gale

Wind speed (km/h): 75 - 88

Wave Height (metres): 7 - 10

Sea Conditions: High waves whose crests sometimes roll over. Dense foam is blown along wind direction. Large amounts of airborne spray may begin to reduce visibility.

Land conditions: Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over. Damage to circus tents and canopies.

Beaufort number: 10

Description: Storm, Whole gale

Wind speed (km/h): 89 - 102

Wave Height (metres): 9 - 12.5

Sea Conditions: Very high waves with overhanging crests. Large patches of foam from wave crests give the sea a white appearance.

Considerable tumbling of waves with heavy impact. Large amounts of airborne spray reduce visibility.

Land conditions: Trees are broken off or uprooted, saplings bent and deformed. Poorly attached asphalt shingles and shingles in poor condition peel off roofs.

Beaufort number: 11

Description: Violent Storm

Wind speed (km/h): 103 - 117

Wave Height (metres): 11.5 - 16

Sea Conditions: Exceptionally high waves. Very large patches of foam, driven before the wind, cover much of the sea surface. Very large amounts of airborne spray severely reduce visibility.

Land conditions: Widespread damage to vegetation. Many roofing surfaces are damaged; asphalt tiles that have curled up and/or fractured due to age may break away completely.

Beaufort number: 12

Description: Hurricane

Wind speed (km/h): ≥118

Wave Height (metres): ≥14

Sea Conditions: Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility.

Land conditions: Very widespread damage to vegetation. Some windows may break; mobile homes and poorly constructed sheds and barns are damaged.

Debris may be hurled about.

Scale now reads up to Force 17 determining varying strengths of hurricane:

13 Bft > 72-80 kts

14 Bft > 81-89 kts

15 Bft > 90-99 kts

16 Bft > 100- 108 kts

17 Bft > 109- 118 kts