Beaufort Windscale

0-1 0-1 Calm Sea surface smooth and mirror-like Calm, smoke rises vertically
1-3 1-3 Light Air Scaly ripples, no foam crests Smoke drift indicates wind direction, still wind vanes
4-6 4-7 Light Breeze Small wavelets, crests glassy, no breaking Wind felt on face, leaves rustle, vanes begin to move
7-10 8-12 Gentle Breeze Large wavelets, crests begin to break, scattered whitecaps Leaves and small twigs constantly moving, light flags extended
11-16 13-18 Moderate Breeze Small waves 1-4 ft. becoming longer, numerous whitecaps Dust, leaves, and loose paper lifted, small tree branches move
17-21 19-24 Fresh Breeze Moderate waves 4-8 ft taking longer form, many whitecaps, some spray Small trees in leaf begin to sway
22-27 25-31 Strong Breeze Larger waves 8-13 ft, whitecaps common, more spray Larger tree branches moving, whistling in wires
28-33 32-38 Near Gale Sea heaps up, waves 13-20 ft, white foam streaks off breakers Whole trees moving, resistance felt walking against wind
34-40 39-46 Gale Moderately high (13-20 ft) waves of greater length, edges of crests begin to break into spindrift, foam blown in streaks Whole trees in motion, resistance felt walking against wind
41-47 47-54 Strong Gale High waves (20 ft), sea begins to roll, dense streaks of foam, spray may reduce visibility Slight structural damage occurs, slate blows off roofs
48-55 55-63 Storm Very high waves (20-30 ft) with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility Seldom experienced on land, trees broken or uprooted, "considerable structural damage"
56-63 64-72 Violent Storm Exceptionally high (30-45 ft) waves, foam patches cover sea, visibility more reduced  
64-71 73-83 Hurricane Air filled with foam, waves over 45 ft, sea completely white with driving spray, visibility greatly reduced