Gwynt grym 0 - Calm

Effaith ar y ddaear

Calm, smoke rises vertically

Môr y wladwriaeth

Sea surface smooth and mirror-like

Cyflymder
  • 0-1 km/h
  • 0-0,54 noeuds (knot)
  • 0 - 0,621 mph
hauteur
  • 0 m
  • 0 ft
 Signe

Gwynt grym 1 - Light Air

Effaith ar y ddaear

Smoke drift indicates wind direction, still wind vanes

Môr y wladwriaeth

Scaly ripples, no foam crests

Cyflymder
  • 1-5 km/h
  • 0,54-2,7 noeuds (knot)
  • 0,621 - 3,11 mph
hauteur
  • 0 - 0,1 m
  • 0-1 ft
 Signe

Gwynt grym 2 - Light Breeze

Effaith ar y ddaear

Wind felt on face, leaves rustle, vanes begin to move

Môr y wladwriaeth

Small wavelets, crests glassy, no breaking

Cyflymder
  • 5-11 km/h
  • 2,7-5,9 noeuds (knot)
  • 3,11-6,84 mph
hauteur
  • 0,1 - 0,5 m
  • 1-2 ft
 Signe

Gwynt grym 3 - Gentle Breeze

Effaith ar y ddaear

Leaves and small twigs constantly moving, light flags extended

Môr y wladwriaeth

Large wavelets, crests begin to break, scattered whitecaps

Cyflymder
  • 11-19 km/h
  • 5.9-10,2 noeuds (knot)
  • 6,84-11,81 mph
hauteur
  • 0,5 - 1,25 m
  • 2-3,5 ft
 Signe

Gwynt grym 4 - Moderate Breeze

Effaith ar y ddaear

Dust, leaves, and loose paper lifted, small tree branches move

Môr y wladwriaeth

Small waves. becoming longer, numerous whitecaps

Cyflymder
  • 19-28 km/h
  • 10,2-15 noeuds (knot)
  • 11,81-17,4 mph
hauteur
  • 1-2 m
  • 3,5-6 ft
 Signe

Gwynt grym 5 - Fresh Breeze

Effaith ar y ddaear

Small trees in leaf begin to sway

Môr y wladwriaeth

Moderate waves taking longer form, many whitecaps, some spray

Cyflymder
  • 28-38 km/h
  • 15-20,5 noeuds (knot)
  • 17,4-23,61 mph
hauteur
  • 2-3 m
  • 6-9 ft
 Signe

Gwynt grym 6 - Strong Breeze

Effaith ar y ddaear

Larger tree branches moving, whistling in wires

Môr y wladwriaeth

Larger waves , whitecaps common, more spray

Cyflymder
  • 38-50 km/h
  • 20,5-27 noeuds (knot)
  • 23,61-31,07 mph
hauteur
  • 3-4 m
  • 9-13 ft
 Signe

Gwynt grym 7 - Near Gale

Effaith ar y ddaear

Whole trees moving, resistance felt walking against wind

Môr y wladwriaeth

Sea heaps up, waves , white foam streaks off breakers

Cyflymder
  • 50-61 km/h
  • 27-33 noeuds (knot)
  • 31,07-37,9 mph
hauteur
  • 4-5,5 m
  • 13-19 ft
 Signe

Gwynt grym 8 - Gale

Effaith ar y ddaear

Whole trees in motion, resistance felt walking against wind

Môr y wladwriaeth

Moderately high waves of greater length, edges of crests begin to break into spindrift, foam blown in streaks

Cyflymder
  • 62-74 km/h
  • 33-40 noeuds (knot)
  • 37,9-45,98 mph
hauteur
  • 5,5-7,5 m
  • 18-25 ft
 Signe

Gwynt grym 9 - Strong Gale

Effaith ar y ddaear

Slight structural damage occurs, slate blows off roofs

Môr y wladwriaeth

High waves, sea begins to roll, dense streaks of foam, spray may reduce visibility

Cyflymder
  • 75-88 km/h
  • 40-47,5 noeuds (knot)
  • 45,98-54,68 mph
hauteur
  • 7-10 m
  • 23-32 ft
 Signe

Gwynt grym 10 - Storm

Effaith ar y ddaear

Seldom experienced on land, trees broken or uprooted,considerable structural damage

Môr y wladwriaeth

Very high waves with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility

Cyflymder
  • 89-102 km/h
  • 47,5-55 noeuds (knot)
  • 54,68-63,38 mph
hauteur
  • 9-12,5 m
  • 29-41 ft
 Signe

Gwynt grym 11 - Violent Storm

Effaith ar y ddaear

Widespread devastation

Môr y wladwriaeth

Exceptionally high waves, foam patches cover sea, visibility more reduced

Cyflymder
  • 103-117 km/h
  • 55-63 noeuds (knot)
  • 63,38-72,2 mph
hauteur
  • 11,5-16 m
  • 37-52 ft
 Signe

Gwynt grym 12 - Hurricane

Effaith ar y ddaear

Considerable destruction

Môr y wladwriaeth

Air filled with foam, sea completely white with driving spray, visibility greatly reduced

Cyflymder
  • >118 km/h
  • >63 noeuds (knot)
  • >72,2 mph
hauteur
  • >14 m
  • >46 ft
 Signe