Beaufort Wind Scale, Hurricane Scale, and Marine Radio Frequencies

Beaufort Wind Scale

The Beaufort Scale reflects both wind strength and sea conditions. Developed in 1805 by Admiral Sir Francis Beaufort of the British Navy. The scale divides wind and sea conditions into 12 “Forces” ranging from calm to hurricane. It describes typical conditions offshore in large bodies of water.

Beaufort Number or Force Wind Speed and Description Effects Land/Sea Probable Wave Height
MPH Knots Description
0 <1 <1 Calm Still, calm air, smoke will rise vertically. Smooth like a mirror. 0
1 1-3 1-3 Light Air Rising smoke drifts, wind vane is inactive. Small ripples like fish scales. ¼ – ½ foot
2 4-7 4-6 Light Breeze Leaves rustle, can feel wind on your face, wind vanes begin to move. Short, small pronounced wavelets with no crests. ¼ – ½ foot
3 8-12 7-10 Gentle Breeze Leaves and small twigs move, light weight flags extend. Large wavelets, crests start to break, some whitecaps. 2 feet
4 13-18 11-16 Moderate Breeze Small branches move, raises dust, leaves and paper. Small waves develop, becoming longer, whitecaps. 4 feet
5 19-24 17-21 Fresh Breeze Small trees sway. Moderate lengthening waves, with many white caps and some spray. 6 feet
6 25-31 22-27 Strong Breeze Large tree branches move, telephone wires begin to “whistle”Large waves, extensive white caps, some spray. 10 feet
7 32-38 28-33 Near Gale Large trees sway, becoming difficult to walk. Heaps of waves, with some breakers whose foam is blown downwind in streaks. 14 feet
8 39-46 34-40 Gale Twigs and small branches are broken from trees, walking is difficult. Moderately large waves with blown foam. 18 feet
9 47-54 41-47 Strong Gale Slight damage occurs to buildings, shingles are blown off of roofs. Rolling seas, dense foam, Blowing spray reduces visibility. 23 feet
10 55-63 48-55 Whole Gale or Storm Trees are broken or uprooted, building damage is considerable. Very high waves with long, overhanging crests. The sea looks white, visibility is greatly reduced. 29 feet
11 64-72 56-63 Violent Storm Extensive widespread damage. Wave edges are blown into froth, and the sea is covered with patches of foam. 37 feet
12 73+ 64+ Hurricane Extreme destruction, devastation. The air is filled with foam and spray, and the sea is completely white, little visibility. 45 feet

Hurricane Scale

Category Wind Strength/Pressure Effects
1 65 to 83 knots
74 to 95 mph
119 to 153 kph
980 mb
Storm surge generally 4-5 ft above normal. No real damage to building structures. Damage primarily to unanchored mobile homes, shrubbery, and trees. Some damage to poorly constructed signs. Also, some coastal road flooding and minor pier damage. Hurricanes Allison of 1995 and Danny of 1997 were Category One hurricanes at peak intensity.
2 84 to 95 knots
96 to 110 mph
154 to 177 kph
980 – 965 mb
Storm surge generally 6-8 feet above normal. Some roofing material, door, and window damage of buildings. Considerable damage to shrubbery and trees with some trees blown down. Considerable damage to mobile homes, poorly constructed signs, and piers. Coastal and low-lying escape routes flood 2-4 hours before arrival of the hurricane center. Small craft in unprotected anchorages break moorings. Hurricane Bertha of 1996 was a Category Two hurricane when it hit the North Carolina coast, while Hurricane Marilyn of 1995 was a Category Two Hurricane when it passed through the Virgin Islands.
3 96 to 113 knots
111 to 130 mph
178 to 209 kph
964 – 945 mb
Storm surge generally 9-12 ft above normal. Some structural damage to small residences and utility buildings with a minor amount of curtainwall failures. Damage to shrubbery and trees with foliage blown off trees and large tress blown down. Mobile homes and poorly constructed signs are destroyed. Low-lying escape routes are cut by rising water 3-5 hours before arrival of the hurricane center. Flooding near the coast destroys smaller structures with larger structures damaged by battering of floating debris. Terrain continuously lower than 5 ft above mean sea level may be flooded inland 8 miles (13 km) or more. Evacuation of low-lying residences with several blocks of the shoreline may be required. Hurricanes Roxanne of 1995 and Fran of 1996 were Category Three hurricanes at landfall on the Yucatan Peninsula of Mexico and in North Carolina, respectively.
4 114 to 134 knots
131 to 155 mph
210 to 249 kph
944- 920 mb
Storm surge generally 13-18 ft above normal. More extensive curtainwall failures with some complete roof structure failures on small residences. Shrubs, trees, and all signs are blown down. Complete destruction of mobile homes. Extensive damage to doors and windows. Low-lying escape routes may be cut by rising water 3-5 hours before arrival of the hurricane center. Major damage to lower floors of structures near the shore. Terrain lower than 10 ft above sea level may be flooded requiring massive evacuation of residential areas as far inland as 6 miles (10 km). Hurricane Luis of 1995 was a Category Four hurricane while moving over the Leeward Islands. Hurricanes Felix and Opal of 1995 also reached Category Four status at peak intensity.
5 135+ knots
155+ mph
249+ kph
< 920 mb
Storm surge generally greater than 18 ft above normal. Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. All shrubs, trees, and signs blown down. Complete destruction of mobile homes. Severe and extensive window and door damage. Low-lying escape routes are cut by rising water 3-5 hours before arrival of the hurricane center. Major damage to lower floors of all structures located less than 15 ft above sea level and within 500 yards of the shoreline. Massive evacuation of residential areas on low ground within 5-10 miles (8-16 km) of the shoreline may be required. There were no Category Five hurricanes in 1995, 1996, or 1997. Hurricane Gilbert of 1988 was a Category Five hurricane at peak intensity and is the strongest Atlantic tropical cyclone of record.

Marine Radio Frequencies

Channel Number MHz Use
01A 156.050 Port Operations and Commercial. VTS in selected areas.
05A 156.250 Port Operations. VTS in selected areas.
06 156.300 Intership Safety
07A 156.350 Commercial
08 156.400 Commercial (Intership only)
09 156.450 Boater Calling. Commercial and Non-Commercial.
10 156.500 Commercial
11 156.550 Commercial. VTS in selected areas.
12 156.600 Port Operations. VTS in selected areas.
13 156.650 Intership Navigation Safety (Bridge-to-bridge). Ships >20m length maintain a listening watch on this channel in US waters.
14 156.700 Port Operations. VTS in selected areas.
15 156.750 Environmental (Receive only). Used by Class C EPIRBs.
16 156.800 International Distress, Safety and Calling. Ships required to carry radio, USCG, and most coast stations maintain a listening watch on this channel.
17 156.850 State Control
18A 156.900 Commercial
19A 156.950 Commercial
20 161.600 Port Operations (duplex)
20A 157.000 Port Operations
21A 157.050 U.S. Coast Guard only
22A 157.100 Coast Guard Liaison and Maritime Safety Information Broadcasts. Broadcasts announced on channel 16.
23A 157.150 U.S. Coast Guard only
24 161.800 Public Correspondence (Marine Operator)
25 161.850 Public Correspondence (Marine Operator)
26 161.900 Public Correspondence (Marine Operator)
27 161.950 Public Correspondence (Marine Operator)
28 162.000 Public Correspondence (Marine Operator)
63A 156.175 Port Operations and Commercial. VTS in selected areas.
65A 156.275 Port Operations
66A 156.325 Port Operations
67 156.375 Commercial. Used for Bridge-to-bridge communications in lower Mississippi River. Intership only.
68 156.425 Non-Commercial
69 156.475 Non-Commercial
70 156.525 Digital Selective Calling (voice communications not allowed)
71 156.575 Non-Commercial
72 156.625 Non-Commercial (Intership only)
73 156.675 Port Operations
74 156.725 Port Operations
77 156.875 Port Operations (Intership only)
78A 156.925 Non-Commercial
79A 156.975 Commercial. Non-Commercial in Great Lakes only
80A 157.025 Commercial. Non-Commercial in Great Lakes only
81A 157.075 U.S. Government only – Environmental protection operations.
82A 157.125 U.S. Government only
83A 157.175 U.S. Coast Guard only
84 161.825 Public Correspondence (Marine Operator)
85 161.875 Public Correspondence (Marine Operator)
86 161.925 Public Correspondence (Marine Operator)
87 161.975 Public Correspondence (Marine Operator)
88 162.025 Public Correspondence only near Canadian border.
88A 157.425 Commercial, Intership only.


NOAA Weather Radio Frequencies (MHz)


WX1 162.550
WX2 162.400
WX3 162.475
WX4 162.425
WX5 162.450
WX6 162.500
WX7 162.525