Safe harbour, Safe water mark, Sagging, Sail, Sail loft, Sailor, Sail plan, Samson post, Sandwaves, SatNav, Scaffie, Scandalise, Scantlings, Scharnow turn, Schooner, Scope, Screw, SCUBA, Scull, Scupper, Scuttle, Scuttle butt, Sea, Sea anchor, Sea boots, Sea chest, Sea state, Seasickness, Seaworthy, Sectored light, Seize, Sennet whip, Sentinel, Set, Settee, Sextant, Shackle, Sheathing, Sheave, Sheer, Sheet, Ship, Shoal, Shoal draught, Shore, Shoulder of mutton, Shroud, Sic, Sidewheel, Sink, Skaffie, Skeg, Skiff, Skipper, Skyscraper, Slack water, Slate, Sling, Slipway, Slivit board, Sloop, Slush, Slush fund, Smack, Snotter, Snow, Soft eye, Soft shackle, SOG, SOLAS, Sole, SONAR, Sound, Sounder, Sounding the deep, South, Sou'wester, Spanker, Spar, Special mark, Spider band, Spinnaker, Spirit room, Splice, Splice the mainbrace, Split lug, Sponson, Spray, Spreader, Spring, Sprit, Spritsail, Squall, Square, Square meal, Square-rigged, Squared away, SS, SV, Stability, Staff, Stain, Stall, Stanchion, Standard port, Standing lug, Standing rigging, Stand on, Starboard, Starter, Stay, Staysail, Steaming light, Stem, Step, Stern, Stern post, Sternway, Stitch and glue, Stiff, Storm, Stow, Stowaway, Straight, Strake, Stream, Stretcher, Strike, Strip plank, Studding sail, STV, Submarine, Surge, Sway, Sweep, Swell, Swim, Swing, Swinging circle, Swing the compass, Swinging the lead, Synoptic chart
My engines are going full astern
Safe Water mark
A buoy which indicates the end (or the beginning) of a channel and the presence, all round the mark, of safe water.
The concept of 'safe water' is relative, not least to the size of the ship or boat, and should be interpreted from the chart. The tiny SWM placed in the river by the yacht club would have no relevance for the 600 ton freighter using the same river.
Trinity House says "Safe Water Marks may be used mid-channel, as a centreline or at the point where land is reached. These buoys indicate the presence of safe, navigable water all around the buoy".
n A sheet of flexible material used by a sailing vessel to convert the movement of the wind into motive force to drive the vessel through the water.
A sail is raised into position by a ha'lyard and (sometimes) brought down by a downhaul. The angle of the sail to the wind is controlled by a sheet (line). The forward, more or less vertical, edge of a sail is the luff, the after edge is the leech*. The bottom, more or less horizontal, edge of the sail is the foot. The top edge of a four sided sail, the head, is usually attached to a gaff or a yard.
The forward lower corner of a sail is the tack, the after lower corner is the clew. The top corner of a sail is the peak. The upper forward corner of a four-sided sail is the throat.
The tension in the luff of a sail is a balance between the ha'lyard, pulling upward, and either a kicking strap or a tackline (or both), pulling downward.
Sails are not parachutes.
The wind flows along both sides (windward and leeward) of a sail from luff to leech. Because of the angle of the sail to the wind (the angle of attack) and the different speed of the wind on the two sides of the sail the air on the leeward side is at a lower pressure than the air on the windward side: the sail is drawn (or pushed) toward the lower pressure. The balancing resistances and forces of the hull and keel result in the boat moving forward.
If the angle of attack is too small there is no pressure difference between the two sides of the sail.
If the angle of attack is too great the wind on the leeward side becomes turbulent, and the sail stalls.
Crab claw sails and lateen sails are exceptions: their power depends upon vortex turbulence on the leeward side of the sail, with a large angle of attack.
Sails are not simple flat, two-dimensional, sheets of material; they are constructed of panels of material joined together so that the sail has a three dimensional shape. When filled with wind a sail becomes an aerofoil.
See also Balanced lug, Bermudan, Crab claw, Dipping lug, Gaff, Gunter, Jib, Lateen, Leg-o’-mutton, Raffee, Settee, Shoulder o' mutton, Skyscraper, Standing lug, Spinnaker, Split lug, Spritsail, Square, Staysail.
*Falconer (in 1815) referred to our luff as a 'foreleech' and to our leech as an 'afterleech', probably because the two vertical edges of the sails of square-rigged vessels were interchangeable and depended on the tack: the tack and the clew were also interchangeable.
v To sail; to operate a sailing boat; to use the wind to move a vessel through the water.
More generally, to operate any vessel.
A large open space, usually above the workshop, where sails can be laid out on the floor to be measured, cut and sewn. See Loft.
A set of drawings showing the arrangement of the sails.
Named after the Biblical strong man betrayed by Delilah.
Not a sampson post.
The workboat Provider is moored to a floating pontoon at Westminster Pier: the bowline is attached to a metal samson post
The largest sandwaves, tens of metres high with wavelengths of hundreds of metres, occur outside San Francisco Bay; they are caused by the huge tidal outflow through the narrow entrance to the bay.
Satellite Navigation. The terrestrial equivalent of GNSS (Global navigation and satellite systems)
A way of reducing the effectiveness of a sail quickly.
The dimensions of a vessel's individual components.
Used by power driven vessels to turn onto a reciprocal course when the point to turn toward (the MOB) is significantly further astern than the radius of the turning circle.
Put the rudder over hard toward the MOB.
After deviating from the original course by about 240 degrees, shift the rudder hard to the opposite side.
When heading about 20 degrees short of the reciprocal course, put the rudder amidships so that vessel will turn onto the reciprocal course.
Where the rode is all chain, the RYA tells us that the scope should be at least four times the depth of water. Where the rode is mostly line the scope (it says) should be at least six times the depth. When deciding the scope attention should be paid to the swinging circle of the boat around its anchor and to the proximity of other boats.
“Chain in the locker is wasted chain”
Slang for propeller.
Self Contained Underwater Breathing Apparatus
v To scull. To move a boat using an oar over the stern.
n A special type of oar used by recreational oarsmen in long narrow boats.
Often, the long narrow boat itself.
v To scuttle a vessel is to open holes in the hull so that she sinks. In wartime, ships may be scuttled to prevent them being used by the enemy or to block the entrance to a harbour. In peacetime, redundant ships may be scuttled to form artificial reefs to provide breeding grounds for marine life and to provide 'wrecks' for recreational diving.
Originally, a cask (specifically, a butt) of water on deck, with a scuttle in the lid and a pannikin, from which the crew could help themselves. In relaxed moments, the crew might gather around the scuttlebutt to gossip and yarn.
A butt (or a pipe) is half a tun, or two hogsheads: 108 Imperial gallons for ale, 128 Imperial gallons for wine (see cask).
coll: Shipboard gossip; "Have you heard the scuttlebutt about the new First Officer?".
n The water which covers most of the earth, being salt at about 3.5%.
High, waterproof boots, worn by sailors.
A box with a hinged lid in which a seaman keeps his personal effects.
The general appearance of the surface of the sea.
Nausea and vomiting induced by the movement of a vessel at sea.
There are many folk and patent remedies for seasickness; different remedies seem to work for different people.
Certificated for sailing.
v To bind two lines together with many turns of small stuff.
The seizing may be frapped with two or more turns of the same small stuff at right angles.
A sennet is a plait or weave of cordage or rawhide with three, four or more strands.
A sennet whip was usually of plaited rawhide.
The table of diamonds and the tidal atlas are arranged in 1-hour periods either side of the High Water hour of the reference port. The figures imply that the set and drift are constant during each tidal hour and that they change abruptly at the end (and beginning) of each hour; in fact, there is a progressive change from one hour to the next.
A covering of material (originally copper, felt, etc., but now more probably fibreglass) placed over a portion of the ship’s surface to protect it. Copper sheathing covered the immersed part of a wooden ship to protect it from fouling with marine growth.
The sheerclamp is a timber piece linking the inside tops of the frames together, from stem to stern, and supporting the deck beams.
The sheet-line of a square-rigged sail is attached to a cringle at the lower, aftermost (for the time being) corner of the sail. On all sails except the course it runs to a block near the end of the yard below, along the yard to the mast and down the mast to the fife-rail.
The course sail sheet-line runs from the aftermost lower corner of the sail to a block near the rail or the side-deck. The corresponding line at the forward end of the foot of the course sail is tacked down to a block on the beam forward of the mast.
A staysail or jib has two sheet-lines (or sheets), both attached to the same clew cringle. The one to leeward is hauled taut by a block (or, more usually, a winch) near the leeward beam. The other is loose and idle.
A boomed fore-and-aft mainsail has an outhaul (line) (used to increase the tension on the foot of the sail) attached to the clew cringle and passing through a block near the end of the boom. The sheet is attached (often by a complex system of pulley blocks) to the boom, not the sail. In this respect the sheet (line) of a fore-and-aft mainsail is more akin to the brace of a square-rigged yard, or perhaps to a vang.
A boomless fore-and-aft mainsail has its sheet attached to the clew cringle.
Coll A vessel which carries one or more boats.
See Brig, schooner, sloop.
There are, and have been, very many types of ships, such as galleys, galleons, destroyers, frigates . .
It’s not always clear how the names arose, and the definitions have never remained constant. A sailing frigate was simply a small fast ship with few guns, quite different from a 21st Century frigate. The best definition of frigate might be that such ships mounted their principal armament on a single continuous upper deck. It seemed that the type name stuck while the ship itself evolved through the centuries.
v To ship something is to deploy it. An oarsman would ship his oars ready to move his boat.
A shallow area of water, presenting a hazard to navigation.
n A stout post used as a temporary support or brace.
v To prop up or support (a boat) using shores.
Shoulder of mutton
A triangular sail attached at its luff to a mast. The angle of the tack is not square, as a Bermudan sail's is, but acute, so that the clew is higher than the tack; the foot and the leech may be of equal length. The clew may or may not be extended by a sprit-boom, controlled at the mast by a snotter. The sheet is attached either to the clew or to the tip of the sprit-boom. See Leg of mutton.
Latin: sic erat scriptum: “thus was it written”.
It usually means “The chap who wrote this spelled it this way, but I don’t agree.”
The paddle wheels at the sides of a paddle steamer.
Deliberately to fill one's own vessel with water so that it sinks to the bottom is to scuttle it.
n The round or rectangular container where dishes, hands and vegetables are washed. A sink usually has one or more taps providing water (sometimes hot and cold) and a drain.
A vertical fin below the keel, at the stern, in front of the rudder. It might form an attachment for rudder mountings, or it might form the third 'leg' of a tripod for a twin-keel vessel to take the ground. On a dinghy, a skeg provides directional stability. Its area contributes a little frictional resistance to the flow of water so that the stern trails behind the stem.
Falconer's yawl had four to six oars and no sails.
Now (early 21st century) it is a small light rowing boat, sometimes with sails.
A person (not necessarily qualified) in charge of a boat.
Any person in charge of a small group of people. Scoutmasters are called 'skipper'.
According to Falconer, "a small triangular sail . . . sometimes set above the royal."
A modern equivalent is the slate of the clapper-board used to identify a scene in a film.
v To use a sling to hoist or lower something.
Someone asked to leave might be told to "sling yer 'ook"; 'hook' being slang for an anchor.
A slope, or ramp, into the water for launching and recovering small boats.
The slope, often with a railway and slides, for launching newly-built ships.
Sailing boats are now (early C21) defined by their rig. In earlier centuries they were defined more by their purpose or size. As the purpose, size and rig evolved over decades and centuries names tended to linger, so that in two different centuries boats with the same type-name might be very different.
A 21st Century sloop has two fore-and-aft sails. The mainsail is usually Bermudan, but may be gaff or gunter, occasionally a sprit-sail. The foresail is hanked to a forestay between the stemhead and the mast. The foresail may be small, in that it barely fills the fore triangle between the mast and the forestay, or its clew may extend well abaft the mast.
The mast is usually supported by Marconi stays.
A sloop of war is not to be confused with a sloop.
In the Royal Navy the rating of a ship depended on the rank of the officer in command: the frigate Blossom was rated a ship when commanded by a captain and, on her next cruise, was rated a sloop when commanded by a commander. A sloop of war carried 10 to 18 guns and might be rigged as a ship, or a brig, a schooner or a cutter; Blossom was ship-rigged.
HMS Blossom, sloop of war
n Water which precipitates from clouds in the form of grouped hexagonal crystals, and which forms white layers of crystalline water on exposed surfaces.
The delight of children; the bane of travellers.
An eye splice without a thimble.
International Convention for the Safety Of Life at Sea: a document which recommends and mandates safety procedures for ships and boats.
n A kind of flatfish, prized for its delicate taste.
SOund Navigation And Ranging. A transceiver in the hull of a vessel sends sound signals into the water and detects the echoes which return. An electronic device measures the time taken for the echo to return and displays the answer as range, the distance of the object which caused the echo, and direction.
See Echo Sounder.
The SONAR of a submarine sends sound signals in all direction and detects both the distance and the direction of the echo.
n A noise. What is heard.
n A narrow channel of water (across which one might swim) from the sea. From the Old Norse 'a straight' or 'swimming'
adj Perfect. Without defect.
vb To make a noise, as in speaking, playing music or using an echo-sounder.
A device for measuring the depth of water.
Sounding the deep
An echo sounder sends a short duration of noise down to the sea bottom, and detects the echo which is returned. The time between sending the sound and receiving the echo is proportional to the depth of water; this is calculated by the electronics inside the instrument.
The word 'sound' has had, and has, several meanings, two of which are:
n A noise, as heard by the ear.
vb From the old Germanic source that yielded the Old English 'sund', meaning 'water' or 'sea'.
'The deep', in Medieval times, was 'unknown', 'mysterious'. The concept of depth, being the distance from the sea surface to the sea bottom, was equally mysterious. The word (and the concept) was also applied to the points on a lead line where there was no mark. See Marks and deeps.
From any point on the Earth, True South is the direction in which the South pole lies.
From any point on the Earth an imaginary line (a meridian) passes through that point and the South pole and the North pole.
The South and North poles are the tips of the axis on which the Earth rotates once every 24 hours.
From most points on the Earth, Magnetic South is not in the same direction as True South. The Magnetic South pole lies between South Africa and the True South pole, and moves toward India at about 40 miles per year.
It follows that a magnetic compass points to magnetic South and not to true South; the variation* between true South and magnetic South is different for almost every point on the Earth, and must be taken into account when navigating with a magnetic compass.
* not variance, which is a statistical concept.
A waterproof hat, with a gutter around the brim and a long brim behind to drain water away from the wearer's head and neck.
With the wind on the port side of the boat (the port tack), the wind flows across the the sail from the luff, on the port side, to the leech, on the starboard side, creating a low-pressure area ahead of the sail. The spinnaker pole, from the mast to the tack of the spinnaker, extends the foot of the sail to windward, and is held by a guy-line (a brace?) to the port quarter. The clew is held and controlled by a guy-line (a sheet) to the starboard quarter.
The tack is changed by gybing the boat and by moving the spinnaker pole from the previous tack to the previous clew.
A spinnaker behaves in much the same way as a square-rigged sail. It is physically different in that there is no yard at the head (which is peaked rather like a skyscraper or raffee); where a course sail might have a cro'jack yard from tack to clew a spinnaker has a boom from the tack to the mast.
Cooke suggests that the sail derived its name from the yacht Sphinx, which the crew called "Spinks": its sail became known as a 'spinker' and then a 'spinnaker'. Before that, in a slightly different form, it was known as a 'balloon sail'.
The purser's storeroom.
Originally the room where the spirits (mostly rum) were stored.
Splice the mainbrace
A brace is a line from a yardarm to a point on the sheer further aft; it is used, in conjunction with those of other yards and the other ends of the yards, to alter the angle of the square yards when trimming sails.
The braces might need to be spliced (repaired, rejoined) when they have been shot through in battle.
It was a colloquial expression, used as an order to issue the rum ration, or perhaps an extra ration as a reward.
The after-sail is laced along its luff to the mast and tacked down to the heel of the mast. Its clew may or may not be extended by a boom with a gooseneck or jaws at the mast. The sheet is attached to either the clew or to the tip of the boom.
Folkard suggested that the split lug sail was created by a young lieutenant from a balance (what we would now call a dipping) lug sail by cutting a sail close to the mast, attaching a sheet to the fore part and lacing the after part to the mast. He did so because changing the tack of his balance (our dipping) lug was difficult for a novice crew.
n A line from a quarter or a bow to a shore-side bollard amidships to prevent the boat surging fore and aft. If the boat has a centre cleat amidships then the mooring springs may run from the centre cleat to shore bollards forward and aft. In the diagram below, 3 and 4 are springs.
A sprit-boom carries the clew of a sail out horizontally, in much the same way as a boom, except that a spritboom is held to the mast by a snotter and a boom is attached to the mast (or even the deck) by a gooseneck or by jaws.
A sprit (or spreet) carries the peak of a four-sided sail above and abaft the mast head.
This Thames sailing barge, moored at West Mersea without her sails, has her bowsprit steeved up at a steep angle and her spreet rigged.
This Thames sailing barge, moored alongside at Maldon, has her bowsprit steeved almost vertical.
Her brailed mainsail is held upward and outward by her spreet. A pair of vangs can be seen extending from the top of the spreet to the quarters.
n A four sided sail extended by a sprit (or spreet).
Spritsails evolved as working sails on oyster boats and Thames barges on the East coast of England. The height of the sail was advantageous, especially in the East Coast rivers, by being above the banks and trees. The huge power of the sail can be reduced to nothing in moments by brailing.
This sprit-sail dinghy has her sail extended upward by a spreet held at the mast by a snotter. This sail has no boom, no vangs and no brail.
n A geometric figure with four sides of equal length, each connected to two adjacent sides at right angles.
n A right angle (an angle of 90°), or an instrument for measuring right angles.
As in square sail, refers not to the shape of the sails (which are never square!) but to the fact that the yards (and therefore the heads of the sails) are at right angles (square) to the mast. 'Square sail' is a verbal contraction of 'square-rigged sail'.
A good meal; enough food. During the Age of Sail (and since) food aboard ship was more plentiful (and possibly better) than food ashore.
Shipboard plates were square wooden plates.
Smart, tidy, correctly stowed. All difficulties resolved.
Steam Ship. A 'steamer'
A ship operated by high-pressure steam.
Water is boiled in a vessel (a boiler) constructed to withstand high pressures. The steam drives pistons within cylinders or turbines. The movement of the pistons or the rotation of the turbines rotates the paddle wheel(s) or propellers which move the ship. The steam may also be used to drive electricity generators and other machinery.
The heat to boil the water was originally generated by burning wood and, later, coal. Most 20th Century ships burned oil, often heavy oil, to boil the water. Some modern ships and submarine (vessels) use nuclear power to boil water.
Measurements of static stability assume the boat to be stationary in calm water & no wind and relate the boat's centre of gravity (CG) to its centre of buoyancy (CB) The Angle of Vanishing Stability (AVS) is the angle of heel (at rest in calm water and no wind) at which the boat shows no tendency either to right or to capsize: its CG and CB are vertically exactly in line.
Measurements of dynamic stability, with the boat moving through waves and wind, are more difficult.
A post which supports the guardwires.
n The group of people which operates a unit, such as a ship or company or office.
n A pole or stick which carries a flag.
n A dye used to add colour and a degree of waterproofing to wood.
To stop, or to become ineffective.
A rudder stalls when, at a high angle of attack, the water on its leeward face becomes turbulent and the rudder becomes ineffective.
A rudder can also stall at low angles of attack if the flow of water across its surface is too slow. This can happen when the speed through the water is very slow; when the propeller is not turning or when running downwind the water in a wave overtakes the boat.
A secondary port does not have tide tables, but has a table of differences from a nearby standard port.
The four-sided sail is bent to a yard which is fore-and-aft, and not square to the mast. The tack (or fore-clew) is tacked down close to the heel of the mast or to the boom. The clew (after-clew) may be extended by a boom held at the mast by a goose-neck or jaws. the sheet is attached to the clew or tip of the boom. See Lugsail.
See Running rigging.
v To maintain the same course and speed.
Where there is potential for a collision between two vessels the IRPCS provides rules (Rule 11 to Rule 18) for which is the 'stand on' vessel and which is the 'give way' vessel. It also provides rules (Rule 16 and Rule 17) for the action to be taken by the stand on vessel and by the give way vessel.
Viking long-boats were pointed at both ends, so the steering oar was mounted on the right hand side (because most men were right-handed) near the stern: this side became known as the steering board, or st’(a)r’board.
n The wire or line between the stem, stern & the sides of the boat and points high up the mast which support the mast. Those at the sides may be called shrouds: those at the stem or from the foredeck are forestays: those at the stern are called backstays. Adjustable backstays may be preventer backstays or running backstays.
v To stay a vessel is to change from one tack to another. A vessel 'in stays' has come to the eye of the wind but has failed to fall onto the new tack; in irons. a vessel which fails to tack, and falls back onto the original tack, has 'missed stays'.
IRPCS, Rule 21 "Definitions" says:
"(a) "Masthead light" means a white light placed over the fore and aft centre line of the vessel showing an unbroken light over an arc of the horizon of 225 degrees and so fixed as to show the light from right ahead to 22.5 degrees abaft the beam on either (both; each) side of the vessel."
IRPCS, Rule 23 "Power-driven vessels under way" says:
"(a) A power-driven vessel under way shall exhibit:
(i) a masthead light forward;
(ii) a second masthead light abaft of and higher than the forward one . . . . "
A power driven vessel of less than 50m in length need carry only one masthead light.
A masthead light is not at the top of the mast, but ahead of it. It is not an anchor light or a tricolour light. "Steaming" refers to the power driving the vessel which would, originally, have been high-pressure steam in an external combustion engine.
The structural member which links the bows together and to the keel.
Stitch and glue
v To put away; to secure; to make tidy.
The individual planks of a strake may be joined together with butt joints or scarph joints.
A flow of water, as in a river or tideway.
The flow of the tide, as distinct from the rise and fall of the tide.
The tidal stream has direction and rate. The direction in which the tidal stream flows (the set of the tide) is measured in degrees True. The rate of flow (the drift of the tide) is measured in knots.
Values for tidal streams are shown in Tidal Stream Atlases and in the Table of Diamonds on Admiralty charts for one-hour periods relative to the Reference Port of the chart or atlas. It is assumed (although it is not true) that the stream remains constant during the hour and changes abruptly at the cusp.
The High Water hour is the hour either side of the time of High Water at the Reference Port (The HW hour begins 30 minutes before the time of HW and ends 30 minutes after the time of HW). The previous hour is the -1 hour: the following hour is the +1 hour, and so on.
In the stream atlas, the set of the tide for the hour is given as the direction of an arrow which can be measured with parallel rules or a plotter: the drift is given as two numbers, in tenths of a knot. The first number is the drift at the neap tide, the second at the spring tide; the dot (or comma) is not a decimal, it is the point where the stream is measured.
In the Table of Diamonds on the chart, the set for the hour is given in degrees True, the drift is two numbers; the first is the drift at the Spring tide, the second is the drift at the Neap tide.
There are more dots than diamonds, but each diamond represents a dot.
n A flat, horizontal device, with handles at each end, for carrying an unconcious or incapable person.
To strike a tent is to take it down and pack it away; there is no suggestion of surrender.
An adjective describing anything below sea level, such as a submarine cable or pipeline.
The adjective has become nominalised when used to describe a submarine vessel, which is specialised for working under water for extended periods of time. Most submarines have been used for warfare but many are now used for exploration and for working with submarine equipment such as oil and gas rigs, pipelines and cables.
A transient, horizontal movement.
v To remove dust or small debris from a surface with a brush or broom.
The up-and-down movement of the sea: waves which do not break.
vb to move through the water by moving of arms and legs.
To move backwards and forwards at the end of a line (like a pendulum) under the effect of gravity alone, or in combination with a regular impetus such as a clock escapement or a person's arm.
A criminal might swing at the end of a rope whilst being hung for murder (this no longer happens in most civilised countries).
When a vessel swings to its anchor rode it describes an arc of a circle over the ground. When the tide turns this arc may become a full circle with a radius only slightly less than the scope of the rode.
Swing the compass
Deviation changes with the vessel's heading; it is normal to measure at five or ten degree intervals. The vessel is sailed or sprung in a circle and the steering compass is compared with a hand-held compass or with a gyroscopic compass.
The deviation card is unique to the vessel measured, in the state in which it was measured. Changes to any electronic equipment or ferrous metal objects (like engines) will alter the deviation.
Strictly speaking, it is the ship which is swung, not the compass.
Swinging the lead
In fact, swinging the lead was skilled, hard, dangerous work. Leadsmen stood on the channels, leaning outward and held in place by a light line or belt. They were frequently soaked with spray or immersed in waves. The safety of the ship and the lives of the crew depended on their skill.
A synoptic chart describes the atmospheric pressure systems for the area covered by the chart, typically 1,000km or more across. The Meteorological Office (MetOffice) provides daily synoptic charts (and predictive charts for 72 hours) of the North Atlantic to include the Eastern seaboard of North America, Greenland, Iceland and the Western seaboard of Europe, including the British Isles.
Synoptic charts are useful for predicting the weather.
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