Hourly tidal streams, English Channel West (NP250)

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TIDAL STREAMS – Land’s End to Start Point :

 
Westward and southward of Land’s End and Runnel Stone the streams are rotatory  near Land’s end and Runnel Stone, though the stream is probably fairly strong, its direction, northward or southward past Land’s End and eastward or westward past Runnel Stone, depends on the direction of the offshore stream towards, past, or away from the land.  The direction of a rotatory stream may be affected by wind and other circumstances, so the times during which the stream runs northward and eastward, or southward and westward off the south-western extremity of the coast of Cornwall is rather uncertain.
 
In Mounts bay the streams are very weak, and, though a rotatory stream runs with some regularity in the middle of the entrance, in the bay itself the streams are quite irregular.

Between Lizard point and Start point the streams turn rather earlier near the land than in the fairway of the English channel, but the time difference is much less between the English coastal stream and the mid-channel stream than it is between the French coastal stream and the mid-channel stream.

Off Lizard point and off Start point the streams are fairly strong and nearly rectilinear, but in the bay between these points the streams are weak and tend to become rotatory in a clockwise direction.  At their strongest the streams run in about the direction of the land, thus, north-north-eastward off Manacle rocks, north-eastward off Killygerran head and Dodman point, eastward off Looe bay, and east-south-eastward off Bigbury bay.  Though the streams are, as stated, weak generally, their rates increase off salient points, and over rocks and shoals, where overfalls may occur; the east-going stream is strongest at about the time of high water at Devonport, the west-going stream is strongest about 6 hours before and after high water at Devonport.

In this section, the “east-going stream” is the stream which runs in general directions up Channel; thus, off Manacle rocks the direction of the east-going stream is about north-north-east.  Similarly, the “west-going stream” is the stream which runs in general directions down Channel.

At a position about 5 miles southward of Lizard head, the stream is slightly rotatory in a clockwise direction, the east-going stream, direction 065°, begins – 0330 Devonport (+0315 Dover); the west-going stream, direction 245°, begins +0250 Devonport (-0250 Dover); spring rate in both directions 2.3 knots, neap rate 1.1 knots.

At a position about 4¾ miles eastward of the outer Manacle rock the stream is rotatory in a clockwise direction.  It is weakest, spring rate 0.2 knot neap rate 0.1 knot, in a westerly direction, -0400 Devonport (+0245 Dover); strongest, spring rate 1.1 knots neap rate 0.5 knot, in an east-north-easterly direction, H.W. Devonport (-0540 Dover); weakest, spring rate 0.2 knot neap rate 0.1 knot, in a southerly direction, +0220 Devonport (-0320 Dover), and strongest, spring rate 0.9 knot neap rate 0.4 knot, in a south-westerly direction, +0540 Devonport (H.W. Dover).  About 2½ miles nearer the rocks the stream is more nearly rectilinear; the east-going stream runs in directions changing from 018° to 044° and begins -0345 Devonport (+0300 Dover); the west-going stream, direction 218° begins +0200 Devonport (-0340 Dover); spring rate in both directions 1.3 knots, neap rate 0.6 knot.

At a position about 5 miles eastward of St. Anthony head, the stream is nearly rectilinear; the east-going stream, spring rate 0.7 knot, neap rate 0.3 knot, direction 040°, begins -0400 Devonport (+0245 Dover); the west-going stream, spring rate 0.7 knot, neap rate 0.4 knot, direction 215°, begins +0210 Devonport (-0330 Dover).

At a position about 3 miles offshore southward of Looe island, the stream is rotatory in a clockwise direction.  It is weakest, spring rate 0.3 knot neap rate 0.2 knot, in a northerly direction, -0300 Devonport (+0345 Dover); strongest, spring rate 0.9 knot neap rate 0.5 knot, in an east-by-north direction, +0020 Devonport (-0520 Dover); weakest, spring rate 0.3 knot neap rate 0.2 knot, in a south-south-westerly direction, +0345 Devonport (-0155 Dover); and strongest, spring rate 0.8 knot, neap rate 0.4 knot, in a west by south direction, -0610 Devonport (+0035 Dover).

At a position about 6 miles southward of Yealm head, the east-going stream, which is more or less rotatory, begins, in a north-easterly direction -0230 Devonport (+0415 Dover), attains its greatest rate, one knot at springs 0.5 knot at neaps, in a direction 100°, +0020 Devonport (-0520 Dover), and ends in a southerly direction +0340 Devonport (-0200 Dover), the west-going stream, which is nearly rectilinear in a direction 285°, spring rate 0.8 knot neap rate 0.4 knot, begins +0340 Devonport (-0200 Dover).

At a position about 3 miles southward of Start point, the stream is nearly rectilinear; the east-going stream, direction 060°, spring rate 2.0 knots neap rate one knot, begins -0150 Devonport (+0455 Dover); the west-going stream, direction 240°, spring rate 2.1 knots neap rate one knot, begins +0420 Devonport (-0120 Dover).
 
 
TIDAL STREAMS PRAWLE POINT TO NEEDLES CHANNEL

TIDAL STREAMS – The stream is fairly strong off Start point, and very strong off The Bill of Portland, but its rate decreases eastward of Start point and westward of the Bill, about 48 miles east-north-eastward, and is not more than about 1.5 knots at springs midway between the points.

In the western part of the bay between Start point and the Bill of Portland the stream is weak, but becomes stronger and eastward towards Portland peninsula (Lat. 50° 32’ N., Long. 2° 27’ W.).

The streams near Portland peninsula, in West and East bays and off the Bill, provide outstanding examples of eddies from a salient point; their effects, namely a set northward into West and East bays, and a set southward, southward of the Bill, are noticeable as much as 8 to 10 miles westward and eastward, and 5 to 6 miles southward of the Bill; vessels bound up or down Channel are advised to keep well southward of the Bill in order to avoid them.

The streams again lose strength eastward of Portland peninsula, but remain fairly strong to off St. Alban’s head and Durlston head.

About 3 miles southward of Start point the east-going stream, direction 060°, spring rate 2.0 knots, begins -0150 Devonport (+0455 Dover); the west-going stream, direction 240°, spring rate 2.1 knots, begins +0420 Devonport (-0120 Dover).

Nearer the point the streams probably begin half an hour or more earlier, and are stated to attain a rate of 4 knots at springs, but to be irregular at neaps.  With strong winds a race may extend up to about one mile south-eastward from the point.

At a position about 4 miles east-north-eastward of Hope’s nose, the stream is rotatory in a clockwise direction.  It is weakest, spring rate 0.2 knot neap rate 0.1 knot, in a direction 310°, - 0145 Devonport (+0500 Dover); strongest, spring rate 0.8 knot, neap rate 0.4 knot in a direction 040°, +0130 Devonport (-0410 Dover); weakest, spring rate 0.1 knot neap rate 0.1 knot, in a direction 120°, +0440 Devonport (-0100 Dover), and strongest, spring rate 1.1 knots neap rate 0.6 knot, in a direction 215°, -0400 Devonport (+0245 Dover).

At a position about 3 miles south-by-eastward of Beer head, the stream is more or less rotatory in a clockwise direction.  The east-going stream begins, in a northerly direction, -0140 Devonport (+0505 Dover), attains its greatest rate, 0.8 knot at springs 0.4 knot at neaps, in a direction 070°, +0125 Devonport (-0415 Dover), and ends in a south-easterly direction; the west-going stream begins, in a southerly direction, +0500 Devonport (-0040 Dover), attains its greatest rate, one knot at springs 0.5 knot at neaps, in a direction 255° – 0430 Devonport (+0215 Dover), and ends in a north-westerly direction.

At a position in Portland West bay 7.4 miles 295° from the Bill of Portland lighthouse, the stream is rotatory in a clockwise direction.  It is weakest, spring rate 0.9 knot neap rate 0.5 knot, in a direction 040°, -0115 Devonport (+0530 Dover); strongest spring rate 1.7 knots neap rate 0.8 knot, in a direction 120°, +0245 Devonport (-0255 Dover); weakest, spring rate 0.2 knot neap rate 0.1 knot, in a direction 270°, +0540 Devonport (H.W. Dover), and strongest spring rate 1.9 knots neap rate 0.9 knot, in a direction 305°, -0445 Devonport (+0200 Dover).  The stream at this position is affected by the West bay eddy, and has a noticeably east-north-easterly set.

At a position 4.7 miles 171° from the Bill of Portland lighthouse, the stream is nearly rectilinear; the east-going stream, direction 110°, spring rate 3.7 knots neap rate 1.8 knots, begins -0100 Devonport (+0545 Dover), the west-going stream, direction 265°, spring rate 3.6 knots neap rate 1.8 knots, begins +0520 Devonport (-0020 Dover).  The stream at this position is affected by the south-going eddy stream from the bill, has a noticeably southerly set, and always turns though south.



 
Adapted from Admiralty Sailing Directions, English Channel 1947
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