Hourly tidal streams, East Solent area (NP337)

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TIDAL STREAMS SPITHEAD AREA

Tidal Streams – The terms “east-going stream” and “west-going stream,” in the accounts given below, are descriptive only, and the true directions of the streams may differ very considerably from east and west.

At a position about 1¼ miles 275° from Horse Sand fort, there is no slack water, but the east-going stream may be said to begin +0315 Portsmouth (+0330 Dover), when direction is southward, spring rate 0.3 knot, neap rate 0.1 knot.  The direction changes rapidly anti-clockwise and the stream attains a first maximum rate of 0.5 knot, at springs, 0.3 knot at neaps, in a direction 153°, +0345 Portsmouth (+0400 Dover); the rapid anti-clockwise change continues, with a small decrease in the rate during the next 1¼ hours, and then an increase, and by +0600 Portsmouth (-0610 Dover) direction is 080°, spring rate 0.6 knot, neap rate 0.3 knot; the direction then changes clockwise, whilst the rate increases, and the greatest rate, 1.4 knots at springs, 0.7 knot at neaps, in a direction 117°, is attained -0400 Portsmouth (-0345 Dover); after this time the direction again changes anti-clockwise, slowly at first but then very quickly, and the east-going stream may be said to end, and the west-going stream to begin, - 0130 Portsmouth (-0115 Dover), when direction is north-ward, spring rate 0.3 knot, neap rate 0.1 knot.  The direction of the west-going stream changes rapidly anti-clockwise, and its rate increases, slowly at first but then quickly, and by H.W. Portsmouth (+0015 Dover) the direction is 290°, spring rate 1.2 knots, neap rate 0.6 knot, and, maintaining the same direction, the greatest rate, 1.8 knots at springs, 0.9 knot at neaps, is attained +0100 Portsmouth (+0115 Dover).  The rate then decreases, but the direction remains unaltered during the next hour, after which it changes rapidly anti-clockwise till the stream ends.

Off the eastern side of Warner shoal, the east-going stream begins, in a southerly direction, +0250 Portsmouth (+0305 Dover), changes direction in an anti-clockwise direction, and attains a first maximum rate of 0.9 knot at springs, 0.5 knot at neaps, in a direction 150°, +0400 Portsmouth (+0415 Dover); the anti-clockwise change in direction continues, whilst the rate decreases to a minimum of 0.4 knot at springs, 0.2 knot at neaps, in a direction 110°, +0600 Portsmouth (-0610 Dover), after which the direction changes clockwise, the rate increases, and the greatest rate, 1.3 knots at springs, 0.7 knot at neaps, in a direction 130°, is attained -0415 Portsmouth (-0400 Dover); the rate then decreases rapidly, the direction changes anti-clockwise, and the stream ends in an east-north-easterly direction.  The west-going stream begins, in a north-north-westerly direction, -0225 Portsmouth (-0210 Dover), but its direction changes very quickly to, and remains, about north-westerly, and its greatest rate, 1.7 knots at springs, 0.9 knot at neaps, in a direction 310°, is attained +0100 Portsmouth (+0115 Dover), the rate then decreases, but the same direction is maintained for the next hour, after which it changes clockwise, and the stream ends.

At a position about 1½ cables south-south-westward of the Nab End light-buoy, the stream is more regular, but is rotatory in an anti-clockwise direction.  It is weakest, spring rate 0.6 knot, neap rate 0.3 knot, in a direction 130°, +0500 Portsmouth (+0515 Dover); strongest, spring rate 1.3 knots, neap rate 0.6 knot, in a direction 085°, -0500 Portsmouth (-0445 Dover), weakest, spring rate 0.6 knot, neap rate 0.3 knot, in a direction 005°, -0215 Portsmouth (-0200 Dover), and strongest, spring rate 1.5 knots, neap rate 0.7 knot, in a direction 280°, +0030 Portsmouth (+0045 Dover).

At a position about half a mile eastward of Nab tower there is no slack water and the stream is more or less rotatory in an anti-clockwise direction.  The east-going stream may be said to begin, in a direction about 100°, spring rate 0.4 knot, neap rate 0.2 knot, +0545 Portsmouth (+0600 Dover); the direction changes slowly, and the greatest rate, 1.8 knots at springs, 0.9 at neaps, in a direction 078°, is attained -0400 Portsmouth (-0345 Dover); the slow anti-clockwise change continues till -0200 Portsmouth (-0145 Dover), when direction is 145°, spring rate 0.9 knot, neap rate 0.4 knot, after which the direction changes, and the rate decreases, rapidly, till the stream ends.  The west-going stream may be said to begin -0100 Portsmouth (-0045 Dover), when its direction is 345°, spring rate 0.2 knot, neap rate 0.1 knot; the direction changes anti-clockwise, and the rate increases rapidly till H.W. Portsmouth (+0015 Dover), when direction is 280°, spring rate 1.3 knots, neap rate 0.7 knot; the direction then changes, and the rate increases, more slowly, and the greatest rate, 1.6 knots at springs, 0.8 knot at neaps, in a direction 255°, is attained +0200 Portsmouth (+0215 Dover); after this time the direction changes, and the rate decreases slowly till +0400 Portsmouth (+0415 Dover), when direction is 220° spring rate 0.9 knot, neap rate 0.4 knot; the direction then changes, and the rate decreases rapidly till the stream ends.

 
 
 
 
 
TIDAL STREAMS ST CATHERINES POINT TO FORELAND

TIDAL STREAMS – Between St. Catherine’s point and Foreland the east-going offshore stream does not turn appreciably into the eastern entrance to the Solent, but meets the east-going Solent stream, combines with it, and runs east-north-eastward past the shoals off Selsey bill.  Similarly, the west-going stream from off Selsey bill divides, and runs north-westward towards the Solent and west-south-westward past the Isle of Wight.

Nearer the land, however, the east-going stream follows the direction of the coast and meets a south-south-east going branch of the Solent east-going stream in St. Helen’s road (page 220) where the streams are weak.  At certain times, the west-going stream runs from near Nab tower (see page 216) towards Foreland, divides, and runs north-north-westward and south-south-westward.

At a position, about 4½ miles east-south-eastward of Dunnose, the east-going stream, spring rate 2.7 knots, neap rate 1.3 knots, mean direction 070°, begins +0520 Portsmouth (0535 Dover); the west-going stream, spring rate 2.6 knots, neap rate 1.3 knots, mean direction 250°, begins -0045 Portsmouth (-0030 Dover).

At a position about 3.6 miles 189° from Nab tower, the stream is more or less rotatory in an anti-clockwise direction.  The east-going stream, spring rate 2 knots, neap rate one knot, begins, in a direction 090°, +0540 Portsmouth (+0555 Dover), but changes to a direction about 080° as it gains strength, and when strong changes gradually to about 065°; the change continues as the stream weakens and it ends in a direction abut 045°.  The west-going stream, spring rate 2.1 knots, neap rate one knot, begins in a direction about 270°, - 0045 Portsmouth (-0030 Dover) changes to about 260° as it gains strength, and when strong runs in directions between about 260° and 245°; the change continues as the stream weakens and it ends in a direction about 235°.

Along the coast between St. Catherine’s point and Dunnose streams are strong, up to a maximum of about 5 knots at springs in both directions.  The east-going stream begins about +0500 Portsmouth (+0515 Dover), the west-going stream begins about H.W. Portsmouth (+0015 Dover).  There are probably many eddies near the land when the streams are strong.

A race occurs off Dunnose.


 
 
 
TIDAL STREAMS GENERAL – Durlston Head to Selsey Bill – The streams in this area are much affected by shallow water; the effects are most apparent in Poole harbour, Southampton Water; the Eastern Solent and Portsmouth harbour.  In Poole harbour the flood stream runs for about 5 hours only, the ebb stream runs in two periods, separated by an interval of slack water, or even of weak flood stream, and has a total duration of about 7½ hours.  In Southampton water, the Eastern solent and Portsmouth harbour, these circumstances are reversed; the flood stream runs in two periods, separated by an interval of slack, or nearly slack, water, and has a total duration of about 7¼ hours; the ebb stream runs for about 5¼ hours only.  In Southampton water and off the entrance to Portsmouth harbour, though the durations of the streams are not affected, the ebb stream also runs in two periods, though less evidently than the flood stream.

The streams run directly through the Solent and cannot well be referred to as in-going and out-going, or as flood and ebb, for the in-going stream in the Western Solent is the out-going stream in the Eastern Solent, and the flood stream, which is actually the east-going stream, runs in a direction away from Portsmouth harbour.  The Solent streams are therefore called east-going and west-going, but these directions are general only; the east-going stream, for instance, runs north-eastward in Needles channel, but south-eastward in the eastern approach to the Solent and Portsmouth harbour.  The streams running into and out of Southampton water and Portsmouth harbour, which must be distinguished from the Solent streams, are called the flood and ebb streams

 
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