Tides and tidal streams 1 lrg

Grunt Productions 2006
Tides and TidalTides and Tidal
StreamsStreams
Using Admiralty TidalUsing Admiralty Tidal
PublicationsPublications
A brief by Lance GrindleyA brief by Lance Grindley

“Everyone can just put down their loot and plunder
- Sven here has something to say to us all!”

NWC AssessmentNWC Assessment
 Award of MCA certification is subject toAward of MCA certification is subject to
successful completion of writtensuccessful completion of written
examination in “Tides and Times”.examination in “Tides and Times”.
 Criteria for evaluating competence -Criteria for evaluating competence -
“Calculations and measurement of“Calculations and measurement of
navigational information are accurate.”navigational information are accurate.”
 Use Tide Tables to work out height ofUse Tide Tables to work out height of
tide at any place or time a chosentide at any place or time a chosen
height is achieved.height is achieved.

Range of LessonRange of Lesson
 Calculating heights and depths fromCalculating heights and depths from
levels and datums.levels and datums.
 Calculating predicted heights for anyCalculating predicted heights for any
Standard Port (European and Non-Standard Port (European and Non-
European)European)
 Calculating predicted heights forCalculating predicted heights for
European and Non-European SecondaryEuropean and Non-European Secondary
Ports (including Solent)Ports (including Solent)
 Calculating tidal streams using tidalCalculating tidal streams using tidal
diamonds and Tidal Stream Atlasesdiamonds and Tidal Stream Atlases

IntroductionIntroduction
Basic principles of tides.Basic principles of tides.
The tide raising forces ofThe tide raising forces of
the Moon and the Sun.the Moon and the Sun.

The Earth-Moon SystemThe Earth-Moon System
Moon
Earth
Gravitational
Attraction
Barycentre

Daily Tidal PeriodDaily Tidal Period
Moon
Earth
Start - HW
+ 6 hours
+ 12 hours
+ 18 hours
+ 24 hours
+ 25 hours

Tidal PeriodTidal Period
 The Lunar Day lasts just under 25The Lunar Day lasts just under 25
hours.hours.
 In each period of 24 hours there willIn each period of 24 hours there will
be two HW and two LW.be two HW and two LW.
 Each HW and LW will occurEach HW and LW will occur
approximately 6 hours 10 minutesapproximately 6 hours 10 minutes
after each other.after each other.
 The predicted times of HW and LW getThe predicted times of HW and LW get
progressively later each day by aboutprogressively later each day by about
one hour.one hour.

The Sun-Moon SystemThe Sun-Moon System
New MoonNew Moon
Moon
Earth
Lunar Tide
Solar Tide

Full MoonFull Moon
Moon
Earth

First/Last QuarterFirst/Last Quarter
Moon
Earth
Moon

Spring and Neap TidesSpring and Neap Tides
 In each Lunar Month there will be a NewIn each Lunar Month there will be a New
Moon and a Full Moon.Moon and a Full Moon.
 At this period the range will be aAt this period the range will be a
maximum range which is called a Springmaximum range which is called a Spring
Tide.Tide.
 The Moon will also pass two period ofThe Moon will also pass two period of
quadrature and the range will be aquadrature and the range will be a
minimum which is called a Neap Tide.minimum which is called a Neap Tide.
 Tides of this pattern are called Semi-Tides of this pattern are called Semi-
Diurnal Tides and occur throughout theDiurnal Tides and occur throughout the
Atlantic region.Atlantic region.

Tidal PredictionTidal Prediction
 Admiralty Tide Tables (4 volumes)Admiralty Tide Tables (4 volumes)
 Volume 1 UK and Channel CoastVolume 1 UK and Channel Coast
 Volume 2 European and AtlanticVolume 2 European and Atlantic
WatersWaters
 Volume 3 Indian OceanVolume 3 Indian Ocean
 Volume 4 Pacific Ocean.Volume 4 Pacific Ocean.

Limits of Tide TablesLimits of Tide Tables

Heights and DatumsHeights and Datums
 All depths and drying heights areAll depths and drying heights are
measured from the Chart Datum.measured from the Chart Datum.
 Chart Datum is usually set at LATChart Datum is usually set at LAT
 Tidal levels LAT, MLWS, MLWN, MSL,Tidal levels LAT, MLWS, MLWN, MSL,
MHWN, MHWS and HAT are given asMHWN, MHWS and HAT are given as
heights above Chart Datum.heights above Chart Datum.
 All heights are measured from MHWS.All heights are measured from MHWS.

TidalTidal
LevelsLevels
andand
DatumsDatums
DATUM FOR HEIGHTS
DATUM FOR DEPTHS
LAND LEVELLING
DATUM

Tidal DatumsTidal Datums
MHWS
Chart Datum
MLWS
MHWN
MLWN
HAT
LAT
MSL

Mean Spring RangeMean Spring Range
MHWS
Chart Datum
MLWSMean Spring Range

Charted HeightCharted Height
MHWS
Chart Datum
Charted
Height
Height
above
waterline
Height of TideHeight of Tide
Height of MHWSHeight of MHWS
above Chartabove Chart
DatumDatum

Underkeel ClearanceUnderkeel Clearance
DraughtDraughtHeightHeight
of Tideof Tide
Charted DepthCharted Depth
Tide + Depth - DraughtTide + Depth - Draught
Chart DatumChart Datum

Minimum Clearance 2mMinimum Clearance 2m
DraughtDraught
MinimumMinimum
Charted DepthCharted Depth 2m minimum2m minimum

Masthead ClearanceMasthead Clearance
MaximumMaximum
MHWS
Charted HeightCharted HeightMasthead ClearanceMasthead Clearance
MastheadMasthead
HeightHeight

ExampleExample
 Port of MILFORD HAVENPort of MILFORD HAVEN
 Power cable with charted height 24mPower cable with charted height 24m
 Minimum charted depth 4mMinimum charted depth 4m
 Vessel details:Vessel details: - masthead heightmasthead height
22m22m
 - draught 6m.- draught 6m.
 Clearances:Clearances: - masthead 3m- masthead 3m
 - underkeel 2m- underkeel 2m

DiagramDiagram
Cable
Seabed
22m
6m Chart Datum
4m
HoT
MHWS
7m
24m
3m
2m
4m6m

Max/min height of tideMax/min height of tide
 Minimum HoTMinimum HoT = 6m+2m-4m == 6m+2m-4m = 44
metresmetres
 Maximum HoTMaximum HoT = 24m+7m-= 24m+7m-
(22m+3m)(22m+3m)
 31m - 25m =31m - 25m = 66
metresmetres
 Height of tide must lie between 4Height of tide must lie between 4
and 6 metresand 6 metres

The Tidal CurveThe Tidal Curve
Time
Height
of
Tide
Chart
Datum
HW
Predicted Height
LW
Range of
Tide
Duration
Rise of
Tide
LW
Interval
Height
of Tide

Express Range as PercentageExpress Range as Percentage
 Difference between the Mean NeapDifference between the Mean Neap
Range and the Mean Spring Range isRange and the Mean Spring Range is
100%.100%.
 Any range can be expressed as aAny range can be expressed as a
percentage increase from the MNR.percentage increase from the MNR.
 Example (Portsmouth) MSR 3.9m MNRExample (Portsmouth) MSR 3.9m MNR
1.9m1.9m
 Difference of 2.0m represents 100%Difference of 2.0m represents 100%
SpringsSprings

Range of 3.0m is 3.0-1.9/2.0 =Range of 3.0m is 3.0-1.9/2.0 =
1.1/2.0 = 55%1.1/2.0 = 55%

Hourly PredictionsHourly Predictions
 Found in ATT Volume 1 Part 1aFound in ATT Volume 1 Part 1a
 Eight ports are included:Eight ports are included:
 Plymouth; Poole Harbour;Plymouth; Poole Harbour;
Southampton; Portsmouth;Southampton; Portsmouth;
Rosyth; Liverpool; Avonmouth;Rosyth; Liverpool; Avonmouth;
St. HelierSt. Helier

European PortsEuropean Ports

 Admiralty Tide Tables Volume 1Admiralty Tide Tables Volume 1
(United Kingdom and Ireland)(United Kingdom and Ireland)
(Including European Channel Ports).(Including European Channel Ports).
 Admiralty Tides Tables Volume 2Admiralty Tides Tables Volume 2
(Europe excluding United Kingdom(Europe excluding United Kingdom
and Ireland) Mediterranean Sea andand Ireland) Mediterranean Sea and
Atlantic Ocean.Atlantic Ocean.
 Admiralty List of Radio SignalsAdmiralty List of Radio Signals
Volume 2 (Radio Time Signals).Volume 2 (Radio Time Signals).

Standard PortsStandard Ports
 List of ports inside front cover of ATT.List of ports inside front cover of ATT.
 Predictions are given in thePredictions are given in the OfficialOfficial
Standard TimeStandard Time for the country. (Thisfor the country. (This
happens to be Universal Time in the Unitedhappens to be Universal Time in the United
Kingdom.)Kingdom.)
 If necessary times must be adjusted forIf necessary times must be adjusted for
Daylight Saving Time (DST) usually oneDaylight Saving Time (DST) usually one
hour ahead of standard time.hour ahead of standard time.
 First page of standard port predictions willFirst page of standard port predictions will
be the tidal curve unique to that port.be the tidal curve unique to that port.

Tidal Curve - DoverTidal Curve - Dover
+1 +2 +3 +4 +5 +6HW-1-2-3-4-5
0 4 862
0 42 6
MEAN RANGES
Springs 6.0m
Neaps 3.2m
DOVER

Tidal Curve - SouthamptonTidal Curve - Southampton
+1 +2 +3 +4 +5 +6LW-1-2-3-4-5
0 2 431
0 21 3
MEAN RANGES
Springs 4.0m
Neaps 1.9m
SOUTHAMPTON

Tidal Prediction FormTidal Prediction Form
STANDARD PORT……………………TIME/HEIGHT REQUIRED…………
SECONDARY PORT…………………..DATE…..……….TIME ZONE……...
STANDARD PORT
TIMES HEIGHTS
HW LW HW LW RANGE
Seasonal Change
Seasonal Change
SECONDARY PORT
Duration/DST
Standard Port -
Secondary Port +

Portsmouth PredictionsPortsmouth Predictions
ENGLAND - PORTSMOUTH
Lat 50°48’N Long 1°07’W
TIME ZONE UT (GMT) TIMES AND HEIGHTS OF HIGH AND LOW WATERS YEAR 1998
JUNE JULY
Time m Time m Time m Time m
0338 4.1 0301 4.3 0458 0.8 0435 0.9
1 0911 1.4 16 0838 1.1 1 1144 4.8 16 1119 4.6
1819 4.1 1543 4.4 1723 0.6 1657 0.7M
2140 1.7
F
2109 1.3
M TU
• 2347 4.7
0427 3.9 0356 4.2 0015 4.8 0515 0.8
2 1008 1.6 17 0937 1.3 2 0539 0.8 17 1200 4.6
1715 4.0 1641 4.3 1227 4.7 1738 0.6TU
2244 1.8
SA
2213 1.4
TU
1803 0.6
W
0527 3.7 0459 4.1 0056 4.7 0027 4.7
3 1114 1.8 18 1044 1.3 3 0618 0.8 18 0555 0.6
1819 3.9 1747 4.3 1306 4.7 1242 4.7W
2354 1.9
SU
2324 1.5
W
1840 0.7
TH
1817 0.5
0638 3.7 0609 4.1 0133 4.7 0108 4.8
4 1221 1.8 19 1157 1.3 4 0654 0.9 19 0635 0.6
1924 4.0 1857 4.3 1343 4.5 1324 4.7TH M TH
1914 0.8
F
1857 0.5
0058 1.8 0037 1.4 0208 4.6 0150 4.8
5 0746 3.8 20 0722 4.2 5 0728 1.1 20 0716 0.6
1320 1.7 1307 1.2 1419 4.4 1407 4.7F
2019 4.1
SA
2003 4.5
F
1946 1.0
SA
1939 0.6
0151 1.6 0144 1.2 0243 4.5 0233 4.7
6 0841 3.9 21 0830 4.3 6 0802 1.3 21 0800 0.8
1408 1.5 1409 1.1 1455 4.2 1452 4.5TU
2105 4.2
SU
2103 4.6
SA
2019 1.2
SU
2023 0.8

STANDARD PORT
TIMES HEIGHTS
HW LW HW LW RANGE
Seasonal Change
Seasonal Change
SECONDARY PORT
Duration/DST
Standard Port -
Secondary Port +
Portsmouth
5 June
1100
A
0746 3.8m1320 1.7m 2.1m
0846A
10% Sp

Tidal Curve - PortsmouthTidal Curve - Portsmouth
HW +1 +2 +3 +4 +5-1-2-3-4-5-6
0 2 43 51
0 21 3
MEAN RANGES
Springs 3.9m
Neaps 1.9m
PORTSMOUTH
0846A
HW 3.8m
1100ALW 1.7m
3.3m

Secondary PortsSecondary Ports
 Times and heights are obtained byTimes and heights are obtained by
applying time and height differences toapplying time and height differences to
Standard Port predictions.Standard Port predictions.
 Obtain Port Number from GeographicalObtain Port Number from Geographical
Index at back of ATT.Index at back of ATT.
 Use Part II (page 300-323) to obtain:Use Part II (page 300-323) to obtain:
 Standard PortStandard Port
 Secondary Port time ZoneSecondary Port time Zone

Secondary Port differencesSecondary Port differences..

ExampleExample
 Find out what time the height of tideFind out what time the height of tide
will first rise to 5.0 metres atwill first rise to 5.0 metres at
WATCHET (531) on 26th July, 1989.WATCHET (531) on 26th July, 1989.
 Page 2A-102 for Secondary PortPage 2A-102 for Secondary Port
Differences.Differences.

Secondary Port DifferencesSecondary Port Differences
WALES; ENGLAND, WEST COAST
No PLACE TIME DIFFERENCES HEIGHT DIFF (METRES)
Lat Long High Water Low Water MHWS MHWN MLWN MLWS
N W Zone UT (GMT)
0200 0800 0300 0800
523 PORT OF BRISTOL and and and and 13.2 9.8 3.8 1.0
(AVONMOUTH) …(see page 158) 1400 2000 1500 2000
531 Watchet 51 11 3 20 -0035 -0050 -0145 -0040 -1.9 -1.5 +0.1 +0.1

STANDARD PORT
TIMES HEIGHTS
HW LW HW LW RANGE
Seasonal Change
Seasonal Change
SECONDARY PORT
Duration/DST
Standard Port -
Secondary Port +
Avonmouth 5.0m
Watchet 26 Jul A
0858 12.8m0328 1.1m 11.7m
92% Sp

High Water DifferencesHigh Water Differences
N W Zone UT (GMT)
0200 0800 0300 0800
531 Watchet 51 11 3 20 -0035 -0050 -0145 -0040 -1.9 -1.5 +0.1 +0.1
1400 - 0858 - 0800
-0035 -0050
-48 min

Interpolation of HW TimesInterpolation of HW Times
0800 0900 1000 1100 1200 1300 1400
Times of HW at Bristol
Watchet Differences
-50 min -35 min-48m --45m -43m -40m -38m

Low Water DifferencesLow Water Differences
N W Zone UT (GMT)
0200 0800 0300 0800
531 Watchet 51 11 3 20 -0035 -0050 -0145 -0040 -1.9 -1.5 +0.1 +0.1
0300 - 0328 - 0800
-0145 -0040
-0138

Interpolation of LW TimesInterpolation of LW Times
0300 0400 0500 0600 0700 0800
Times of LW at Bristol
Watchet Differences
-105m -92m --79m -66m -53m -40m

High Water CorrectionHigh Water Correction
N W Zone UT (GMT)
0200 0800 0300 0800
531 Watchet 51 11 3 20 -0035 -0050 -0145 -0040 -1.9 -1.5 +0.1 +0.1
12.8m
13.2m 9.8m
-1.9m -1.5m
-1.9m -1.8m -1.7m -1.6m -1.5m
13.2m 12.4m 11.5m 10.7m 9.8m

Low Water CorrectionLow Water Correction
N W Zone UT (GMT)
0200 0800 0300 0800
531 Watchet 51 11 3 20 -0035 -0050 -0145 -0040 -1.9 -1.5 +0.1 +0.1
1.1m

STANDARD PORT
TIMES HEIGHTS
HW LW HW LW RANGE
Seasonal Change
Seasonal Change
SECONDARY PORT
Duration/DST
Standard Port -
Secondary Port +
Avonmouth 5.0m
Watchet 26 Jul A
0858 12.8m0328 1.1m 11.7m
-0048 -0138 -1.9m +0.1m
0810Z 0150Z 10.9m 1.2m
0910A
92% Sp

Tidal Curve - AvonmouthTidal Curve - Avonmouth
+1 +2 +3 +4 +5 +6HW-1-2-3-4-5
0 4 862
0 42 6
MEAN RANGES
Springs 12.2m
Neaps 6.0m
AVONMOUTH
10 12 14
0910A0550A

Solent PortsSolent Ports
 Times and heights are obtained byTimes and heights are obtained by
applying time and heightapplying time and height
differences to PORTSMOUTH.differences to PORTSMOUTH.
 All ports 37 to 70 are listed onAll ports 37 to 70 are listed on
pages 323/324 (2A-90).pages 323/324 (2A-90).
 Curves listed on pages xxii to xxivCurves listed on pages xxii to xxiv
using separate curves for eachusing separate curves for each
group of ports.group of ports.
 Curves are based on Low Water.Curves are based on Low Water.
 Obtain differences in the normalObtain differences in the normal
way.way.

Stansore Point CurveStansore Point Curve
LW-1-3 -2-5 -4-7 -6 +1 +4+3+2 +6+5 +70 1 2 3 4 5
50 1 2 3 4
Bucklers Hard
Stansore Point
Lee
Folly Inn
Newport
Range at Portsmouth
Sp 3.9m
Np 1.9m

Lymington/Yarmouth CurveLymington/Yarmouth Curve
LW-1-3 -2-5 -4-7 -6 +1 +4+3+2 +6+5 +70 1 2 3 4 5
50 1 2 3 4
Lymington
Yarmouth
Range at Portsmouth
Sp 3.9m
2.6m
Np 1.9m

ExampleExample
 What time will the height of tide firstWhat time will the height of tide first
rise to 3.0 metres at STANSORErise to 3.0 metres at STANSORE
POINT on 2 June?POINT on 2 June?
 Portsmouth predictions LW 2140Portsmouth predictions LW 2140
1.7m, HW 0427 3.9m1.7m, HW 0427 3.9m

STANDARD PORT
TIMES HEIGHTS
HW LW HW LW RANGE
Seasonal Change
Seasonal Change
SECONDARY PORT
Duration/DST
Standard Port -
Secondary Port +
Portsmouth 3.0m
Stansore Pt 2 Jun A
0427Z 2140Z 3.9m 1.7m 2.2m
15%Sp

Solent Port DifferencesSolent Port Differences
ENGLAND, SOUTH COAST
N W Zone UT (GMT)
0000 0600 0500 1100
65 PORTSMOUTH and and and and 4.7 3.8 1.9 0.8
1200 1800 1700 2300
37 Bournemouth 50 43 1 52 -0240 +0055 -0050 -0030 -2.7 -2.2 -0.8 -0.3
38 Christchurch 50 43 1 45 -0230 +0030 -0035 -0035 -2.9 -2.4 -1.2 -0.2
39 Hurst Point 50 42 1 33 -0115 -0005 -0030 -0025 -2.0 -1.5 -0.5 -0.1
40 Lymington 50 46 1 32 -0110 +0005 -0020 -0020 -1.7 -1.2 -0.5 -0.1
43 Stansore Point 50 47 1 21 -0050 -0010 -0005 -0010 -0.9 -0.6 -0.2 -0.0
Isle of Wight
45 Yarmouth 50 42 1 30 -0105 +0005 -0025 -0030 -1.6 -1.3 -0.4 0.0
46 Totland Bay 50 41 1 33 -0130 -0045 -0040 -0040 -2.0 -1.5 -0.5 0.1
48 Freshwater 50 40 1 31 -0210 +0025 -0040 -0020 -2.1 -1.5 -0.4 0.0
51 Ventnor 50 36 1 12 -0025 -0030 -0025 -0030 -0.8 -0.6 -0.2 +0.2
53 Sandown 50 39 1 09 0000 +0005 =0010 +0025 -0.6 -0.5 -0.2 0.0
53a Foreland (Slip) 50 41 1 04 -0005 0000 +0005 +0010 -0.1 -0.1 0.0 +0.1
54 Bembridge Hbr 50 42 1 06 -0010 +0005 +0020 0000 -1.6 -1.5 -1.4 -0.6
58 Ryde 50 44 1 07 -0010 +0010 -0005 -0010 -0.2 -0.1 0.0 +0.1

Interpolation of HW TimesInterpolation of HW Times
0000 0100 0200 0300 0400 0500 0600
Times of HW at Portsmouth
Stansore Point Differences
-50 min -10 min-43m --37m -30m -23m -17m
0427
-20m

STANDARD PORT
TIMES HEIGHTS
HW LW HW LW RANGE
Seasonal Change
Seasonal Change
SECONDARY PORT
Duration/DST
Standard Port -
Secondary Port +
Portsmouth 3.0m
Stansore Pt 2 Jun A
0427Z 2140Z 3.9m 1.7m 2.2m
15%Sp
-0020 -0009 -0.6m -0.2m
0407Z 2131Z 3.3m 1.5m
2231A

Stansore Point CurveStansore Point Curve
LW-1-3 -2-5 -4-7 -6 +1 +4+3+2 +6+5 +70 1 2 3 4 5
50 1 2 3 4
Bucklers Hard
Stansore Point
Lee
Folly Inn
Newport
Range at Portsmouth
Sp 3.9m
Np 1.9m
2231A
0415A

Non-European PortsNon-European Ports

 Admiralty Tides Tables Volume 2Admiralty Tides Tables Volume 2
(Europe excluding United Kingdom and(Europe excluding United Kingdom and
Ireland) Mediterranean Sea and AtlanticIreland) Mediterranean Sea and Atlantic
Ocean.Ocean.
 Admiralty Tide Tables Volume 3 (IndianAdmiralty Tide Tables Volume 3 (Indian
Ocean and South China Sea) & VolumeOcean and South China Sea) & Volume
4 Pacific Ocean) (including TS Tables)4 Pacific Ocean) (including TS Tables)
 Admiralty List of Radio Signals VolumeAdmiralty List of Radio Signals Volume
2 (Radio Time Signals).2 (Radio Time Signals).

Standard PortsStandard Ports
 List of standard ports inside front coverList of standard ports inside front cover
of ATT.of ATT.
 Predictions are given in thePredictions are given in the StandardStandard
Time ZoneTime Zone for the country.for the country.
 If necessary times must be adjusted forIf necessary times must be adjusted for
Daylight Saving Time (DST) usually oneDaylight Saving Time (DST) usually one
hour ahead of standard time.hour ahead of standard time.
 Use standard tidal curve drawn forUse standard tidal curve drawn for
duration between 5 and 7 hours..duration between 5 and 7 hours..

Standard Tidal CurveStandard Tidal Curve
+1 +2 +3 +4 +5 +6HW-1-2-3-4-5
0
0
4
2
8
4
6
3
2
1
0
0
2
4
1
2
3
6
+7-6-7
10
5
12
6
14
7

ExampleExample
 Calculate the height of tide at 0900Calculate the height of tide at 0900
on 9th April at SINGAPORE.on 9th April at SINGAPORE.
 Page 2C-33 (Extract from Volume 3)Page 2C-33 (Extract from Volume 3)
 HW 1011 2.5m LW 0407 1.1mHW 1011 2.5m LW 0407 1.1m

STANDARD PORT
TIMES HEIGHTS
HW LW HW LW RANGE
Seasonal Change
Seasonal Change
SECONDARY PORT
Duration/DST
Standard Port -
Secondary Port +
Singapore 0900
-89 Apr
1011(-8) 0407(-8) 2.5m 1.1m 1.4m
6h 04m
-

+1 +2 +3 +4 +5 +6HW-1-2-3-4-5
0
0
4
2
8
4
6
3
2
1
0
0
2
4
1
2
3
6
+7-6-7
10
5
12
6
14
7
1011(-8)
2.4m

Seasonal ChangesSeasonal Changes
Usually caused by meteorological trends orUsually caused by meteorological trends or
effect of river water on height of tide.effect of river water on height of tide.
See notes on page 2B-7.See notes on page 2B-7.
ATT Standard Port predictions alwaysATT Standard Port predictions always
includeinclude expected seasonal changes so noexpected seasonal changes so no
correction is required.correction is required.
When comparing the standard portWhen comparing the standard port
predicted height with mean levels the effectpredicted height with mean levels the effect
of seasonal variations should beof seasonal variations should be removed.removed.

Having removed the effect of seasonalHaving removed the effect of seasonal
change for the standard port, the effect ofchange for the standard port, the effect of
seasonal change must be included in theseasonal change must be included in the
secondary port prediction.secondary port prediction.
Tidal prediction forms (box 6) should beTidal prediction forms (box 6) should be
used to remove standard port seasonalused to remove standard port seasonal
change (change sign) and include secondarychange (change sign) and include secondary
port change (box 11) to calculate finalport change (box 11) to calculate final
heights.heights.

 Method is similar to EuropeanMethod is similar to European
Secondary Ports but time differencesSecondary Ports but time differences
not interpolated.not interpolated.
 Use sinusoidal curves as for standardUse sinusoidal curves as for standard
port.port.
 Times zones do not need adjustmentTimes zones do not need adjustment
except for Daylight Saving Time (DST).except for Daylight Saving Time (DST).
 Seasonal changes are more likely andSeasonal changes are more likely and
should be incorporated.should be incorporated.
 Use standard tidal curve drawn forUse standard tidal curve drawn for
duration between 5 and 7 hours.duration between 5 and 7 hours.

ExampleExample
 Calculate at what time after 0600Calculate at what time after 0600
local, the height of tide will first falllocal, the height of tide will first fall
to 2.0 metres at BROTHERS LIGHTto 2.0 metres at BROTHERS LIGHT
(4766a) on 11th August?(4766a) on 11th August?

Brother’s Lt - DifferencesBrother’s Lt - Differences
SUMATERA, NORTH EAST COAST
No PLACE TIME DIFF HEIGHT DIFF (MTRS)
Lat Long MHW MLW MHWS MHWN MLWN MLWS
N E (Zone –0700)
4718 SINGAPORE (see page 111) 2.8 2.1 1.2 0.5
Mandol
4764 Bandong 0 32 103 18 -0007 -0007 +0.9 +0.5 +0.4 0.0
Gelam Strait
4765 Tanjungbalai 0 59 103 26 -0051 -0051 +0.1 -0.1 +0.1 0.0
4766 Kenipaan 0 55 103 20 -0035 -0035 +0.1 +0.1 -0.2 -0.2
4766a Iyu Kecil (Brothers Light) 1 11 103 21 -0108 -0035 +0.2 +0.1 0.0 -0.1
Seasonal Changes in Mean Level
No. Jan 1 Feb 1 Mar 1 Apr 1 May 1 Jun 1 Jul 1 Aug 1 Sep 1 Oct 1 Nov 1 Dec 1
4663-4686 0.0 -0.1 -0.1 -0.1 0.0 +0.1 +0.1 0.0 0.0 0.0 0.0 0.0
4695 -0.1 -0.1 -0.1 -0.1 0.0 +0.1 +0.1 0.0 0.0 +0.1 +0.1 0.0
4704 0.0 -0.1 -0.1 -0.1 0.0 0.0 0.0 0.0 0.0 +0.1 +0.1 0.0
4718-4749 +0.1 0.0 0.0 0.0 0.0 0.0 -0.1 -0.1 -0.1 0.0 +0.1 +0.1
4751-4763 +0.1 0.0 0.0 0.0 0.0 -0.1 -0.1 -0.1 -0.1 0.0 +0.1 +0.1
4764-4783 0.0 -0.1 -0.1 0.0 0.0 0.0 0.0 0.0 0.0 +0.1 +0.1 0.0
4784-4795 -0.1 -0.2 -0.2 -0.1 0.0 +0.1 +0.1 +0.1 0.0 +0.1 +0.1 0.0

STANDARD PORT
TIMES HEIGHTS
HW LW HW LW RANGE
Seasonal Change
Seasonal Change
SECONDARY PORT
Duration/DST
Standard Port -
Secondary Port +
Singapore 2.0m
-711 AugBrothers Lt
1335 1935 2.6m 0.6m 2.0m
+0.1m +0.1m
-0108 -0035 +0.2m -0.1m
0.0m 0.0m
1227 1900 2.9m 0.6m
6hr 33min

+1 +2 +3 +4 +5 +6HW-1-2-3-4-5
0
0
4
2
8
4
6
3
2
1
0
0
2
4
1
2
3
6
+7-6-7
10
5
12
6
14
7
1227(-7)
2.0m
1515(-7)

Tidal StreamsTidal Streams

Visual Evidence of StreamVisual Evidence of Stream

Sources of Tidal Stream DataSources of Tidal Stream Data
 Tidal diamonds on chartsTidal diamonds on charts
 Admiralty Tidal Stream AtlasesAdmiralty Tidal Stream Atlases
 Sailing DirectionsSailing Directions
 Tidal Streams in the Approaches to HMTidal Streams in the Approaches to HM
Naval Bases (NP 167)Naval Bases (NP 167)
 Gibraltar Straits Surface and Sub-Gibraltar Straits Surface and Sub-
surface Water Movements (NP 629)surface Water Movements (NP 629)
 Admiralty Tide Tables Vol III & IVAdmiralty Tide Tables Vol III & IV

Tidal DiamondTidal Diamond
201746Z
3.3

Tidal DiamondsTidal Diamonds
Tidal Streams referred to HW at PORTSMOUTH
Hours
Geographical
Position
50°33.9’N
1°29.2’W
50°35.9’N
1°22.9’W
50°30.4’N
1°16.6’W
50°33.5’N
1°16.6’W
6 094 1.9 0.9 129 1.3 0.6 084 1.2 0.6 072 2.3 1.2 -6
5 100 2.3 1.2 127 1.7 0.9 100 3.6 1.8 070 3.7 1.8 -5
4 102 2.7 1.3 125 1.8 0.9 100 4.5 2.2 080 3.3 1.6 -4
3 101 2.5 1.2 120 1.4 0.7 100 4.5 2.2 079 2.9 1.5 -3
2 102 1.8 0.9 109 0.7 0.4 100 3.5 1.7 077 2.4 1.2 -2
1 106 0.9 0.4 320 0.6 0.3 092 1.3 0.6 066 0.3 0.1 -1
High
Water
282 0.6 0.3 302 1.8 0.9 290 1.2 0.6 262 2.4 1.2 0
1 285 1.8 0.9 300 2.1 1.1 276 3.9 1.9 257 3.4 1.7 +1
2 286 2.3 1.2 300 1.6 0.8 276 4.3 2.1 252 3.8 1.9 +2
3 281 2.2 1.1 301 0.9 0.4 276 4.1 2.0 260 3.4 1.7 +3
4 283 1.6 0.8 290 0.2 0.1 276 3.1 1.5 255 2.3 1.2 +4
5 310 0.5 0.2 135 0.5 0.2 294 1.2 0.6 247 0.8 0.4 +5
6 090 0.9 0.5 129 1.1 0.6 068 0.7 0.4 075 1.6 0.8 +6
AfterHigh
Water
AfterLow
Water
Directionsofstreams(degrees)
Ratesatspringtides(knots)
Ratesatneaptides(knots)
D E F G

Limits Of Admiralty TidalLimits Of Admiralty Tidal
Stream AtlasesStream Atlases

Channel TS Atlas HW+2hChannel TS Atlas HW+2h

Solent TS Atlas at HWSolent TS Atlas at HW

ExampleExample
 What is the percentage of the MeanWhat is the percentage of the Mean
Spring Range and the predicted tidalSpring Range and the predicted tidal
stream in position 49stream in position 49oo
50’N 00150’N 001oo
15’W15’W
(North of Pointe de Barfleur) at 1400A(North of Pointe de Barfleur) at 1400A
on 27th May?on 27th May?
 Channel TS Atlas based on DoverChannel TS Atlas based on Dover
Time Height
HW HWLW LW Range
1157 6.9m1933 0.6m 6.3m
1257A 1400 is 1 hr after HW

Percentage of MSRPercentage of MSR
MEAN RANGES
Springs 6.0m
Neaps 3.2m
6.3m - 3.2m 3.1m
6.0m - 3.2m 2.8m
110%

1 Hr after HW DOVER1 Hr after HW DOVER

Dover InterpolatorDover Interpolator
0 02 04 06 08 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100
0 0 2 0 4 06 08 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100
COMPUTATION OF RATES
TIDAL STREAM RATE (in tenths of a knot): assumed to vary with range of the tide at Dover
Mean
Range
Dover
Mean
Range
Dover
METRES METRES
7
6
5
4
3
6.8
6.6
6.4
6.2
5.6
5.4
5.2
4.8
4.6
4.4
4.2
3.8
3.6
2.8
2.6
2.4
2.2
2
Neaps
6.8
6.6
6.4
6.2
5.6
5.4
5.2
4.8
4.6
4.4
4.2
3.8
3.6
2.8
2.6
2.4
2.2
7
6
5
4
3
2
Neaps
SpringsSprings

Calculation of RateCalculation of Rate
MEAN RANGES
Springs 6.0m
Neaps 3.2m
6.3m - 3.2m 3.1m
6.0m - 3.2m 2.8m
110%
Predicted Neap Rate 1.8 kts
Predicted Spring Rate 3.5 kts
Increase 1.7 kts
Multiply increase by percentage
1.7kt x 110% = 1.9 kts
Direction WNW Total rate 1.8 + 1.9 = 3.7 kts

NP 167 - PortsmouthNP 167 - Portsmouth

Any Questions?Any Questions?

Tides and tidal streams 1 lrg

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