TIDE TABLES Torres Strait and Great Barrier Reef 2017 TORRES STRAIT AND GREAT BARRIER REEF TIDE TABLES 2017 Section one - Torres Strait - Hourly Predictions Booby Island Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Goods Island Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Turtle Head Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Nardana Patches Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ince Point Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Twin Island Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Frederick Point Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Poll Island Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Coconut Island Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Stephens Island Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Section two - Great Barrier Reef - Hourly Predictions Wideawake Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Pelican Island Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Leggatt Island Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Dent Island Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Thomas Island Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Section three - Great Barrier Reef - Prediction of high and low waters Cairns Jan / Feb / Mar / Apr May / Jun / Jul / Aug Sep / Oct / Nov / Dec Hay Point Jan / Feb / Mar / Apr May / Jun / Jul / Aug Sep / Oct / Nov / Dec Bugatti Reef Jan / Feb / Mar / Apr May / Jun / Jul / Aug Sep / Oct / Nov / Dec Section four - Torres Strait Tidal Stream Predictions Varzin Channel Jan / Feb / Mar Apr / May / Jun Jul / Aug / Sep Oct / Nov / Dec Harrison Rock Jan / Feb / Mar Apr / May / Jun Jul / Aug / Sep Oct / Nov / Dec Hammond Rock Jan / Feb / Mar Apr / May / Jun Jul / Aug / Sep Oct / Nov / Dec Nardana Patches Jan / Feb / Mar Apr / May / Jun Jul / Aug / Sep Oct / Nov / Dec Alert Patches Jan / Feb / Mar Apr / May / Jun Jul / Aug / Sep Oct / Nov / Dec The Australian Maritime Safety Authority acknowledges the assistance of the Australian Hydrographic Service in the preparation of these predictions and permission to reproduce the Hammond Rock stream predictions. Predictions for Cairns and Hay Point reproduced by permission of Maritime Safety Queensland This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without written permission from the Australian Maritime Safety Authority. Inquiries should be directed to: Public Relations, AMSA, GPO Box 2181 Canberra ACT 2601. NOTES ON PREDICTIONS Predictions are based on analyses of the following data sets: Station Data Base MSL Geographic Position Booby Island 1990 – 2014 2.426 10o 36' S 141o 55' E Goods Island 1990 – 2014 2.142 10o 34' S 142o 09' E Turtle Head 1990 – 2014 1.748 10o 31' S 142o 13' E Nardana Patches 2005 – 2014 1.786 10o 30' S 142o 15' E Ince Point 1990 - 2014 1.716 10o 31' S 142o 18' E Twin Island 1 year 74 - 75 1.694 10o 28' S 142o 26' E Frederick Point 1 year 74 - 76 1.806 10o 43' S 142o 35' E Poll Island 129 days 94 - 95 1.850 10o 15' S 142o 49' E Coconut Island 76 days 92 1.954 10o 03' S 143o 04' E Stephens Island 1974 – 1975 1.985 09o 30' S 143o 33' E Wideawake 100 days 05 - 06 1.566 13o 18' S 143o 48' E Pelican Island 1988 and 2003 1.910 13o 55' S 143o 50' E Dent Island 88 days 97 2.152 20o 22' S 148o 56' E Leggatt Island 174 days 95 - 96 1.700 14o 32' S 144o 51' E Thomas Island 62 days 94 2.330 20o 33' S 149o 07' E Cairns 28 years 85 - 13 1.730 16o 56' S 145o 47' E Hay Point 23 years 85 - 13 3.400 21o 16' S 149o 18' E Bugatti Reef 160 days 96 - 97 1.580 20o 05' S 150o 18' E Predicted heights are expressed in metres. Times are Eastern Standard Time (UTC+10). Zero of the predictions is approximately the level of Lowest Astronomical Tide. IN TORRES STRAIT THE ACTUAL TIDE MAY DIFFER CONSIDERABLY FROM THAT PREDICTED DUE TO METEOROLOGICAL CONDITIONS OR LONG AND SHORT TERM FLUCTUATIONS IN MEAN SEA LEVEL. REFER TO THE GENERAL INFORMATION SECTION FOR INFORMATION ON TRANSMITTING TIDE GAUGES. The predictions in this publication have been prepared by the Australian Bureau of Meteorology National Tidal Centre, copyright reserved. The Australian Maritime Safety Authority (AMSA) will not accept liability for any errors or omission contained herein. AMSA does not warrant the accuracy of the predictions in this publication. 5 1 TORRES STRAIT AND GREAT NORTH EAST CHANNEL General Information 1 Tide Gauges and Current Meter 1.1 Tide gauges which transmit real-time tidal heights on VHF channel 68 are operated by AMSA in Torres Strait. The Nardana installation also transmits tidal stream rates and direction. 1.2 Mariners are strongly advised to make use of this service as actual tidal heights may differ considerably from predicted heights due to meteorological effects and Mean Sea Level fluctuations. 1.3 Transmitting stations are located at:- Booby Island 10o 36' S 141o 55' E Goods Island 10o 34' S 142o 09' E Turtle Head 10o 31' S 142o 13' E Nardana Patches 10o 30' S, 142o 14' E Ince Point 10o 31' S 142o 18 'E 1.4 The Nardana installation includes an Acoustic Doppler Current Profiler which measures tidal stream rate and direction in mid-water column at a distance of 50 metres from the structure to avoid turbulence effects. 1.5 Stations are identified on Channel 68 by morse code identifiers transmitting in the following sequence:- Booby Island BB Goods Island GD Turtle Head TH Nardana (tidal height) NT Nardana (streams) NS Ince point IP B B = Dash G D = Dot T H N T N S I P 6 2 1.6 Examples of the format of the tide height broadcasts are shown below: Example 1- Positive Tide Height, Goods Island, 4.0 metres G D 4 . 0 Silence Tide Heigth Example 2 - Negative Tide Height, Ince Point, -0.4 metres I P ~ 0 . 4 Silence Tide Heigth Scale: Dot = 160 msecs Dash = 480 msecs Space = 160 msecs Silence = 3.0 secs Letter space = 0.7 secs Decimal point = 1.0 secs Minus sign = 1.5 secs (Warble) 1.7 The tidal stream information from Nardana has the station identifier (NS) followed by the rate of the stream in knots broadcast in dash / dot format. East-flowing streams are treated as positive and west as negative. West flowing streams are preceded by a warbling note. Examples as follows: Nardana east-going 3.2 knots Nardana west-going 2.5 knots ~ Nardana west-going 0.3 knots ~ Easterly flow is approximately in the direction 080 degrees true. Westerly flow is in the general direction 260 degrees true. Telephone link The real-time height and stream information from the five gauges is available by voice in English by phoning 07 4069 2821. 2. Unpredicted Influences on Tidal Levels 2.1 Tidal levels are subject to short and longer term fluctuations of MSL; these fluctuations can not be predicted in Torres Strait at this time due to the complexity of the tidal regime. 2.2 Tidal levels in Torres Strait may also be affected by wind-generated tidal surges. Easterly winds with strong velocities produce positive surges, with subsequent increases in sea levels, at Frederick Point and Twin Island, while negative surges are produced at Turtle Head, Goods Island and Booby Island. Westerly winds have the reverse effect. The highest recorded surge in a particular 14 month period of study produced an increase in tide of 74 centimetres at Booby Island. A negative surge of similar magnitude may be expected under particular meteorological and oceanographic conditions. 7 3 3. Tidal Streams in Torres Strait 3.1 Predictions are contained in Section 4. All predictions are based on recent continuous observations except for those at Hammond Rock which rely on observations from 1945. Attempts to obtain a reliable data set at Hammond Rock continue. 3.2 In 2009 spot observations at Hammond Rock, taken at times of maximum westerly flow, indicated that the actual rates were only slightly less than predicted. The maximum rate of tidal streams in Torres Strait shipping routes is experienced at Hammond Rock (10o 30' S, 142o 13' E). Rates of up to 8 knots can be expected in this location noting the tidal stream predictions are based on past and very limited data. Tidal streams in either direction will rapidly reach their maximum through a series of plateaus rather than traditional curve forms. Nardana Patches tidal streams appear to closely follow the predicted times and rates although the effects of the south-easterly trade winds will be clearly apparent. 3.3 Observations completed in 1998 indicate that the following may be experienced at Hammond Rock when strong south east winds pertain: – slack water periods will be very brief; – the change from west flowing to east flowing stream may occur half an hour to an hour later than predicted; – the change from east flowing to west flowing may occur half an hour to an hour earlier than predicted; and – at neaps weak predicted easterly flows may be overwhelmed by wind generated westerly flows.