General
Cook Strait is a natural wind funnel bordered by high geographic features on the North and South Islands and at times creates a formidable challenge for boats sailing to and from the South Island. The following information is provided to help you cross the strait safely.
Wind
Wind direction in Cook Strait is normally NW or S to SE. Storm force winds occur on average about 25 times a year. Gale force NW winds are usually very localised but S gales affect the whole strait. SE gales are more pronounced on the western side of the strait.
Tidal Streams
Tidal streams in Cook Strait generally flow towards the NW for 5 hours and SE for 7 hours, however they are unreliable and the surface currents are affected by prolonged periods of strong winds and the shoreline configuration which can cause counter currents if close inshore.
High water occurs on the western side of Cook Strait about 4 hours later than Wellington at spring tides and slightly less at neap tides. This difference causes the strong streams. The streams are stronger during spring tides, which occur at two-weekly intervals, when high water Wellington is about 0600 and 1800.
Tidal stream predictions for Tory Channel have generally been found to be very accurate.
Sea
Broken water is experienced in different parts of the strait. This is caused by the cold north setting bottom current being forced to the surface on meeting the steep slopes of submarine canyons, which will also cause modification
of the tidal stream. Broken water is also caused when the wind flow is against the tidal stream especially between Sinclair Head and Cape Terawhiti, off the eastern entrance of Tory Channel and in the vicinity of the Brothers Islands.
Sailing Instructions
The combination of broken water and strong wind gusts between Sinclair Head and Cape Terawhiti make it advisable to transit this section of the passage (commonly known as the RIP) at slack water. This section of your voyage is generally the most uncomfortable and should not be attempted by small craft or the inexperienced except in favourable conditions. Strong southerly winds with a SE setting tidal stream can make this area a real horror show and in the interests of safe boating and harmonious crew relations, should be avoided. The times given are assuming a speed of 6-7 knots.
Traveling Westbound
Leave Wellington to arrive at Sinclair Head 1 hour before HW Wellington. You will then have a favourable tidal stream across Cook Strait.
Alternatively, leave Wellington to arrive at Sinclair Head 1 hour before LW Wellington. You will have an adverse tidal stream across Cook Strait but this may be preferable in northerly winds. Tory Channel will be reached at slack water.
Traveling Eastbound
Leave Tory Channel 2 hours after the tidal stream commences setting E. You will have a favourable tidal stream in the Cook Strait – Cape Terawhiti – Sinclair Head area.
Alternatively, in southerly winds leave Tory Channel as the tidal stream starts setting W. You will have an adverse tidal stream across Cook Strait but this may be preferable in southerly winds. Cape Terawhiti – Sinclair Head area will be reached at slack water.
Clearing Marks
Thoms Rock
This is situated between Karori Rock and Sinclair Head and lies 0.35 miles (650 metres) outside a line joining these points. Rock hopping in this area is not advisable.
By Day – Keep Pencarrow Lighthouse visible through Sinclair Head until Karori Rock is open from Cape Koamaru
By Night – Keep Pencarrow Light visible (red or white) until Tongue Point Light changes from red to white
Sinclair Head
By Day – To pass about one mile off Sinclair Head keep Pencarrow Lighthouse (lower) and Old Lighthouse (upper) in line
By Night – Keep in the white sector of Pencarrow Light to pass 0.7 miles south of Sinclair
Checking on Tidal Set
By Day – Observe Karori Rock relative to Sinclair Head or Turakirae Head. Observe Tory Channel entrance relative to Mount Stokes
By Night – Observe Tory Channel Entrance Leading Lights
Tory Channel Eastern Entrance
Ships make frequent use of Tory Channel and you must keep clear of the mid channel at the eastern entrance when large ships are present. All ships transiting the entrance are required to give a 10-minute warning of this on VHF Channel 18 (Port Operations Channel). Whether a warning is heard or not, the entrance should be navigated with caution at all times.
Ferry and shipping timetables are subject to seasonal changes and skippers are reminded that they must keep clear of all shipping lanes at all times.
Marlborough District Council Navigation Bylaws 2002 Part 3.3 – Tory Channel, in Subsection 3 requires that ”… every ship whether inward bound or outward bound shall broadcast or cause to have broadcast a radio message giving 10 minutes warning of transit of the eastern entrance to Tory Channel and failure to do so is a breach of Harbour Bylaws. …radio reporting procedures for Tory Channel are to be broadcast on VHF Channel 18. This frequency is the Port Operations frequency…”
There are procedures for vessels transiting Tory Channel operating at less than 15 knots. The broadcast to all ships shall be based on the following criteria:
In Bound Vessels
When on an arc of 3 nautical miles to seaward centred on East Head Light make a broadcast on VHF Channel 18 advising of the intention to transit Tory Channel inward bound and providing the ETA at the Controlled Navigation Zone boundary as well as at East Head at the ship’s anticipated speed. Subsequent broadcasts, confirming pr amending ETA is to be made at intervals not exceeding 10 minutes.
All Ships Call Example:
All ships, all ships all ships. This is the vessel [name]. The vessel [name] is proceeding inbound to Tory Channel Entrance and has an ETA at East Head of [time]. I repeat, the vessel [name] proceeding inbound to Tory Channel Entrance and has an ETA at East Head of [time]. Vessel [name] is standing by on channel one eight.
Out Bound Vessels
When abeam of Te Uira-Karapa (Clay Point) East light, make a broadcast on VHF Channel 18 advising all ships of the intention to transit Tory Channel outward bound and providing the ETA at the Controlled Navigation Zone boundary as well as East Head, at the ship’s anticipated speed. Subsequent broadcasts, confirming or amending ETA is to be made at intervals not exceeding 10 minutes.
All Ships Call Example:
All ships, all ships all ships. This is the vessel [name]. The vessel [name] is proceeding outbound from Tory Channel Entrance and has an ETA at East Head of [time]. I repeat, the vessel [name] proceeding outbound from Tory Channel Entrance and has an ETA at East Head of [time]. Vessel [name] is standing by on channel one eight.
The above broadcasts may be repeated on VHF Channel 16.
Radio
Ships maintain a listening watch on the following frequencies:
- Within Wellington Harbour limits – VHF Channel 14
- Within Marlborough Harbour limits – VHF Channel 18
- Cook Strait – VHF Channel 16