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Strategies for both directions

Feb 27, 2014

From Tonga to NZ: The most eastern departure point has some advantages and some disadvantages. From here we are looking to leave in the top of a high pressure as the wind swings from southeast towards the east. But being so far east means that once the wind is in the east, the high-pressure system below is also well east and you will only have its influence for a short time. The advantage is that you can use the Minerva Reefs as a stop off point if required and sit for the next window.

From Minerva you are only 800 miles to NZ; at an average of 5.5 knots, or 130 miles per day, this will take five to six days. Again it’s likely you won’t be able to do this in one weather system so you need to plan to have a frontal system somewhere along the way. This is going to have less punch if you are still north of 30° south. With the wind direction changing to west and southwest behind the front, the plan is to have put in enough westing so that you can ease sheets for the last leg into NZ.

We usually plan to aim for a spot directly north of North Cape, New Zealand’s most northerly point, at 30° south. This means quite a dogleg from Tonga, but is well worth the effort. If things change as you head south then the strategy can be changed. If you do decide that the high is moving slowly enough to change your mind and head straight for NZ, make sure you can get there before the front comes through, because those lovely NW winds you are enjoying will be right on the nose after the front passes. You are also likely to get an uncomfortable 18 hours as the front passes. It’s this decision to take the shortcut that causes most of the horror stories you hear about.

So in a nutshell, leaving Tonga, if you plan to stop at either North or South Minerva (North is a more secure anchorage) then wait until a high pressure (of around 1020 to 1025 hectopascal [millibar] central pressure) is giving an easterly flow. You should be two to three days to Minerva with the wind tending northerly when you get there. Because you will be looking to put some westing in on the next leg, you can leave Minerva as the next high arrives when the wind is still in the southeast. Your progress and how fast the high is moving will dictate your strategy as you progress south. Remember it’s better to take a front at 30° south even if you have to heave-to for a day and wait; better still, use the time to get west. Remember the old expression, west is best.

From Fiji: On the other hand, the trip from Fiji doesn’t have the advantage of a stop on the way and is the longest of the passages at 1,260 miles, so you will need to leave a little earlier as the high starts to fill in; you are still looking for a high of around 1020 to 1025 hPa central pressure. This will undoubtedly mean leaving Fiji in a little more wind than most would like, but again you will want to get westing in from here too, so ease those sheets and go for it. There is quite likely to be a squash zone along the coast of Viti Levu if you are leaving from the Lautoka area; this usually starts to drop 12 to 18 hours out.

By leaving on the leading edge of the high-pressure system you are also more likely to run through the middle of the high as you progress south where winds will be light. Your strategy forward from here will be dictated by your use of the motor. If you have plenty of diesel and don’t mind the donkey clattering away, put pedal to the metal and start heading for the same point as described above — 30° south, directly north of North Cape. If the high is slow and you will make it in before the next front then great, go for it. You should get strengthening northerly and northwesterly winds on the back of the high. Remember when it swings northwest, the front is imminent.  

Regardless of how you think you are doing, don’t vary your approach too much. If you want to cut the corner and you feel you have the time, change your waypoint to make North Cape directly. The fronts have a tendency to jump up from down south very quickly; if you are hugging the Northland coast by then you will be in relatively protected waters.

From Vanuatu and New Caledonia: These departures can be regarded as having the same strategy. Leaving from Port Vila, Vanuatu, unless you wait for easterlies (when the high is directly below) you will be hard pressed to get past the Isle of Pines, New Caledonia, on port tack. From there look to head for Norfolk Island.

There is no need to be hard on the wind here as the high will go through and give northeast, north, and then northwest winds before the next front. It is only 415 miles from Norfolk to North Cape, and we have waited here for systems to pass, then reached into NZ with west and southwest winds on the beam.

From New Zealand to the islands: These passages are easier than coming south. The ideal timing is to leave on the back of a low-pressure system, once the associated frontal band has gone through. This will put you in a disturbed southerly or southwesterly flow on the leading edge of the next migrating high pressure. The intensity of the high will dictate the winds you can expect. Aim for one with a central pressure of 1020 to 1025 hPa to get 18 to 25 knots of wind.

Your destination and the speed of the high will dictate your strategy after the first four days.

To Tonga, current also plays a part. If you’re heading there in May, you can expect a counter-current running south along the western side of the Kermadec Islands. With a southerly wind, this area — nicknamed the “South Pacific washing machine” — sets up short, steep seas and is best avoided. Shifting your course to the west of the rhumb line and heading for the Minerva Reefs will get you out of this. It will also put you in a favorable current heading north once you are clear of the North Cape of NZ. All good news. As above, Minerva is worth a stop and is a good place to wait for the next system if it catches up to you before you reach Tonga.

For Fiji, the simplest option is to follow the rhumb line. You enjoy the favorable current upon leaving NZ and you should be able to make it north of 30° south before the next frontal system passes. Alternatively, you can make for Minerva and then enjoy a more downwind run to Fiji afterwards.

Vanuatu and New Caledonia share the same solution. As they are farther to the west than Tonga and Fiji, they are already in the new high-pressure system when you are just leaving NZ. This means there is less time available before the next low and trough moves through. Again, get your northing in first so you are close to or above 30° south on the front’s arrival; the farther north, the less effect you’ll get.

Expect an area of lighter winds before the next high establishes. Keep in mind that the “V” behind one system and before the next is often an area where you will find troughs, many of which are not forecast.

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John and Lyn Martin have spent the last 20 years and 100,000 miles exploring the SW Pacific on their boat Windflower, a 43-foot Hartley Fijian sloop. In 2007 they took over the Island Cruising Association, running annual rallies to and from NZ and the islands — www.islandcruising.co.nz.
 

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