One of the toughest passages to figure out weatherwise is from the tropical islands of the South Pacific to New Zealand. There are several hundred boats getting ready to depart Fiji and Tonga just about now, and they are all discussing strategy, watching faxes, and checking their boats. Here’s an exchange of e-mails between a cruiser in Tonga, SetSail’s Steve Dashew, and Bob McDavitt, the ultimate South Pacific weather guru (who works for the New Zealand Met service).
One of the toughest passages to figure out weatherwise is from the tropical islands of the South Pacific to New Zealand. There are several hundred boats getting ready to depart Fiji and Tonga just about now, and they are all discussing strategy, watching faxes, and checking their boats. Here’s an exchange of e-mails between a cruiser in Tonga, SetSail’s Steve Dashew, and Bob McDavitt, the ultimate South Pacific weather guru (who works for the New Zealand Met service).
Email from Cruiser
Steve: I passed along your regards to Bob McDavitt, and he sends his back. His comments about strategy (I sent him yours) are attached below.
How’s the World Series? I wasn’t sure if you’re a loyal S Cal fan or maybe a Giants fan?
Heading south from Vava’u to Ha’apai tomorrow. Should leave Tongatapu in the first few days of November, windows permitting.
Regards and thanks…
Bob McDavitt’s Email
Hi there to you (and regards to Steve of the Dashews next time you email him).
I’m flattered by Steve’s confidence in me. All I do is convert the models back into text for the sailor. Sometimes I can comment on how the model handles the situation – and I’ve seen certain things happen a few times so I have experience on my side. Yes, if you have access to sat imagery you learn to respect baroclinic leaves. If you have access to 500hPa you learn to check if for first signs of trouble (but often it gives you false alarms). If you only have MSL maps (like most sailors) you carry ideas in your head such as the storm of ’92 and bent-back warm fronts. One feature that I keep asking sailors to be wary of is the “squash zone” but with you I’m preaching to the the converted. Steve’s put squash zones in his book (Mariner’s Weather Handbook), and this makes his book the FIRST text book in the world that mentions these easy-to-spot nasties.
Enough talk – for broad scale “weather windows” and for my ideas on what to avoid you have my weathergrams.
Strategy: Jim Lott (a chap I know now high up in our Maritime safety assoc.) advocates the choice that Steve offers. It’s good for fast boats…means you have trade winds to start with and northerlies as you approach NZ. The time it takes for an average High to cross the Tasman/NZ area can be about 5 to 7 days and then this strategy works well. Two problem areas. If the High is too-high (over 1030) then the trade winds at the start of your voyage are going to be over 25kt and swell over 2m (a squash-zone). And, second, towards the end of your voyage its a race between your landfall and that of the next front (racing across the Tasman Sea following the high)…and if it’s the first time you’ve arrived in NZ it isn’t nice to try to make land fall in a grotty front – and all the fronts at this time of the year are followed by strong west to southwest winds, so there is little saving grace in this strategy.
An alternative to consider, and one that I recommend to the 5 to 6kt boats, but will work for you as well, is to treat the voyage as an adventure, and time it so that you go thru a front mid-voyage at about 30S. This has the following advantages: You get to leave the tropics is pleasant moderate E to NE winds. Then you have your adventure at sea, the front tossing you about a bit (but at 30S these fronts are not so bad)…maybe a day of two of motor sailing into yukky SW winds, then the conditions relax and you have good visibility as you approach NZ (in the following ridge, maybe 4 days away to the next front).
Spacing between fronts is currently about 4 to 6 days (shorter than the normal 5 to 7), but under my alternative strategy this still gives you about 3 to 4 days to get from 30S to landfall, and under Jim Lott’s strategy you have 1 to 2 days (on average).
Anyway let me know when you are about to go and I’ll be able to do a voyage forecast. – Bob
Further Comments by Steve Dashew
Re Bob’s comments, he is 100% correct. Whatever you do, try to avoid making your first landfall in nasty weather. Entrance to the Bay of Islands can be confusing, even with electronic charting, and if it is raining hard the radar won’t be much help due to rain clutter. So, if you are going to get nailed, best to do it well offshore where you have room to maneuver.
Squash zones he refers to are always more of an issue in that part of the world than anything else, and especially high central pressures for the highs are a good signal.
The real key is the boat speed you can average. The boat can usually do more than the crew. Assuming you maintain speed by motoring in light, or upwind, on a normal year you ought to be able to do the trip in five days and some hours. But that will require some pushing.
Once again, avoid the temptation of trying to close with the New Zealand coastline if getting in ahead of the weather is not 100% certain. The risks are usually much less riding the weather out offshore. And you will be getting updates from Bob, and he will know the timing of what is coming, so he can advise.
Have a safe trip. New Zealand will be lovely when you get there, and the fresh bread and veggies will have you fat and happy in no time! – Steve
Additional Resources
Find out more about weather analysis and tactics in the following books:
Posted by Sarah.Dashew (November 14, 2002)
