Lots of stuff to consider here... I will try to hit some of the queries.
Sailing to NZ from any of the usual tropical islands -- I haven't used the pilot charts
in a long time, for they seemed never to reflect the conditions that I experienced. But I am surprised that they don't mention that the Tasman is affected by frontal passages on a roughly weekly schedule. These vary in intensity, and tend to be milder north of ~28 S. They will typically be preceded by SE backing around through N and NW and followed by a period of SW. Duration and strength of the winds varies, but gale force is common and storm force not unknown. This pattern prevails in the winter months, and certainly continues into November. So, imagine my surprise to hear that the Pilots predict force 4 from favorable directions! Were it only so...
The official start of the cyclone season is 1 November, and many seem to feel that they must be in NZ or Oz in early October. There is always a mass exodus from Vanuatu
and NC in that month. The "Port to Port" rally leaves in late October if that sort of madness appeals. But, Ann and I rarely leave before mid to late November, and have stayed as late as early December. In general, the early cyclones don't impinge upon the route
between NC/VAnuatu and mid to southern Qld. On the other hand, a few years ago cyclone Xavier popped up in the mid Coral Sea
in mid October, and was tracking directly towards Luganville where we were. Wasn't predicted... big surprise, resulting in a fairly unpleasant beat in 35-45 knots to get to Port Sandwich (our choice of cyclone anchorages
in Vanuatu). So, there is always an element of chance in making one's plans. I would not presume to advise anyone on the best solution to the riddle.
But, going from the Sollies to Qld in December seems quite risky to me. While few full blown cyclones develop on that route
in that month, there are usually a series of lows that do form... often quite a few of them... and while not devastating, they would make for a very uncomfortable passage
. Further, by December the seasonal NE winds that sometimes blow along the north and central Qld coast are gone, leaving the persistent SE trades along the route south. While one certainly can make that trip, it isn't easy beating into 20-30 knots every day. Most "cruisers" motor
the whole way down the coast, at least as far as Gladstone.
Oh, as to leaving your boat in north Qld: Not many places to do that safely. Cairns would be the northernmost spot, and there the marinas
(at least the major one, Marlin marina) requires that if a cyclone comes along, all the boats evacuate to the mangroves. There is a well developed cyclone plan, but the evacuation requires someone to move the boat and secure it. Hard to do by remote
control! Gladstone is a possibility... better protected marina and no mandatory evacuation. We've left our boats there untended, albeit nervously. Bundaberg is a popular boat abandonment location, but IMO an unsafe one. The Bundaberg Port Marina is very exposed, both to storm seas/wind and the more devastating flooding. A lot of boats on the Burnett river were lost/damaged during last years cyclone/rain depressions.
By the time you get as far south as Moreton Bay things get a lot safer, and there are a number of nice marinas
that would love to have you leave your boat with them.
As to your route to the Coral sea
area -- so many islands, so little time!
We enjoyed both the Marquesas
and the Tuamotus both times we traversed the area, and of course the Societies are beautiful, if a bit crowded and touristy. We only visited Raratonga in the Cooks... interesting, but a very poor anchorage for yachts. Niue
is a great stop, weather permitting... and so on. I guess my overall advice would be to spend the greatest part of your discretionary time in the eastern part of the route, since it is easy to get back to NC, VAnuatu
and even Fiji
in a single
Leaving your boat in NZ after a summer cruising there would be a good move, too.
Finally, a good source for wx info is to subscribe to Bob McDavitt's free "Weathergram" via his website (sorry, no link available right now). Bob is a met officer in NZ and has been offering this service
for years. He also does wx routing for a fee as well, but the free bit is very useful for the route you will likely be travelling.
This has been a bit rambling, hasn't it? But, until you determine your starting point, it is all a bit moot, isn't it?
Anyway, hang in there and good luck searching, wherever you end up.