Jimmy Cornell's World Cruising Routes , Queensland to New Caledonia advises best times April -May, mid-September to October he goes on to say, in part, that;

“This can be a difficult passage at all times because of the certainty of encountering contrary winds for at least part of the voyage, if not the whole of it. It is therefore important to wait for a forecast for westerly winds, which at least will ensure a speedy start. “

IMPORTANT: The Down Under Rally is not in the business of weather forecasting.
It is not my intention to frighten or disturb anyone however IT MUST BE understood that the passage to New Caledonia is expected to take between 5-7 days dependant upon the vessel and the conditions encountered.
A weather forecast is really only an INDICATION of what might be expected based on the information available at the time of the generation of the forecast and it therefore cannot be relied upon to be accurate. It is exactly what it is intended to be A FORECAST. This is especially true for the period after the first 72 hours has passed.

Our prior experience with this voyage

In June 2009 we departed Brisbane, Queensland and arrived in New Caledonia 6.5 days later having encountered 3.5 days of westerly winds of up to 30 kts and then 3 days of very light variable winds which necessitated our motoring / motor sailing for this period. As far as we are concerned this was an excellent voyage. (Bob McDavitt provided our weather routing for this voyage).

In April 2015 we departed Newcastle New South Wales, bound for Fiji but arrived in New Caledonia some 7 days later after what was less than a good voyage where we encountered conditions that we hope not to ever find ourselves in again ! This was neither the fault of either the forecast or the routing services and weather tools we used but rather a combination of several events that resulted in our encountering these conditions and a couple of poor decisions that I made such as choosing to depart from a port well to the south AND departing much too early in the year. As the saying goes: We Live , We learn!

In 2016, 2017 & 2018 & 2019 the Down Under "Go East" Rally departed the Gold Coast Queensland.

On each occasion the majority of the fleet completed the voyage in 5 1/2 - 6 days with the slower vessels arriving on day 7. Conditions encountered were as predicted by our weather router and PredictWind.

Weather Routing

We ALWAYS employ the services of a professional weather router to assist us in choosing our departure date based on what they interpret from the information available to them. 
As a participant in the Down Under Rally from Australia to New Caledonia you will be provided with the forecast, routing and any other relevant information in regard to the passage from Australia to New Caledonia, however it is the responsibility of the captain of the vessel to choose to depart or not based on his level of confidence and comfort with regard to the information that is provided to him.
The function of the weather router is to analyse the weather conditions, if the conditions appear to be similar to those the mariner requested, the mariner will be provided a route for the voyage to take advantage of the conditions and the changes that are expected during the course of the voyage.
Click here for an example of how a weather router can be of assistance both before and during a voyage. 

Those vessels that have the capability of receiving email offshore will be able to receive updates to the forecast and the suggested routing.
As well as employing the services of a professional weather router we will also be using Iridium Go & PredictWind software to generate our own weather forecasting & routing.
We will be comparing this information both before and during the voyage along with the weather routers previously supplied forecast.
During the voyage, we will be checking for any updates and changes to the forecast and the suggested route using our Iridium Go & PredictWind. 
For more information about Iridium Go & PredictWind click here.
The video below is a real time demonstration we did in 2018 whilst on passage from New Caledonia to Fiji of the PredictWind Offshore App being used in conjunction with an Iridium Go.

Disclaimer: The models used to generate forecasts & routing information follow the mathematical pattern that weather is a mix of pattern and chaos !
It must be understood and accepted as a condition of entry by all who participate in this rally that there is NO GUARANTEE that the weather conditions encountered will reflect those of our "wish list" 
It must also be understood & accepted as a condition of entry by all who participate in the rally that the Down Under Rally Pty Ltd & or John Hembrow personally cannot be held responsible for the conditions encountered during the voyage or the consequences of these conditions.

Other Weather Info

Viki Moore of Astrolabe Sailing recently share a post about Meteorology /Weather forecasts that readers of this page might also find interesting. You can view the post at: www.astrolabesailing.com/2016/09/26/meteorology-weather-forecasts