Weather analysis -Sydney Hobart

by Tommy Addis / Brett Filby on 28 Dec 2006
Tommy Addis is an expert meteorologist and navigator, last year winning the Transpac on the TP 52 Rosebud in his debut in that race. He is currently working with Roger ‘Clouds’ Badam analysing the weather for Team New Zealand America’s Cup challenge in 2007.

Here he gives his expert weather analysis of the 2006 Rolex Sydney to Hobart..


The early stages of this year's race were a classic example of a critical element of yacht racing - a gain hasn't been made until it has been consolidated!

Analogous to paper profits in share trading, a yacht cannot honestly say it is ahead of another until it has crossed its bow - whether that occurs on the finish line or at some stage before that.

Out of the start of this year's race there was a classic split in the breeze and a definite decision had to be made by every yacht - and it had to stand by that decision for quite some time! Offshore from the seamark meant more breeze, more positive current, more seaway and more right in the breeze direction.

Inshore from the seamark meant less current assist, less breeze and more left in the breeze direction especially in the afternoons with the sea breeze component.

Right hand air on the left side of the course and left hand breeze on the right makes it extremely costly to tack back to consolidate your position as the tack back to the opposition is very much headed compared to theirs. This has the effect of locking boats into their chosen side of the course until conditions changed.

Out of the start, the boats offshore looked very good - ABN Amro, Secret Men's Business and Merlin especially so. They had the extra power available to them but all the time - they were committed into their side as they had more west in the breeze than the boats inshore and a tack back to cross their inshore opponents would have been disastrous. Likewise, if an inshore boat wanted to get some of the action offshore, a tack out would have been just as costly due to their headed starboard tack.

The next shift however was to the right ahead of the next front, this would be felt mostly in Bass Strait and the far south coast so for the inshore boats, it was a case of hanging on and waiting for their turn - they would get the right shift before the offshore boats and also have a freer angle to sail across Bass Strait.

As it happened, the potential gains made by the offshore boats (which were significant) were wiped out eventually as the inshore boats reached across their bows finally consolidating a gain for them.

Once in the right hand shift, the next shift should be (and has been!) to the left as the following high could finally ridge up the NSW Coast and the low in the Tasman cleared away - this is starting to occur now and can be seen in this morning's quikscat pass.

Most boats in the mid-fleet are currently footing off on starboard tack, sailing towards the header to give them the lifted tack into Tasman Light. The whole race essentially has been like a giant 600mile windward leg of an everyday Windward/Leeward course with 2 major shifts determining the outcome but within that of course there is much detail, which can never be ignored!

That all gets people to Tasman Light in good shape - after that, it gets very tricky and very dependent of the time of day, tides etc as to how you get to the finish line from there. An early afternoon arrival at Tasman would generally be the favoured time but rules go out the window here in the generally softening breeze.

Differences in corrected times can easily be accounted for in this stage of the race.