WEATHER WATCH - BY ROGER BADHAM

TUE 15   

INSTALLMENT  #1

It’s that time of year again and important to start thinking and planning – though not yet in any detail! Your real homework starts at the weekend or net week when there is some certainty in the forecast.


THIS YEAR
Same format as previous years – but a few changes. Same format with the outlooks – they will run up the start and on the morning of the start I will send notes etc – along with relevant charts and grib files by 6am’ish. I will have hard copy at the CYCA that morning from 8.45-9am and a computer if you need anything else on memory stick.

This year I have the current grib file – the actual current and not a forecast of the current. I believe that it is possible to subscribe to Tide Tech for a forecast grib file, and I will leave that to you - to figure out whether that was a good investment. I will be using GFS and EC models (models) and have both those grib files. I also have a high res WRF model with grib file – cost is an extra $50. With regards this hi res model -  I am not convinced that it will be that useful – but you won’t know unless you try it and find it helped, or did not!!  If I were doing the race, then I would probably not use it – but that does depend on the actual weather pattern for the race and that’s not yet a call that I would make – so when we are much closer to the start – I will canvas this option again as to whether it might be useful.

CURRENT
The current pattern at present do not look too complicated or interesting. Up until end of November, there has been a cold eddy off the central NSW coast – and that has pushed the main arm of the EAC well offshore. This is still the case and looks to be the case for the race. So the only current offering for the race is the secondary arm of the EAC around the warm eddy centred not too far offshore from Montague Island. So the favourable current is offering from around Ulladulla to Eden and pretty much down and just off the shelf. No reason to go well offshore – until down near Gabo, when that flow does head away to the SE and that maybe worth chasing – depending upon the winds at the time and how far east of the line you’d want to be entering northern Bass St.

OUTLOOK
TC Laurence, presently west of Darwin and tracking WSW towards the Kimberly coast pretty much holds the key for our weather from 23rd the 26th. The remnants of that TC are likely to be drawn into the central Australia and then interact with a Southern Ocean front. Obviously this system will have a great deal of cloud and rain with it and may well hold up and ‘complicate’ the movement of the front over SE Australia on Christmas eve and Christmas Day. And the intensity and movement of that front will in turn determine the pressure rises and thus movement of the following high pressure system as well as the intensity and duration of stronger W winds across Bass St.

Over the last 3-4 weeks the weather pattern for SE Australia has been very October’ish – with bouts of strong W flow over Bass St and rapidly weakening fronts and S changes on the NSW coast. This pattern looks set to continue through to the start of the race – but with the added complication of the ex-TC. The strong W winds over Bass St have been quite solid – call Wharro of you need an ‘on the spot’ report! S changes on the NSW coast are frequent but brief with the wind turning around in well less than 24 hrs.

MODELS
The GFS well and truly covers the race period and is NOT yet consistent. This morning it has a SE-NE/10-15 for Day 1 and N/25-35 for Day 2 and SW/20-25 for Day 3. The EC model does not yet cover the race period – it runs out on Christmas eve – but this model is playing more with the ex TC and develops a very wet front to cross the Sydney region on Christmas eve to early Christmas Day. It also ends with the promise of 1 to 2 days of solid W winds for Bass St – but in late December, it is very difficult for the strong W winds to last more than 2 days???

FORECAST
Back to NE on the 26th but with a further brief front (S-SE/20-25) possible on the NSW coast? WSW-SW/30-20-10 over Bass St on 27th  and NE-NW/10-15 on 28th and NW-W/10-20 29th. Very rubbery and probably very wrong.