Submitted by Craig on Wed, 03/05/2014 - 13:20
South Australian Forecast (issued Wednesday 5th March)
Best Days: Thursday on the Mid, Saturday morning down South and then on the Mid into the afternoon, Sunday down South, Tuesday on the Mid Coast
A great day of waves was seen across both coasts yesterday with a fun small swell across the South Coast under morning offshore winds while the Mid Coast saw the arrival of a new W/SW groundswell, pulsing to a good 2ft with the incoming tide during the afternoon with glassy conditions.
Today a weak change has moved through creating poor conditions across both coasts with a drop in W/SW swell.
This week (Mar 5 - 7)
The Mid Coast will offer the best waves tomorrow as a new W/SW and SW groundswell fill in offering 1-2ft waves under offshore SE winds. The South Coast will offer much larger surf but poor conditions with the onshore SE breeze.
This mix of W/SW and SW groundswell was generated by a strong mid-latitude front pushing under WA earlier in the week (generating the westerly component) and then towards Tassie through yesterday and today (generating the south-west component).
Friday will only see tiny leftovers on the Mid as clean conditions continue, while the South Coast will remain poor with SE winds (possibly tending E/SE during the morning).
This weekend onwards (Mar 8 onwards)
The weekend is still looking great with the arrival of a long-range SW groundswell under favourable and improving winds.
The source of this swell is a vigorous polar low that fired up just west of Heard Island at the start of the week and has since moved east along the polar shelf while slowly weakening. The system is now south-southwest of WA and will continue east through tomorrow while continuing to weaken.
Satellite observations confirm the forecast fetch of 35-55kt winds (shown right) at the peak intensity of the low, with this fetch producing long-period fore-runners that are expected to arrive overnight Friday. The bulk of the swell will be in the 16s range, filling in strongly Saturday afternoon peaking during the evening before easing slowly Sunday.
Winds on Saturday as the swell builds won't be perfect for the South Coast and from the E/NE, favouring slightly protected locations. SE sea breezes will also spoil the strong afternoon kick in size. The Mid Coast however should offer tiny 1-1.5ft peelers Saturday afternoon with glassy conditions.
Sunday will be the day to head South with a drop in swell from a very inconsistent 3ft to occasionally 4ft across Middleton and 4-5ft at Waits under moderate to fresh N/NE winds. We'll probably see an afternoon glass off as well as winds tending variable into the afternoon ahead of an approaching change due Monday.
Longer term, an amplification of the Long Wave Trough will intensify just south-west of WA over the weekend and then push slowly east towards us next week. What this will effectively do is steer polar fronts up directly behind it (to the west), initially up towards WA (pictured right) before steering them through the Bight as it moves east.
This will result in a series of W/SW groundswells with an initial good pulse due Tuesday, reaching an inconsistent 2ft on the Mid Coast and building to 3ft at Middleton with 3-5ft sets out at Waits.
A secondary pulse is then due Wednesday and Thursday but this will be a mix of W/SW and SW swell similar to that due tomorrow. We'll look at this again on Friday though as well as the local winds.