We have a deep low (985hPa) adjacent to Tasmania and another attached low centre further E in the Tasman with the long E/NE infeed into this complex low gyre focussed near the west coast of the North Island and slowly sliding out of the swell window.
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The circulation in the trough line has increased wind speeds in the fetch as the air mass moves from high to low pressure. As a result we’ll see an increase in wave heights and period through tomorrow.
A trough is currently clearing the coast, expected to anchor a broad E’ly fetch generated by a monster high straddling New Zealand. This anchored trough fetch, or trough block pattern is favourable for swell production for almost the entire Eastern Seaboard and will come with mostly offshore winds until the weekend brings a more S’ly biased flow to temperate NSW.
An inland trough eventually clears the coast later Tues or Wed and the broad E’ly infeed into the trough transforms a typical but out of season tradewind fetch into a more broadscale “trough block” feature which will send swell to most of the Eastern Seaboard.
The “trough block” pattern mentioned on Wed looks to set-up as the clearing trough Mon sets up a long N-S oriented line in the Tasman to Coral Seas and focusses a long E’ly fetch through this vast area. Windspeeds are the limiting factor but we should see a steady increase in E-E/NE swell from Thurs into next weekend.
A low in the Tasman is moving north with a slingshot fetch of S-SE winds expected to rebuild wave heights from the S-SE later today and into tomorrow while a trough of low pressure in the Coral Sea is sending more E’ly angled swell into the sub-tropical Points. The combination of low and high pressure is maintain a firm ridge along the eastern seaboard with plenty of S-SE wind.
Although the constant S-SE winds will be problematic there’ll be heaps of swell as low pressure remains in the Tasman, with a slingshot fetch expected as the low moves N during the week.
Late afternoon is on target for a sneaky long range/long period pulse of southerly groundswell, sourced from a tight but intense polar low skirting the ice shelf this weekend.
Our benign outlook runs into the weekend and right through it so there’ll be a few days better suited for rockfishing/inshore diving ahead.
The Tasman Sea, by contrast, is looking very mellow with a weak high pressure cell over NSW and a few decaying remnants of the long lasting Tasman Low sitting near New Zealand. Those weak pressure gradients across our main S-SE swell window will lead to a very quiet week swell wise, with mostly offshore winds.