A sub-tropical low north of the North Island scooted away to the SE over the weekend and as a result the long range E/SE swell is likely to be closer to 2ft than 3ft.
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The system reaches peak strength over the weekend in Tongan longitudes, with a long fetch of E'ly winds, but it is moving away as it deepens, which limits swell growth.
995 hPa low still sitting in the Central Tasman, but the supporting high pressure cell has slipped in underneath the low and as a result we’re seeing a slowly diminishing fetch and easing pressure gradients both in the Tasman and along the coastal fringe.
That low is expected to slowly drift and dissipate through the week, maintaining elevated surf through too mid-week with a very slow easing trend in place.
A secondary front pushing into the Tasman coalesces with a deepening low near New Zealand and the system then retrogrades back into the Tasman over an already active sea state delivering powerful S/SE swell before taking up residency in the Central Tasman for a few days next week with a slow, slow easing in big swells expected.
Following that a secondary front coalesces with the primary front to form a complex Tasman which is expected to occupy the Tasman for a meaningful period of time, even retrograding back towards the East Coast over the weekend. The result will be multiple swell pulses from the S to S/SE (some very significant) right through until mid next week.
Thursday is where things really get active. A deep Tasman Low will have been forming from Wednesday onwards, displaying a broad belt of S/SW winds that’ the entire length of the eastern seaboard, from the southern tip of Tasmania up to about Mackay.
I’m expecting a small, slow start on Saturday with residual energy from today, however by lunchtime...
Troughy remnants remain off the North Coast and South Coast interior and these troughs are expected to deepen and reform into another surface low through Fri into the weekend with another round of E/NE infeed swell and S swell although much more subdued than last weekends swell.
A trough line connected to the low remains angled SW/NE in the Tasman with a N-N/NE infeed along the trough line. With the movement of the low into the coast, winds on the southern flank are now out of the swell window so we’ll be relying on the NE infeed into the trough and potential small lows forming in the trough line for swells in the short term once the current S'ly swell fades out.