Effective from: Wed 19 Jun '13, 09:15AM

Forecast prepared by Craig Brokensha
Next update Fri 21/6 5pm.

Previous day's summary:

A fresh pulse of SE groundswell filled in yesterday across the Sydney coast, pulsing to a solid 5-6ft across south facing beaches with the rare bigger bomb set at swell magnets. Conditions were clean during the morning before a freshening S'ly kicked up during the afternoon leaving the best waves to protected southern corners.

Today the groundswell has been replaced by a shorter-range S/SE swell with wave heights ranging between 3-6ft across the Sydney coast with the best conditions being found north of the harbour.

Swell events within the forecast period:

Large waves will continue across the coast through tomorrow and Friday owing to a broad fetch of strong to gale-force S/SE winds on the western flank of the Tasman Low responsible for the current swell episode, pushing up through the central Tasman Sea today.

Tomorrow should see open beaches persisting at 3-4ft with 4-6ft sets at south facing locations, but a much stronger S/SE groundswell is due on Friday. This will be linked to a broad fetch of severe-gale S'ly winds pushing up through the Tasman Sea this evening and tomorrow.

This swell should build strongly through the day Friday, reaching 4-5ft at open beaches during the day with the odd bigger bomb at swell magnets. The swell should then swing more SE into Saturday while easing from 3-5ft across most locations. From here on the SE swell will ease, signalling the end of the week long S-SE swell event from the Tasman Low.

Now, before we even get to see the end of the SE swell over the weekend, a new weather system will start to affect the coast. This will be in the form of a low pressure system deepening off the Central NSW coast as a surface trough drifting south from the Coral Sea feeds off a deep pool of cold air in the upper atmosphere.

The models are still divergent on the intensity and positioning of this system, with GFS leaning towards an East Coast Low, while ECMWF has a weak easterly dip. We'll probably see something in between, with building levels of E'ly storm-swell likely later Sunday, ahead of a larger pulse Monday. Check back here on Friday for a clearer idea on this system and the corresponding swell and winds.

Long term forecast (6+ days):
The longer term outlook revolves around the developments of the low pressure system off the East Coast over the weekend, so check back here on Friday for a better idea on what this system will bring.