Informally, May is the surfers' month here in Australia.

We expect to get a lot of swell, and that's because, on the East Coast at least, all our swell windows are open - to the north, the east, and the south. Late summer north swells are staggered with early winter souths as the seasons overlap.

This week is typical of May; the East Coast has been bombarded by swell, and from many directions.

Today, the East Coast received a large, long-period easterly groundswell generated by an extra-tropical low that developed north of New Zealand on the weekend.

As the surf subsides, we'll receive another dose of large easterly groundswell later this week, followed quickly by an oversized southerly swell. (Interestingly, the coming southerly energy will be created by a redevelopment of the same polar low that generated yesterday's swell in Western Australia.)

There are a few aspects to the coming easterly groundswell.

The first thing to note is the extra-tropical low that generated today's east swell will re-strengthen again this evening, however its new position means northern NSW and south-east Queensland will see the most benefit - the rest of NSW will be shadowed by the North Island of NZ. The new energy won't be as big as today's waves across southern NSW but still strong and powerful when the sets roll in.

The re-intensification of the low will see a more prolonged fetch of storm-force E/SE winds work on an active sea state, north-east of New Zealand. The system will even retrograde slightly, moving back to the west.

With 24 hours of storm-force winds projected towards the East Coast we'll see another large, long-period E/SE groundswell arriving Friday afternoon across northern regions, holding into Saturday morning.

As for size, this will be similar in size to the current swell, pushing to 6-8ft across most open locations with the odd cleanup possible at its peak, easing Saturday afternoon, and then down from 3-5ft Sunday.

Further south, the size is tricky to estimate with Sydney likely to see swell sneaking around the North Island but arriving very late Friday, possibly reaching 3-5ft, but coming in at 4-5ft Saturday morning, then easing steadily.

However, of greater importance to the southern NSW coast, will be the oversized southerly swell which will develop at the same time. Told you there was a bit on, didn't I?

The southerly swell will be the product of an intense Tasman Low, which will project a broadening and strengthening fetch of southerly gales up the whole East Coast through Friday.

The swell will jump rapidly in size on Friday afternoon across the southern NSW region, likely reaching 8-10ft by dark across south-facing beaches, peaking Saturday morning to 10-12ft.

And that's not all...

On Saturday, a secondary, stronger burst of severe-gale S/SE winds on top the active sea state in the Tasman Sea will generate a reinforcing, oversized S/SE groundswell for Sunday, keeping 10-12ft waves hitting regions from about Ulladulla to Newcastle.

Further north we'll see the first pulse of oversized S'ly groundswell coming in around 10-12ft across the Mid North Coast magnets on Saturday morning, arriving a little later further north but in by midday, dropping off temporarily early Sunday ahead of the secondary pulse of S/SE groundswell back up to 10ft+ through the afternoon, easing slowly Monday.

The only issue with the coming south swells will be the local winds, and with the size, options will be severely limited. Strong to gale-force S/SW-S winds are expected Friday afternoon, strong and S/SW Saturday morning, shifting a touch more southerly into the afternoon. Sunday will remain windy with winds possibly tending more SW in select locations through the morning but remaining mostly fresh to strong from the S/SW. Fresh SW tending S winds will play out as the large S/SE groundswell eases Monday, likely cleaner Tuesday morning.

Keep an eye on the regional Forecaster Notes and graphs here:

Click for Swellnet's Northern Beaches Forecast Page
Click for Swellnet's Ballina Forecast Page
Click for Swellnet's Gold Coast Forecast Page