We’re smack bang in the middle of winter, yet instead of writing up an analysis article on a big Southern Ocean cold outbreak, it’s the opposite with a near-record breaking high pressure system due to setup across south-eastern Australia’s prime swell window.

For surfers, low pressure systems might get the bulk of our attention, yet lately the highs have been making the news. Largely, this has been the result of the jetstream splitting over the Indian Ocean, which in turn results in anomalous, slow-moving highs over the continent. Without an upper air stream to 'nudge' it along the high parks itself and becomes a blocking high.

The significance of the coming blocking setup can be put into perspective, with it forecast to get very close to the highest ever recorded pressure in Australia. That happened in Launceston, Tasmania, on June 7, 1967 with a reading of 1044.3hPa.

Both major global weather forecasting agencies GFS (American) and ECWMF (European) have the surface pressure hitting 1044hPa across Tasmania this Thursday and possibly again on Saturday.

Mean sea level pressure anomaly (GFS) for this Thursday, with parts of Tasmania possibly reaching 1044hPa

Regardless of whether the pressure breaks the record or not, the influence on the coming fortnight of surf will be felt far and wide.

For South Australia and Victoria, out of season and persistent winds from the northeastern and eastern quadrants respectively, are due along with no significant swell sources. This will be thanks to the self-described blocking effect the high will have on approaching frontal systems from the Indian Ocean, deflecting them southeast, towards the polar shelf.

While poor for the Surf Coast, more exposed locations should see a good run of surfable days which is rare during winter.

It'll be all about the beach breaks in Victoria (Arklay)

It’s also worth noting that with the significantly higher than normal sea level pressure, we’ll see accordingly lower tides. This is thanks to the inverse barometer effect with the sea level depressing 10cm for every 10hPa increase in pressure above the ‘normal’ 1013hPa. For Tasmanian locations, the decrease in sea level will be a very noticeable 30cm, 25cm+ across Victoria and between 20-25cm in Sydney and surrounds.

Margaret River will also benefit over the coming week as the western arm of the high brings offshore winds along with large surf from the frontal activity projecting from the Indian Ocean. This will turn pear shaped from the weekend, however, as the high shifts a bit more east, opening the region to poor, north-west winds.

On the East Coast, we’re currently seeing the eastern arm of the building high bringing polar air, showers, and varying levels of south-southeast swell that will clock more easterly next week and beyond as the high shifts further east into the Tasman Sea. Onshore winds will present a problem for much of the coast.

The strong and slow movement of the high will itself generate a prolonged, moderate-sized easterly trade-swell event, but as a bonus, increasing tropical activity in the Coral Sea looks to super-charge the fetch, generating larger surf later next week onwards.

Winds initially look troublesome along with heavy rain but we can expect an inland trough to migrate eastward and offshore sometime over the weekend of the 14/15th, bringing cleaner conditions and drier weather.

July 2022 also saw a deepening tropical low generating strong, out of season easterly swells (Brokensha)

One final point worth noting is where the high's eastern influence lies, and the low pressure activity beyond it. With the high stretching from Western Australia to New Zealand, a corridor of low pressure is open up NZ's east coast, with a series of significant polar storms firing up the slot. Right in Teahupoo’s prime swell window.

We’re looking at a large to possibly extra-large southwest groundswell event for mid-late next week, just a few weeks out from the Olympics which kicks off on the 27th of July. At this distance, it'll likely be beyond the realm of paddling but will capture the eyes of the world - not to mention the Olympic surfers.

Severe-gale to storm-force fetch aimed squarely at Tahiti and namely, Teahupoo

Keep an eye on the comments below for running updates on how this significant synoptic event plays out.