From west to east, the stage is set
As the run of fun surf continues across the East Coast, keen weather watchers may have noticed some juicier developments in next week's forecast.
Apart from a couple of larger southerly swells, since May we've mostly seen small to moderate-sized events from the south and east, along with favourable winds. Next week's swell, however, looks to be more significant.
When looking at these scenarios on the long-term charts, we usually have to take them with a grain of salt, yet in this case there's reason to be more confident as the pre-cursor to the event is already moving across Australia.
More observant weather watchers may have picked up the initial source of this activity. That being, a strong mid-latitude low that formed just west of the Margaret River region last weekend.
The low brought strong to gale-force onshore winds, decent rainfall totals, and a stormy swell to SW WA yesterday, and it's currently clearing slowly to the east in a weakened form. The remnants of said low are now sitting just west of the Bight and it's the developments through today that will likely provide the catalyst for the weather system in the Tasman Sea next week.
A couple of shots of cold, polar air will be advected from the Southern Ocean, up and into the backside of the weaker low today and tomorrow. The cold air will then be transported slowly east-northeast across South Australia, Victoria, and then New South Wales later this week and through the weekend.
This upper cold pool will likely become separated and cut-off from the general zonal flow of cold air, meandering across New South Wales before finally moving offshore early next week.
At the surface level, the remnants of the aforementioned low at the beginning of the article will also drift east and move off the southern NSW coast as a trough. With an infeed of moist north-easterly winds from the Coral Sea and upper cold pool to feed off, the likelihood of a significant low pressure system is very high.
The only real questions are, where will it form and how strong will it be. The models are struggling to pick this at the moment, and the location will dictate the quality and local conditions when the developing south-east energy starts to muscle up.
The closer to the coast the low forms, the more rainfall and damaging the winds and swell will be, while a more distant Tasman Low will spare the coast mostly of significant ran but deliver a wider-ranging swell event.
What we can count on is that any low that develops will likely linger instead of being shunted off to the east. This is due to an upper level ridge (opposite to the Long Wave Trough) sitting across the Tasman Sea. The ridge will effectively cradle the low, helping to prolong the swell event and even nurture a cluster of events. This will have to be watched closely over the coming week and in the Forecaster Notes.
Sitting west of the upper level ridge will be a significant node of the Long Wave Trough, focussed across Western Australia and this in turn will bring a fresh dose of extra-large and windy surf to that region.
Check in Monday, Wednesday, and Friday for the updated Forecaster Notes over the coming fortnight, with greater detail provided on the coming swell events and local winds.