A strong, but decaying cold front tied to a mid-latitude low is pushing gales through a wide swathe of the lower Tasman, with a handy S swell now being generated for the region. A relatively weak high (1025hPa) is pushing though the Bight with a transitory ridge, quickly breaking down and tending N’ly mid week , before another mid-latitude low pushes through and brings a NW to W’ly flow across the weekend.
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A longer period swell originating from storm force winds around the parent low is then scheduled to arrive across Northern NSW on Wednesday.
The Tasman low is out of the swell window and a large high is now moving over Tasmania to take up position in the Tasman Sea at a southerly latitude typical of the high pressure belt under the La Niña phase of the ENSO cycle. The high will move E with a N’ly flow rapidly developing as pressure gradients get tightened by an approaching front, complex low and trough line.
Conditions should settle down quite quickly through the first half of the week as the rambunctious low which passed over Lord Howe Island on the weekend quickly scoots across to the North Island and beyond, generating some nice pulses of swell from fetches near the South Island and Cook Strait.
Complex and dynamic weekend ahead, with an upper trough, surface trough and front forming a surface low in the convergence zone off the North Coast. This low is expected to rapidly deepen through Sat.
The current pattern- with weak high pressure drifting across Central NSW and a soft ridge along the coast- will be replaced in emphatic fashion by a much stronger front and trough on Friday, forming a surface low off the Mid North Coast, anchored by a monster high moving into the Bight at the same time. Well to the south of that set-up will be a deep polar low and associated fronts with severe gales to storm force winds generating long period S’ly swells to make landfall early next week.
Not a great deal of action on the charts to start the last week of Winter. A strong high (1040hPa) is on the other side of New Zealand but pressure gradients in the Tasman are weak, with minimal swell energy being generated from that source. Later in the week, Tradewinds do poke their head up over New Zealand and generate some useful E swell.
Strong trades through the central and northern Coral Sea over the weekend will gradually extend south by late Sunday, nosing just far enough into SE Qld’s eastern swell window to allow for a minor increase in short range E/NE energy.
The current robust but compact low is driving near gales in a thin fetch adjacent to the Central/Mid North Coast, with a tail of weaker winds extending out into the Central Tasman, with the whole show moving eastwards quickly today. Another, much weaker front, pushes up the coast tomorrow before a large high pressure system sets up a ridge along the temperate to sub-tropical coast of NSW.
Synoptic charts this week look typical of a seasonal transition with mobile high pressure up at sub-tropical latitudes and a strong front poised to sweep into the Tasman with a robust low forming on the front line before rapidly shifting eastwards. Behind that typical seasonal pattern lurks signs of La Niña with a persistent trough line in the Coral Sea and a very strong high expected to track through the Southern Bight later this week.