We are now on the cusp of a low pressure event as a complex inland trough of low pressure forms a new low off the Central NSW Coast, backed by an advancing strong high pressure cell.
Yet another inland trough forms an interior low mid-week, likely in Southern NSW, and this low is looking like a solid S-SSE swell producer as it moves offshore Wed/Thurs and becomes cradled by a strong high moving well south of the Bight. It’s not the type of pattern we would expect to see in late Sep, but with so much La Niña mediated troughiness in the Tasman, it’s just been a matter of time until something kicked off.
Models are now starting to firm on quite a significant swell producing system as the low moves offshore and a strong high moving all south of the Bight offers a supporting pressure gradient squeeze on the Western flank of the low.
The complex low and huge trough line (extending across most of Australia!) are still tracking across the interior as forecast, with a high in the Tasman generating a NE flow across the majority of the Eastern Seaboard. The pressure gradient is tightened as the low approaches with an increase in NE winds and swell expected through the end of the week.
We have a typical looking Spring pattern with a weak high over the NSW interior and some flabby fronts passing South of Tasmania. An approaching trough series and inland low adds action mid-week as it tightens the pressure gradient with a more southerly located low, developing a N’ly fetch off the NSW Coast and another round of chunky NE windswell.
Still, no major change to the weekend f/cast. A complex low linked to multiple troughs and cold fronts is now approaching from SW of Tasmania. A main coastal trough linked to an Indian Ocean NW cloud band is clearing the area with a mostly offshore flow across the weekend and no major swell sources on tap.
Typical Spring pattern with a slight La Niña/IOD twist unfolding at present. A large high is now moving into the Tasman, directing a N’ly flow along most of the Eastern seaboard. That flow intensifies in response to an approaching series of troughs and a complex low in the Bight.
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.
Next week looks typical of Spring with a series of strong fronts transiting through our south swell window, although at somewhat low latitudes.
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.