A dual-centred high straddles New Zealand with an elongated monsoonal low pressure trough located in the Coral Sea and extending into the near South Pacific. This is creating a long and broad E’ly fetch which is slowly extending southwards. As we near the end of the week, a more discrete surface low hives off the end of the monsoonal low pressure trough and retrogrades back into the Tasman Sea as it intensifies, generating large E’ly swells over the last days of 2022 and first days of 2023.

The broad pattern will be setting up by Boxing Day with a dominant, slow moving high in the Tasman and low pressure expected to form along the monsoon trough line in the Coral Sea and in the South Pacific near the North Island. That will see at least dual swell producing fetches aimed at the Eastern Seaboard, favouring our subtropical region for most size.

The combination of a Tasman low and strong high moving through the Bight has supplied a stack of S swell to the f/cast region since late last week, with an intensification and N’ward movement of the low upping the size and local winds through today on the MNC, and across the rest of the region through tomorrow. Pressure gradients will now slowly ease as the low starts to dissipate and the strong high weakens as it moves South of Tasmania through tomorrow.

The main synoptic feature for the short term period is a developing complex Tasman Low that'll spin up east of Bass Strait overnight, and reach peak intensity on Friday, but actually remain active within our swell window until next Wednesday.