Subtropical low to bring heavy rain, strong winds and high seas

A subtropical low moving towards New Zealand is forecast to bring heavy rain, strong winds, and large swells across much of the country starting midweek and intensifying by Friday.

Weather Watches Issued for Northland

Weather watches have been issued for Northland, lasting from Wednesday through Friday, due to forecast heavy rain and severe easterly gales. MetService meteorologist Alanna Burrows stated that these watches are “just the beginning,” and that more watches and warnings are likely as the system approaches.

The heavy rain watch for Northland is in place for 53 hours, beginning at 10 a.m. Wednesday. A strong wind watch has also been issued for the region, lasting 48 hours from 6 p.m. Wednesday to 6 p.m. Friday.

System to Spread Southward

Overnight Wednesday into Thursday, the system is expected to move further south, bringing rain to Auckland, the Coromandel Peninsula, and northern and central parts of the North Island. By Friday, heavy rain is expected to extend into the upper South Island, including Nelson/Tasman, with potential rain also for Westland, Bay of Plenty and northern Gisborne/Tairāwhiti.

Strong winds may also affect parts of Taranaki, inland central North Island and Banks Peninsula by Friday.

Potential for Tropical Cyclone Development

The system had a moderate chance of developing into a tropical cyclone over the eastern Coral Sea on Monday and Tuesday morning, but conditions are expected to become “unfavourable” as it approaches New Zealand. Even if it does not become a named cyclone, Burrows explained that the system has collected a significant amount of moisture and warm air, resulting in a prolonged weather event and substantial rainfall.

Unusually Large Swells Forecast

The system is also expected to generate dangerous marine conditions, with unusually large northerly swells. New Zealand typically experiences southwesterly swells, but this system is bringing “large northerly waves.”

Areas like Northland could see heavy swells, potentially exceeding 4 meters on Thursday, which Burrows described as “quite unusual from the north.” The West Coast of the South Island could experience waves exceeding 6 meters, while the west of the Coromandel Peninsula could see swells up to 3 meters.