A feed of sub-tropical air is bringing rain and higher temperatures to New Zealand for the first working week of spring - a marked contrast to the chilly south-westerlies that dominated the past month of winter.
MetService meteorologist Juliane Bergdolt said the rain band had stalled more over Coromandel and Great Barrier Island.
There was a risk of thunderstorms this afternoon particularly during downpours in Northland, she said.
“The thunderstorm risk comes down to the very top of the Auckland area, not into Auckland City,” she said.
“Auckland will get periods of rain but shouldn’t get the downpours.”
Coromandel is only under a heavy rain watch as less than 100mm of rain is expected over 24 hours, but this could be upgraded to a warning.
“There’s so much uncertainty in this system...we’re literally watching it to make sure it doesn’t get too much,” Bergdolt said.
Populated areas of the Coromandel such as Whitianga and Waihi had seen around 50mm of rain over the past 12 hours, with 80mm further inland.
Slow-moving rain band brings risk of downpours
“Due to the slow nature of this weather feature, there is a risk it could become stationary over a particular area for some time, leading to higher rainfall accumulations for localised areas,” MetService meteorologist Jessie Owen said on Monday.
There is a chance that thunderstorms will form over western Auckland and Northland this afternoon and tonight. If these thunderstorms form, they are likely to bring impactful downpours to these areas.
Surface and/or flash floods may result from these downpours, which may deliver localised rainfall rates of 25–40mm/hour, with or without accompanying thunderstorms.
Great Barrier Island, eastern Auckland, the Coromandel Peninsula, and the western Bay of Plenty will all experience one rainband in the morning with the potential for heavy downpours.
The likelihood of thunderstorms and locally-heavy downpours above 25mm/h is minimal in this area. These downpours are more likely to happen before daybreak and could happen with or without thunderstorms.
During the early hours, a second rain band moves southward over Northland with little likelihood of thunderstorms. Once more, isolated heavy rain may fall with or without thunderstorms.
A heavy rain watch is in place until 9am, however, Owen said another watch would likely be put in place today.
There is also a slight chance of a few thunderstorms in additional western North Island regions, ranging from western Waikato to Taranaki, as well as in northern and western South Island regions.
Mt Taranaki, Tasman west of Motueka, Buller, and Westland are all under a heavy rain watch today.
This week’s temperatures are also being impacted by the subtropical air.
The warmest day of the week is expected to be Wednesday, with several locations in the North Island and eastern regions of the South Island expected to reach 20, Owen forecast.
Also anticipated are much warmer overnight lows with no return of the frosts from last week.
Another high-pressure system is predicted to arrive on Friday, bringing calm weather to the country by the end of the week.
