Weather forecasters continue to monitor a low pressure zone which is approaching the North Island from the east.

The low, which one week ago was short-lived Cyclone Eva’s “twin”, has continued to spiral well east of NZ as Eva’s remnants fell apart fast in the north Tasman Sea. Eva went west, and this low drifted east. Now, as this “twin” low starts to drift back towards NZ, it will likely be centred north of East Cape on Monday then stall for a number of days. It may then also start to deepen.

But – where the centre of the low stalls is the big question. At the same time the low drifts in westwards towards northern NZ an exceptionally powerful late summer high pressure zone will be drifting into towards southern NZ. If this high moves in faster, or pushes further north – it may significantly impact how far south down the eastern side of NZ the rain may go. Likewise, if the high holds back from moving in, then the rain may be heavier further southwards. So this is what we say is “one to watch”. The data over the past 48 hours certainly leans towards very heavy rain for the eastern North Island but for some people still in need of rain this may not deliver what you want.

While this incoming low isn’t directly related to the flooding rains in eastern Australia, it is a similar set up where low pressure will stall along part of our eastern coast and it also has the potential to remain there for days hugging the eastern coastline. However our totals don’t look as big as the Aussie numbers and there is still a chance that rainfall totals will back off from where they are today. Updates over the weekend will help firm up the scenario looking most likely, so check back for our morning updates.

Easterlies and lows coming in from the east are more likely during a La Nina summer. While La Nina has now peaked, it does still remain with us and adds a bit more fuel to the easterly winds and chance of low pressure zones in the north of the country.

• VIDEO: Our latest video goes into detail about the set up next week and the chances of heavy rain and slips/flooding for the eastern North Island. Watch below or in our Free App via WeatherWatch. Or to view via our YouTube page (and to subscribe) Watch Here.
  
• METSERVICE has already started talking about the chances of heavy rain in the eastern North Island. You can monitor any potential watches or warnings via our Warnings page here at WeatherWatch. At the time of publishing this story, this potential rain event was too far out for a watch/warning – but you can see South Island warnings which, in fact, are for another event which is actually connected to the low that brought flooding to NSW/Sydney this week. (that low is just clipping the South Island today/Friday with some wind and rain).

• RAIN ACCUMULATION MAPS – Can be found here.

• MONITORING YOUR RAINFALL POTENTIAL
  RuralWeather.co.nz has the most detailed, accurate and hyper-local rain forecast data in New Zealand. If rain matters to you then keep an eye on your totals there. Our data via IBM is updated hourly (great for monitoring on the day and day before), while the main global data we get updates about two times a day (so check morning and evening to keep an eye on next week’s totals). An event like this with heavy rain hugging one part of the country as high pressure moves in elsewhere means there is a fine line between wet and dry – this means rainfall totals and % of rain will move around a bit over the weekend as we continue to fine tune the data.

• WILL RAIN REMAIN AT SEA?
  As we saw with ex-tropical Cyclone Cody an incoming high pressure zone from Tasmania can influence how much rain we get thousands of kilometres away around NZ’s East Cape from a low pressure zone. There is a fine line between heavy rain and dry weather next week in the North Island and our hyper-local forecasts on top of our Video explanations and free-to-access maps should help you paint a picture of what is most likely in your area. We’ll have more updates over the weekend as we continue to fine tune the overall rainfall chances

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THE MAPS:

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Early estimates show over 200mm possible in isolated locations of the eastern North Island next week.

Still too early to lock in, but rain may start Monday & continue on through next week.https://t.co/gb7E1qcpZ3 will have weekend news/map updates as we continue to lock it in. pic.twitter.com/U04c8AcuBw

— WeatherWatch.co.nz (@WeatherWatchNZ) March 11, 2022