Wet start to the week for North Island as Tasman tempest approaches

Those in the upper North Island might want to avoid outdoor activities for the next day or two, with heavy rain to start the week.

A low over the north Tasman Sea would move onto the North Island Sunday night, bringing heavy rain on Monday from Auckland, across through Coromandel and Western Bay of Plenty for Monday, with several weather watches in place.

That low would become slow-moving as it crossed over the island late Monday and on Tuesday, bringing periods of heavy rain with isolated thunderstorms to the northern parts of the North Island.

The heaviest falls were expected about Coromandel Peninsula and Bay of Plenty west of Te Puke from Monday afternoon to Tuesday evening, and a heavy rain watch was in force for these regions.

Over the next few days, much of the South Island will be exposed to a S'ly quarter flow of air, resulting in colder than average temperatures. pic.twitter.com/OdEHI2nb2k

— NIWA Weather (@NiwaWeather) September 8, 2019

It comes after a widespread burst of thunderstorms tracked across Northland and Auckland early Sunday morning - and more than 1300 lightning flashes were detected within an hour.

On Monday Auckland's forecast included periods of rain, heavy and thundery at times, with northerlies and a high of 16C.

Quick lightning recap with last night's ⛈️.

10,000+ strikes from 12 midnight to 9 am over New Zealand and adjacent waters.

Who had an early wake-up call from Mother Nature? 🙋‍♂️🙋‍♀️ pic.twitter.com/TN3e1ghKOI

— NIWA Weather (@NiwaWeather) September 7, 2019

MetService forecaster Paul Ngamanu said the South Island and lower North Island were in for a mostly fine day Monday, with just some cloud and a few showers.

The slow moving front should continue to affect the North Island on Tuesday, with rain expected for many areas.

On Wednesday, the front over the North Island should move away to the northeast, and a narrow ridge would spread fine weather over the country.

Bush-fires over northern New South Wales continue to send plumes of smoke over the Tasman Sea. The frontal system over the lower North Island extends westwards towards the mid-Tasman Sea and also way to the northwest past Norfolk Island https://t.co/rcECVuGXOw ^PL pic.twitter.com/mWARDYtH8Q

— MetService (@MetService) September 8, 2019

Another front would then move on to the southwest of the South Island Thursday night, and continue northeast on to the North Island later Friday while weakening.

The front would be preceded by a strong northwest flow, and followed by disturbed westerlies.