A low is deepening in the western Tasman Sea near Sydney and will affect northern New Zealand as it passes by to our north on Thursday, predicts WeatherWatch.co.nz.

A thin area of high pressure is currently building over northern New Zealand while the main part of that same high stays firmly anchored over the southern Tasman Sea. Lows rarely push through highs so the likely path is one of least resistance – seeing the low travel around the northern fringes of the high.

That means this developing low will push into the sub-tropics where it could tap into more humid air and create heavier rain. 

The centre of this then mostly sub-tropical system will pass near Cape Reinga over Thursday.  Depending on how close the centre of the low gets will depend on how much strenght is left in the narrow ridge of high pressure over the upper North Island – if the high weakens and retreats just a little then heavy sub-tropical rain could make its way further south over Northland.

90% of the heavy rain is expected to offshore.

Auckland and Coromandel Peninsula remain on the southern fringes of the rain clouds and may only receive a few showers, but there is a 30% risk of heavy rain moving in.

While this low has the potential to produce torrential rain it isn’t classed as a storm, with the air pressure not very low. In fact, it’s a fairly small low – but it’s tapping into tropical air which can create flooding rains.

By the weekend this sub-tropical low will be well east of NZ and will be absorbed by a very large Southern Ocean low south east of the country – the two will merge into another major winter storm – however, this one will form just east of the International Date Line and won’t impact New Zealand..

Image / MandenoMoments.com

– WeatherWatch.co.nz