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Another significant rain event on horizon forecasters say another significant rain event may be on the horizon as various long range computer models show yet another large, and this time deeper, Tasman Sea low for next week.

The weather news authority says the low could linger for the entire week in the Tasman, held up by a large blocking high to the east.  Head weather analyst Philip Duncan says farmers and local authorities should especially be closely tracking the incoming low.

Track the rain maps up to 14 days in advance

“This low looks like it will be deeper and even slower moving than the current system.  Again it may well tap into sub-tropical air which is not only warm but rich in moisture.  Another concerning factor is that the heaviest rain may once again hit the same regions affected by flooding this week”.

Mr Duncan says Waikato and Coromandel Peninsula waterways are especially under pressure with the Waikato, Waipa, Waihou and Ohinemuri rivers all dealing with significant flood runoff. 

“This incoming low on its own may not be so newsworthy if it wasn’t for the fact it is following quickly after some significant North Island flooding”. says every low has a different personality and can affect different parts of regions from previous systems.  “We’re not talking about a carbon copy but generally speaking the regions hit by flooding this week will be most exposed to heavy rain from this next low, based on current computer guidance”.

Long range models from New Zealand and overseas all point to a low which will not only be deeper than the current low but longer lasting. 

“Longer lasting can work both ways. It means areas with dry weather may have that for a day or two, but it also means other regions could have heavy rain for a day or two, then see it return again later in the week as the big low slowly churns by”. says rain clouds could roll in as early as this Sunday and linger for some areas until the end of next week.

A week of solid rain is not forecast but each day has a high risk of rain at some point, with some days much wetter than others.  A few regions may be fairly sheltered from the rain clouds too – but further updates were needed before confirming exactly where the rain will and won’t fall.

Northern and western areas look likely to be most exposed however heavy rain may also swing back around into the east, as it did this week. says it is still too early to know predicted rainfall figures but advises farmers and local authorities to keep up to date with the latest weather news and forecasts for their regions.  Mr Duncan says even a low end rain warning could cause more flooding and slips with the ground so saturated.

It’s not just the North Island that could see rain – the western, northern and eastern coastlines of the South Island may also be exposed to heavy rain. will have more details on Friday and across the weekend.



Rachael on 25/07/2012 11:09pm

Will this rain event also mean more warm rain to the ski fields damaging the snow base even further?

WW Forecast Team on 25/07/2012 11:23pm

Yes and no Rachael – some ski fields in the South Island may get snow next week from this rain event – but the North Island mountains don’t look quite so positive unfortunately.

– WW

Peter of Dunedin on 25/07/2012 7:27pm

What about us in he deep south. Any sign of any significant rain in your models for us – we do need a substantial fall of rain – yes we are relatively dry again – a continuing theme that goes back to the period prior to the last La Nina event. Although we have had the odd rsin event, overall we are behind the 8 ball so to speak.

WW Forecast Team on 25/07/2012 8:56pm

Yep and if we head back to El Nino that’s even worse news for you.  At ths stage the models are conflicted for the lower South Island (which is why we didn’t have too much about it in our story).  Some show a big high pushing in and cutting off your rain chances, others show heavy rain sliding down the east coast.  Should have a more solid idea tomorrow.



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