A low in the Tasman Sea and its associated fronts continue to creep towards New Zealand.  As predicted last week a warm northerly wind is spreading over many parts of the country for the start of this week thanks to the departing high – but between this departing high and incoming low lies a front with sub-tropical connections.

WeatherWatch.co.nz says it’s this sub-tropical connection that could see isolated pockets of heavy rain for some parts of the country – mainly for north, but the low may also generate bands of heavy rain further south separate to the sub-tropics.

The two air pressure systems will also create blustery winds in exposed parts of the upper North Island on Tuesday – but it should be short lived with calmer conditions returning overnight and on Wednesday before a sou’west change arrives for the rest of the week for many.

In this rain map (right) we’ve highlighted where these bursts of heavy rain lie (circled in red).  This is the rain map prediction for Tuesday thanks to Weathermap.co.nz.

These areas of heavy rain are all linked together with cloud and showers – but while some areas may receive rain heavy enough to prompt a rain warning, centres and regions just 100kms away may only receive a few brief falls, or even showers only.

Government owned forecaster, MetService, says they have “high confidence” of heavy rain for Bay of Plenty on Wednesday and now have a Watch in force for Northland, Westland and Fiordland.

WeatherWatch.co.nz says Northland, Westland and Fiordland are our western most regions, which explains why they are likely to experience the rain first.  The Nelson ranges, Mt Taranaki and East Cape may also receive heavy rain for at time – although it depends on the exact tracking of those heavy rain cells.

Meanwhile dry parts of Canterbury and Otago may get some rain once the low moves east of the country around Wednesday and Thursday, however computer guidance – and forecasters – are conflicted about how much rain will fall.   Latest data suggests a 90% chance of rain overnight Wednesday and into Thursday for Canterbury – up from 60% earlier today.

The state forecaster is also monitoring Canterbury suggesting the low could drive in easterly rain – but their confidence was “low” as of Monday afternoon due to “significant uncertainty” about timing and exactly where that heavy rain might fall – again highlighting the fact this low will bring isolated bursts of heavy rain for some, but not all.  We’ll keep you posted on Tuesday.

– WeatherWatch.co.nz