A low in the Tasman Sea to the northwest of the country is set to rapidly deepen and move towards the North Island on Thursday, before moving over central NZ during Friday. Weather impacts will be felt right across the North and upper South Island as a result of the low; the first significant system to affect the country since mid-September 2017.
UPDATE FOR THE NORTH ISLAND
With wild weather on the way tomorrow as a rapidly deepening low moves down from the Tasman Sea, MetService has issued a number of Severe Weather Warnings and Watches for the North Island and upper South Island to indicate the potential for heavy rainfall and strong winds. The current warnings can be seen in the images below, with more details provided at http://bit.ly/SWWarnings.
Today, we have also seen a Severe Thunderstorm Watch issued for the central North Island and Northland, associated with isolated convection which is popping up over the North Island this afternoon. The details of which can be found here; http://bit.ly/STSWatch.
Despite issuing a severe thunderstorm watch, it is quite possible that within that area you could have clear skies and not see a thunderstorm all day! This is due to the isolated nature of thunderstorms and showers; subtle wind convergences or areas which have slightly more moisture in the air can be all it takes to fire up a storm in one location but 10km’s down the road you will just be left feeling hot and sticky with no relief from a cold shower or storm!
With a Severe Weather Warning, like those issued for tomorrow’s system, the effects are widespread. Most will experience the phenomenon which is forecast as it is driven by large scale synoptic weather patterns; for example, large rain bands with fronts which extend for hundreds of kilometres like we will see tomorrow on the North Island. For more information on this check out one of our blogs, which explains NZ’s Severe Weather Warnings; http://blog.metservice.com/OutlookWatchWarning
In the meantime, take care in the wild weather we are experiencing today and into the weekend. Remember to regularly check up on the latest severe weather advice on the above links and keep up to date with us @metservice on twitter and Facebook for updates throughout the day.
UPDATE FOR THE SOUTH ISLAND
With a deepening low already spreading heavy rain over the Far North and set to affect most of the North Island by this evening parts of the South Island will also be experiencing severe weather of it’s own.
A Heavy Rain Warning is out for Marlborough and Nelson starting from late this evening associated with the low in the north. Rain accumulations could reach up to 160mm about the Kaikoura ranges by midnight Friday with strong southeast winds. Canterbury is also under a Heavy Rain Watch, with the bulk of the rain expected also on Friday – updated Severe weather will be made later this morning which you can check here http://bit.ly/AllWarnings
Outside of the grip of the low, severe thunderstorms which delivered Palmerston North a downpour of 36.9mm late yesterday afternoon could occur in isolated places over the lower South Island today.
A Severe Thunderstorm Watch has been issued for inland parts of the lower South Island as high humidity will provide the fuel for isolated thunderstorms to from from midday. Downpours of up to 40mm/h are possible under thunderstorm cells. The rain here will not be as widespread and prolonged as with the rain band further north but impacts could still affect those outdoors. Rainfall of this intensity can cause flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips.Visibility in these heavy showers can also cause hazardous driving conditions for the few unlucky enough to be caught out. You can check for more details on the thunderstorm risk here http://bit.ly/STSWatch