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Cyclone-strength storm in North Tasman


A small but intense low – predicted position at midnight Thursday.  Image / MetService


A storm in the northern Tasman Sea has strengthened today and now has the same wind speed as a category 1 Tropical Cyclone says

The storm isn’t very large in size but is described as a “vigorous depression” in a severe weather watch issued this afternoon by state forecaster MetService. head weather analyst Philip Duncan says it’s been tough to work out the path of this particular storm but weather models and forecasters are starting to agree now.  “This low is especially hard to track due to a large high to the east of the country.  If the high strengthens just a little the low may hardly affect northern New Zealand if the high weakens then the heaviest rain may well indeed move over Northland and Coromandel”.

“It’s now becoming clear that heavy rain will affect northern and western extremities in both islands with blustery winds north of Waikato and south of Dunedin”.

Mr Duncan says Anzac dawn ceremonies across the country may be affected by the low which is likely to continue deepening for another 24 hours.   The wet spots are likely to be Northland, Taranaki, Nelson, the West Coast and Southland.  

Strong winds are likely to affect Auckland and northern New Zealand and Southland.  No frosts are expected anywhere unlike previous years. 

He says as the day progresses rain may spread to many regions.

“Hopefully the rain will hold off in most populated places until after dawn services” says Duncan.  “The data suggests this will be the case in most places but we’ll have a much clearer idea on Thursday afternoon”.

MetService has updated their severe weather outlook for northern New Zealand with “moderate” confidence heavy rain will affect places north of Whangarei and across the Coromandel Peninsula also the entire northern and western coastline of the South Island.   Latest data provided by the government forecaster shows the low in the Tasman has sustained winds of 65km/h – gale force is 62km/h.  

The central air pressure is 996hPa which is likely to drop in to the 980s.  Duncan says a low of that depth situated near northern New Zealand is always worth monitoring.

He says despite the low having such strong winds it can’t be classed as a tropical cyclone as it’s not in the tropics. 


Douglas on 22/04/2009 6:57am

Being outside of the tropics has nothing to do with whether it can be classified as a tropical cyclone.
It’s not been named or classified as a tropical cyclone…..simply because it is not a tropical cyclone. The structure is not there, with no CDO, and it’s already being impacted by an upper trough. It’s a halfway house between our normal depressions and a tropical cyclone.

Dave on 22/04/2009 4:43am

Yes it sure looks ugly, but it looks like going down the Tasman doesn’t it. I know these things are unpredictable but all the maps appear to agree on that. It looks to me like Monday could in fact be the wettest day, or maybe starting Sunday afternoon.

I was going to the Coromandel at the weekend but I have changed my mind.


WW Forecast Team on 22/04/2009 4:57am

Hi Dave,

We’re convinced there’ll be rain starting late Friday and going through Saturday in the Far North but still have mixed feelings about Coromandel.  40 to 50% confidence in rain "setting in".  You’re right in saying it’s tracking down the Tasman – in a SSE direction which wont take it near the NI but right into Fiordland.  However, the strongest winds and heaviest rains will be in the SE corner – well away from the centre…which is why northern NZ has a big question mark over it.

I think by 4pm Thursday we’ll have a clearer idea and will post an update on things then.


Philip Duncan

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