This morning twin cyclones continue to churn north of New Zealand.  Tropical Cyclone Winston strengthened overnight to a Category 2 cyclone and may continue to strengthen a little more today and tomorrow between Vanuatu and Fiji.  Winston is tracking south towards New Zealand but a narrow wedge of high pressure to our east is likely to stop Winston’s direct track to us.  

Meanwhile Tropical Cyclone Tatiana continues to strengthen and like her twin brother may also become a Category 2 cyclone, higher than Australian forecasters were expecting yesterday.

FUTURE OF THEM BOTH – AND HOW IS NEW ZEALAND IMPACTED?
CYCLONE WINSTON — As we’ve said all week our first and foremost concern with Cyclone Winston would be dangerous beach conditions.  Because Winston is still deepening – and will be a cyclone for the next few days before weakening – the storm is already churning up the sea.  This means that the very dangerous swells are now being generated north of the country and as Winston slides south towards New Zealand (before stopping due to the high being in the way) the swells will head south too.  Even as Winston weakens and falls apart next week well north to north east of Cape Reinga, it will still drive in messy beach conditions.  Unlike Victor, which was more straight cut, Winston may deliver a really messy set up with beach conditions next week around the North Island. We’ll update you about that next week. Winston is more likely to bring dangerous beach and marine conditions to some in the north, not severe weather.  

Winston may actually end up being pushed back further north into the tropics again – that’s how significant and blocking this large high just east of New Zealand. If this is the set up then the remnants may impact Tonga next week.

CYCLONE TATIANA — The smaller of the two Cyclone Tatiana isn’t expected to last a cyclone beyond Saturday. However Tatiana will drift towards the upper North Island next week as a weak tropical low.  It’s this weak tropical low that may connect up with a standard low forming in the Tasman Sea next week.  And this is where it gets interesting…

NEXT WEEK IN NZ
With Cyclone Winston weakening well north east of Cape Reinga and Cyclone Tatiana falling apart well before New Zealand we’d normally end the updates by now – but next week a large low is forming around New Zealand/Tasman Sea area – and we may end up with a scenario we have a giant (not aggressive) low in the Tasman Sea/New Zealand area and combined with the remnants of both Tatiana and Winston this Tasman Sea low may act as a giant ‘cog’ – turning around and pulling down all that tropical air and moisture left over by the two lows.

It is a very messy set up – but goes a long way to explain why a couple of days ago one reliable model picked a low hitting New Zealand while its main competitor picked (more accurately) this likely set up.  

Set up mid to later next week in NZ shows the two ex-cyclones working with a new low in the southern Tasman Sea. This could drive very humid weather down over the country and rain heavy enough to prompt rain warnings and possibly thunderstorms. Too early to lock in, but most models have been aligning this way for the past few days.

THE GOOD NEWS
No direct hit from either cyclone is expected by WeatherWatch.co.nz.  A large low next week around New Zealand looks like it will tap into humid tropical air – which could bring in rain to areas that need it most, but without the damaging winds a cyclone may bring.

THE BAD NEWS
Cyclones don’t need to hit – or even get close to land – to cause problems in New Zealand.  Victor was a weak offshore ex-cyclone but it sadly contributed to an increase in drownings and those caught in dangerous rips and beach conditions in the upper North Island.  Winston and Tatiana’s swells, combined with this new Tasman Sea/NZ low means many beaches may be dangerous for a time next week – and not just the North Island, but also the south.

Next week looks likely to have no actual storm in New Zealand – but possibly some localised stormy weather if heavy rain (due to the combination of a colder front and tropical air over New Zealand) slowly crosses new zealand with that tropical air flow.  This could lead to some flooding – and not just the North Island, the South Island’s West Coast is also exposed, as is the upper South Island.  More details over the weekend on this developing story.

With 3 lows around New Zealand in the next five days, and two of those ex-cyclones, expect dangerous beach conditions next week for a time pretty much everywhere.  We will be more specific next week. Check out the swell maps at MetOcean, by going to weathermap.co.nz 

– WeatherWatch.co.nz