Transition to La Nina?

[David]

I see niwa has predicted a 50 percent chance of a La Nina developing in the coming months.

I think it should mean more NE and E up here and more anticyclones down south. Could mean a wet spring up here?
Was hoping for a nice spring this year.
I do not know much about how the patterns in NZ change during these different patterns - any thoughts?

[Michael]

Be better than southwesterlies the whole spring though
Usally it doesnt start till the end of spring like 1988

[Manukau heads obs]

will mean more NE rain events
but plenty of nice weather , with less strong cold SW winds, in between those events

[spwill]

Would mean a better spring if it develops but not such a good summer here. There would be a good Thunderstorm season for central and western area's of the NorthIsland mostly south of Auckland so I'm hoping La nina does develop.

[Cameo1]

What ever happened to us having NORMAL Springs and Summers?

[tich]

What ever happened to us having NORMAL Springs and Summers?

When has NZ ever had a 'normal' season? Always some place breaking a record of some sort.

[Cameo1]

What ever happened to us having NORMAL Springs and Summers?

When has NZ ever had a 'normal' season? Always some place breaking a record of some sort.

Well, one without la nina or el nino involved

[Michael]

probably 30 years ago when people didnt expect anything different

What ever happened to us having NORMAL Springs and Summers?

[NZstorm]

La Nina has been on the horizon since March. We were hoping for a La Nina tornado season in USA but it never happened.
The latest from NOAA is that there is a slightly better than 50% chance of La Nina developing this spring. Like everybody else, I hope it happens although it can mean real crappy weather for the upper North Island. But anything that can stymie the subtropical high pressure belt over summer I am in favour of as it will mean an unstable summer.

[David]

At least if a La Nina does develop it will be warmer - very disappointed about last summer, what a rubbish December
And the gardens will hopefully receive more rainfall, last two February's here have been very dry, both totals under 20mm.

I think with a La Nina weather patterns alternate mainly between E and NE rains with anticyclones and sunshine here
...which means less showery unsettled weather coming off the Tasman

More humid air and surface moisture may bring some nice thunderstorms as well

[David]

La Nina pattern is now developing.

From metservice seasonal outlook:

LA NINA conditions are now developing across the tropical Pacific.
Sea surface temperature anomalies have become more negative in the eastern equatorial pacific and remain positive in the western equatorial pacific. Recent observations show that the trend towards LA NINA is continuing, with the cooler water extending westwards. Nearly all of the dynamic computer models predict that a La Nina episode is likely for October and November. The probability of such an occurrence is judged to be 60%.
At this stage the computer output is suggesting this LA NINA will only last a few months and we may well be back in neutral balance by the start of 2008.
The Indian Ocean has developed a large area of warmer-than-normal sea in the tropics along with some cooler-than-normal seas further south. This is accentuating the westerly flow onto and across Southern Australia and may affect the New Zealand weather occasionally by delivering warm northwesterly winds.
Closer to home, a large region of warmer-than-normal sea continues to extend from the Solomons across Fiji and to the southeast with some warm patches in the Tasman Sea and east of the North Island. The extra warmth is affecting the North Island and may well help enhance showery weather. There is also an area of cooler-than-normal sea south of the Chatham Rise and this might exacerbate the chilling impact of any southerly winds over the next few months. The strong temperature gradient in the sea off Canterbury increases the risk of thunderstorms and hail.

I know the last phrase of that will excite some people...

[NZstorm]

yes, but does it make sense? Colder sea temperatures would premote stability/low level temperature inversion/stratocumulus.

[David]

Where does it say cooler seas? Doesn't a La Nina pattern usually cause SST anomalies around New Zealand to be positive?

yes, but does it make sense?

How about we leave that part up to them....I don't mind what happens as long as it isn't very dry.

[TonyT]

Where does it say cooler seas? Doesn't a La Nina pattern usually cause SST anomalies around New Zealand to be positive?

yes, but does it make sense?

How about we leave that part up to them....I don't mind what happens as long as it isn't very dry.

If you bother to read the whole thing, instead of just the last sentence, you will see they refer to cooler than normal seas. And please dont be so arrogant as to suggest NZstorm dare not question what you or your original quote says.

[David]

If you bother to read the whole thing, instead of just the last sentence, you will see they refer to cooler than normal seas. And please dont be so arrogant as to suggest NZstorm dare not question what you or your original quote says.

What's your problem? And speaking of arrogance, I was simply asking in my last question doesn't La Nina mean warmer waters around NZ, not stating that NZstorm was wrong. Just because I am not too familiar with every detail of these patterns does not mean I am being arrogant, I actually read the whole thing twice.

If you know so much about it then why don't you set me right and explain what equatorial Pacific regions are and their relation to NZ?

[mikestormchaser]

Fantastic day here in chch very warm! great to get out and about like i did this afternoon! brings me to life, im so over winter and any snow chances.
Not sure exactly on how warm it was, i missed that on the weather tonight

cheers

[TonyT]

If you bother to read the whole thing, instead of just the last sentence, you will see they refer to cooler than normal seas. And please dont be so arrogant as to suggest NZstorm dare not question what you or your original quote says.

What's your problem?

Well, since you asked, my problem is two fold. First, when NZstorm constructively replied to your post you asked "where does it say cooler seas?" when the passage you quoted says "There is also an area of cooler-than-normal sea south of the Chatham Rise".

Second, when NZStorm queried MetService's interpretation and asked "but does it make sense", you advised "How about we leave that part up to them".

Next time try reading the material you post before asking redundant questions, and dont treat respected members of this forum so arrogantly. This is a place to share views and opinions, not dismiss them.

[Manukau heads obs]

seems this has all been blown out of proportion?
(and landed people in hot water?)

[David]

seems this has all been blown out of proportion?

Yeah I'd say. All I want to know is what the sea surface temps are like around NZ not over the whole pacific ocean. And I already said I've read it several times. I just need some clarification of what it means for NZ, and getting rubbished for it. I have not intentionally dismissed anyone on this forum. My 'how about we leave that part up to them' was a sarcasm because I could not make simple sense of the material.

I posted it here for others to see and for someone to make sense of it. And no one has tried to explain yet, so I am trying to research it instead.
(And can we please stop this argument??)

[spwill]

There is also an area of cooler-than-normal sea south of the Chatham Rise and this might exacerbate the chilling impact of any southerly winds over the next few months. The strong temperature gradient in the sea off Canterbury increases the risk of thunderstorms and hail.

Is it not the upper air temps and pre frontal surface conditions that are mostly responsible for Thunder in Canterbury .
A cooler surface to the SE would help stabilize post frontal air from that direction would it not.

[RWood]

On the original topic, what's of interest to me is that these are MetService forecasts. When the great "split" of services between NIWA and MetService was originally set up I'm pretty sure that seasonal and other forecasting beyond the "short" range was supposed to be done by NIWA only. I think this is probably one of several situations where the two are stepping on each other's toes. My wish is that a remarriage will occur some day - resources in NZ are thin enough without this sort of wastage, surely!

[TonyT]

To answer your question,

Where does it say cooler seas? Doesn't a La Nina pattern usually cause SST anomalies around New Zealand to be positive?

I am not aware of any distinctive SST anomaly patterns around the NZ coast which are associated with EN or LN, although I would expect its something NIWA have looked into (come on you NIWA lurkers out there, log on under a funny name and tell us). There are, of course, distinctive SST anomalies in the tropical Pacific associated with EN/LN.

[Willoughby]

The claim about the "strong temperature gradient" is a little dubious I must admit... SST's off the Wairarapa-Kaikoura coast are only 1-2C above 'normal', whilst off the Otago/Canty coast they're just about 1C below 'normal'. Might be a fantasy claim? Who knows...

Are we going to see a Summer similar to that of 2005/2006 where Central Otago/Southland had it's fair share of thunderstorms, as well as the Wanganui region with the unstable northeasterlies?

Note the very warm SST's centered between the Fiji islands and Vanuatu.. and the cool waters to the SW of the Australian continent in the Indian Ocean... just have a feeling western Aus is going to be cool, in turn giving NZ moist airflows and instability.

And surely soon time is ripe for a cyclone.

[Manukau heads obs]

I think sea temperatures around NZ tend to be cooler after a series of elninos, because of the more SW winds pushing colder water from more south of the tasman sea onto us?
(and then a series of more la nina's with more ne winds would push warmer water from the north of nz onto us?)

anyway, i think things are shaping up where the NI will get a few TC's this summer

[David]

anyway, i think things are shaping up where the NI will get a few TC's this summer

Great! But now that we northerners are all getting our hopes up there'll probably only be several tropical depressions but nothing exceptional
But apparently NZ gets its most intense tropical systems when the SOI is neutral...but I imagine there's still a reasonable chance with a La Nina pattern. In the material from metservice I posted there is a mention of conditions returning to neutral by 2008. Hopefully this will last into Autumn (isn't March the most likely month a TC will affect NZ?)