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Could La Nina return this summer?

During the past few weeks, I’ve been asked frequently about the weather for summer – are we having La Nina or El Nino? (Rough translation: La Nina equals wet, humid and warm; El Nino equals cloudy and cooler in the west, hot and dry in the east).

I was still waiting for Niwa’s latest island-climate update but decided to make a guess, based on the current set-up across the Pacific and around New Zealand.

My prediction was that we have no real driving force for our weather at present – no La Nina and no El Nino. I predicted that if we had a neutral period over summer then we could expect a summer similar to our last one – long, dry, hot spells but still some decent rain to keep the grass growing and the water tanks topped up.

Niwa said this week there was “a possibility of La Nina resurgence or neutral conditions during summer”. If this is the case, my forecast may not be too far off the mark.

Although, as Niwa’s Andrew Lorrey pointed out, this is just one part of New Zealand’s weather equation – meaning you can’t just look at the El Nino/La Nina prediction on its own.

If we do have a La Nina spell, there is certainly no evidence of it being like the incredibly strong one last summer. Hopefully, we won’t have another Cyclone Yasi making landfall – although neutral years (and La Nina episodes) can often lead to increased tropical cyclone activity in our part of the world.

So how confident is Niwa that we may see another La Nina episode in the coming months? Well, not too confident. “All of the models Niwa monitors are predicting Enso-neutral conditions during spring.

“Several dynamical models suggest cool conditions the next few months, but only one indicates La Nina redeveloping over summer.”

In my view, this could be a positive early indicator for our summer weather. Last summer gave holidaymakers awesome weather and the farmers were mostly looked after with decent rain events to avoid serious droughts.

Fingers crossed we get a similar summer this year with hot spells but briefly significant rain events, too.

– Philip Duncan writes a weekly column for the Herald on Sunday


Ken Ring on 13/09/2011 11:43am

The neutral phase is not likely to form another La Nina even though some have been saying it might, including NIWA and CSIRO. I think they are guessing and will be shown to be incorrect. Actually sea-surface temps stayed quite high this winter, despite the La Nina, because the kingtides came on full moons, and that’s the decider. A look at past records will reveal the pattern if anyone wishes to do the legwork. That swapped over to new moon kingtides in August. When the kingtides come on a new moon the sea surface temperatures tend to lose heat, and that gets transferred to the land. It takes a while to kick in which is why the warm start to spring was predicted to be short and misleading, because a cooler late winter was expected to click in and last through almost to November in places. It is turning out that way. No surprise because we’ve got these new moon kingtides until December. Also, it appears that more than usual whales have stayed south instead of migrating north to the Coral Sea.

Peter of Dunedin on 13/09/2011 10:35am

If we end up with another La Nina summer then I’m afraid that we, south of the Waitaki River , will have another terrible summer. i.e. cooler cloudier windier and somewhat wetter conditions. We in the main missed out on the summer to remember that everyone else received. Therefore if there is a choice, give me El Nino.

Guest on 13/09/2011 12:20am

Last summer wasn’t a great one for us down in Christchurch. Lots of cool NE winds and relatively few hot days. Hoping for a neutral to el nino summer down here with more consistent off shore winds and sunnier warmer weather.

Ken Ring on 14/09/2011 1:43am

I would suggest people forget about La this and El that as they mean different things to different people and to different places at different times. That’s why you can get wet and dry and cool and warm La Ninas AND El Ninos. If they see any SST difference between Darwin and Tahiti going either way these met-folk declare a “condition” then they wait till the end of the year to say in hindsight whether or not it was an “episode”. If it wasn’t what they initially said they still claim they were correct but they term it a fizzer. It all arises from the southern declination index which is a lunar cycle, and really, that should be the main discussion focus.

Basically this coming summer will be late because spring will extend into January, and next autumn will be warm and dry like a late summer. Much of the country should be sunny from February to June, and warm until March. There will probably be a heatwave around the end of February for some, particluarly the east of the NI. Auckland should be dry from mid October onwards, with only about 3 rain days from then until mid November. Also, the region may be mostly dry from mid January to the end of Febriuary, with the second half of Feb the best time to take a break.

In Christchurch for October, after the first week the rest of the month should be mostly dry. The first half of December should be uncomfortably wet, as will most of January. The 6-19 February would be my pick for a Canterbury holiday and/or haymaking. You’ll also get a second cut during April, once the wet first week has passed over. However those easterlies should prevail for most of February and March

I don’t post often here because I respect the fact that it is someone else’s forum and there are knockers here who always attack my posts. But these comments may be helpful.

Guest on 12/09/2011 11:32pm

Just wondering, if last summer was La Nina, how come we got record breaking heat in the sth island with NW winds? I thought El Nino bought conditions like this to the south/east? What sort of conditions would we see in Canterbury as a result of Neutral conditions? Cheers.

WW Forecast Team on 13/09/2011 12:39am

Hi there – good question!  What you’re describing are actually two different things – La Nina, which is the climate, and the nor’wester – which is weather.  So La Nina is part of our climate – it produces more sub-tropical lows for us and warmer sea surface temperatures in our part of the world.  In turn, that affects our weather =- bringing more nor’easters.   But a La Nina forecast is not a weather forecast – so while we, overall, tend to get more nor’easters, it is never a rule.  We still get the usual weather with winds from any direction.  It’s just that overall, over many months, we tend to have more rain events and more easterlies.  So the nor’wester was just part of the normal weather pattern – it’s just that the air was super warm as it came from the Australian desert (which is why is broke that record).  Hope that all makes sense?!  Can be a bit confusing at times.

– WW

sw on 12/09/2011 11:03pm

Hope so more NE winds/humidity the better.

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