El Nino 2015/16

[spwill]

An idea how the Southern Annular Mode influences the El Nino?

The SAM will influence weather patterns onto NZ, in general more westerly flow onto NZ with a negative SAM, less westerly with a positive SAM.

[Richard]

not good for dairy farmers really....low payout and looking like an early dry , for some dairy areas
and not good for North Canterbury

Its bad enough now,even saw a irrigation sprinkler going a few days ago, have had only one descent rain producing weather system in the last 10 months back in June with 43mm

[NZstorm]

Interesting to see the Reserve Bank factoring in El Nino into the economic outlook. I don't recall the weather being part of an economic forecast before!

The North Island dairy looks a risk for a dry out but currently the precip numbers look good.

[Manukau heads obs]

places like the manuwatu and south taranaki and BOP can dry out in el nino, being sheltered from showers in prevailing SW winds
and they are major dairy areas

[spwill]

Interesting to see the Reserve Bank factoring in El Nino into the economic outlook. I don't recall the weather being part of an economic forecast before!
.

It worked

[treetop]

Prognosis not "elninolike" next week or two with SE/E winds over much of the country. Been some unusual setups at times this winter.If this continues there may be some serious large hail events prior to Christmas.

[NZstorm]

Prognosis not "elninolike" next week or two with SE/E winds over much of the country. Been some unusual setups at times this winter.If this continues there may be some serious large hail events prior to Christmas.

Canterbury looks to be the most likely spot but Bay of Plenty could be good also.

[treetop]

agreed . Also inland Hawksbay/Golden Bay I would expect with cold pools above and good seabreeze convergents.

[NZ Thunderstorm Soc]

Prognosis not "elninolike" next week or two with SE/E winds over much of the country. Been some unusual setups at times this winter.If this continues there may be some serious large hail events prior to Christmas.

Yes, I thought that too
Could be some decent thunderstorm activity with big hail, hopefully not here, but then the possibilities look possible if the westerlys don't develop prior to the southerly changes, and of course, you have to rely on timing.
However, some storms could start out and then fizzle out as what it did on Friday.

[treetop]

As sun and relative sea temps warm up intrusions from the deep south will become more spectacular eg NSW/Queensland peak in NOV/Dec as the highs anchor themselves on the bight and cold upper air gets drawn up into the hot thermals/sea breezes along the east coast.. [most of us know this already].Really miss those Ozzie holidays!.Down side is witnessing the cost to property and lively hood of course,I never get used to the emotional roller coaster that is storm chasing..

[tich]

Prognosis not "elninolike" next week or two with SE/E winds over much of the country.

Yeah, persistent easterlies over NZ with lows over the north. Looks much more La Nina weather.

[treetop]

Would be expecting nw/sw fronts at the mo, ? mmm interesting.

[NZ Thunderstorm Soc]

Yes, these lows seem to be persistently popping out of the mid to north Tasman Sea ?

[JP.]

Top story on the NZ Herald site

http://www.nzherald.co.nz/nz/news/artic ... d=11517072

[Manukau heads obs]

Gisborne/Hawkes Bay drought will have been put off a month after the recent rain

[treetop]

Yes, these lows seem to be persistently popping out of the mid to north Tasman Sea ?

With the position of the highs currently ,abnormally cold air is moving north around Tasmania and forming an unstable region in the north Tasman where the sea is a lot warmer.. Its often an area of light winds ,relatively high cape/jet stream and lows tend to form from clumps of T storms there.We are seeing them drift east now rather than as deepening depression moving SE [the norm]towards the S Island

[Richard]

Looking at the S.O.I archives from 1878 to now i see in May 1886 it pecked at -42.2 where in 1998 it only reached -28, i would like to know well were they able to measure it back then.

http://www.bom.gov.au/climate/current/soihtm1.shtml

[spwill]

The very strong El Nino in 1982 produced a wet October in Otago/Canterbury, not suggesting it will be wet this October but there is always some hope for those wanting the rain.

[TonyT]

Looking at the S.O.I archives from 1878 to now i see in May 1886 it pecked at -42.2 where in 1998 it only reached -28, i would like to know well were they able to measure it back then.

http://www.bom.gov.au/climate/current/soihtm1.shtml

Since the SOI is simply the air pressure difference between Tahiti and Darwin, it can be calculated retrospectively for as long as the air pressure readings are available. Now we have many other measures of El Nino than just the plain old SOI, (eg the MEI which is very useful, the Nino3.4 temperature anomalies, etc) but the SOI does have that advantage of going back in time the longest. Of course there are many different ways of analysing those pressure values (daily, monthly, 3 monthly, running means etc).

Also, I notice a lot of people saying the current pattern is not "El Nino-like". I have said this so many times over the years (including many times on this forum) that I hesitate to repeat it again for fear of sounding like either a broken record or a conspiracy theorist (I am probably both), but I say look at the trend not the value. My experience suggests that until the El Nino peaks (i.e. most of the indices which measure El Nino stop getting stronger and level off) you will see variable weather patterns which can bring rainy spells, and also sometimes large slow moving anticyclones. Once we get to the peak in El Nino, and start the descent into La Nina, we tend to get the long periods of westerly flow, which in this year's case is more likely to be southwesterly flow. (Incidentally, I smile at all the journalists who write without thinking about expecting "a long hot dry summer" - I would prefer to suggest "a long cool dry summer" for this season!). We often continue, more or less, with the predominantly westerly flow right through the transition point into La Nina, and well towards the peak of the La Nina. Only when we get near the peak of the La Nina do we then see the shift back to less westerly and more variable patterns.

Given that this El Nino is a big one, and that I can see indications of a moderate to large La Nina on the far horizon (we are well overdue for one), I suggest the "transition" from peak El Nino to peak La Nina will be long and intense (high amplitude peak to trough). The implications of this for east coat rainfall may be quite serious.

[Richard]

Thanks for explaining that Tony

[cantygal]

Excellent Tony. Any idea when the peak of El Nino will be?

[TonyT]

Excellent Tony. Any idea when the peak of El Nino will be?

There are, of course, as many different opinions of that as there are forecasters! The modelling is all over the place, take your pick from your model of choice.

figure4(26).gif

And if you factor in what I wrote above about the many different ways of measuring El Nino, you can quickly see that the peak in one measure may not be the peak in others. Which is one reason why the MEI (Multivariate El Nino Index, i.e. covering a basket of different measures, some atmospheric, some oceanic) can often be the best to use. Typical El Ninos often peak mid to late summer, so January to March. My own view is that this has been a rather atypical event, with a number of unusual characteristics, and I would expect it to peak sooner rather than later, i.e. before the end of this year. One very interesting bit of non-tested non-peer reviewed research (which I have read and rate very highly because its been remarkably accurate for the last 3 years) suggests a peak in October, i.e. soon.

[James J.]

Gisborne/Hawkes Bay drought will have been put off a month after the recent rain

Yes, imagine how wet it would have been without the El Nino.........

[Manukau heads obs]

the current 'Low index' weather pattern can happen at any time randomly (does not happen all that often though)...regardless or El nino of La nina

[TonyT]

the current 'Low index' weather pattern can happen at any time randomly (does not happen all that often though)...regardless or El nino of La nina

Correct, but just because it can happen at any time it doesnt follow that it is always a random occurrence. In certain phases of teleconnections like ENSO and the MJO it is more or less likely to occur (which is not to say that ENSO or the MJO necessarily cause a low index situation, but the two are more likely to occur together).