El Nino 2015/16

[Razor]

Tony- thank you for the most informative posts. I feel I have learnt something today now.

[NZ Thunderstorm Soc]

Yes, I have too, but the due to the complexity of the El Nino/La Nina weather systems which is largely based on the positioning of warm sea temperatures, I get buggered up of weather systems affecting NZ.
With this La Nina, sorry, El Nino weather we are expecting, I'm not expecting a cold SW with hail scenario, now but then there could be, but probably not....
...but then there could be??

[treetop]

clear as mud!!.Not going to be packing the skis away yet.

[TonyT]

Yes, I have too, but the due to the complexity of the El Nino/La Nina weather systems which is largely based on the positioning of warm sea temperatures, I get buggered up of weather systems affecting NZ.
With this La Nina, sorry, El Nino weather we are expecting, I'm not expecting a cold SW with hail scenario, now but then there could be, but probably not....
...but then there could be??

John, 82/83 was a strong El Nino season with the airflow more west to southwest, at least until December, so we got a lot of blustery cold SW changes (what nzstorm likes to call a southerly buster) which brought a much higher than usual frequency of hail and thunderstorms, and generally cooler temperatures. 97/98 was a strong El Nino which had more west to northwest flow so we got a warm summer with lots of NW days early in the season, high evaporation rates, and very quickly into drought and high fire risk.

Why the difference? I'm not sure if anyone has a truly convincing answer, but the late Neil Cherry had a theory which is as good as any. He argued that something called the QBO (Quasi Biennial Oscillation - i.e. approximately two year oscillation) had an impact on the type of El Nino we got. The QBO is a high level wind anomaly over the tropics, and when I say high level we are talking really high level, i.e. about 30mb, so basically in the stratosphere. The QBO alternates between a westerly anomaly and an easterly, and propagates downwards towards the troposphere over time.

Neil found a correlation between these phases of the QBO and the intensity of El Ninos, also with the strength of westerly airflow in the Southern Hemisphere, and also with the incidence of northerly or southerly airflow in the Tasman Sea. He also had an explanation for the possible mechanism why this works, that the QBO modulates the westerly wave pattern of the troposphere. I can't remember the details.

He showed that a positive QBO (westerly) produced a weaker westerly in the troposphere, and was associated with La Ninas, more northerly and less westerly airflows over NZ . While, a negative QBO (easterly) enhanced the westerlies in the troposphere, and was associated with El Ninos, more southerly and westerly wind flow over NZ.

So his tip was to check the movement of the El Nino and La Nina index, and see if it correlates with a peak or trough in the QBO. If the QBO is positive the El Nino should be weaker and have more northerly component, if the QBO is negative the El Nino will be stronger and have more southerly component to it. And nice versa for La Ninas.

So, the question is, what is the current state of the QBO?

qbo_wind.jpg

Finding a graph is not easy, but this one shows positive QBO as shaded grey, negative as white. It is up to August this year. Through the autumn and winter it reached a negative peak (white), which ties in nicely with the more frequent southerly and southwesterly flows, and also ties in with the rapid and steep development of the current El Nino. We are currently going through the transition from negative to positive. From mid summer we will be in the positive (grey) side of the anomaly, which if Neil's theory is right, will lead to a weakening of the E Nino and a shift to a more northerly airflow anomaly in the Tasman Sea. So, our frequent cold SW changes might not last for too much longer, and we may see a warmer than usual late summer and autumn. I've been meaning to check up on this for all of this year, so thanks for your question John, you nudged me into action! There, I too have learnt something important today, and must go away and modify my long range forecasts accordingly!

Incidentally, if you look at 82/83 you can see the timing of the shift from negative to positive was almost exactly the same as this year, so that ties in with the frequent SW changes that spring and early summer as well. And 97/98 had the positive QBO come in earlier in the year, hence the more northerly enhanced spring and summer airflows. So, although poor old Neil has long passed away, and I'm not sure if he ever got to publish this theory formally, there does seem to be something in his ideas.

[NZ Thunderstorm Soc]

Thanks for that , Tony.
I had forgotten about Neil Cherry's theory about the QBO, which I can remember vaguely in a lecture that I attended in my early NZThS days.
...so maybe with this current negative El Niño, it maybe an interesting season, or rather boring???

[TonyT]

I'l go with interesting till December, John.

[treetop]

I see MetVuw has things looking back to normal for a while from Sat nxt week.

[TonyT]

Courtesy of Joe D'Aleo at Weatherbell, here are a couple of SST comparison charts (sorry they are so small, but the idea is give you a broad global overview, not focus on details) of the 1982/83 El Nino (top) and 1997/98 (bottom). In each case this year's SST (to a few days ago) is the right hand panel.

Screen_Shot_2015_09_23_at_12_49_02_PM.png

Screen_Shot_2015_09_23_at_12_46_53_PM.png

[treetop]

Sea temps around Australia holding up while the E Ninos influence on Nth/Sth America looks particuarily strong .the reason for all the alarm bells no doubt.

[Storm Struck]

Would you call the weather of the past week more neautral/stationary rather than any typical El Nino or La Nina pattern?.
I know its been a complex wedged system but its certainly taken a break from the NW to SW flow anyway.
From what I can see its returning again from mid next week, so moving out of the cooler days and damp low clag.

[Richard]

Looking at 1982/83 El Nino and the 1997/98 they were both mainly confined to the western Pacific, but the current event shows warmer than normal waters in many other areas all around globe, given this, maybe the weather in the next few months wont behave similar to those past El-Ninos

[treetop]

Warmer seas around Australia may enhance moisture feed across the Tasman. S Is may indeed have a very wet stormy summer with some spill over to the high country..

[treetop]

Sorry I mean the west coast of S Is

[NZ Thunderstorm Soc]

I'l go with interesting till December, John.

....or from December?

[Willoughby]

El Nino shifting into 4th gear, ravaging PNG with drought as SST anomalies continue to drop below average over the east maritime continent (very similar to 97/98).

Could be a long Summer season for firies ahead, judging by recent heat in NSW and the eastern South Island.

http://www.abc.net.au/news/2015-10-07/c ... ng/6833028

[Willoughby]

Posting this for posterity sakes. Current SST anomaly map shows a very-strong El Nino episode with a signature significant cooler-than-normal area over the Maritime continent, extending to Tonga.

anomnight.10.19.2015[1].gif

TRMM satellite last 30 day anomalies show the signatures of a strong El Nino event;

new_big_anomaly[1].gif

Drought over Indonesia, Malaysia and a large part of south Asia including India. Extreme drought over New Guinea and the Solomons. Developing drought over the North Island of NZ. Higher than normal rainfall over southwest USA. Dry over northern South America.

[Richard]

And i see BOM are now saying that it may not peak till about autumn

[Nev]

And i see BOM are now saying that it may not peak till about autumn

Where did you hear that Richard?

I'ts just that everything I've read to date still says that the BoM expect this El Nino to peak around Xmas and is likely to remain above El Nino thresholds until at least early autumn.

[TonyT]

SSTs are now dropping in some of the Nino zones, combine that with the weather patterns over NZ lately and I suggest the peak is happening right now.

[Richard]

And i see BOM are now saying that it may not peak till about autumn

Where did you hear that Richard?

I'ts just that everything I've read to date still says that the BoM expect this El Nino to peak around Xmas and is likely to remain above El Nino thresholds until at least early autumn.

I cant found the link but who ever wrote it took what BOM said out of context, what they are saying is "It now looks set to attain record levels, not quite there at the peak of the 1982 or 1997 events, which were records in the recent history, but we forecast it to get there eventually around Christmas and the phenomenon could persist well into autumn," - BoM director Dr Rob Vertessy

You can see how someone could misinterpret this , peaking from around Christmas and remaining there till autumn

[NZstorm]

El Nino has transported Auckland's climate into the southern oceans with a lot of cloudy coolish weather lately. Not much precip though.

[jamie]

El Nino has transported Auckland's climate into the southern oceans with a lot of cloudy coolish weather lately. Not much precip though.

I think it's fair to say this weather is rubbish. We have had 30+km winds for the past 21 days, from the SW with cloud and trace amounts of rain from these showers.

It sucks!!!!

[Nev]

SSTs are now dropping in some of the Nino zones, combine that with the weather patterns over NZ lately and I suggest the peak is happening right now.

You might be right. While Nino 3.4 SST's have continued to rise, some models suggest that they may be plateauing, and NOAA's latest Weekly ENSO Update shows a recent decline in Nino 3 and Nino 1+2.

NOAA Weekly ENSO SST Update - Oct 19, 2015.png

NOAA Pacific SST Chart - Oct 19, 2015.gif

BoM Nino 3.4 Model Outlook - Oct 11, 2015.png

[spwill]

El Nino has transported Auckland's climate into the southern oceans with a lot of cloudy coolish weather lately. Not much precip though.

I think it's fair to say this weather is rubbish. We have had 30+km winds for the past 21 days, from the SW with cloud and trace amounts of rain from these showers.

It sucks!!!!

Has been less windy here than normal or atleast no strong winds this Spring so far, the complaint here would be the cloudiness of the last couple of weeks.
I see much of NZ has been sunnier than normal this October so far

[Razor]

Happy with the weather in Christchurch so far, very happy! Although wish it would rain a bit for the rural folk