Technical Current & Forecast Climate Drivers

Michael Hauber

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Not exactly convincing with a couple weeks of weak westerly anomalies in the central Pacific. But its always risky reading too much into short interruptions as the MJO goes through a contrary phase.

surface.png


But while it looked like the MJO was coming around again and the next trade surge has now started to build from the far west, I look to see that this has popped up in the latest GFS forecast. And something similar in the last three forecasts as well. Forecasts at day 11-14 for trade surges are sort of reliable (or at least better than throwing darts at a board), especially when compared to forecasts for smaller scale features at that range. However less so when the forecast is contrary to what MJO suggests is likely, which is a trade surge. And it wouldn't take too much to shift that westerly burst further south and out of the equatorial region.

forecast.png



Current MJO forecast shows an unusual surge in the far west Indian Ocean zone right at the start, and then getting right into the La Nina favorable zones for the rest of the two week forecast period, but getting quite weak.

ensplume_full (12).gif


There is definitely some contrary indicators going on, and a borderline La Nina state or cool neutral can cope with at least some contrary stuff going on. But yet to be convinced that this cooling trend is going to stick.
 

Stumer1

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Yep been two big back to back lows pushing up from the south-west the last week.

Making surf like this!

Impressive.
Dramatic cooling of the -PDO warm tongue off Japan in the last week.

Looks like the -PDO could be shifting back into a more neutral/positive phase.
They have a few tropical storms up that way which could be cooling it.
 
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rocketboy

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Latest iri.columbia.edu forecast is looking like a medium la nina


SON21_World_pcp.gif




August 2021 Climate Forecast Discussion for Sep-Nov through Dec-Feb 2022

The IRI NMME seasonal forecast for Aug 2021 uses 3 models, CanSIPSv2, NCEP-CFSv2, and COLA-RSMAS-CCSM4.

The SST temperatures in the tropical Pacific are slightly cooler than normal, and ENSO-neutral conditions are in place. Forecasts from the North American Multi-Model Ensemble (NMME) predict that SSTs will continue to cool and produce a second La Nina event over the next several seasons. SST anomalies in equatorial Atlantic are above-normal in the strongest Atlantic Nino ever observed. The equatorial Atlantic SSTs are likely to remain above-normal through the boreal summer. SST anomalies in Indian ocean are also above-normal, and these also are predicted to persist through the rest of the boreal summer.

The precipitation forecast shows enhanced probability for above-normal rainfall over parts of the Maritime continent, eastern Brazil, and much of Australia during the next four seasons, though the probabilities are much weaker by DJF. The seasonal precipitation forecasts favor below-normal precipitation for the band extending from Senegal to southern Sudan during the SON season. During the first two seasons (SON and OND), precipitation is also forecast to be below-normal over much of the Greater Horn of Africa countries, Uruguay, southern Argentina and Brazil, and northern Europe. In OND the southeastern United States and southwestern Asia also show forecasts favoring below-normal precipitation. The southeastern US region favoring below-normal precipitation evolves in the following seasons – first to Texas and northern Mexico, and then encompassing the southwest.

Surface temperatures over southern/mideastern United States are likely to be above-normal for the SON season, and subsequently evolves toward Texas and northern Mexico, and then across the southern tier of the US. Above-normal temperatures are forecast over northern Asia for all seasons. Below-normal temperatures are forecast for northern Canada in NDJ, and that below-normal forecast area grows in DJF to include most of Canada, Alaska, and north-central US.
 

Michael Hauber

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Some suggestion of a weak warm Kelvin wave. In response to the weak westerly anomalies of the last couple of weeks? Surprising if so as I would have thought they were too weak and too far east to cause a kelvin wave response.

time_lon_EQ_hf_iso20_uwnd_anom_anom_202011_202108_inline_2021081817.png


Sort of persistent warm subsurface in the far east is odd as well. To me far east is more of a symptom rather than a driver, but in this case a symptom of what? Maybe a mix of warm kelvin waves and cool kelvin waves, combined with the fact that warm kelvin waves seem to have stronger impact in far east and cool a bit more towards central east (personal observation - can't nail down anything definite and is not backed up by any research I've seen). Or maybe the westerly anomalies north of the equator have boosted the counter-current north of the equator and resulted in an injection of warm water in the far east

surface 5N.png
 
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Craig B

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I just posted this update in an article I did on Swellnet..

Update:

Things are continuing to slowly bubble away with cool sea surface temperature anomalies setup through the central Pacific from anomalous easterly trade winds, warmer to the west.

1629342791254.png


The big key to the coming double-dip Niña is the sub-surface temperatures. They're cooler than normal and waiting to be upwelled with the next burst of easterly trades, which looks to occur over the coming week.

1629342806990.png


Here's the forecast wind anomalies at 1500m above the surface at the equator, showing we've got good easterly trades on the way (dark blue box) through the central and western Pacific which should help upwell that cooler water. Blue = stronger than normal east winds, red = west winds.

1629342816205.png


And finally NOAA is going a 70% (upgraded from 66%) chance of La Niña conditions through their winter, our summer.

1629342829313.png
 

Michael Hauber

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Been a lot of easterly a long way west for a while. Look at SLP patterns for last 90 days (and similar patterns last 30 and last 7 days). High pressure along the equator right through to north of Australia. The only low pressure anomalies in the tropics are in NE Pacific which is a bit el nino like, but all the high pressure everywhere else is good for enhanced trade winds. And low pressure anomalies over the Asian land mass but not in the NW Pacific. Is it too much to hope for that we get a similar pattern for summer? That would be not much coral sea cyclone activity, but lots of rain over the continent.

slp_90b.fnl (1).gif


source
 
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POW Hungry

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This is a really interesting read. Here's the paper on it:

It's also linked with the negative pressure anomalies to the SE of the ridge, which have been particularly prominent this winter season (neutral-positive AAO).
1630202437806.png
 
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Craig B

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The Australian Bureau will update their climate driver outlook today. I wonder if they'll go on La Niña watch? http://www.bom.gov.au/climate/enso/outlook/

NOAA forecast models have strengthened a little, pointing to SST anomalies in the important Nino 3.4 region being about -1 below average into the end of the year. This is the threshold for La Niña.

1630363034993.png


Also the negative zonal (meaning easterly) wind forecast anomalies are expected to broaden across the Pacific into that 3.4 region (blue and purple shading).

This should lead to further upwelling of cool sub-surface temperatures, and really get things turning over. If this goes to forecast it looks like we'll be well under way into the middle of September..

1630363045368.png
 

Hermon

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IOD looks to be retreating to Neutral by our summer. It might be wet along the East coast of Australia, but probably getting dry in Vic (and it already is!). Part of me wonders that we might get a rather lively storm season later in Spring.
 
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Thunderstruck'

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I have to say the Negative IOD atm has certainly been less than spectacular for SA, traditionally August and September are good months with a moderate to strong IOD in place. Despite good looking SST's, there is lack of NW cloudband activity that has been largely absent since July where a good month was had though a large portion of that can be attributed to the negative SAM.

With the first half of September looking dry, a lot of farmers are in deep strife with tomorrow likely to wipe millions of any crops and blow the flowers off some nice canola crops in the Mid North. Some areas east of the ranges are dustbowls one could be forgiven to think that we were in a positive IOD. The lack of Indian influence is concerning for now...I do think the bad timing of the positive SAM on the back of a dry August is re-enforcing the dryness. The poor summer, dry autumn and lack of sub soil moisture is not allowing much room for error so with the Negative IOD comes around many have seen this as a potential saviour but alas right now that is not the case. This smells a bit like 2014 atm however I would be surprised if we see a westward propogation of the warmer anomalies in the Indian. Once the SAM eases back to more neutral levels, we should see a good balance of shortwaves/longwaves off the westerly belt mixing with tropical influences favouring more cut off lows into later September and October. We could well end up with an average spring at least, however, a lot of the rain could be too late for some.

TS :cool:
 

POW Hungry

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Once the SAM eases back to more neutral levels, we should see a good balance of shortwaves/longwaves off the westerly belt mixing with tropical influences favouring more cut off lows into later September and October.
I kinda get your drift but we've had prevailing neutral AAO/SAM throughout the Austral Winter.
I think that's been the catalyst for the aforementioned deficiencies TBH.

There's only be 2-3 decent swings of AAO all winter:
Screen Shot 2021-09-01 at 8.47.06 pm.png
 

Thunderstruck'

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I kinda get your drift but we've had prevailing neutral AAO/SAM throughout the Austral Winter.
I think that's been the catalyst for the aforementioned deficiencies TBH.

There's only be 2-3 decent swings of AAO all winter:
Screen Shot 2021-09-01 at 8.47.06 pm.png

This issue here is the timing. Put simply, the on ground impacts are not like a Negative IOD year at all for August and September. The good years we even get regular floods through the hills and associated districts. There is simply not enough moisture feeding in from the NW and to now see a movement of the SAM to a more positive phase when we really still don't have that moisture sitting in the right spot like July is concerning and against past events. A good positive SAM is only helpful when we are further into warm season with more negative influences being less desirable.

With regards to the history of this winter, July saw values more negative than positive without being ragingly negative. The strong and dominant longwave trough node sitting at the WA longitude combined with the strong vertical motion off Sumatra combined for the perfect combination for WA whilst SA saw the downstream effects of that with a few strong fronts slipping through. It was one of the windiest months I can remember in any winter with high pressure well north. Come to August the retreat of the westerlies was very obvious and not reflected so well in the actual SAM itself but this will show a further retreat into September with more easterly winds across southern SA. Already late August we had some downslope katabatics at night which is something I can't recall since 2006.

I do expect things to come back because the pattern is there in the Indian, but it will be too late for many grain growers in SA, certainly so across northern Eyre Peninsula, the Upper North from Jamestown and north and most of the Mallee. Northern Yorkes is 50/50 in spots.

TS :cool:
 

Craig B

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Yeah besides that July rain, it has really dried and warmed up across the south-east eh. The IOD impact seemed to be seen mostly in the build up to it, not during.

Hopefully the rain comes back.
 
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Claude Cat

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BOM Vic Winter summary up.


Close to average rainfall​

  • Winter rainfall was close to average across most of Victoria.
  • It was wetter than average in parts of Gippsland and Western districts.
  • Averaged across Victoria, rainfall was around 5% above the winter mean of 205 mm, the highest winter rainfall since 2016.
  • The state's highest daily rainfall total this winter, 280.6 mm, was recorded at Mount Baw Baw on 10 June; this was the fifth-highest daily rainfall total on record for Victoria for any month.
  • Many sites had their highest winter daily rainfall on record on 9 and 10 June, including Port Campbell Post Office, Macedon Forestry, Cobden Post Office and Terang, all of which have more than 100 years of measurements.
  • With 755.8 mm recorded during this winter, the wettest place in Victoria was Falls Creek (Rocky Valley).
  • Averaged across the state, the year-to-date rainfall total was around 440 mm, 1% above average.

Warmest winter nights since 2013​

  • Night-time temperatures were above average across Victoria, with large parts of the state experiencing much warmer than average nights.
  • State-wide, minimum temperature for winter was 1.11 °C warmer than average, the fourth warmest on record, and the warmest since 2013.
  • The highest daily minimum temperature of 14.6 °C was recorded at Lakes Entrance on 28 July.
  • Swan Hill had its highest winter mean daily minimum temperature on record, while several sites had their highest winter mean daily minimum temperature for at least 20 years.
  • Daytime temperatures during winter were above average in most of the state, and much above average in parts of the south and the far north-west.
  • Averaged across the state, maximum temperature was 0.74 °C warmer than average, the warmest since 2013.
  • The highest daytime temperature in Victoria this season was 27.6 °C, recorded at Mildura Airport on 31 August, in a warm north-westerly airflow preceding the approaching cold front.
  • Year-to-date mean maximum and mean minimum temperatures were 0.22 °C and 0.36 °C above average respectively.
 

POW Hungry

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If you’ve been wondering why you were skunked by rainfall last La Niña phase, last Spring; here’s your answer:
It’s no longer a secret that seasonal models (AXS S1) over-predicted warmer SST’s in the Northern Aus region and undercooked the MJO influence in equatorial IO.
 

Craig B

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If you’ve been wondering why you were skunked by rainfall last La Niña phase, last Spring; here’s your answer:
It’s no longer a secret that seasonal models (AXS S1) over-predicted warmer SST’s in the Northern Aus region and undercooked the MJO influence in equatorial IO.
Very interesting!
 

AshestoAshes

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The SSTs around the north of Australia are boiling at the moment, could be a lively TC season.
It will all depend on how much tropical activity occurs to the east of us (well at least for QLDers). We can't keep getting our easterlies getting cut up by lows/cyclones around Fiji and Vanuatu, if that pattern breaks could be a very big season.
 

PeteJ

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It has finally happened. Big low developed near French Polynesia causing pressures to plunge over Tahiti. Constant massive outbreaks of cold dry air pushing well north and huge highs over Australia keeping pressures high over Darwin, and eroding the above normal SST's. Hope this situation will come to an end soon. I always give it(assuming SOI does a plunge for a while) a month before really starting to become concerned.
 
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Craig B

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It has finally happened. Big low developed near French Polynesia causing pressures to plunge over Tahiti. Constant massive outbreaks of cold dry air pushing well north and huge highs over Australia keeping pressures high over Darwin, and eroding the above normal SST's. Hope this situation will come to an end soon. I always give it(assuming SOI does a plunge for a while) a month before really starting to become concerned.
What are you concerned about? Also that's a relative weak low. All still on track for the developing Nina.
 

Craig B

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Update:

The Niño 3.4 index is plummeting from all that anomalous easterly trade-wind activity along the Equator.
1632955644787.png


Interestingly looking at the position of the cool water anomalies, they're quite far west which puts it in the La Niña Modoki category.
1632955657130.png


Modoki's usually see the rainfall across Australia more focussed towards the west, ie away from the East Coast and more towards central Australia, the NT and north-east WA.

Looking at the cool sea surface temperatures off south-east Qld this looks to correlate as well.

Rainfall correlation across Australia with La Niña Modoki left and traditional La Niña right (blue = rainfall increase)..

1632955680056.png


Not ideal for SE QLD/NNSW etc.
 
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