La Nina 2017/18

Discussion in 'Weather' started by rocketboy, Sep 26, 2017.

  1. rocketboy

    rocketboy Dedicated Member
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    And here comes the rain ....

    [​IMG]

    The ENSO wrap up for Sep 24 is now posted
    http://www.bom.gov.au/climate/enso/

    Tropical Pacific Ocean cooling expected to continue

    The El Niño–Southern Oscillation (ENSO) is neutral. However, sea surface temperatures (SSTs) have cooled in the central to eastern tropical Pacific since mid-winter. These SSTs are currently cooler than average but within the neutral range. Waters beneath the surface are also slightly cooler than average. Other indicators of ENSO, such as the Southern Oscillation Index (SOI) and trade winds, also remain at neutral levels.

    All international climate models surveyed by the Bureau suggest further cooling of the tropical Pacific Ocean is likely. Five of the eight models suggest SSTs will cool to La Niña thresholds by December 2017, but only four maintain these values for long enough to be classified as a La Niña event.

    While unusual, it is not unheard of to see La Niña develop this late in the year—the Bureau will keep a close watch for further, or sustained, cooling of the equatorial Pacific. Of the late-developing La Niña events, their effect on summer rainfall has been mixed, with some leading to widespread wet conditions across eastern Australia, and others having minimal effect.

    The Indian Ocean Dipole (IOD) is neutral and the model consensus suggests it will remain so. Three of the six climate models surveyed suggest positive IOD thresholds may be reached during spring, but it may now be too late to become an event. If a positive IOD eventuated it would be short-lived, as events typically decay by December.

    The dial remains at neutral.
     
    #1 rocketboy, Sep 26, 2017
    Last edited: Sep 26, 2017
  2. Jellybeans1000

    Jellybeans1000 Dedicated Member
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    Most models are going for Borderline La Niña or Cool Neutral, with CFS being the outlier for a stronger La Niña.

    This is a history of ENSO predictions, showing the obvious outliers that are never achieved in reality (black line).

    The 30 day SOI is +6.8, 90 Day SOI being +3.3
     
  3. Kletterer

    Kletterer Addicted Member
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  4. POW_hungry

    POW_hungry Part of the Furniture
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    I think there will be a reluctance to adjust the status based the cooling SST's, the other climate drivers (SOI & IOD) have remained quite neutral and cloudiness in the average range.
     
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  5. Kletterer

    Kletterer Addicted Member
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    Hopefully this has some accuracy.
     
  6. Kletterer

    Kletterer Addicted Member
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    Whats your take on the SAM/ South Tropic Ridge situation/forecast ?
     
  7. Hermon

    Hermon Dedicated Member

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    Well the AAO is strongly +ve at the present. We'll probably see a fair bit of Pacific Ocean tropical air drift inland from the NE before too long...
     
  8. Jellybeans1000

    Jellybeans1000 Dedicated Member
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    Long Range GFS suggests the Subtropical High moves north over Southern Australia.

    In other news, SH Polar Vortex still decaying....

    Once it's finished, the STR will go into place IMO.
     
  9. POW_hungry

    POW_hungry Part of the Furniture
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    I was looking at the Southern PV last night and we're seeing solid + anoms (at 10mb PV level) which is suggestive to me it's got a bit left in it, the problem is the sub-trop ridge will only strengthen as it re-establishes itself with heating through the sub trops - namely over Aus. Whether that means we'll see an increase in block patterns and cut off lows, I am not too sure but it does appear the PV will have an uphill battle against the transition into warmer SH patterns. I guess this partly why climate models suggest a decline in the SAM/AAO value.

    Sorry, it's not a definitive answer/opinion... If there's one area I learn the most on it's the climate drivers, the complexity of influences is massive and I struggle to keep up with a lot of it most of the time.
     
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  10. Jellybeans1000

    Jellybeans1000 Dedicated Member
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    Yeah, you can kind of see it looking on the EC 10mb SH charts on AccuProWx. The vortex is dying as the stratospheric hot anomaly overpowers the vortex as it weakens. I reckon it will all be gone by the end of October/early November.

    GIF of the SH polar vortex on EC.

    If it doesn't work
     
  11. MarkV

    MarkV Active Member
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    How will an eruption of Mount Agung be likely to effect any potential La Nina?
     
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  12. POW_hungry

    POW_hungry Part of the Furniture
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    I think you may have your wires crossed, the PV doesn't 'die', it's a persistent upper level low. It simply strengthens and weakens. Generally speaking, in winter it's strengthened, in summer it's weakened.
    Right now, late-winter/early spring it's at it's weakest (as 'normal'), hence why we're seeing the models throw up cold snaps and cut-off scenarios.

    But yes, as EC models it, it is running a little 'hot'.
    [​IMG]
     
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  13. Jellybeans1000

    Jellybeans1000 Dedicated Member
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    I was probably exaggerating a bit, but I think my point is still there. The STR will fall into 'summer mode' when the polar vortex weakens fully.
     
  14. POW_hungry

    POW_hungry Part of the Furniture
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    A major event would most certainly tip the scale in favour. But TBH it'd need to be major - it 'aint the only active volcano on earth.
     
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  15. Jellybeans1000

    Jellybeans1000 Dedicated Member
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    I am not quite sure about that, but if it does what it did in 1964 (pump millions of tons of sulfur compounds into the stratosphere), global temperatures will take somewhat of a dive for a year or two. Cooler weather = more snow.
     
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  16. Hermon

    Hermon Dedicated Member

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    That's got me wondering whether the recent solar flares had an influence in the recent spike in temps?
     
  17. Jani Makaraiinen

    Jani Makaraiinen New Member

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    Not necessarily , more likely maybe.
     
  18. POW_hungry

    POW_hungry Part of the Furniture
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    It's and interesting point, but it also coincides with the seasonal diminishing of the ozone.
    It's a decent shift from what I can see.
    [​IMG]
     
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  19. Jellybeans1000

    Jellybeans1000 Dedicated Member
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    Actually ABC out of the blue just did a story on it.

    Back to the ENSO topic....
    EC Seasonal prediction for SSTs in November. You can see the cooler SSTAs in the Niño region.



    All gone by March though....
     
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  20. rocketboy

    rocketboy Dedicated Member
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  21. Rush

    Rush Pool Room
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    Most climate models predict NINO 3.4 exceeding La Nina thresholds by December, but most of these models predict a return to neutral levels by February.

    It's very rare for La Nina events to initiate during the southern hemisphere summer.

    The NOAA dynamic model is an outlier compared to other model forecasts for NINO 3.4 anomalies in the next few months.
     
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  22. Rush

    Rush Pool Room
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  23. J_-W_-X

    J_-W_-X New Member

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  24. Kletterer

    Kletterer Addicted Member
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  25. Jellybeans1000

    Jellybeans1000 Dedicated Member
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  26. J_-W_-X

    J_-W_-X New Member

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    You are correct it was apparently proven many years ago QBO has no affect on enso.
     
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  27. Jellybeans1000

    Jellybeans1000 Dedicated Member
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    I read something about a QBO and ENSO relationship, but I am not convinced. Very interesting especially if we get a couple more studies done.
     
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  28. Kletterer

    Kletterer Addicted Member
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    Around 2010/ 2011 ? Just been catching up on some reading and as i am still a rookie jumped the gun a little. :oops: At least its weather and not porn i am looking at.:D
     
  29. Kletterer

    Kletterer Addicted Member
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    ENSO modulates QBO properties apparently.
     
  30. J_-W_-X

    J_-W_-X New Member

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    You likely find looking @ sexy girly models more interesting than strat winds filtering
    down into the pacific..models :)
     
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  31. Falls expat

    Falls expat Dedicated Member

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    It amazes me how slow agencies like BOM and NOAA are at predicting the onset of a La Nina. The fact is we have been in a La Nina pattern since last spring.

    Trade winds have been elevated, OLR is high and a building deep cold sea temp anomaly pool. 150m Sea temp anoms are now -3 deg C below normal. Upper Ocean heat anoms are already stronger than this time last year.

    We are not only going to see a La Nina, but I predict it will reach moderate status at -1 or lower. I would expect a cloudier, wetter and cooler eastern coast of Australia on average this summer due to enhanced easterly trade winds. However, as is often the case this means severe heat builds up in central Australia. If this gets a chance to break out it will bring a short lived but severe heatwave probably in Jan or Feb.
    [​IMG] [​IMG] [​IMG]
     
  32. FourSquare04

    FourSquare04 Dedicated Member

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    Cheers @Falls expat always love seeing your input on here :)
     
  33. Rush

    Rush Pool Room
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    Big call. Let's see how you go in February. BTW 'big agencies' can't flip flop and declare ENSO events at the drop of a hat. There are innumerable actions that are set in motion within the public and private sectors once a La Nina or El Nino is declared. You build better trust with your stakeholders w.r.t. dealing with uncertainty and risk management if you don't flip-flop and change your mind everyone month.

    NINO3.4 is back to neutral at the moment.
     
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  34. J_-W_-X

    J_-W_-X New Member

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    And with all that above there is still warmer anoms being sampled.

    [​IMG]

    Cdas is not always reliable data. Its always a wise choice to match it against
    other sources. It does appear to be on par atm with proprietary data graphic below.
    3.4....... 02.


    [​IMG]
     
  35. Falls expat

    Falls expat Dedicated Member

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    All I am saying is observations support the current neutral weak La Nina to build into a weak to moderate La Nina. Deep SSTs are 3 deg below normal, Upper ocean heat content is cooler than last year already, trade winds are above normal basin wide, the global patterns are adopting a La Nina like zonal shape with enhanced subtropical highs and strong westerly Jets. Why on earth is NOAA saying there is only a 55-60% chance of La Nina forming when we have already seen SST anoms reaching La Nina levels in relevant regions? Last year there was residual warmth in the western basin which broke out as a kelvin wave. This year there is little evidence of this.

    Queensland is about see it's first tradewind induced wet event over the coming week (week beginning 16 Oct 2017) with widespread 100+ mm rainfall. This fits in well with the type of pattern that eastern Australia sees in a neutral or La Nina like Pacific SST pattern.

    [​IMG]
    Odds are, the east coast of Australia is in for a coolish, fairly wet summer period with the odd severe heatwave breaking out from interior Australia during short periods when the trades shut down.
     
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  36. Rush

    Rush Pool Room
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    [​IMG]
    That's a big burst.
     
  37. Majikthise

    Majikthise Sage
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    yeah I reckon its on... troughy summer for east coast.
     
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  38. Hermon

    Hermon Dedicated Member

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    MJO gonna move very fast:
    [​IMG]

    Apparently a similar thing happened in late-1985. (I remember the Summer of 1985-86 being a non-Summer in Central Vic).
     
  39. J_-W_-X

    J_-W_-X New Member

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    FYI.
    Convectively coupled kelvin waves travel fast, the mjo does not and never will.

    Your more than welcome to prove me wrong.