Technical General Stratospheric Observations

Discussion in 'Daily & Chat' started by crikey, Jul 6, 2019.

  1. Michael Hauber

    Michael Hauber One of Us

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    The cooler SST's result in only a few percent reduction in evaporation. The primary reason why the atmosphere is so much drier in unfavourable IOD (and/or ENSO) is the introduction of large scale sinking air and stability. This dries out the atmosphere from above. Any cold pool/cut off upper level low will reverse this tendency, at least locally near the location of the system.

    Some research on IOD impacts suggest that along the east coast of Australia a +ve IOD enhances easterly flows and increases moisture supply and rainfall. Only in a fairly thin strip near the coast and on the eastern slopes of the ranges which are far more sensitive to surface level trade wind moisture supply, and/or orographic benefits from an easterly regime.
     
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  2. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    Hear hear.
     
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  3. snowbarbie

    snowbarbie Hard Yards

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    Interesting to see the context of a cooling trend at 10hpa -I think the base for climatology begins 1979. I assume the green threads are ensemble members -
    [​IMG]

    Ensemble mini maps(under Elliptical Diagnostics on stratobs website) GEFS modelling what looks to me like 2 of 21 ensemble sets have weak easterlies by 19 October. The other two models CMC and FNOMC(the latter us navy I think) dont quite have it dipping that far. These do jump around a bit. FNMOC is now pretty bullish, previously GEFS was more bullish on the cooling at 10hpa and stronger zonal wind towards end of model runs. Not sure who is following who.
     
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  4. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    Typically the temperature declines after a SSW, as the SPV recalibrates what is left of it.
    Then we will see it proceed to the final warming over the next month or so.
     
  5. snowbarbie

    snowbarbie Hard Yards

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    A strong persistent stratospheric high in the pacific sector, I believe, often accompanies final warming. I think the stripping out of pv is visible below(counter to the circulating vortex).
    [​IMG]

    At ~10hpa, it's difficult to see any marked siphoning of pv though the high cell does appear to be possibly migrating towards s. pacific

    sunday
    [​IMG]

    monday
    [​IMG]

    Below ~10hpa the presence of stratospheric high cell looks weaker and/or bipole . At least on Images available https://acd-ext.gsfc.nasa.gov/Data_services/Current/antarctic/index.html

    Perhaps a lagging transition to a high cell consolidating throughout the pacific lower stratosphere, and may signal that final warming will be triggered soon
     
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  6. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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  7. snowbarbie

    snowbarbie Hard Yards

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    Above SH charts now forecasting negative sam ahead. Been here before I know, so have to be cautious..though this time seems to descend from second negative node of sam forecast to form in mid to lower stratosphere...
     
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  8. Bello Weather

    Bello Weather One of Us

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    Looks like it could be a decent drop too if it comes off close to forecast. Amazing to see how much it changes from day to day @ the end of the run (actually seems to repeat every couple of days, would be interesting to know what makes it work in that way), but starting to look like this one could come off:

     
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  9. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    It's an ensembles outlook, yeah?
    I would hazard a guess that it's the just the long range variability of the members i.e. favours a handful of members and jumps back and forward between them.
     
  10. Simmo_snow27

    Simmo_snow27 Hard Yards

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    It's as if the model knows there will be a drop, but doesn't know when exactly.

    Given how late it's getting, perhaps the drop with be the final warming?
     
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  11. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    It’s actually deterministic IIRC.
    Just the way long range GFS rolls.
     
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  12. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    I reckon we are onto it.


    A real propagation of the SSW associated anomalies to the troposphere is on the cards.

    GFS has been onto it for a few days now, all the GEFS members are heading into -AAO territory.
     
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  13. snowbarbie

    snowbarbie Hard Yards

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    I've seen it described as dripping paint analysis which seems very well chosen. If we do get to see it - particularly in the downward drift of colour schematics in gph anomaly charts.
     
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  14. MegaMatch

    MegaMatch One of Us Ski Pass: Silver

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    Who's seen the recent AAO predictions for the next week or two? I wonder if it's related to the SSW, or just a coincidence?

    -AAO lines up pretty nicely with the below chart too I think? West coast of NZ and Tasmania to cop another walloping of westerlies with more moisture being pulled down from the north by powerful cold fronts:

     
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  15. nfip

    nfip Cold n' Rusty Ski Pass: Gold

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  16. PeteJ

    PeteJ One of Us

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    Relieved I decided to read the excellent posts in this thread before I was going to post this in the SE QLD/NE NSW thread. I have been watching that huge Low moving under Australia and its effects. The prospects for any sort of drought easing rain for northern NSW and southern QLD (away from the coast) is looking very grim.
     
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  17. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    Coldfronts over NZ IIRC tend to be correlated (with the limited data we have) with SSWs.

    The -AAO predictions are certainly associated with the SSW.

    The reality is that the spring seasonal mode has kicked in, and the STRHs will negate precipitation and cold impacts of this for much more than Southern Australia.

    And it looks like the lower strat and troposphere -ve anomalies will stick around into November. Just a note that the stratobserve site will change over to NH mode on November 1st, so after that point we will have to use the CPC and the GEFS charts.
     
  18. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    EC bearing fruit of the SSW propagation, long way out but there's significant volitaility in the LR, across multiple global models:
     
  19. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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  20. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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  21. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    Funnily enough, I've been pondering whether the strong +ive IOD is the catalyst for the SSW event; given we're in uncharted territory for both climate drivers...
    It could be both (catalyst and pacifier) yet, I guess.
     
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  22. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    It might be a part of it, but these things tend to be a combination of factors.
    We do know that the +Andes MT played a big role in the actual event.
    QBO and Ozone transport both may have parts to play in this as well.
     
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  23. Bello Weather

    Bello Weather One of Us

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  24. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    Agreed, although MT only changes due to climatic variables. Given the Andes are a static feature, it’s not a root cause.
    The influencing factors have to be upstream.
     
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  25. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    Of course. The weird thing is that it was a period of strong +MTs in response to a relatively weak Nina-esque atmosphere budget. And of course there are synoptics involved. Since then, the budgets have tanked, and then come back.
    The torques tend to be used as a climate driver themselves though. Because all climate drivers are influenced by each other eventually.
     
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  26. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    Yeah it looks like he is running both hemispheres, he might stop it when the SAM fully weakens.
     
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  27. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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  28. MegaMatch

    MegaMatch One of Us Ski Pass: Silver

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  29. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    Early signs of split scenario for NH, in the months ahead:
     
  30. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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  31. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    Northern Hemisphere:
     
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  32. Delta-T

    Delta-T Hard Yards

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  33. Bello Weather

    Bello Weather One of Us

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    Looks like another big drop in the SAM at the end of the run, could see more fire weather kicking in for those areas that miss out on any rain this week:
     
  34. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    Strat observersers are suggesting NH PV is out of the gates strong and looking like an early SSW event.
     
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  35. Karicta

    Karicta A Local Ski Pass: Gold

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    I can’t help but wonder weather (ha!) this seeming increase in SSW events isn’t related to /early signs of the magnetic field reversal?
     
  36. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    I doubt it.

    I certainly can tie the SH SSW down to the anomalous +IOD, which creates a unique tropical forcing that affects the QBO and the stratosphere via the tropical stratosphere, and also via the changing of torques in the extra tropics.
    The solar minimum could also be an agent in causing the SH SSW.

    And last SSW in the NH was certainly interesting, but I don't think the anomalous stratosphere is a sign of large-scale geomagnetic change.
     
  37. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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  38. Majikthise

    Majikthise Sage Moderator Ski Pass: Gold

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    Lots to digest there... .
     
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  39. teleroo

    teleroo Lincoln Turns at the Pass Ski Pass: Gold

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    A couple of take home messages for me:
    1. Strong El Nino has traditionally been associated with low (-ve) SAM in the Oct - Dec period. I'm guessing this manifests as more cold fronts passing south eastern Australia in this spring period, probably not bringing much rain, but regular "hair dryer" blasts from the pre-frontal norwesters. Probably followed by dry westerlies and southerlies, so basically a relatively dry winter type pattern persisting into spring. Bit like the current spring perhaps, though we aren't in El Nino at the moment.
    2. They are suggesting that continued ocean warming (due to global warming) may be associated with weakened "strong" El Ninos
    3. The "strong ENSO" - low SAM relationship also weakens under continued ocean warming.
     
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  40. Michael Hauber

    Michael Hauber One of Us

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    If I understand correctly they model each of the extreme el ninos - 82,97 and 2015 starting from September during the first year of the event. They modify initial conditions according to the trends in the observational record. These trends are towards a more La Nina state. El nino peak is largely baked into the system by September, with a simple statistical model reliably predicting peak based on strength in September, so effectively the model weakens the el nino state at initialisation in September and it is no surprise that the resulting peak in January is therefore weaker. More La Nina like conditions in September are all but guaranteed to lead to more La Nina like conditions in January. However it is possible that more La Nina like conditions just preceding el nino initiation (just before or after the new year) might cause more extreme el nino conditions in the following year.

    Models are predicting that the average trend should be towards a more el nino like average state, in contrast to the observed trend towards more La Nina like conditions so this is another reason to be sceptical of these results. The observed trend is towards a more La Nina like average conditions, but towards more extreme el nino events. 82,97 and 15 are stronger than anything occurring earlier in the 20th century, although records indicate an el nino of similar strength in the 1890s. Not sure how reliable that data is though. This event was associated with an extreme La Nina bounce back and extreme flooding in SEQ likely beyond anything in the modern record (four floods similar to or more extreme than 74 and 11 floods)
     
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  41. Michael Hauber

    Michael Hauber One of Us

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    Is this figure still being updated? I had a look at StratObserve.com and couldn't find it, and would be curious to see how things are looking.
     
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  42. Bello Weather

    Bello Weather One of Us

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    Nope, no longer running on that site sadly...only one now is this one:

     
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  43. SAsurfa

    SAsurfa One of Us

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    Yeah I emailed about it, no response, aggh was so useful.
     
  44. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    Don't forget this one, just chucking this here for posterity:
     
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  45. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    I just want it to go away at this point, as it’s helping to cause these heatwaves and propping up these bushfire dangers.

    Should weaken completely any moment now.
     
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  46. POW_hungry

    POW_hungry Old n' Crusty Moderator Ski Pass: Gold

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    We're seeing another feedback/circ event.
    It maybe a short lived cycle but we look to resurface momentarily and duck negative again.
    Perhaps the biggest catalyst to see another LW Trough peak through Southern Aus first 8-10 days of Jan.
    [​IMG]
     
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  47. snowbarbie

    snowbarbie Hard Yards

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    yes...I thought there was occasional hint of something there in recent deterministic gfs forecast for about that period...last few days seems to be something suggesting some extent of cold pool(for southern w.a at least) in each run.
     
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  48. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    Perhaps a cold pool for Tasmania in those first 10 days. It’s probably behind the system on 31st Dec, along with a MJO influence.

    A -AAO in summer is typically counter-productive to activity from the north.
     
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  49. Jellybeans

    Jellybeans not woke enough Ski Pass: Gold

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    SPV is back for the SH season, and already some interesting patterns emerging high above.
     
  50. dogski

    dogski One of Us

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