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so the SOI is +29

Discussion in 'Alpine & Southern' started by TC, Apr 12, 2006.

  1. TC

    TC Pool Room Ski Pass: Gold

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    +29 we should be under water
    so wheres the rain????
     
  2. hair-raiser

    hair-raiser Hard Yards

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    Today, BOM: http://www.bom.gov.au/climate/enso/#current

    "Summary: Pacific remains neutral. Cool phase nearly over

    The recent cool phase in the Pacific, which briefly approached La Niña-like conditions, is showing signs of decay. Sea-surface temperatures have continued to warm in the central to eastern Pacific and are now close to average. More importantly, the large body of cooler than average sub-surface water in the east has contracted considerably during the past month.

    Nonetheless, the SOI has continued to rise, with the latest 30-day value being about +18. "

    Where did you see +29? The above is:

    "CURRENT STATUS as at 12th April 2006"

    There is no La Nina, all the talk about it was a beat-up.
     
    #2 hair-raiser, Apr 12, 2006
    Last edited by a moderator: Nov 14, 2013
  3. Vermillion

    Vermillion Pool Room Ski Pass: Gold

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    SST's in the east pacific are slightly below average, but not by much.

    this is good.
     
  4. snowcrazed

    snowcrazed One of Us

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    Yeah I think people were saying the SOI index at slightly positive is what we're after? More precip, but not so warm?
     
  5. churchy

    churchy One of Us

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    could the 4 recent TCs in the last few weeks have anything to do with a wildly overstated soi?
     
  6. Sandy

    Sandy Dark Sith Lord of the Pool Room Moderator Ski Pass: Gold

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    These fluctuations are common. The difference in SOI amounts to just a few point difference in the pressures in Tahiti & Darwin:

    Date . . . . . . . . Tahiti . . . . . . . Darwin . . . . . . Daily SOI

    04-Apr-2006 . . . 1012.39hPa . . . 1004.95hPa . . . 36.40
    11-Apr-2006 . . . 1012.83hPa . . . 1009.35hPa . . . 7.80

    Churchy, yes the TCs have a significant effect on the SOI. However, TCs this late MAY also be an indication of an approaching La Nina....
     
  7. TC

    TC Pool Room Ski Pass: Gold

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    i saw the +29 on ABC news a couple of nights ago
     
  8. BlueMountains

    BlueMountains First Runs

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    Yes, neutral conditions to persist throughout winter looks the go for mine. With the cooling of the SST's in the Bight now, we could well see some big highs blocking for a while. No surprise in late autumn/early winter though. RE SOI, I tend to look at the 30 day running average but its not really a concern at the moment for me.
     
  9. Vermillion

    Vermillion Pool Room Ski Pass: Gold

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    there is very cold water upwelling at the moment in the east pacific, up to 4C below the average. this could be significant if it continues.
     
  10. snowcrazed

    snowcrazed One of Us

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    Where'd you see that? Got a link to a chart or something?
     
  11. slalom pete

    slalom pete Hard Yards

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    For us lay people could you please explain why this could be significant.Thanks
     
    #11 slalom pete, Apr 18, 2006
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  12. Bugski

    Bugski A Local

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    Possible La Nina.
     
    #12 Bugski, Apr 18, 2006
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  13. Vermillion

    Vermillion Pool Room Ski Pass: Gold

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    dont put words in my mouth [​IMG]

    no, a cooler SST for a prolonged period of time (more than a month or so) does mean the walker circulation should shift further to the west pacific, which is typical of la nina. This is not to say that this will happen because there are other factors involved.

    i just said it was encouraging [​IMG]
     
    #13 Vermillion, Apr 18, 2006
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  14. Falls expat

    Falls expat One of Us

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    This can be seen with these two SST anomaly charts one from March 14th and the other April 15th.


    March 14th

    [​IMG]

    April 15th
    [​IMG]
     
    #14 Falls expat, Apr 18, 2006
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  15. Vermillion

    Vermillion Pool Room Ski Pass: Gold

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    falls, you would know this better than me, is this significant? what do u think could possibly be the implications if this continues?
     
  16. snowcrazed

    snowcrazed One of Us

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    I'm confused, we've been saying a slightly positive SOI is ok, but doesnt that mean its slightly warmer than average nearest Australia during winter? So, wouldnt a strong el-nino be better for our winter, where temps off the east coast are below average?

    I have no idea about all this, just wondering, hopefully some of you weather folks can answer [​IMG]
     
    #16 snowcrazed, Apr 19, 2006
    Last edited by a moderator: Nov 11, 2013
  17. Cliff-jumper_2000

    Cliff-jumper_2000 First Runs

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    el nino drier but colder generally
    la nina warmer and wetter generally but mild ones of but can be good for the australian so season! I think anways.
     
  18. Sandy

    Sandy Dark Sith Lord of the Pool Room Moderator Ski Pass: Gold

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    1. A strong El Nino(SOI of less than about -12) mean very little precipitation, so we DON'T want that. Lower than SSTs (Sea Surface Temperatures) tend towards high pressure, higher than average SSTs tend toward low pressure formation. Look at the SST maps for March/April... it's not all that surprising that there's been tropical cyclones forming this late off NE Australia with all of that warm water in the Coral Sea.

    2. SOI SLIGHTLY higher than normal will tend towards more low pressure, and the CHANCE of more snow as well. If the SOI gets too high (+10), then the air temps also climb, so there may be less snow and more rain.

    I like to think that a good sustained winter SOI range is between -7 and +3
     
  19. BrentC

    BrentC Hard Yards

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    If anyones intrested I compiled some graphs a few weeks back on SOI vs Snow depth.
    SOI Vs Snowdepth

    And another graph with same Data but different axis (easier for comparing good seasons and bad ones me thinks)
    SOI vs Snow depth graph 2
     
    #19 BrentC, Apr 19, 2006
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  20. cashie

    cashie One of Us

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    looking at the graphs that BrentC has, it appears the best ski season came with a SOI of around 8 or 9
     
  21. Stratus

    Stratus A Local

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    Yes, but the 2nd best one came with an SOI of around -5 or -6.
     
  22. Sandy

    Sandy Dark Sith Lord of the Pool Room Moderator Ski Pass: Gold

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    Big seasons with SOI greater than +7(average thru July/Aug) only happened prior to 1982.

    Most of the big seasons since 1981 were generally around the -6 to +3 area(Jul/Aug).

    SOI measures comparative pressures between Tahiti and Darwin. However it doesn't measure any overall increase in SSTs in the Pacific in the last 25 years.
     
    #22 Sandy, Apr 19, 2006
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  23. Vermillion

    Vermillion Pool Room Ski Pass: Gold

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    i would like to see SST's incorporated into these graphs also.
     
  24. Falls expat

    Falls expat One of Us

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    It seems to me that the snow depth is particularly poor in the transition period from a strong El Nino to a strong La Nina which often go in pairs.
     
  25. Falls expat

    Falls expat One of Us

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    My understanding of upwelling along the pacific S American coast is due to strong southerly winds which cause Ekman currents that induce the coastal upwelling.

    If this is the case then this implies a strong high pressure system to the west of S America which also implies that there will be strong SE Trades along the central and eastern tropical pacific (south of the equator). If this is so then one would also expect to see a subsequent cooling along the intertropical convergence zone SSTs in this area in the next few weeks. This would reverse the recent warming trend of the SSTs here and thus revert back more towards a La Nina scenario.

    There is definitely a warm pool in the western tropical Pacific and as far as I am concerned this is not going anywhere in a hurry. So I favour a La Nina side of neutral this winter, but not extreme. If Sandy's stats are right then this must favour a better than average snow season.

    Having said that there have been some disturbing side shows which temper my enthusiasm. One being how much snow that Mammoth Mountain got and continues to get at the moment. The last time this amount of snowfall fell was in the northern winter of 92-93 and we know how much snow Australia got in 1993. [​IMG]
     
    #25 Falls expat, Apr 19, 2006
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  26. TC

    TC Pool Room Ski Pass: Gold

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    the soi continues to rise to record highs ...but still no rain
     
  27. snowcrazed

    snowcrazed One of Us

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    No rain? All I've seen for about a week is rain! I've found mushrooms growing in the parks near my house, havent seen them grow since 2004, last year was bone dry all through winter [​IMG]

    (this is melbourne i'm talking about by the way)
     
    #27 snowcrazed, Apr 24, 2006
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  28. Vermillion

    Vermillion Pool Room Ski Pass: Gold

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    chief ill agree with you. as far as i know all parts of the state east of melbourne have already recieved their monthly average rainfall.

    some of these changes take a while to get through TC. Recall that the maximum summer temperatures are towards the end of Jan/early Feb due to lag. SOI has a similar lag.

    Also, have a look up north, cairns is having record rainfall, so did katherine not long ago and most of the top end, the monsoon is kicking royal ass up there.

    And with the fronts due to come through in the next few weeks, it looks like plenty more rain is on the way.
     
  29. TC

    TC Pool Room Ski Pass: Gold

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    unfortunately im in sydney

    I miss my melb
     
  30. Sandy

    Sandy Dark Sith Lord of the Pool Room Moderator Ski Pass: Gold

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    The SOI should take a HUGE spike into the positives in the next couple of days..... [​IMG]

    My guess would be +100 or more......
     
    #30 Sandy, Apr 24, 2006
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  31. TC

    TC Pool Room Ski Pass: Gold

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    ahh monica my darling
     
    #31 TC, Apr 24, 2006
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  32. Vermillion

    Vermillion Pool Room Ski Pass: Gold

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    but that wont be sustained because its a running 30 day average [​IMG]
     
    #32 Vermillion, Apr 24, 2006
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  33. Sandy

    Sandy Dark Sith Lord of the Pool Room Moderator Ski Pass: Gold

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    Isn't that what "spike" means?? :p
     
    #33 Sandy, Apr 25, 2006
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  34. Vermillion

    Vermillion Pool Room Ski Pass: Gold

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    but but but....ahhh :p
     
  35. TC

    TC Pool Room Ski Pass: Gold

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    well whats happening
     
  36. Vermillion

    Vermillion Pool Room Ski Pass: Gold

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    well the SOI is around 15 if i remember correctly, or maybe 12, and SST's are still cool in the upwelling region in the east pacific. Look at April's rainfall and you'll see that more than 50% of the country had above average rainfall. with the fronts lining up like they are for the SE it looks like we'll be above average again this month if it goes to plan.
     
  37. snowcrazed

    snowcrazed One of Us

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    The next update from BOM should come out tomorrow, well... today... should be interesting!
     
  38. Sandy

    Sandy Dark Sith Lord of the Pool Room Moderator Ski Pass: Gold

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    The Current SOI is +2.3
    30 day average is +11.24
    90 day average is +8.05

    "Fronts lining up" do not generally give us much better than average rainfall in the SE, it's cut off lows that provide the elevated levels of rain. Why? Generally, if we have one front after another before winter, we have lower than average temperatures (April was one degree lower than average in Melbourne) but the fronts are weak and the pressure remains higher.

    For example in Melbourne, we two episodes of "fronts lining up" in April, 11th & 14th(with rain on 14,15,16th of 15mm), again on 18th, 20th, 21st & 23rd(with rain on 20,21,22nd of 11.8mm). The pressures dropped to 1005.5hPa on the 11th and 1008.9hPa on the 19th. These pressures don't provide the "whack" for sustantially higher levels of monthly rain.

    If you look at December on the other hand, Melbourne had 38% more rainfall than average.

    This was mainly made up of a series of cut off lows. There was 38.2mm with a pressure of 995.7hPa around 3rd-4th, 33.2mm with a pressure of 1001.5hPa around 6th-7th, and 6.2mm with a pressure of 999.3hPa around 12-13th.


    At 44.8mm Melbourne had 13% less than its average rainfall for April.

    At 46mm Hobart had slightly above average rainfall for April. (+7%)

    At 9.8mm Sydney had 91% less than its average rainfall for April.

    So I'd hardly say "looks like we'll be above average again this month", since we haven't really had above average rain LAST month.

    The SOI figures for March/April have been skewed to a large extent due to the number of tropical cyclones in QLD/NT/WA. This drops the SOI sharply, although briefly. The late TC season may be indicative of warming off NE Australia, however. Now that the TC season is "over", I'd look at the daily SOI for the next few weeks, and at the SST maps.

    Here is the SST anomoly chart for 2nd May. It shows why we've had a few TCs form in the Coral Sea.

    [​IMG]

    You can also see the current cooling off Chile & Peru.
     
    #38 Sandy, May 3, 2006
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  39. Vermillion

    Vermillion Pool Room Ski Pass: Gold

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    i wasnt just talking about melbourne and tassie, australia is bigger than that [​IMG]
     
    #39 Vermillion, May 3, 2006
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  40. adminvb

    adminvb First Runs

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    "At 9.8mm Sydney had 91% less than its average rainfall for April."

    Conditions in NSW generally are starting to look really dire again. Made a trip out west of the Blue Mountains a week or so ago and it's parched. East of the Blue Mountains isn't much better.
     
  41. Sandy

    Sandy Dark Sith Lord of the Pool Room Moderator Ski Pass: Gold

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    You said "with the fronts lining up like they are for the SE it looks like we'll be above average again" :p
     
    #41 Sandy, May 3, 2006
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  42. snowcrazed

    snowcrazed One of Us

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    #42 snowcrazed, May 3, 2006
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  43. TC

    TC Pool Room Ski Pass: Gold

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    se australia looks good
     
  44. Misses Frog

    Misses Frog First Runs

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    yeah SOI looks good for a nice fall in late May I reckon.
     
  45. Rednut

    Rednut First Runs

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    thanks misses frog [​IMG]
     
    #45 Rednut, May 9, 2006
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  46. slalom pete

    slalom pete Hard Yards

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    So frog's wife is doing forecasts now [​IMG]
     
    #46 slalom pete, May 10, 2006
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  47. TC

    TC Pool Room Ski Pass: Gold

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    the SOI has nose dived to +7
     
  48. Sandy

    Sandy Dark Sith Lord of the Pool Room Moderator Ski Pass: Gold

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    SOI can often change quite a lot from day to day. Here's the last 10 days(oldest to newest)
    +2.3
    -2.8
    -5.1
    -10.5
    -4.8
    +8.5
    +12.2
    -1.2
    +8.6
    +6.6

    30 day average is +4.9
    90 day average is +8.64

    SOI graph for 2004-2006 Trending towards the low + values:

    [​IMG]
     
    #48 Sandy, May 12, 2006
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  49. TC

    TC Pool Room Ski Pass: Gold

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    looks messy
    whats causing such fluctuations
    or is that normal so the avg smooth out the fluctuations
     
  50. Sandy

    Sandy Dark Sith Lord of the Pool Room Moderator Ski Pass: Gold

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    That's normal.

    SOI measures the difference in pressure between Darwin and Tahiti (in Standard Deviations, I think) if you get a spike in the pressure in either place, it changes quite a lot.