ENSO & IOD

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Re: ENSO & IOD

Post  Anthony Violi on Sat Aug 01, 2009 5:16 am

Your right Andrew, El Nino means nothing in regards to this. What is important is the amount of rainfall we have had. Last 13 years been very dry so that in itself means the fire risk is much higher. For us to have a worse fire year than last summer, we would need to be very very unlucky.

First off, it rained a fair bit in Nov/Dec 08, first time grass was green at Xmas time in many years. This provided so much fuel when the heatwave came that it was an unstoppable force. This year been very dry also so the amount of fuel in theory should be less. So unless we get good rains again early on in the summer, i would think it wont reach the biblical proportions we saw 6 months ago.

And we wont see 47 again with those gales, virtually all the planets aligned that day for a once in many years event.
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Re: ENSO & IOD

Post  hillybilly on Sat Aug 01, 2009 1:16 pm

First thing to remember is that global warming is changing everything - the source region for our heatwave (about 20S) is warming up rather quickly (http://www.bom.gov.au/cgi-bin/climate/change/trendmaps.cgi?map=tmean&area=aus&season=0112&period=1970). It's a noise trend, but essentially now we have air that is frequently extremely hot ready to dive south.

You actually find that El Nino summers are usually "cooler than average" but have a small number of very dry very hot windy days. In contrast, La Nina summers are usually "warmer than average" but most usually lack very dry hot windy days. La Nina summers tend to have a lot of northeasterlies and El Nina summers tend to have a lot of southwesterlies. This is in the average - however - as I'll explain below...

As it turns out the two hottest spells in Victoria's history - 1939 and 2009 were both La Nina summers. These were both characterised by a extended block with little change in air mass. I suspect there is a bit of sting in the tail of the northeasterly pattern common in La Nina. The La Nina pattern means the summers are often very blocked and occasionally these blocks lead to the build up of extreme heat.

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Re: ENSO & IOD

Post  Johnno on Thu Aug 13, 2009 9:44 pm

Intresting about how El Nino Summers and Nina summers usually work there DJ thanks for that.

Speaking of.. Whats your and others thoughts on this? Latest Equatiorial sub-surface...

http://www.bom.gov.au/bmrc/ocean/results/ocean_anals/SEQ_Equator/2009/Aug


Well to me looks like the warm sub-surface has weakened quite alot of late with a Cool patch now showing up in the Eastern sub-surface equatioral. interesting now how the NASA Model now peaks this NINO in the coming weeks (September early October) rather than November, December as it was orginally... Looks like in general this El Nino may be running out of puff already very unusual to have the Equatioral sub-surface weakening this much in August isn't it? It didn't happen in 1997, 2002 and 2006 unless theres another explaination for this?

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Re: ENSO & IOD

Post  Karl Lijnders on Sat Aug 15, 2009 5:35 pm

Very interesting developments there John. Do we take it seriously considering that August is not usually the time for El Ninos to break down?
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Re: ENSO & IOD

Post  windyrob on Sun Aug 16, 2009 8:46 am

Apparently this is the first el nino to come off the back of la nina in over 30 years (ie since the PDO was last negative)
Under this scenario they tend to be small and short lived. I suspect that a lot of the energy may be used up neutralising the negative anomalies of the la nina which reduces the power of the el nino to force the rest of the system.

I also suspect that part of the initial heating mechanism of el nino is disruption of convection over the western warm pool. this leads to energetic imbalance that allows the ocean to warm since cooling is reduced. After a period of time the convection becomes re-established (potentially in another area) and the oceans start transferring energy to the atmosphere again.
This would explain the lag between ocean temp and satellite temps. It would also mean that the amount of lag is proportional to the amount of ocean heating and size of el nino.
In the 97/8 el nino there was a long lag and a large el nino. The current warming period had a very short lag, very little negative OLR anomolies, and may not even reach official el nino status, unless we get a second round of warming.
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Re: ENSO & IOD

Post  Johnno on Mon Aug 17, 2009 3:59 pm

Great to see you Rob thanks for your input.

Yeah Karl heres the latest BOM site updated today 17th August and we can see how much the positive sub-surface anomalies have weakened the past few weeks since July wouldn't suprise me to see this El Nino finished before even the end of year this isn't how things normally pan out in a traditional El Nino August. Love to hear your thoughts DJ?

http://www.bom.gov.au/bmrc/ocean/results/ocean_anals/SEQ_Equator/2009/Aug.gif

And here it is looking it from another angle at 150 metres sub-surface level and as you can see ssts are almost back to Neutral East of about 160W along the Equator back to South America with the warmest Ssts now laying West & North of there

http://www.bom.gov.au/bmrc/ocean/results/ocean_anals/SEQ_Pacific/2009/Aug.gif


Starting to look messy and very disorgainsed to me

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Re: ENSO & IOD

Post  hillybilly on Wed Aug 19, 2009 5:43 pm

Latest BoM outlook was updated today http://www.bom.gov.au/climate/enso/ . The current event is shaping up as very messy - the waters around northern Australia are staying very warm (when they should be cooling) and the Indian Ocean dipole is refusing to go positive. This would suggests that the rainfall response for OZ will be tempered somewhat by local moisture sources.

It's possible the odd behaviour of the SOI reflects the record heatwave which has lead to lower pressures in the north as the spring heat lows comes a month early.

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Re: ENSO & IOD

Post  Johnno on Tue Aug 25, 2009 10:45 am

Johnno wrote:It wouldn't suprise me if parts of NSW and Southern/SE Qld end up with a record dry in some areas for the last 6 months of the year there (July-December) mother nature works in funny ways and after the incredible wet up there the 1st 6 months this year and the past 2 years in general I kind of expect this to happen now if July is anything to go by after being so dry up there this month(rainless in some areas even for July standards thats very poor considering Brisbanes & other places up there averages are actually bit wetter than Melbourne for July) I expect this pattern to continue the coming months up there with the dry extending right into Victoria with the odd brief interuption of wet spells for Coastal areas of Victoria. Anyway thats my 2c worth and how I see things for the coming months feel free to shoot me down in flames Laughing

Well still 4 months to go til the end of the year but I made that comment over a month ago and since then thats exactly how its been happening we have had some OK or SPORATIC rain down here in Victoria as a whole since that comment so far but record HEAT & with it record DRY has started in Northern NSW and Qld as I predicted back in July and I expect this to continue well into Spring up there and see records broken in both the Dry side and temp side of things in the coming months (Its already been happening)

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Re: ENSO & IOD

Post  hillybilly on Wed Aug 26, 2009 5:56 pm

BTW looks like the stop-start El Nino is now back on. There has been a very strong westerly wind burst move across the Pacific with a rapid warming of surface and subsurface waters. This will probably be the last kick the system needs to flip into a full blown El Nino (as has been predicted by the models all year).

The weather over OZ is actually pretty El Nino like - though perhaps the westerlies are a little further north than usual (which is why Tas/Vic/southern SA are doing OK). Hopefully the westerlies continue...

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Re: ENSO & IOD

Post  Johnno on Mon Aug 31, 2009 3:23 pm

Winter 2009 Deciles
http://www.bom.gov.au/cgi-bin/silo/rain_maps.cgi?map=contours&variable=deciles&area=aus&period=3month&region=aus&time=latest

August 2009 Deciles
http://www.bom.gov.au/cgi-bin/silo/rain_maps.cgi?map=contours&variable=deciles&area=aus&period=1month&region=aus&time=latest

Lucky Tassie!!! And El Nino starting to take hold in the Eastern states mainly NSW and Qld

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Re: ENSO & IOD

Post  Karl Lijnders on Mon Aug 31, 2009 4:45 pm

http://www.bom.gov.au/cgi-bin/silo/rain_maps.cgi?map=contours&variable=deciles&area=vic&period=36month&region=vic&time=latest

Guess that puts it into perspective!!!
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Re: ENSO & IOD

Post  droughtbreaker on Mon Aug 31, 2009 9:30 pm

The decile maps for winter and August are a good graphical description of just how dominant NW to W winds have been over the past 3 months with areas in lee of the ranges in VIC below average yet again thanks to the west central rain shadow and almost all of Tas above or well above average, basically the more vigorous the westerlies the higher the rainfall for Tas, particularly the western half of that state.

El Nino getting organised now and ready to unleash on us later into Spring. The good August rains (and likely to continue through the first half of September) are a godsend given the outlook for the second half of spring would be a bit grim at this stage. Hopefully it can be a weak and short lived El Nino this time. Good to see the atmosphere hasn't really responded that much yet with SOI figures remaining neutral.

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Re: ENSO & IOD

Post  hillybilly on Fri Oct 09, 2009 6:00 pm

Reflecting the El Nino September 2009 has come out as the hottest September on record on the earth's surface according to NASA GIS.
http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts.txt

2009 is now likely to be the second warmest (if not warmest) on record. With an El Nino 2010 is likely to be even hotter.

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Re: ENSO & IOD

Post  droughtbreaker on Fri Oct 09, 2009 6:24 pm

Makes us all the more fortunate to have had such cool and wet weather for a prolonged period in the middle of one of the warmest periods for the globe.

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Re: ENSO & IOD

Post  Karl Lijnders on Fri Oct 09, 2009 7:21 pm

Well we certainly helped at the start of the year, now the rest of the planet can have a turn... monkey
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Re: ENSO & IOD

Post  Guest on Sat Oct 10, 2009 8:10 am

Recent rainfall across southeastern Australia gives further proof that ENSO itself has little effect on us.
SST are warming up again across northern Australia after a brief cool down although we are moving into the time of the year where the northern SST effect is reduced.

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Re: ENSO & IOD

Post  hillybilly on Sun Oct 11, 2009 5:43 am

David ENSO has a decent impact on us - but it tends to operate through the Indian Ocean which usually, but not always, follows the lead of ENSO. The last two spring we had a +ve Indian Ocean dipole (despite a weak La Nina) which is at least a partial explanation for the dismal rainfall despite La Nina. In contrast this year we have had a near zero Indian Ocean Dipole and rainfall has been pretty close to average.

If you look back through the history about every second El Nino has given "drought" to southeast Australia, so about every second one didn't. However, it has been a bit worse than that in recent years.....
1994 was a drought, 1997 was a drought in parts, 2002 was a terrible drought, 2006 was a terrible drought, 2009 has been OK in many areas.

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Re: ENSO & IOD

Post  droughtbreaker on Sun Oct 11, 2009 8:10 am

What we are seeing now is not a 'proper' El Nino. I don't think it has actually been declared as one yet, it hasn't met the criteria. Similar to the last La Nina which only very briefly met the criteria but even so I never remember it actually being formally declared although pretty sure it was a genuine La Nina.

A full blown El Nino, the concept that I have of it anyway, develops earlier in the year, around mid Autumn to Winter and lasts for a whole year or relatively close to that on average. The SOI clearly mirrors what is happening with the oceans and vice versa and there is reinforcing feedback between those two variables that keep the event developing and persisting. Eventually the IOD generally goes positive as anomalously cool water flows across Northern Aus from the western Pacific and into the eastern Indian Ocean. I think the mechanism that causes this is called the 'Indonesian throughflow'.

This just hasn't happened this year and I put it down to a weak and disorganised warm neutral SST pattern in the Pacific that just hasn't been able to evolve into an organised El Nino event. Of course we could still get one developing next year but with the cool phase PDO in place this should be less likely than at other times in the past decade or two.

Still this is just my amateur knowledge, I don't profess to know all that much about this but that's the way i interpret the situation atm.

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Re: ENSO & IOD

Post  droughtbreaker on Sun Oct 11, 2009 8:19 am

Looking at the latest SST anomalies I can see another solid influx of warmer water heading east-west across northern AUS towards the eastern Indian Ocean whilst, at the other end, there is a rather intense cold patch off the equatorial South American coast. Without wanting to be premature about things it looks like this warm neutral pattern is definitely on the way out just going from current indications.

No signs whatsoever that the 'tap will be turned off' over the next month or so at least. If anything we should continue to see good rainfall.

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Re: ENSO & IOD

Post  hillybilly on Mon Oct 12, 2009 6:04 pm

What we are seeing now is not a 'proper' El Nino.

Unless things develop quickly, I suspect this event will be a non-event. It reminds me of the protracted warm Pacific Conditions which pretty much dominated from about 2001 to 2006 and is more global warming than "El Nino". The temperatures which have been seen in the central/eastern Pacific are certainly warm enough to be labeled "El Nino" but at the same time waters northern Australia has been very warm (also).

The big worry then is that if this build up of heat is not El Nino - then what happens when we actually get a full blown El Nino affraid

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Re: ENSO & IOD

Post  Karl Lijnders on Mon Oct 12, 2009 8:27 pm

Maybe enjoy the rain while it's here!!!
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Re: ENSO & IOD

Post  droughtbreaker on Tue Oct 13, 2009 4:30 pm

Well, yes, when we look at the bigger picture it becomes more disturbing, in a way though warmer oceans can provide the source moisture for heavier than normal rain if everything else goes right but 'everything else' rarely does go right these days as we know. Rolling Eyes

I am enjoying this rain whilst it lasts, it is falling at the right time of year IMO, nothing worse than a dry spring, makes summer even drier. The wheat crops should do well this year and other agricultural products. Dairy industry would be loving the pasture growth. Gardens and forests/bushland can put on some decent growth to recover somewhat from the damage of previous years. Of course some people, particularly those ignorant ones in the media are claiming the 'drought is over' which is mind numbing stuff but any decent period of rainfall we get is something to rejoice these days.

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Re: ENSO & IOD

Post  Johnno on Tue Oct 13, 2009 6:14 pm

Models have us going back to neutral (Cool) or even back to weak La nina by Winter/Spring next year so can't see us having another El Nino or warm phase next Winter and Spring for 2010 given this will peak in the next couple of months and wane out normally this is the expected when you get a Warm pacific 1 year it goes back to Neutral or Cool the other year Prime examples of this are 1997 then by Winter/Spring 98 it was La Nina.. 1994 then by Winter/Spring 95 was Neutral to Cool.. 2006 by Winter/Spring 2007 Moderate La Nina even 2002 it bounced back to smack bang Neutral by the Winter and Spring of 2003 so not sure why there is talk of another El Nino in 12 months time when nothing indicates this

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Re: ENSO & IOD

Post  Power Storm on Tue Oct 13, 2009 6:46 pm

The thing I am most worried about, is that the El Nino that is supposedly developing now, stops our great rainfall that we have been seeing over the next few weeks or the next month, and causes temperatures to rise back to above normal. I would hate to see what the Summer bushfire season would be like after all this rain and growth. It does not take much for a dry wind and several hot days to make the new growth burn-ready these days.

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Re: ENSO & IOD

Post  Karl Lijnders on Wed Oct 14, 2009 10:30 am

True Jake however the conditions of last summer was under extreme la niƱa conditions. I think the summer will be somewhat normal.

One week at a time Smile
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