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#1434518 - 20/09/2017 18:16 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Kino]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3214
Loc: Buderim
Originally Posted By: Kino
Originally Posted By: Mike Hauber

My opinion: IOD has little impact on eastern seaboard, or possibly opposite to that of the rest of the country.

Paper's position: IOD has an impact on the eastern seaboard opposite to that of the rest of the country.

According to this paper's position the recent weak +ve IOD should be enhancing rainfall on the eastern seaboard, and suppressing it west of the range.


Well, maybe submit a paper?

But that's not how I read it, and I'm sure your colleagues would be disappointed to see you feel that way too.


How do you read it then? To directly quote from the paper:

Quote:
...with positive IOD increasing both onshore winds and rainfall over the coastal strip, while decreasing rainfall elsewhere in southeast Australia.


And what about my colleagues? I do not work for the BOM or anything weather or climate related.

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#1434519 - 20/09/2017 18:26 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Mike Hauber]
ColdFront Offline
Meteorological Motor Mouth

Registered: 29/06/2008
Posts: 18464
Loc: Burnett Heads
Originally Posted By: Mike Hauber
Originally Posted By: Kino


I sure didn't see CF's reply as being insulting towards you? He was generalising I thought about the way things change over time as we get better evidence or understanding.


That things change over time is a valid point to make. However there are less insulting ways to make such a point than to bring up flat earth theory as a comparison.


The point was that things change and views can change dramatically. The comparison was fine. No-one said you believe the earth is flat but that once upon it was a wide held view and probably based entirely on someone's opinion.

I can see what you are trying to do. Good luck !



_________________________
"When it comes to the weather, "occasionally" is better than "not at all".

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#1434520 - 20/09/2017 18:42 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mega Offline
Meteorological Motor Mouth

Registered: 03/02/2003
Posts: 7123
Loc: Maryborough, Wide Bay, QLD
Good paper, but doesn't it just re-enforce what Mike has been saying, at least for our part of the world?

Quote:
During the June–October period, Ummenhofer et al. (2009a) noted that positive IOD events are associated with significant easterly moisture flux anomalies over the Australian continent in southeast Australia, while negative IOD events are associated with strong westerly moisture flux anomalies from the Indian Ocean into the continent. These patterns are consistent with the moisture flux anomalies associated with extreme dry and wet periods for southeast Australia (south of 35°S), respectively (Ummenhofer et al. 2011), with air parcels with trajectories originating in the Indian Ocean substantially more likely to cause rain in southeast Australia west of the Great Dividing Range (e.g., Brown et al. 2009; McIntosh et al. 2012).


Quote:
Because of the proximity of the warm Pacific Ocean, easterly winds increase moisture advection into the coastal region and consequently enhance rainfall along the ESB. This region is bounded by the Great Dividing Range, a mountain range which lies approximately perpendicular to the zonal wind flow and acts as an impediment to rain-bearing systems (Fig. 2): westerly driven systems such as cold fronts can produce rainfall across much of southeast Australia, particularly on the western slopes of the divide because of orographic forcing, but are less likely to produce rainfall to the east of the ridgeline owing to subsidence. As a consequence, the Great Dividing Range acts as a clear boundary for weather regimes, with the relationship between rainfall and zonal wind anomalies differing between areas east and west of the divide.


But then, if you take this piece, you could easily say a -IOD actually has a worse influence on the ESB like we've been saying:

Quote:
When the influences of ENSO and the IOD are separated (Figs. 7e,f), positive IOD events are associated with anomalous southeasterly moisture flux anomalies across most of the Australian landmass, regardless of ENSO state. This weakens the prevailing westerly circulation and consequently the moisture source to western southeast Australia. However, along the eastern seaboard, this acts as an enhanced source of tropical moisture from the warm western Pacific and Tasman Sea. In contrast, negative IOD events are associated with a strengthening of the westerly flow and enhanced rainfall in western southeast Australia, with subsiding offshore winds and drier conditions over the ESB.

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#1434521 - 20/09/2017 18:48 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Mega]
ColdFront Offline
Meteorological Motor Mouth

Registered: 29/06/2008
Posts: 18464
Loc: Burnett Heads
Originally Posted By: Mega


But then, if you take this piece, you could easily say a -IOD actually has a worse influence on the ESB like we've been saying:

Quote:
When the influences of ENSO and the IOD are separated (Figs. 7e,f), positive IOD events are associated with anomalous southeasterly moisture flux anomalies across most of the Australian landmass, regardless of ENSO state. This weakens the prevailing westerly circulation and consequently the moisture source to western southeast Australia. However, along the eastern seaboard, this acts as an enhanced source of tropical moisture from the warm western Pacific and Tasman Sea. In contrast, negative IOD events are associated with a strengthening of the westerly flow and enhanced rainfall in western southeast Australia, with subsiding offshore winds and drier conditions over the ESB.


Precisely, it is conflicting which was my earlier point. Note too it says when separated? So what then when they are not?

The rules are not set in stone. Hence why the impact of La Nina is so varied when compared to other La Nina events . Same with El Nino.

http://www.bom.gov.au/climate/enso/ninacomp.shtml

...and your article link says "less likely" not "unlikely.


Edited by ColdFront (20/09/2017 18:58)
Edit Reason: added bits
_________________________
"When it comes to the weather, "occasionally" is better than "not at all".

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#1434523 - 20/09/2017 19:00 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mega Offline
Meteorological Motor Mouth

Registered: 03/02/2003
Posts: 7123
Loc: Maryborough, Wide Bay, QLD
Yeah, I just don't understand the attacks on Mike on this. He said:

Originally Posted By: Mike Hauber

My opinion: IOD has little impact on eastern seaboard, or possibly opposite to that of the rest of the country.

Paper's position: IOD has an impact on the eastern seaboard opposite to that of the rest of the country.

According to this paper's position the recent weak +ve IOD should be enhancing rainfall on the eastern seaboard, and suppressing it west of the range.


So he has a point, imo. I agree with all of this except he sort of contradicts himself when he says the IOD has little effect on the ESB when if anything, it has the opposite effect.

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#1434525 - 20/09/2017 20:43 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
S .O. Offline
Weatherzone Addict

Registered: 31/01/2011
Posts: 1540
Loc: Southern Victoria
Guys and girls .
I think everyone needs to step away from the computer .
I love all of your inputs and even those that take things too seriously or condescend people who don't have as much time to construct detailed analysis of their points or even attached reference data .

The classic IOD if positive with the combination of El Niño will enhance the drying effect in Coastal Qld . Where as the central / South Indian Ocean with cooler SST's coupled with ElNino will have drying effect on coastal NSW .
South of the Divide Vic will be the SAM , mid Indian and ENSO .
Many different synopsis will effect each region . And with this I wouldn't envy BOM's job . But the sooner they split their season outlooks into 12-15 zones In the Eastern states and perhaps 4 in the Nth and 3 in the SW the better .
That and actually having done balls and making a prediction ( with a human error caveat and confidence percentage ) ontop of what the models spit out for them .


Edited by S .O. (20/09/2017 20:45)
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#1434528 - 20/09/2017 21:02 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Chris Stumer Offline
Weatherzone Addict

Registered: 28/01/2010
Posts: 1804
Loc: Kingaroy
The IOD is having a major impact at the moment in many areas of eastern Australia. If it doesn't rain soon it will start having economic effects, nothing will be flowering because it's too dry and the bee season will grind to a halt. Let's hope and pray that summer delivers much needed rain.


Edited by Chris Stumer (20/09/2017 21:02)

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#1434531 - 20/09/2017 22:31 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Chris Stumer]
Nature's Fury Offline
Weatherzone Addict

Registered: 29/11/2009
Posts: 2118
Loc: Brisbane Western Suburbs
Wars have been fought with less passion than I've seen in this thread...

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#1434532 - 20/09/2017 22:50 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Chris Stumer]
adon Offline
Meteorological Motor Mouth

Registered: 19/08/2004
Posts: 5325
Loc: Not tellin!
Originally Posted By: Chris Stumer
The IOD is having a major impact at the moment in many areas of eastern Australia. If it doesn't rain soon it will start having economic effects, nothing will be flowering because it's too dry and the bee season will grind to a halt. Let's hope and pray that summer delivers much needed rain.


It started having a major economic effect in May bud. Most of western NSW, Qld and part of SA and vic are struggling big time with crop losses. A friend of mine who does contract harvesting in 3 states will now not even venture out of Vic after his biggest client told him that a severe frost basically killed off the remaining wheat that had potential to make it through to harvest and the sheep are now eating what is left.

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#1434533 - 20/09/2017 22:59 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Mike Hauber]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2464
Loc: Wollongong, NSW, Aus
Originally Posted By: Mike Hauber


Quote:
...with positive IOD increasing both onshore winds and rainfall over the coastal strip, while decreasing rainfall elsewhere in southeast Australia.



I often find it useful to read part-quoted paras to make sure context is right...glad I did, this was delib misleading and NOT what was implied:

Quote:
When the influences of ENSO and the IOD are separated (Figs. 7e,f), positive IOD events are associated with anomalous southeasterly moisture flux anomalies across most of the Australian landmass, regardless of ENSO state. This weakens the prevailing westerly circulation and consequently the moisture source to western southeast Australia. However, along the eastern seaboard, this acts as an enhanced source of tropical moisture from the warm western Pacific and Tasman Sea. In contrast, negative IOD events are associated with a strengthening of the westerly flow and enhanced rainfall in western southeast Australia, with subsiding offshore winds and drier conditions over the ESB.


Pretty sure that’s what I also said....

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#1434535 - 20/09/2017 23:39 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: adon]
Chris Stumer Offline
Weatherzone Addict

Registered: 28/01/2010
Posts: 1804
Loc: Kingaroy
Let's hope that this La Nina can get her act together and delivers over summer.

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#1434543 - 21/09/2017 07:11 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Kino]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3214
Loc: Buderim
Originally Posted By: Kino
Originally Posted By: Mike Hauber


Quote:
...with positive IOD increasing both onshore winds and rainfall over the coastal strip, while decreasing rainfall elsewhere in southeast Australia.



I often find it useful to read part-quoted paras to make sure context is right...glad I did, this was delib misleading and NOT what was implied:

Quote:
When the influences of ENSO and the IOD are separated (Figs. 7e,f), positive IOD events are associated with anomalous southeasterly moisture flux anomalies across most of the Australian landmass, regardless of ENSO state. This weakens the prevailing westerly circulation and consequently the moisture source to western southeast Australia. However, along the eastern seaboard, this acts as an enhanced source of tropical moisture from the warm western Pacific and Tasman Sea. In contrast, negative IOD events are associated with a strengthening of the westerly flow and enhanced rainfall in western southeast Australia, with subsiding offshore winds and drier conditions over the ESB.


Pretty sure that’s what I also said....


The bit I quoted states that +ve iod has one effect. The bit you bolded says that a -ve iod has the opposite effect. My quote was not deliberately misleading.

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#1434544 - 21/09/2017 07:23 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Mega]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3214
Loc: Buderim
Originally Posted By: Mega


I agree with all of this except he sort of contradicts himself when he says the IOD has little effect on the ESB when if anything, it has the opposite effect.


Interesting question. Some of the stuff i had quoted earlier seemed good reason to say no effect (or maybe weak opposite effect). This seems a good reason to say opposite effect. My guess is that the no effect is closer to the truth, but maybe someone has a reason better than just a guess to prefer one or the other.

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#1434581 - 21/09/2017 14:50 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Mike Hauber]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2464
Loc: Wollongong, NSW, Aus
Originally Posted By: Mike Hauber
Originally Posted By: Mega


I agree with all of this except he sort of contradicts himself when he says the IOD has little effect on the ESB when if anything, it has the opposite effect.


Interesting question. Some of the stuff i had quoted earlier seemed good reason to say no effect (or maybe weak opposite effect). This seems a good reason to say opposite effect. My guess is that the no effect is closer to the truth, but maybe someone has a reason better than just a guess to prefer one or the other.


Sorry, but can you explain what you mean? I've read it prob 50 times and I still don't understand.

My general guide is:
+IOD & EL NINO = drier everywhere, chance of wetter than average sw WA
+ IOD & Neutral ENSO = drier than average western and central; 50/50 for eastern coastal
+IOD & La Nina = wetter than average right across eastern and northern Aus; drier in western & southern aus
-IOD & El Nino = wetter than average western, southern & central; drier coastal e/ne aus
-IOD & Neutral ENSO = wetter than average western, southern & central; 50/50 for coastal e/ne aus
-IOD & La Nina = wetter than average for whole of Aus except SW WA where its 50/50
Neutral IOD & El Nino = 50/50 western, southern and central Aus; drier eastern aus
Neutral IOD & Neutral ENSO = 50/50 across Aus
Neutral IOD & La Nina = 50/50 western & southern aus; wetter than average eastern Aus

Then you have to factor in SAM.

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#1434583 - 21/09/2017 15:10 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mega Offline
Meteorological Motor Mouth

Registered: 03/02/2003
Posts: 7123
Loc: Maryborough, Wide Bay, QLD
I don't know about Mike but the point I'm trying to make is that the IOD isn't what it's cracked up to be if you live east of the Great Dividing Range. According to that paper, -IOD if anything seems to decrease rainfall along the ESB as opposed to +IOD which seems to enhance it. Influence is the opposite west of the GDR.

http://journals.ametsoc.org/na101/home/l...00554.1-f8.jpeg

Right now the +IOD is imo taking its toll on central/southern Australia (there's no moisture infeed from the NW), but something else is clearly effecting the east coast that we don't seem to know about.

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#1434585 - 21/09/2017 15:21 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mega Offline
Meteorological Motor Mouth

Registered: 03/02/2003
Posts: 7123
Loc: Maryborough, Wide Bay, QLD
And I know I'm starting to sound like a broken record, but run a loop of https://www.tropicaltidbits.com/analysis...2017092100&fh=0 and you'll see our highs off the east coast are consistently further north than those anywhere else in the SH right now. Not sure what's causing it, tbh.

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#1434586 - 21/09/2017 15:22 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Mega]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2464
Loc: Wollongong, NSW, Aus
Originally Posted By: Mega
I don't know about Mike but the point I'm trying to make is that the IOD isn't what it's cracked up to be if you live east of the Great Dividing Range. According to that paper, -IOD if anything seems to decrease rainfall along the ESB as opposed to +IOD which seems to enhance it. Influence is the opposite west of the GDR.

http://journals.ametsoc.org/na101/home/l...00554.1-f8.jpeg

Right now the +IOD is imo taking its toll on central/southern Australia (there's no moisture infeed from the NW), but something else is clearly effecting the east coast that we don't seem to know about.


My comment/question wasn't directed at you. I understood your point.

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#1434587 - 21/09/2017 15:24 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: Mega]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 2464
Loc: Wollongong, NSW, Aus
Originally Posted By: Mega
And I know I'm starting to sound like a broken record, but run a loop of https://www.tropicaltidbits.com/analysis...2017092100&fh=0 and you'll see our highs are consistently further north than those anywhere else in the SH right now. Not sure what's causing it, tbh.


As I said previously, Hadley Cell. The monsoon trough has been very active across Asia; and as a direct result we are getting their dead/dry air dumped over us, which then interacts with the IOD. End result - no NW cloud bands and heat across Northern and Central Australia.

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#1434588 - 21/09/2017 15:28 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3214
Loc: Buderim
IOD no effect means neither drier nor wetter during a +ve IOD for a thin coastal strip from NSW/VIC border to far north Qld, going inland maybe a couple hundred kilometers to the dividing range. Some of the stuff I quoted earlier supports this view, although some of it also hints at an opposite effect.

Opposite effect means wetter during a +ve IOD for the same thin coastal strip, (but still drier further west and in Victoria) which is what the paper Kev in Bello quoted claims.

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#1434590 - 21/09/2017 15:35 Re: Climate Driver Discussion 2017 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Chris Stumer Offline
Weatherzone Addict

Registered: 28/01/2010
Posts: 1804
Loc: Kingaroy
I wonder if the monsoon trough will maintain it's strength as it moves to the Southern Hemisphere, hopefully it's a good sign of a La Nina signal although CFS has backed off a little on a wet October.

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