Climate Driver Discussion 2019 (Enso, IOD, PDO , SAM)

All general weather related discussion & questions, including model discussions, longer-term outlooks & anything non-breaking weather.

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weathergasm
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Thu Sep 26, 2019 4:56 pm

The BOM seem to think that a negative SAM results in less summer rain for us here in Victoria because it impedes moist easterly/northeasterly airmasses.

http://www.bom.gov.au/climate/sam/#summer

That in combination with a strong, persistent positive IOD doesn’t seem to bode well for us. Looks like another late onset to the monsoon at this stage.

Granted that amazing summer storms have happened here in Melbourne in poor conditions climate driver-wise, but I’m steeling myself for another subdued storm season with lots of blustery, dry cold fronts. Sigh.
flyfisher
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Sat Sep 28, 2019 9:54 am

So it looks like this SSW is a non event? It was all over the media and talked about a lot but nothing happened? I looked at 10hp on null and it seems the vortex is stable back over Antarctica. It would be interesting to know what went wrong? What was supposed to be the biggest SSW event since 2002 ended up nothing?

I suppose it's a good thing as strong westerly winds in late Spring/Summer combined with the current IOD is bad for fires. We want humid NE winds in summer.
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Didjman
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Sat Sep 28, 2019 10:48 am

Raiderpete wrote:
Sun Sep 22, 2019 9:07 pm

All defined stratospheric pressure levels are seeing new temperature minimums set over the Tropics, this is the 30mb level. The other SH SSW years have not had this kind of response over the tropics. Interesting times ahead.
Hi Flyfisher,
as noted in previous posts on the previous page, there has to be coupling between the Stratosphere and Troposphere for the effects of an SSW to "flow" down to the surface. This appeared to happen over South America last week. As in the above quote from Raiderpete, there appears to be interesting effects above the tropics atm.
weathergasm
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Tue Oct 01, 2019 5:44 pm

Latest ENSO wrap-up from BOM released today indicates positive IOD going from strength to strength:

“The Indian Ocean Dipole (IOD) remains positive, with the latest weekly index value to 29 September at +1.76 °C. This is the highest weekly value observed in the Bureau's dataset which extends from 2001 to present. Last week's value of +1.50 °C is the second highest on record.”

http://www.bom.gov.au/climate/enso/#tabs=Indian-Ocean

Not good news for those of us in the southeast in the next few months, at least. I’m very pessimistic about the chances of good rains before Christmas.
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Didjman
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Tue Oct 01, 2019 6:11 pm

weathergasm wrote:
Tue Oct 01, 2019 5:44 pm
Latest ENSO wrap-up from BOM released today indicates positive IOD going from strength to strength:

“The Indian Ocean Dipole (IOD) remains positive, with the latest weekly index value to 29 September at +1.76 °C. This is the highest weekly value observed in the Bureau's dataset which extends from 2001 to present. Last week's value of +1.50 °C is the second highest on record.”

http://www.bom.gov.au/climate/enso/#tabs=Indian-Ocean

Not good news for those of us in the southeast in the next few months, at least. I’m very pessimistic about the chances of good rains before Christmas.
Couple that with SAM going -ve, and we have bad fire weather!
StratoBendigo
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Wed Oct 02, 2019 12:37 pm

The good news is that there is consensus for a Neutral IOD by mid-Summer. Yes, not much rain for the rest of the year, but I think things may change as summer progresses.

I've been looking through the IOD timeseries data. Some similarity between 1994 and this year (both IOD and ENSO, and snowfalls in Sept). I distinctly remember it being stinking hot and dry that December, but then flooding at the Australian Tennis Open in January 1995.
flyfisher
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Wed Oct 09, 2019 12:32 pm

Look how strong the positive IOD is today - I cannot recall it being that strong. It's the representation of the drought in Australia that big blue patch of cooler waters. Perhaps that might move over to Africa? Would probably warm up on it's journey. I notice the winds have reversed over India so the Indian ocean will begin a transition.

Elsewhere it appears the Indonesian through flow is finally getting some warmer water heading south - that's good. Warm water is also being fed into the Coral sea but persistent strong SE winds rip the heat out of it quickly.

Strong cool waters over near South America, but warmer water north of that keeps injecting in. The Moodki pattern is still in place - which is the worst kind of impact for Australia. I think this will also change for 2020.

The polar vortex at 10hp is wandering around the pole I cannot read much into it but does not look like any real SAM impact at the moment.
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Didjman
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Wed Oct 09, 2019 9:04 pm

The IOD is at record levels, but models are suggesting it will fall sharply to be neutral by the New Year. Nino 3.4 is swinging like a barn door at the moment and I think we dodged a bullet re the SSW. The Polar Vortex and its tropospheric linkage stayed over toward southern South America, so we have not experienced any major effects as yet.
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Didjman
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Tue Oct 15, 2019 6:10 am

IOD is currently at 2.15! GFS is saying SAM will drop to -2/-3 by months end. Not good fire weather IMHO.
StratoBendigo
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Tue Oct 15, 2019 11:15 am

Didjman wrote:
Tue Oct 15, 2019 6:10 am
IOD is currently at 2.15! GFS is saying SAM will drop to -2/-3 by months end. Not good fire weather IMHO.
I note that some hot weather might kick in around this time next week. MJO is wallowing in Zone 1 (Africa), so the dry will continue with several powerful dry cold fronts in the mix I imagine.
StratoBendigo
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Tue Oct 15, 2019 1:04 pm

Incidentally, the tropics to our North have had a dreadfully dry 2019.

Take Singapore for example - just 632 mm YTD up to the end of September. That's the 2nd lowest since 1982 (1997 was the driest).
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Didjman
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Sun Oct 20, 2019 1:33 pm

It seems Sea Surface temps off the NW shelf are increasing:

http://www.bom.gov.au/products/IDYOC054.shtml

https://www.tropicaltidbits.com/analysi ... _aus_1.png

Maybe IOD is about to start coming down from its record high?
StratoBendigo
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Sun Oct 20, 2019 7:36 pm

Didjman wrote:
Sun Oct 20, 2019 1:33 pm
It seems Sea Surface temps off the NW shelf are increasing:

http://www.bom.gov.au/products/IDYOC054.shtml

https://www.tropicaltidbits.com/analysi ... _aus_1.png

Maybe IOD is about to start coming down from its record high?
Looks to be fairly shallow heating at the surface due to cloudless skies in the region. We should see some shift back towards neutral IOD regardless.

Meanwhile, the Top End has seen some dreadfully hot and dry weather this weekend. Ie. 42.3c at Jabiru, 44c at Bradshaw.
StratoBendigo
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Wed Oct 23, 2019 10:41 am

A good summary on the ABC News website:
https://www.abc.net.au/news/2019-10-23/ ... n/11624550

It's interesting to see the parallels between this year and 1961 & 2007 in relation to the extended Indian monsoon and +ve IOD.
JasmineStorm
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Thu Oct 24, 2019 9:24 am

Here comes the sudden stratospheric warming disturbance from September :) SAM starting to fall off the cliff.
Attachments
SSW SAM.jpg
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StratoBendigo
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Thu Oct 24, 2019 12:55 pm

Yep. Certainly the case: https://www.cpc.ncep.noaa.gov/products/ ... _ensm.html

The hole in the Ozone layer is also at the smallest size in decades.
https://www.nasa.gov/feature/goddard/20 ... -discovery
JasmineStorm
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Thu Oct 24, 2019 1:09 pm

BoM now publicly declaring it as well. Interesting November ahead.... Heat spikes, bush fires up the north and big cut off lows on the menu.

https://www.weatherzone.com.au/news/rec ... ace/530389
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Didjman
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Thu Oct 24, 2019 5:39 pm

JasmineStorm wrote:
Thu Oct 24, 2019 9:24 am
Here comes the sudden stratospheric warming disturbance from September :) SAM starting to fall off the cliff.
I Have been watching this develop for a couple of weeks, but GFS has been on / off again repeatedly and has only firmed in the last 3-4 days.
Hawker
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Wed Oct 30, 2019 7:26 pm

Good evening all
I just found this set of forecasts from the https://www.severe-weather.eu/ site
which has this page
https://www.severe-weather.eu/long-rang ... 6vi7JMb4O0
They are talking northern hemisphere but the charts cover the globe.
From my quick and uneducated look it seems that we will have a bit warmer uppers, a bit higher air pressures
and a bit less rainfall than usual. but who knows. Forecast Charts!
But it will be good to see how it turns out.
Edit and I think a continuation to some extent of the positive IOD
Cheers Chris
JasmineStorm
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Tue Nov 05, 2019 7:14 am

Sudden stratospheric warming from September continuing to pump SAM into negative :) Conveyor belt of upper troughs well in place. BoM's Nov outlook underestimating the rainfall impact from the upper troughs over Victoria for November.
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