Opinion "July is the old September in Sydney"

POW Hungry

Old n' Crusty
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So our mates over WZ went bold with this 'statement' headline, indicating the Sydney seasons are back to front in recent years.
And given the last few non-seasonal days in Sydney, I doubt there's much argument in that.

But it seems these dry Westerlies are only paying dividends of a Summer/Autumn that was dominated by neg-zonal flow (East-Nor-Easterlies); conditions that are hallmark to coastal areas further North than here.

...So it got me thinking, Sydney's weather (particularly this and last winter) has more resembled Port Macquarie's climate than it's own.
  • Last month Sydney matched PM's monthly rainfall, whilst exceeding it's own.
  • June '19 mean Min/Max temps were closer to PM's than it's own
  • Sydney's June SST matched the cooler scale of PM's average at 18.8c
So where else along the NSW coast is experiencing latitudinal climate switch in recent years/seasons?
Anyone care to counter argue the above hypotheses?
 

AshestoAshes

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Jul 3, 2019
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Looking at the MSLP anomaly charts posted by the BOM, these are quite hard to come btw. Looks like the mentioned pattern for the past couple of years. It's actually nuts how bad it's been for these past these few winters, just prayers for a drought breaking couple of events.
 

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POW Hungry

Old n' Crusty
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Looking at the MSLP anomaly charts posted by the BOM, these are quite hard to come btw. Looks like the mentioned pattern for the past couple of years. It's actually nuts how bad it's been for these past these few winters, just prayers for a drought breaking couple of events.
Great stuff, I knew BoM had these somewhere and exactly what I was thinking would be a telltale sign.
Where are these published?
 

Mcbobbings

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Jul 10, 2019
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Looking at the MSLP anomaly charts posted by the BOM, these are quite hard to come btw. Looks like the mentioned pattern for the past couple of years. It's actually nuts how bad it's been for these past these few winters, just prayers for a drought breaking couple of events.

Hi Ashes,

Can you please explain these charts? The way I read it is that 2015 had a high pressure anomaly, but the past few years have been average to within +1 to -1 for most of the country. This goes against what I would have thought it was. Unless the charts are the other way around?
 

POW Hungry

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Hi Ashes,

Can you please explain these charts? The way I read it is that 2015 had a high pressure anomaly, but the past few years have been average to within +1 to -1 for most of the country. This goes against what I would have thought it was. Unless the charts are the other way around?
The charts are observational pressure anomalies for July.
One blocking high and it’ll throw the months plots but the trend between them is key.
But I do see indications of a more zonal pattern in the subpolar region south of Aus, for the last 3 years.
It also vaguely supports more Low pressure systems peaking in the West of the country for the last couple of Julys.
The next step would be to see the more ‘seasonal’ variances.
 
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Steve777

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The view from Sydney: we seem to be repeating last year's pattern: firstly, a wet June (~170 mm), characterised by blocking highs, low pressure in the Tasman and South to East winds bringing rain to the coast but not penetrating West of the Divide; then a more Westerly pattern in July, with the rain drying up. Last year, August was also dry, with below average (but close to median) rainfall in September. Rain returned in earnest in October. In 2017, it was quite dry from late June to mid October. In 2016, June was very wet, with July to September rainfall close to average. The 'dry season' was October-November.

We'll see what happens. EC and GFS seem to be showing a switch to a more onshore pattern from mid next week.

With regards to temperatures, OH might not be the best site to compare to Port Macquarie or elsewhere. It seems to be warming more than the rest of Sydney (gut feeling, not evidence). The Airport also seems very UHI affected. Sydney Olympic Park might be better (although a bit of a cold hollow on clear nights, plus short records and a site change). Bankstown is good because of long records, ditto Parramatta.
 
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AshestoAshes

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AshestoAshes

One of Us
Jul 3, 2019
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Voyager Point NSW
The charts are observational pressure anomalies for July.
One blocking high and it’ll throw the months plots but the trend between them is key.
But I do see indications of a more zonal pattern in the subpolar region south of Aus, for the last 3 years.
It also vaguely supports more Low pressure systems peaking in the West of the country for the last couple of Julys.
The next step would be to see the more ‘seasonal’ variances.
Also couldn't have explained it better myself.
 

Steve777

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5 out of the past 6 years in Sydney have had some of the highest July temperature means since records began
Keep in mind the industrialization of Sydney since settlement.

However the last 6 yrs have been right up there for sure.
source
http://www.bom.gov.au/climate/data/
...

I might mention in passing that the Sydney OH site was moved to a less exposed position in 1917, which had the effect of increasing average Winter maxima by nearly 2 degrees, as if it had been moved hundreds of kilometres North instead of a couple of hundred metres or so South.

OH average July maximum:
  • 1921-1950: 16.8 - post move
  • 1891-1920: 15.1 - include a few post move years
  • 1881-1910: 14.8 - the period around 1900 does seem to have been particularly cold.
I don't know why pre 1918 years are included in the Sydney average. They are effectively from a different site, even though it's only a short distance.

The 1918-2018 Sydney OH average July Maximum is 17.2, which in my (non expert, non-professional) opinion is what should be being used as "Sydney's" average July maximum.
 

Wavey

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July is the new September and June was the new August! I say that because we got very strong winds quite regularly in June, and it's usually most common in August.
 
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