Giant High Pressure Systems

Posted by: Eigerwand

Giant High Pressure Systems - 08/07/2018 06:02

Soppose i’ve been watching the weather now for about thirty years. In that time I don’t think I’ve ever seen so many enormous high pressure systems as we have seen over the past 6-8 weeks, singularly big enough to span the entire country.
How unusual is this? Does anyone have any ideas as to why we are seeing such large systems occur?
Posted by: paulcirrus

Re: Giant High Pressure Systems - 08/07/2018 10:00

Nothing unusual about it. Seen bigger events.
But will be more
Posted by: Petros

Re: Giant High Pressure Systems - 08/07/2018 17:18

Pretty typical mid winter scenario by my experience Eiger.
Posted by: retired weather man

Re: Giant High Pressure Systems - 08/07/2018 17:46

Agree. 1972 was also a standout year, my "best" memory of a week long 1035+ high over Victoria was the massive smog in Melbourne which never really lifted. In driving back from Essendon Airport at 2 p.m. one day, the wipers left a green smudge on the windscreen. The following year at Laverton Apt in a similar set up the min temp one day was minus 1 and the max was plus 2C, in a freezing fog(smog) which lifted briefly over the city area giving a more respectable max of 9 deg there.

That was the era before the EPA really got going, and one of their first efforts was to ban the burning of autumn leaves in the gutters outside suburban houses. But the bricketts use was still extremely common then.
Posted by: scott12

Re: Giant High Pressure Systems - 08/07/2018 20:04

Its just par for the course this time of year ..that's what brings the nasty SE tradewinds to the North of QLD..at least they are moving through now whereas a month or so back they were very slow moving, almost stationary...when they are moving along they often offer Nth Qld a few days of slack weather once they pass till the next one pushs through...this gives us a break from the incessant Sou'easters and gives keen fisho's a reason to live.. smile
Posted by: Thunderstruck

Re: Giant High Pressure Systems - 08/07/2018 20:33

2006 was a clear standout for mine with regards to large highs.

TS cool
Posted by: Ronfishes

Re: Giant High Pressure Systems - 09/07/2018 10:39

I remember Peter Byrne, our old win tv forecaster, only getting excited about highs over like 1038-1040
Posted by: Eigerwand

Re: Giant High Pressure Systems - 11/07/2018 06:38

Thanks for the replies folks.
Posted by: Eigerwand

Re: Giant High Pressure Systems - 13/07/2018 18:03

So based on that little Weather Pulse vid put up today, sea surface temps around Aus, in particular NW WA are cooler than usual. I know that dominant high pressure systems are a feature of this time of year but I still think the last couple of months has seen larger more dominant pressure systems than usual. Cooler sea surface temps would make help to contribute to that being the case.
Posted by: ashestoashes

Re: Giant High Pressure Systems - 13/07/2018 22:29

Can i get a goodbye to dominant high pressure systems with the 240hours hopefully staying with EC. Definitely one of our better years compared to the couple few in terms of SAM with no Winter negative since 2015, although the lack of rain has been persistent hence us feeling the pinch.
Posted by: Long Road Home

Re: Giant High Pressure Systems - 14/07/2018 04:26

Yep 2006 definitely a standout, I also remember GFS not updating a few times that autumn and winter (ironically enough) it wouldn't have made a difference anyway because the highs didn't budge and our forecast was "Fine and sunny" for weeks on end. We all seriously wondered if it would ever rain again laugh

Mid 2003 was monotonous too, however nothing like 2006.
Posted by: Eigerwand

Re: Giant High Pressure Systems - 14/07/2018 11:43

Some good cold mornings out of them at least, but yeah, bring on more frontal activity.
Posted by: Eigerwand

Re: Giant High Pressure Systems - 15/07/2018 12:34

Thought I’d noticed some colder than usual and consistently cold minimums over the centre of the continent, a check of the obs confirmed this, Alice Springs is currently a whopping 4.4C below the long term avg for July minima!!! This comes off the back of June that was 2.4C below avg for minimums. So good to see some significant cold stats.

I knew the past couple of months synoptic charts looked different and the evidence is starting to mount up.

Now I’m wondering what will happen as the days get longer as the sun wanders south. If these monster highs continue into August, heat will build unchecked in the centre. When a front comes through that draws a NW’ly airstream ahead of it, we may see some absolutely ridiculous late winter/spring heat events across the SE of the country. Coupled with below avg rainfall we could see some really nasty fire weather.
Posted by: Eigerwand

Re: Giant High Pressure Systems - 17/07/2018 20:27

So this past week has seen some really significant cold
minima over nearly all of NSW and areas of QLD and it’s all due to these abnormally large spanning highs. That single pressure systems have been large enough to span the entire country has made for some incredibly calm conditions, allowing for temps to really plummet at night.

I feel this has now become the defining feature of winter 2018. I would like to see it shift soon. As I mentioned in the last post, I don’t like the prospect of what such conditions may entail as the suns rays grow stronger.
Posted by: Kino

Re: Giant High Pressure Systems - 17/07/2018 21:27

Hopefully it means massive low pressure over Aus in Summer?
Posted by: MOUNTAIN h2o

Re: Giant High Pressure Systems - 17/07/2018 22:31

Those Highs are killing our past climate statistics, we are entering a new age of continuous dry hot conditions in the South East.
Posted by: Eigerwand

Re: Giant High Pressure Systems - 18/07/2018 05:40

Hmmm, I’m not sure (obviously haha). Perhaps this could be a sign of a significant El Niño on the way? In that case the monsoonal lows over the tropics would be less active.
Posted by: Mcbobbings

Re: Giant High Pressure Systems - 18/07/2018 07:39

As someone who has just become interested in weather recently, what would a winter of 30 or 40 years ago have looked like in terms of frontal activity? How often would a front reach Sydney for example? From my own observations of the past 3 years it seems fronts hit Sydney every 3 or 4 weeks from May to October.
Posted by: ozthunder

Re: Giant High Pressure Systems - 18/07/2018 08:56

Originally Posted By: Mcbobbings
As someone who has just become interested in weather recently, what would a winter of 30 or 40 years ago have looked like in terms of frontal activity? How often would a front reach Sydney for example? From my own observations of the past 3 years it seems fronts hit Sydney every 3 or 4 weeks from May to October.


Ones memory gets 'condensed' into remembering the significant events and forgetting the mundane. I am 61 but I am certain there were more snow days at Robertson 30-40 years ago than over the last 10-20 years.

My most vivid memory was around 18 years old and having an after work surf with snow at Robertson clearly visible from the beach. It was that cold that when i got out, I could not wrap my hand around the edge of surfboard to carry it, so had to go dry and warm up before retrieving the surfbaord.

Lastly my trustly "World Weather Guide" which is a book of temperature and rain tables from across the world published near 40 years ago has the average Sydney June and July maximum as 16C, nowdays that is below average.
Posted by: Kino

Re: Giant High Pressure Systems - 18/07/2018 09:48

Nostalgia is an effective filter sorry - I recall the 80's were terribly dry and hot until the massive La Nina at the end. That's one of the problems with climate science - it's always re-writing or downplaying history. But Dorothea McKeller nailed our climate in the 1900's.
Posted by: Thunderstruck

Re: Giant High Pressure Systems - 18/07/2018 10:20

The current LWT node around WA longitudes and the general progs over the coming week or so is definitely one of the most substantial I can remember in my time watching the weather patterns, certainly generating a very impressive swell across the Southern and Indian Oceans...great rains for the southern coastal areas that are getting clipped by it but being so zonal minimising the inland impact for now.

TS cool
Posted by: ozthunder

Re: Giant High Pressure Systems - 18/07/2018 14:29

Originally Posted By: Kino
Nostalgia is an effective filter sorry - I recall the 80's were terribly dry and hot until the massive La Nina at the end. That's one of the problems with climate science - it's always re-writing or downplaying history. But Dorothea McKeller nailed our climate in the 1900's.


The summers of 83/84 and 84/85 were quite brutal..........for ice cream sales. Wollongong University recorded 8 days above 30C all summer in 83/84, and only 4 above 30C in 84/85.

I used to cut out weather maps from the Illawarra Mockery and remember that period well. Plus missed the hot days - I do not mind a 44C day, just the night I hate.
Posted by: Kino

Re: Giant High Pressure Systems - 18/07/2018 15:08

Originally Posted By: ozthunder
Originally Posted By: Kino
Nostalgia is an effective filter sorry - I recall the 80's were terribly dry and hot until the massive La Nina at the end. That's one of the problems with climate science - it's always re-writing or downplaying history. But Dorothea McKeller nailed our climate in the 1900's.


The summers of 83/84 and 84/85 were quite brutal..........for ice cream sales. Wollongong University recorded 8 days above 30C all summer in 83/84, and only 4 above 30C in 84/85.

I used to cut out weather maps from the Illawarra Mockery and remember that period well. Plus missed the hot days - I do not mind a 44C day, just the night I hate.


How many did Albion Park record? Wollongong Uni isn't that good a measuring stick - close enough to the coast to get the moist cooler NE'ers, covered in lush gardens & shade and at the foot of a mountain.
Posted by: Seina

Re: Giant High Pressure Systems - 18/07/2018 20:46

Re opening post, smile :

http://onlinelibrary.wiley.com/doi/10.1029/2009GL037786/abstract
Posted by: ozthunder

Re: Giant High Pressure Systems - 19/07/2018 20:23

Originally Posted By: Kino
Originally Posted By: ozthunder
Originally Posted By: Kino
Nostalgia is an effective filter sorry - I recall the 80's were terribly dry and hot until the massive La Nina at the end. That's one of the problems with climate science - it's always re-writing or downplaying history. But Dorothea McKeller nailed our climate in the 1900's.


The summers of 83/84 and 84/85 were quite brutal..........for ice cream sales. Wollongong University recorded 8 days above 30C all summer in 83/84, and only 4 above 30C in 84/85.

I used to cut out weather maps from the Illawarra Mockery and remember that period well. Plus missed the hot days - I do not mind a 44C day, just the night I hate.


How many did Albion Park record? Wollongong Uni isn't that good a measuring stick - close enough to the coast to get the moist cooler NE'ers, covered in lush gardens & shade and at the foot of a mountain.


I take your point. I think the Illawarra would not have an ideal measurement spot. May be Warrawong? or even my home of Mount Warrigal/ Barrack Heights. Albion Park is rain shadowed badly for southerly rain / drizzle, and also the frostiest place in the Illawarra. Bellambi and Kiama are too far to close to the ocean.
Posted by: Kino

Re: Giant High Pressure Systems - 20/07/2018 11:33

Yeah was thinking Lake Heights area (though elevated) and Oak Flats - seems to be on that boundary line.

Was re-visiting that rainfall map I provided ages ago, and it seems the Lake Heights/Berkeley area does pretty well rainfall wise (1300-1500mm shading) right on the border of the rain shadow effect and some sort of orographic enhancements perhaps?

Posted by: Locke

Re: Giant High Pressure Systems - 20/07/2018 11:57

I grew up around the Shellharbour areas and can recall some brutally hot days in the low 40s in either late November or early December.

One day I was playing golf for school activities and it was so hot I would thoroughly wet my tshirt on the green and it would be dry by the time I got to the next tee.
Posted by: Kino

Re: Giant High Pressure Systems - 20/07/2018 12:10

I distinctly recall 1988 as it was then that piqued my interest as a kid in weather. Huge rains in April that year - Lake Illawarra flooded - Albion Park, Oak Flats, Dapto (if I recall)

I recall coming home from the new Shellharbour Square, as it used to be called, and the rain was hammering down. I think it was an ECL but can't quite recall.

Posted by: Rigger

Re: Giant High Pressure Systems - 20/07/2018 16:52

April !986 was a hot month as I recall. I was visiting my parents at Menangle and we had a 38c day there early in the month then I was fishing on Lake Illawarra on Anzac Day and it was near on 30c from memory....
Posted by: ozthunder

Re: Giant High Pressure Systems - 23/07/2018 15:58

Originally Posted By: Kino
I distinctly recall 1988 as it was then that piqued my interest as a kid in weather. Huge rains in April that year - Lake Illawarra flooded - Albion Park, Oak Flats, Dapto (if I recall)

I recall coming home from the new Shellharbour Square, as it used to be called, and the rain was hammering down. I think it was an ECL but can't quite recall.



That may have been the year that the surf club had the surf boats rowing down Shellharbour Road at Windang, rescueing oldies from the caravan parks.

It will not ever happen again as the Lake Entrance now has breakwalls which have really worked. We even have mangroves starting to thrive west of the bridge.
Posted by: Eigerwand

Re: Giant High Pressure Systems - 25/07/2018 09:04

Listening to ABC radio this morning and caught an interview with one Professor Rogers from the climate science department at the University of Queensland commenting on the current weather situation in the NH w.r.t. fires in Greece and heatwaves effecting Japan (recorded it’s hottest temp on record) , much of Europe and Canada. He said that a large part of it was that the subtropical ridge is extending much further northward that usual this year, and that larger than normal high pressure systems were a feature of the NH summer.

This really took me aback. I would’ve thought that the subtropical ridge extending further in one hemisphere would lead to a withdrawal in another?

I’m starting to think that combined with a better than not chance of an El Niño developing, we really might be in for it this spring/summer.
Posted by: Eigerwand

Re: Giant High Pressure Systems - 06/08/2018 18:46

Get a load of Wednesday 10am’s chart:

http://www.bom.gov.au/australia/charts/4day_col.shtml
Posted by: Nerd65

Re: Giant High Pressure Systems - 06/08/2018 19:16

I don't think the sub tropical ridge being high up over the Australian continent during winter is anything unusual. I remember seeing examples of this in books on climatology. This example from the BOM is the same: http://www.bom.gov.au/climate/about/?bookmark=strexample
Posted by: Eigerwand

Re: Giant High Pressure Systems - 07/08/2018 06:20

Yeah for sure. It’s just the size and stability of that belt this year. I mean the pressure gradient in Wednesday’s map pretty much stays the same over more than half the continent, very calm stable conditions.
Posted by: Eigerwand

Re: Giant High Pressure Systems - 07/08/2018 12:22

Further, I’m getting a little tired of the ‘seen it all before’ mentality. Large parts of Eastern Australia are now the driest they’ve been for some time, daytime maximums were some of the warmest on record for July across large parts of NSW and QLD, while the unusually clear calm conditions allowed for some very significant minimums to be recorded last month from NSW all the way to Alice Springs. I’m sure similar patterns have gripped the country previously but if we look at the conditions experienced over the last couple of months, clearly a more dominant subtropical ridge than normal has been at play.
Posted by: Seina

Re: Giant High Pressure Systems - 16/08/2018 20:47

To my understanding, a number of weather-related dynamics and features have contributed to the current drought conditions across much of Eastern Australia, and further inland.
Posted by: Eigerwand

Re: Giant High Pressure Systems - 16/08/2018 21:14

Yes of course. It wasn’t like this over summer and lots of Eastern Aus has been in drought since then. But a dominant and stable STR has been more pronounced since about May this year compared with years past and has contributed to the worsening dry and also helps to explain other weather we have observed this winter over large parts of the country.
Posted by: Eigerwand

Re: Giant High Pressure Systems - 17/08/2018 06:58

“A stronger than average high pressure system over central and eastern Australia”. That was taken from the latest weatherpulse clip w.r.t. rainfall this winter.
My point in starting this thread was to bring to light something I saw as being unusual, which it did in fact turn out to be and hopefully get some input as to what might be going on to make this so. Sadly most of the replies have been “seen it all before” as the pattern in question fits in well with a certain theory so despised by the experts on here that to bother actually understand what was going on might raise a couple of uncomfortable questions.

That said I am still hopeful someone may jump in and offer some explanation behind the ‘stronger than avg STR of 2018’.
Posted by: Sillybanter

Re: Giant High Pressure Systems - 17/08/2018 07:35

I probably won't add much to help you here but for me this winter is more about the strong frontal systems continually rolling across the southern ocean. This is highlighted by very wet conditions around the SW exposed parts of the country e.g. SE South Australia and SW Wester OZ. I suspect the SAM has a lot to do with this. In the past when we see blocking high pressure in the Souther Ocean and the Tasman Sea we get more cut off cold pools that drift NE out of the bight and trigger rain events over Eastern Australia. This year I have seen none of this activity to remember. Funny enough the set up over the next week 10 days looks like it may finally produce this type of situation, but time will tell if it really happens.
Originally Posted By: Eigerwand
“A stronger than average high pressure system over central and eastern Australia”. That was taken from the latest weatherpulse clip w.r.t. rainfall this winter.
My point in starting this thread was to bring to light something I saw as being unusual, which it did in fact turn out to be and hopefully get some input as to what might be going on to make this so. Sadly most of the replies have been “seen it all before” as the pattern in question fits in well with a certain theory so despised by the experts on here that to bother actually understand what was going on might raise a couple of uncomfortable questions.

That said I am still hopeful someone may jump in and offer some explanation behind the ‘stronger than avg STR of 2018’.
Posted by: Chris Stumer

Re: Giant High Pressure Systems - 17/08/2018 08:10

If this pattern persists into spring and summer, it's going to get very hot because the sinking air in the high pressure system will trigger compressional heating and add to that clear skies, it's going to make for brutal heatwaves.
Posted by: pete28

Re: Giant High Pressure Systems - 17/08/2018 08:56

Originally Posted By: Chris Stumer
If this pattern persists into spring and summer, it's going to get very hot because the sinking air in the high pressure system will trigger compressional heating and add to that clear skies, it's going to make for brutal heatwaves.


If we look at the cycle of what's been happening overseas with exceptionally hot heatwaves then Australia could well be in for it's first 50C temp since 1998....
Posted by: Eigerwand

Re: Giant High Pressure Systems - 17/08/2018 11:35

Originally Posted By: Sillybanter
I probably won't add much to help you here but for me this winter is more about the strong frontal systems continually rolling across the southern ocean. This is highlighted by very wet conditions around the SW exposed parts of the country e.g. SE South Australia and SW Wester OZ. I suspect the SAM has a lot to do with this. In the past when we see blocking high pressure in the Souther Ocean and the Tasman Sea we get more cut off cold pools that drift NE out of the bight and trigger rain events over Eastern Australia. This year I have seen none of this activity to remember. Funny enough the set up over the next week 10 days looks like it may finally produce this type of situation, but time will tell if it really happens.
Originally Posted By: Eigerwand
“A stronger than average high pressure system over central and eastern Australia”. That was taken from the latest weatherpulse clip w.r.t. rainfall this winter.
My point in starting this thread was to bring to light something I saw as being unusual, which it did in fact turn out to be and hopefully get some input as to what might be going on to make this so. Sadly most of the replies have been “seen it all before” as the pattern in question fits in well with a certain theory so despised by the experts on here that to bother actually understand what was going on might raise a couple of uncomfortable questions.

That said I am still hopeful someone may jump in and offer some explanation behind the ‘stronger than avg STR of 2018’.


Yeah just two sides of the same coin for mind. It appears the stronger than usual
STR residing over the continent has kept the westerly belt of polar lows locked down south, preventing much divergence north and by way of that not allowing air from low latitudes to penetrate south.

This article relates to the surf but is relevant for the analysis given to SAM. It’s interesting to note the long range node has seemed to be stationed at such a point to give southern WA a hiding. Perhaps this may shift east before winters end and we may see a little more action in the east of the country at comparable latitudes.

http://www.swellnet.com/news/swellnet-an...east-coast-flat
Posted by: Sillybanter

Re: Giant High Pressure Systems - 17/08/2018 15:32

I actually see it different. I think the westerly belt is higher than usual(further north as indicate by SAM) which is squeezing the high pressure belt into a long week belt of high pressure that sits east to west over Australia. IMO when the polar activity is to high, Australia is dominated by a westerly flow which brings dry and stable weather to 90% of the continent. When the polar activity retreats south we get larger highs that that are slightly further south and produce onshore winds onto the east coast. This moisture travels west across the continent before being picked up by frontal systems.
Originally Posted By: Eigerwand
Originally Posted By: Sillybanter
I probably won't add much to help you here but for me this winter is more about the strong frontal systems continually rolling across the southern ocean. This is highlighted by very wet conditions around the SW exposed parts of the country e.g. SE South Australia and SW Wester OZ. I suspect the SAM has a lot to do with this. In the past when we see blocking high pressure in the Souther Ocean and the Tasman Sea we get more cut off cold pools that drift NE out of the bight and trigger rain events over Eastern Australia. This year I have seen none of this activity to remember. Funny enough the set up over the next week 10 days looks like it may finally produce this type of situation, but time will tell if it really happens.
Originally Posted By: Eigerwand
“A stronger than average high pressure system over central and eastern Australia”. That was taken from the latest weatherpulse clip w.r.t. rainfall this winter.
My point in starting this thread was to bring to light something I saw as being unusual, which it did in fact turn out to be and hopefully get some input as to what might be going on to make this so. Sadly most of the replies have been “seen it all before” as the pattern in question fits in well with a certain theory so despised by the experts on here that to bother actually understand what was going on might raise a couple of uncomfortable questions.

That said I am still hopeful someone may jump in and offer some explanation behind the ‘stronger than avg STR of 2018’.


Yeah just two sides of the same coin for mind. It appears the stronger than usual
STR residing over the continent has kept the westerly belt of polar lows locked down south, preventing much divergence north and by way of that not allowing air from low latitudes to penetrate south.

This article relates to the surf but is relevant for the analysis given to SAM. It’s interesting to note the long range node has seemed to be stationed at such a point to give southern WA a hiding. Perhaps this may shift east before winters end and we may see a little more action in the east of the country at comparable latitudes.

http://www.swellnet.com/news/swellnet-an...east-coast-flat
Posted by: petethemoskeet

Re: Giant High Pressure Systems - 17/08/2018 16:02

Just reading about the Hadley cell and wondering how much influence this circulation is contributing to our current weather.
Posted by: Seina

Re: Giant High Pressure Systems - 17/08/2018 21:29

Originally Posted By: Eigerwand
Yes of course. It wasn’t like this over summer and lots of Eastern Aus has been in drought since then. But a dominant and stable STR has been more pronounced since about May this year compared with years past and has contributed to the worsening dry and also helps to explain other weather we have observed this winter over large parts of the country.

I agree with the above smile .
Posted by: Seina

Re: Giant High Pressure Systems - 17/08/2018 21:51

Originally Posted By: Eigerwand
“A stronger than average high pressure system over central and eastern Australia”. That was taken from the latest weatherpulse clip w.r.t. rainfall this winter.

What is this weatherpulse clip -- is there a link smile ? I can't find one in this thread.

Originally Posted By: Eigerwand
My point in starting this thread was to bring to light something I saw as being unusual, which it did in fact turn out to be and hopefully get some input as to what might be going on to make this so. Sadly most of the replies have been “seen it all before” as the pattern in question fits in well with a certain theory so despised by the experts on here that to bother actually understand what was going on might raise a couple of uncomfortable questions.

A link to an abstract was provided within this thread, which I would understand is very relevant to the discussion smile . Here it is again:
http://onlinelibrary.wiley.com/doi/10.1029/2009GL037786/abstract

Originally Posted By: Eigerwand
That said I am still hopeful someone may jump in and offer some explanation behind the ‘stronger than avg STR of 2018’.


It can be described smile .
Posted by: Mega

Re: Giant High Pressure Systems - 17/08/2018 21:56

Originally Posted By: Sillybanter
I actually see it different. I think the westerly belt is higher than usual(further north as indicate by SAM) which is squeezing the high pressure belt into a long week belt of high pressure that sits east to west over Australia. IMO when the polar activity is to high, Australia is dominated by a westerly flow which brings dry and stable weather to 90% of the continent. When the polar activity retreats south we get larger highs that that are slightly further south and produce onshore winds onto the east coast. This moisture travels west across the continent before being picked up by frontal systems.


I see it the same way. Highs are further north and fronts are continually lashing WA/southern SA & VIC but they have no head because there's no moisture infeed from the IO. When SAM goes + the westerly wind belt retreats further south as do the highs...and finally we get some onshore flow and moisture from the Pacific ocean.
Posted by: Sillybanter

Re: Giant High Pressure Systems - 18/08/2018 09:16

Cheers Mega I forgot to mention the Indian Ocean which is equally important as a moisture source. Which missing in action this year by the way. Living in inland Australia for most of your life you tend to pay close attention to moisture sources because without moisture you have no chance of rain. And you came to realise how many influences have to come together to produce rain in these parts that its almost a fluke when it actually does. And its why we can still have dry conditions in a La Nina. Because its just a small part of the puzzle that has to come together.
Originally Posted By: Mega
Originally Posted By: Sillybanter
I actually see it different. I think the westerly belt is higher than usual(further north as indicate by SAM) which is squeezing the high pressure belt into a long week belt of high pressure that sits east to west over Australia. IMO when the polar activity is to high, Australia is dominated by a westerly flow which brings dry and stable weather to 90% of the continent. When the polar activity retreats south we get larger highs that that are slightly further south and produce onshore winds onto the east coast. This moisture travels west across the continent before being picked up by frontal systems.


I see it the same way. Highs are further north and fronts are continually lashing WA/southern SA & VIC but they have no head because there's no moisture infeed from the IO. When SAM goes + the westerly wind belt retreats further south as do the highs...and finally we get some onshore flow and moisture from the Pacific ocean.
Posted by: ozone doug

Re: Giant High Pressure Systems - 18/08/2018 11:19

+1 for sillybanter . For MY location 90% of my rain comes from the North West and probably 5%from the South and 5% from the east. So we rely whats happening on the weather from the far North West or North. Which is in the dry for a fair while now .
Posted by: Eigerwand

Re: Giant High Pressure Systems - 23/04/2019 20:59

By the looks of the latest MSLP charts this looks like it might be a thing again. I remember last year it kicked off in late May though.

It is of course my own anecdotal experience however over the course of 30years of looking at pressure charts the current ones, like the ones last winter (and we all remember the peculiar weather they produced) are something of an anomaly.
Posted by: Funkyseefunkydo

Re: Giant High Pressure Systems - 23/04/2019 21:16

I expect the same blocking highs with cut off lows in between and constant SW winds on nsw coast.
Posted by: crikey

Re: Giant High Pressure Systems - 28/04/2019 19:50

crikey _eigerwand
The AAO has been mainly positive for many years.
2015 to now has been exceptional( looking at the time series data below.)
I am currently loosely testing a theory that positive AAO and large ballooning highs coincide.
I have noted that the speed of the high pressure belt is slower in a pos AAO and so gives rise to increased blocking events.
The blocking event of nov 2018 to March 2019 was all pos AAO
The high pressure cells balloon possibly because the 'drag' on air parcels is reduced with a slower flow
A slower high pressure belt gives rise also to less frequent troughing.

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/aao/month.aao.gif