Why So Cold?
The calendar on the wall says we're on the doorstep of summer, yet out the window the weather is anything but warm. There's been back to back snow falls, strong westerly winds, and winter quality waves in Vicco.
While strong cold outbreaks through spring and summer aren't uncommon, the current clustering of events is much rarer.
From Western Australia across to Victoria and down to Tasmania the cold outbreaks have brought a return to winter, with the cold air even making its way into New South Wales.
The one positive to go with the return to thicker wetsuits is the accompanying swell, which for the Surf Coast is more than welcome following a well below average autumn and winter.
So where is the cold air coming from?
Since 2019, it's been fascinating tracking how changes in the upper atmosphere (called the stratosphere) filter down into the lower atmosphere (the troposphere) then influence the surface weather and synoptics around the world.
Regular readers would remember the Sudden Stratospheric Warming event in September 2019, which saw temperatures in the upper atmosphere rising 75°C in a period of a couple of weeks.
This then propagated down through the atmosphere resulting in an early breakdown of the polar vortex through late spring. The polar vortex is the strong westerly winds that keep cold air trapped at polar latitudes. When the polar vortex is weak, cold air escapes the poles, pushing towards the equator in the form of frontal activity. This is known as the negative phase of the Southern Annular Mode (SAM). For a quick refresher on the SAM, click here.
Keep the above in mind as we'll come back to it later.
Coming off years of drought and record low levels of soil moisture, exacerbated by the positive Indian Ocean Dipole event, this lift in the storm track dragged hot air that had that pooled throughout central Australia, down to the south-east, leading to the Black Summer bushfires.
We then dramatically transitioned into a wet, cooler signal as the first of our three La Niña's developed through 2020.
Now, here we are over two years later, with the third La Niña event currently peaking, mixed in with a negative Indian Ocean Dipole event.
Traditionally, La Niña's are linked with + SAM events. Remembering that's the retraction of Southern Ocean frontal activity to the poles and higher pressure across the typical westerly storm track.
With this all in mind, and coming back to the original question, what's the link to the current winteresque frontal progressions?
It's mostly thanks to the polar vortex again, which has become larger than the long term averages but more diffuse. In fact, by area, it's currently in the largest 5% of recorded sizes over the past few decades.
Knowing that a strong, tight polar vortex restricts cold air to polar latitudes, the inverse also applies: a broad, weaker polar vortex allows cold air to spread further north towards the equator.
However, rather than expanding in one wide area towards northern locations, we see nodes of cold air pushing up into select regions, while warmer air is drawn south towards polar latitudes either side of the cold nodes. This is effectively the Long Wave Trough and Australia has been under the influence of one such node the since the start of the month, varying its focus between Western Australia and Victoria.
One final and evolving factor to explain the cold air reaching Australia, is the influence of the Hunga Tonga-Hunga Ha'apai eruption way back in January.
Along with various other aerosols, a considerable amount of water vapour and sulphate was injected into the atmosphere (over 5% above normal background levels). The water vapour and sulphate has since spread right around the Southern Hemisphere while also propagating down through the atmosphere. This has blocked incoming solar radiation and in turn cooled the mid-lower stratosphere.
The cooling effect in the stratosphere was significant and up to 10-12°C below normal for the area 60°-90°S in October, focussed south and south-west of the Australian continent.
This cold atmospheric anomaly has persisted into November, and as a result the polar vortex, while significantly wide in area, is also recording record cold temperatures.
Putting this all together, we can see that any stalling node of the Long Wave Trough across the country has access to colder than normal upper atmospheric air, hence bringing the snow, freezing wind chill and cold weather to our south-east.
Aside from what's causing it, people want to know how long it will last.
While the polar vortex is much wider than normal, it is on the decline, with a rapid breakdown due in the coming month.
Extended-range forecasts have the node of the Long Wave Trough staying in the vicinity of the south-east of our continent and New Zealand up until at least the middle of December so expect cooler, crisper days to continue until then.
Thats really interesting Craig.
It's a really schizophrenic synoptic set-up over the Island continent right now.
Cold outbreaks in the south and it looks like an early start to the Northern Australian Monsoon (NAM) is imminent with a nice cross-equatorial flow and NW'ers from Indonesia into the Arafura Sea developing next week.
Meanwhile here on the Northern rivers, which seems particularly sensitive to phase changes in the ENSO cycle it has all of a sudden (over the last 3 weeks) gone dry as a crisp.
What happens as this La Niña breaks down? Watch this space.
Very interesting the suphates are acting as they are known to do, and have such an impact.
Quite happy for this to continue until mid Dec.
The water doesn't seem 'especially cold' here in Vicco for this time of year, which is a plus.
Correct. Water is warmer than expected with all the cooler weather or, probably more accurately, the lack of warmer weather to warm things up. Still wearing a 4/3 though.
Ya reckon? I tried the 3/2 in the last session and was shivering after 2 hours....I just cant stand the thought of wearing a 4/3 in NOVEMBER! I cant do it out of principle...just not right.
Need some better rubber I reckon. I've been in a 3/2 for 6 weeks, at least.
"so expect cooler, crisper days to continue until then."
Drier too? (south coast NSW)
So the positive SAM should keep the cold air down to the south but is bring overridden by the Long Wave Trough?
its annoying that us plebs can not access the LWT on weatherzone anymore. it was easily the most accurate way for a novice like myself to see if cold fronts were going to push up to mexico here in vicco in the forcast ahead. was an excellent tool for planning ahead with some certainly of action for wind and waves.
I'm with you, but it wasn't WZ that took them away, it was NOAA who stopped producing the variable to create the charts, hence ours disapperaing as well.
Here's the next best thing though and harder to read but quite useful. It's ECWMF and the 500hPa height anomaly observations and forecasts.
You can see the nodes and ridges and can get the latest update here: https://charts.ecmwf.int/products/mofc_multi_eps_family_hovmoller?area=S...
Legend cheers CB
Or http://wxmaps.org/fcst.php - select Southern Hemi then 200mb Streamlines
and Isotachs. Give a much easier to visualise the LWT imo.
Thanks stu2d2 :)
If you use windy.com you can move the slider to 500ha and get a fair idea of what's going on for their forecast period too. I was cursing the loss of that simple prognosis map until IB helped me out with this. Super easy as I use windy all the time anyway, just toggle from surface to 500ha.
Yep 500hPa charts are the best level for viewing it, but getting the anomaly helps show where we may see sustained activity, ie a node.
yes, very interesting on the sulphate in the atmosphere.
slightly off-topic, but anyone know if this could potentially cause rain to be more acidic? My quick little search suggests it could... Reason I ask is that my rainwater in tanks (poly) was just tested the other day - ph of 5. I've noticed extra copper staining in the shower, so was concerned. Even after going through the filter system and pipes into the house, the water is still quite acidic at 5.9. I'm now getting another filter system, a calcite filter, so that will fix it, but I wonder what consuming lots of that water could do to you... would appreciate anyone's thoughts on this.
Sulphur dioxide from coal fired power stations was the classic acid rain source in Europe, when the Black Forest was being destroyed, not sure about sulfates.
I think rain is always slightly acidic though, possibly from carbonic acid, which is why over time exposed concrete is gradually etched, exposing the stone.
thanks Distracted. Correct, rain is naturally acidic. Its just a strange one that since the last testing of my tanks that level of acidity has dropped markedly. The water filter guy (expert?) who checks similar tanks all over the region says it is very unusual. He even mentioned possibilities of impacts of cloudseeding or other geoengineering, but that that's likely conspiracy shit. I'm not leaning that way. Just feel this Tongan volcano was massive and is evidently having significant atmospheric effects. Or maybe just the overall increased carbon in atmosphere effect is changing the pH of rain - we know the oceans are getting more acidic as a direct result of that, so maybe...
Ph lowers as water temperature rises though I can’t recall the amount
Tannins will also lower the pH to some extent. Leaf litter making its way in as well?
thanks mcbain. Yes, I'm aware of that one and can rule it out in my case. It remains a mystery
Stratospheric temperature anomaly minus 12, top 5%, impressive stats for
Hunga Tonga-Hunga Ha'apai (thought he was a Wallaby?)
Thx for the deep dive Craigos
Fascinating stuff, I never would have thought that a single volcanic event would have such an impact on the atmosphere. I often wonder how many billions of years of pumping surf I've missed out on in the past. Cheers.
This graph below shows that stratospheric temps have been coldest on record since the middle of the year..
Great article just missing the big white elephant in the room “ Geoengineering “
Surely this has an effect on our crazy weather . Our neighbours in Indonesia along with Thailand are doing it , what’s Australia up to ? I would love for swellnet to deep dive into this topic and do an article
The factors at play here are on a scale so many orders of magnitude bigger than any local cloud seeding/geoengineering etc.
Take the Tongan eruption, the amount of aerosols injected into the upper atmosphere has taken over six months to cause any effect to the upper atmosphere and is only now filtering down into the troposphere.
The water vapour injected was 100Tg (Teragram), that's 100,000,000,000 kg.
Regarding the heated water content to our north-west and around Indonesia, bringing the increased convection and rainfall that's been dragged down across the country, as well as the Pacific wide La Niña signal, the forces at play eclipse those you're hinting at.
It's just not in the same ball park, and also very inefficient. If you're worried about how this could be affecting our weather, take a more macro look at how a warming planet can hold 7% more moisture in the atmosphere per 1°C increase in temperature. That's much more of a worry regarding, heavier, more intense and prolonged rainfall events.
They are pumping that seeding crap out at an alarming ATM.
I don't think you can have the argument both ways ie say the planet is so huge that there is no way humans can have an impact with geoengineering and then in the same breath say humans are seriously threatening the planet and causing global warming.
If seeding doesn't work why are they doing it......and why so much right now when rain is causing serious problems?
"I don't think you can have the argument both ways ie say the planet is so huge that there is no way humans can have an impact with geoengineering and then in the same breath say humans are seriously threatening the planet and causing global warming."
Yes you can.
Issues arising from The Greenhouse Effect have been occurring since the 1700s, seriously ramping up last century, involving chemicals that last for a very long time, and also being, literally, worldwide.
On the other hand, cloud seeding is recent, regional, and temporary. The two things simply aren't comparable.
Any ideas how this will interact with warmer than average water in the Tasman?
My head is slightly hurting from all of that info but also amazing how resources allow us to dissect these types of weather patterns. (by us I mean Craig ;) )
Seems surprisingly toasty over here in NZ at the present, warm, humid and lots of thunder storms.
Changing as we speak, Yendor. The humid NNE flow has been shunted out to the east, and a succession of cold pools are set to move east across NZ. Further showers and thunderstorms, but much cooler.
ive been in West Sumatra most of November "unseasonally" W and WNW swell and wind. Anecdotally "wet season started in August and its been howling onshore more often ever.."
Yep was in Bali around a month ago got four days of typical dry season then the wet hit. Weirdest thing was it was straight south so on/cross for the whole island.
It's climate change. Everyone should go immediately and get the 7th jab.
Looks like the MJO might be on its way thru next week with a change back to some humid weather and east swell
Considering a recent survey determined the Tonga volcano eruption was the largest ever recorded, I would expect the particulate matter ejected into the atmosphere to have an effect on weather in Australia and throughout the southern hemisphere
Yep, it blew out an additional 700m deep crater!!
Nice one Craig. Read another article recently that referred to the effect of the Tonga volcano. It was significant. That article didn’t go into other factors, and in dumbing it down made it wrong, per se. No mention of La Niña, Indian Ocean dipole or southern annular mode, leaving it all to the volcano.
This is much better, as expected.
Now, for something of real local interest, why is the water so cold. Mid north coast last week was still cold, Sydney and cennie coast as cold as I can remember it in November. They keep saying 18 or 19 degrees. Not 19 at my local yesterday, and maybe a bit shy of 18. Half hour body surf In boardies and the cold got into my bones, which doesn’t happen that often.
That is toasty for Victoria 2/2 short sleeve steamer and your good to go.
Or a long arm springy is more than enough memla, but by this time of year I’m generally body surfing in boardies and surfing in springy or boardies and vest. I’m still doing that, it’s just colder.
Has warmed up a bit, but still only 19 locally. (Which is actually a great temp, cool enough to get a little sizzle on getting in, but soon warm enough to enjoy for a while. At 21 I’m complaining about how warm the water is.
Cold with waves recently... better than colder without them over the past few months.
Yeah wow, largest ever recorded. We've all seen how good the sunsets have been over winter.
For reference, here is a chart of all recorded solar cycles - you can see we are in the maxima of a second, smaller cycle in a row. Not quite at Dalton Minimum levels, but not far off.
And here's NASA's observation of the current cycle - at 80 and heading a bit higher (with confidence predictions). At any rate, it's a small cycle, again. A new solar minimum of sorts.
Internet is ablaze with articles linking solar minimum with increased volcanism, but I can't find anything official so here's this summary article and the links it presents, for those interested:
Still in the 4/3 here, and even got the 5/4 (it was dry) and hoodie out on Monday way out there in the wind.
"The results of this study showed very strong correlation between solar activity and the largest seismic and volcanic events, within the continental US and globally. The correlation for volcanic activity was bigger than (> 80%) and for the largest earthquakes was (100% of the top 7 most powerful) versus solar activity lows. Additionally, the research concluded the existence of a strong correlation between global volcanic activity among the largest of classes of eruptions and solar activity lows. With the 80.6% occurrence of large scale global volcanic eruptions taking place (> VEI 5) during solar activity lows and with 87.5% occurring for the very largest (> VEI 6) eruptions during major solar minimums. "
Will have to have a read of those VJ, what's their hypothesis on the causality from solar activity to tectonic/volcanic activity?
Also you might be interested in this..
Thanks Craig, their hypothesis is that big volcanic events correlate with solar minimums, roughly speaking. Important to note that this does not = no climate change, but rather that the processes go on simultaneously.
I think I can see a bit of a correlation with the 11 year solar minimums and blasts in that chart.
What they are going on about is when you get something like Maunder minimum/Dalton minimum you might have more chance to get a significant planet cooling blast like Tambora, give or take a decade. "Year without a summer" for eg. This recent Hunga Tonga one was a huge blast, and we have now had two solar cycles that are significantly less than the modern solar maximum's peak, which was in the 1950s.
Causuality mechanism: my guess based on reading/seeing a bit of the internet's theory.
Solar minimums see solar output, and the solar magnetic field decline. Far fewer sunspots occurs with more chance of large coronal holes, which spew solar rays (plasma?) at us, for longer. (Arrival of coronal hole streams has been shown to immediately affect the weather column, link in the solar thread). Coronal streams follow magnetic field lines into the earth and 'charge' it. This increases the risk of volcanism/earthquake. Earth's protective magnetic field also reduces in this situation.
Alternate take: with the reduction in the heliosphere at significant solar minimums and reduction in the solar and earth's magnetic field, more galactic cosmic rays get in (internet has readings of these being observed to be increasing, for eg), and the galactic cosmic rays may have some influence on it (and even on things like cloud formation, though this is controversial.)
These are rough, and from memory, it's been ages since I looked through this. All are inputs to the system of some kind and force.
This might help with that question.
It's known that during solar minimum, cosmic ray bombardment of Earth increases due to weaker solar wind/magnetic shielding.
This cosmic ray uptick increases the amount of Muons that are able to penetrate the crust and this is theorized to cause magma in the crust to 'fizz' and increase pressure under volcanoes leading to an increase in eruptions.
Earth's magnetic field also seems to be weakening rapidly and we could be heading towards a pole-flip, we are certainly in an excursion event at the minimum.
Since little is actually known about solar-magnetic climate forcing, it is possible that some of the weird weather is related to the weakening field, the developing solar grand-minimum and consecutive weak solar cycles we are experiencing.
Excellent! That's exactly it.
Hmm, I think they're actually using the Muons to analyse/view deeper into the volcanoes to identify possible eruptions?
It's not the muons causing it..
"Cosmic rays continually rain down into Earth’s atmosphere from outer space. When they run into atmospheric particles, they decay into smaller components, including an elementary particle called a muon. Muons’ relatively high mass allows them to penetrate deeply into materials, even solid rock. By placing specialized detectors that record muons passing through a volcano, scientists can use the particles to create more finely defined maps of the interior of the volcano than possible with previous techniques"
Agh reading deeper, there is more research being done on the cosmic ray effect on the magma..
Bigger than Krakatoa?
Sounds like it was equivalent to Krakatoa, Just delving to try and see if the aerosol injection is comparable.
Zack Labe just posted this awesome graphic showing the 'surface' temperature anomalies across the globe, from South Pole to North, left to right.
The Arctic is cooking!
doesn't this article below contradict what you are saying.
Not at all, he's just pointing out some poor understandings of the processes people may have. Doesn't change the end result.
"When air holds as much water vapor as it can for a given temperature (100% relative humidity), it is said to be saturated. If saturated air is warmed, it can hold more water (relative humidity drops), which is why warm air is used to dry objects--it absorbs moisture. On the other hand, cooling saturated air (said to be at its dew point) forces water out (condensation). This is why a container of a cold beverage sweats: it cools the air next to it and moisture from the air condenses on the outside of the can."
It's sometimes tricky getting your head around vapor pressure, humidity and dew point etc, but it's a fact that a warmer atmosphere can hold more moisture content, at about 7% per 1°C.
Another look at it as well..
"Warmer air holds more water because the water vapor molecules it contains are moving at a higher average speed than those in colder air making them less likely to condense back to liquid. According to the Clausius–Clapeyron equation, for each 1.8°F (1°C) of warming, saturated air contains 7 percent more water vapor, which may rain out if conditions are right."
Cheers Craig will stick to CSIRO & NASA websites from now on.
PS - Sth Aust on 20/1/22 had massive 150-200mm rain dump over 24 hours which smashed Eyre & Stuart Hwy. This was around 5 days after the Tongan Volcanic eruption. Question - Do you reckon there was a relationship between these 2 events?
Hey Johno, no, too early in the piece and the aerosols wouldn't have dispersed throughout the atmosphere enough to be linked.
Such an interesting read. I really like these in-depth weather articles. They don't just satisfy my curiosity (and help me understand why we're getting these surf conditions), but they also help me seem so knowledgable when people talk about the weather and / or waves. Just this week on the NSW Central Coast there was a decent long period southerly swell, SSW winds and my local (mainly winter) point break was happening - strange, but very welcome..... Keep 'em up.
Having read weather maps for 50+ years to basically determine the wind direction and surf prospects - and having little formal climate 'knowledge' - thanks for this discussion.
As a casual observer, the number of 'lows' ( and subsequent 'rain events' ) that appear to emanate from NW Australia have increased, as well as the dreaded East Coast 'low' that generates the dreaded easterly storms and smashes any swells and dumps walls of seaweed on every beach.
It's a classic 'old man grizzle' but the predictable interpretations and assumptions have become .. unpredictable. And the water is definitely warmer.
Water temps around Margs is the coldest I've had for November in the last 26 years
Colder than Winter , although early October is usually the coldest water temps here.
The effect of this volcanic eruption shows that our efforts to control the climate are a mere drop in the ocean when all things are considered.
Some say we are now at the start of a grand solar minimum which will last for around three decades, and will cause significant temperature declines.
Meanwhile , arctic ice is now greater than it was in 2007 , when Gore predicted the arctic would be ice free by 2014,
and the Northern Hemisphere Total Snow Mass is now more than one std deviation ABOVE the 1982-2012 mean.
But who cares ?
As long as we give billions to the UN to redistribute , that's all that really matters.
Thanx Craig that's really brilliant...
In our region it's only a rare Rocket / Globe Master / ADF Display that emits Vapour trails.
Last few months Planes climbing from Gold Coast Airport are sporting long lingering Vapour Trails!
SEQ Meteorologist : Needs a Cool + Dry Upper Atmosphere (Can be anytime of year!)
Holding Flight Pattern exploits this dry weather to conserve fuel.
Thereby trailing Vapour lines at this level of atmosphere at Altitude = 38,000 ft or 11,500m
Recently been pointing out these trails to neighbours as it's abnormal for our part of the world.
Abnormal as it only lasts a few hours or days but now it assumes as our default Atmospherics.
tbb pointed out the 4-7 month long spell of unusual SEQ Blue Haze during last neutral phase.
Goldie can slot the procession of Trail Blazing Planes to fit perfectly into Craig's timeline...(Magic!)
Bne / Gold Coast we can actually see & measure the height of Sam with busy Flight schedules.
As Craig's table shows ...we can expect SEQ plane trails to vanish as Bully Sam becomes less Mean!
Not sure how far North to track Sam's trail...will prove difficult with less planes north of here!
Very cool & perfect timing Craig...explains our current SEQ oddity...Cheers!
Explains why today 20 degrees is cold for here & now but with a wind chill factor is nearer 10 degrees.
Interesting that 50% of Oz > whole East Flank from top to bottom > Lightning /Winds /Storms /Floods.
SAM might also be sparking Record lightning of 1-2million strikes / day over each Oz Storm Front.
Nope! Not joking & Yes! People / Animals being struck > In Hospital > killed...Take care!
Just an update on the continued cold weather for the country, it looks to continue across certain locations up until around Christmas time now.
Here's the ECWMF forecast height anomalies at 500hPa for the coming month. Blue basically points to cooler weather as we fall under a node of the Long Wave Trough. The Australian region I've highlighted in blue.
And here are the corresponding, week by week surface temperature anomalies for the next three weeks (blue = colder than normal).
Mon 5 - 12 Dec
Mon 12 - 19 Dec
Mon 19 - 26 Dec
RE the above charts:
I'm heading down to Thredbo tomoz night where the village, not top station, is expecting overnight temps of -6. That's not apparent temperature, wind chill or whatever, but the actual forecast temperature.
Even if it doesn't fall quite that low, it's damn cold considering it'll be two weeks shy of the longest day of the year.
Santa won't need to acclimatise for an alpine southern hemi Christmas :)
No, and it's gonna make those first MTB runs, not to mention lift rides back up, icy affairs.
I'm hooking up with Steve's son for a few runs. From sub-tropical Lennox to sub-zero Thredbo, hope the little fella has some layers.
Friggin freezing down here (and blew a gale last night) must be snowing up in them there hills!
That low in the Tasman next week is mental!
SEQ's most cold hearted technical glitch spells a bummer for Summer records.
2nd Dec 1889 ( 18.9*C)
1st Dec 2022 ( 17.8*C)
However! Not a record due to BoM's Technical Anomaly Conspiracy Glitch...
Nope! Not The BoM Bully..."Leave A. J. alone!"
World Meteorological Clock was accidentally frozen in time during BOM's Smoko!
Bit of a bummer hey...magic shit happens!
The Polar Vortex is still near record area and the Australian region is stuck under a constant upper level cold anomaly.
Here's the recent snowfall across Thredbo..
A couple of more elongated highs next week keeping the cold air down there instead of the more round highs and lows dragging it up?
That is nuts.
Shoutout to Tane_Kakariki above, here's the link again in case you missed it in the thread
It's fucking freezing down here (surf coast) and my god am I sick of it. If I don't get some genuine summer vibes during my Xmas break from work, I'll be a very bitter employee when I return to work mid-Jan...
Only positive is last two weekends have been warm.
What if the Arctic/Antarcticis being forced with more particles like those in coronal hole streams (following magnetic field lines; increasing in relative solar minimums with less sunspot action) as the magnetic field itself weakens? Add to that the heliosphere weakening and increased galactic cosmic rays coming in. Would that affect the polar vortexes I wonder? Would this be significant forcing?
Ha, that's above my pay grade!
"Four days of summer snow
Although southerly winds in summer don't normally bring snow, the origin of this week's is just off the coast of Antarctica.
As the waters surrounding Antarctica take months to warm up after the winter freeze, they can still support conditions to produce Australian snow in December.
Snow fell on Monday above an elevation of about 1,500m and returned late Tuesday to even lower levels as the next pulse of polar air moved in.
Snow will continue across the Alps and Tasmanian Highlands through Wednesday and Thursday and may even accumulate to a depth sufficient for a summer ski."
Here's an update on the surface temperature anomalies for December up until the 19th.
Loving the cooler summer weather, particularly the nights. Last 3 summers were a hellscape of hot, super-humid, still nights where nobody got a good night’s sleep.
Some new research and modelling confirming what was hypothesised above.
That being the Hunga Tonga-Hunga Ha'apai eruption last January was the cause for the colder than normal outbreaks into the end of the year and even the start of this year thanks to the depletion of the ozone layer and significant cooling of the stratosphere.
This study that was released late November "Stratospheric climate anomalies and ozone loss caused by the Hunga Tonga volcanic eruption" concludes..
"The anomalous low polar ozone in 2022 is interpreted in light of the model simulations as being a direct effect of HTHH (Tongan eruption)."
"Because springtime polar temperatures and vortex persistence are closely linked to polar ozone amounts, we anticipate a cold and prolonged polar vortex persisting into December 2022."