Separate names with a comma.
Discussion in 'Daily & Chat' started by crikey, Jul 6, 2019.
All sorts of great stuff in there.
As far as this season goes, I have enjoyed watching the strong correlation in Wave 1 amplitude and snowfalls in our region.
It's been particularly pronounced.
In this particular case, we have to wait for wave-1 and wave-2 planetary waves to fully clear, until we can have propagation of the -AAO anomalies to the troposphere. Good news is it is happening, and the planetary waves are weakening.
We will have to wait until that last wave-2 push, so the 20th onwards intrigues me.
One of the major causes of this SSW is now receding (the South American positive mountain torque) too.
Follow the green line in this case.
..there's a bit about to say the spv may recover somewhat in days ahead but then seems to go into decline again but at end of forecast runs so maybe skill level takes a big dive as well .. bit of guessing needed. I think there's usually a last cold pool or two bursting out before final warming most years anyway. Interesting to see if there's extended period this time.
Reckon that the significantly reduced level of ozone depletion may have a big bearing on what happens next.
Wow lots to digest there, great stuff!
Hello there Mr Moderator. Well deserved.
On topic - I agree
.....persistent in recent runs.. ... massive "peeling" of the pv core
....and what looks like complete disappearance of the upper spv
Eroded by the waves perhaps?
I was just looking at those 3D animations on Stratobserve and was coming here to post about them, but looks like SB beat me to it!!
So is that a top down collapse of the SPV projected? Given were only in Sept once the waves subside will be see a resurgence of the SPV?
Nah, that'd be it, you'd expect.
'The Final Warming' is well and truly underway...
Wow, that would have to be one of the earliest SFW's on record I bet. Shame reliable records only go back to 1979.
I wonder how long it will take to reach the trop and start affecting our surface patterns. Watching with much interest.
So this is good for something to happen down in the Troposphere?
It means that it will be forced to descend, there is no more polar vortex to weaken at higher altitudes within the upper stratosphere. This will happen in that last 10 days of September.
After the 22nd-24th is looking a bit better, but the descending of anomalies is still quite slow.
In other words - we're getting a typical cold front in spring (or any other month for that matter) which will bring colder than average temperatures for a window of time ...
How they get away with this alarmist codswallop I'll never know....
hrrrmm..... Interesting how 'climate change' is filed under Tech...
And SSW is filed under climate change, even after BoM came out with a statement advising the SSW has not been impacted by CC.
Another case of Journo's trying to be Meteos.
Everything is affected by CC. But the tricky question is whether CC made this event stronger. Or perhaps weaker. And changes to ozone depleting chemicals may have had an impact one way or the other as well.
...by any standard an extreme breaking of the record...a gigantic transfer of energy...will be watching for any unusual effect playing out in the whole depth of, or any part of, the atmosphere...snow or no seems such a small and minor facet at this point
A brief -AAO is due around the 24th of Sep.
It looks like +AAO will however potentially carry us into October, still the forecast could change.
Finally we are seeing some stabilisation of the SPV weakening at the 1mb level, which is the key for the SSW to actually propagate into the troposphere.
Looks like we have a reversal of the zonal westerlies?...
Indeed. Just above 3mb though.
Not quite a "technical" SSW yet:
...but no sign at this time of it actually propagating down. To be honest this is actually as good thing, at least as far as NE NSW and SE QLD is concerned. The recent rise in the AAO has finally delivered some welcome rain; with the huge fires burning a quick drop could have been even more disasterous for fire and drought ravaged areas. I saw a post on another forum showing the AAO for the 2002 event - it continued to decline right into November. No sign of that yet though - wonder if we couldget through this event without it connecting down to the surface?
It certainly is possible, happened just last Northern Hemisphere winter. There will be some impact, but it may not be as strong as we think.
Doesn't look like were going to see a wind reversal down to 10hpa, or an ozone hole split like 2002 to be classified as a true major SSW. I note in 2002 the reversal at 10mb was only brief before recovering somewhat, with the final breakdown taking place a few weeks later in early November. Perhaps this year we see a more of a gradual breakdown with an early final warming instead? With a more gradual breakdown maybe we don't see any surface effects until November/December with impacts possibly lingering into early/mid January before petering out?
It's quite difficult to be certain about whether there's an early final warming likely or not. After all, it's been such an unusual year thus far for polar stratosphere.
Ozone mass deficit is generally thought to play a significant role in delaying final warming. Despite the ozone hole being considerably smaller than 2018 (and recent years), total stratospheric column ozone is currently not a lot different from what it was last year (nasa),
though perhaps the difference between top of the median range and the bottom is, and only looks insignificant from scale-I can't say. Incidentally those values are from the area where typically most o3 destruction occurs seasonally. o3 column values where the sampling captures the total stratospheric column, are significantly higher than 2018.
2019 with 2018 total column values will possibly diverge further since the area supporting the formation of polar stratospheric clouds(psc) -1 is very significantly down on last year(and past years).
Enhanced warming might be anticipated to accompany a large reduction in o3 deficit, as sunlight returns(though reduction in psc's may lead to enhanced long wave radiation)
Descent from 10hpa to lower stratosphere is generally thought to range from somewhere around 10-40 days. One easy metric to watch for the start of the process(and there are many) is zonal wind <5m/s. Something like 10 to 40 days from the time zw @60 @10hpa is =/< 5m/s. Just a rough guide.
At the far end of the forecast range zonal winds at 10hpa dont seem to have quite crossed that threshold at least.
Also noted first hint via stratobserve 16/9 of negative sam forecast descent to tropospheric continent about turn of october?
It's likely to be colder in many parts of the SH mid-lats. Just not in the right time of year.
Big squirt of cold air heading to unzed next week
It's not a bad system. But to be fair the brunt of it (anomalous stuff) misses NZ. Doesn't look anything SSW inspired IMO.
Are there any distinctive characteristics that will allow attribution of any surface level event to SSW or is it really something you can really only say post-hoc that SSW seemed to play a role in how season x played out?
... Bom Climate Outlook Overview
A prolonged period of negative Southern Annular Mode (SAM) is forecast by the Bureau's climate model during October and November. This is largely due to a sudden warming of the stratosphere over Antarctica. A negative SAM in the spring months often brings drier than average conditions to parts of eastern mainland Australia by reducing onshore flow, but also brings wetter than average conditions to western Tasmania.
Finally we are going to start to see the SSW anoms drop towards the troposphere.
A little -AAO just before the turn of the month.
But the focus is on October and November now.
I've been trying to get my head around the forecasts so decided to put an animated gif together so we can see the progression and how the forecasts change from run to run...conclusion - pretty steady forecast for up high, struggling with bringing it down to the surface. From what I can see it looks like we're starting to see values drop closer to the surface, but still not locked in:
Prominent filament of PV erupting (only vaguely evident above 380K).This level(380K) possibly close to the dynamic tropopause
Several days later the filament has broken off from the source, yet a sizeable chunk is maintaining its integrity as it drifts eastward
Looks like the SSW is finally going to make it down towards the surface, though could see this change again tomorrow... Could be some significant impacts across Aus through the remainder of this year if it verifies. I've been fascinated by this one - decided to expand the animation to run from the start of August so you can see the development of the event through to the point when it's forecast to transition right now. Once the event is fully over I'll upload a full animation of the entire event.
What I find equally fascinating is teleconnective reverb of low-level influences propagating into upper levels through late July & Early August.
Anyway, signals showing on EC Ensembles of late:
Everyone here watching to see if the massive changes up high make it down to the surface. Can see the surface turning more neutral over the last week or so...but still to see that big drop:
Forecasts still show it heading back down into the negative...but now heading into October and yet to see significant impacts @ the surface. What does seem to have happened is that the SSW has been responsible for turning the AAO positive at the surface through mid September - bringing some showers and increasing humidity at least close to the coast. Still dry as anything inland. Still watching and waiting.
Very interested to see if any of that cold air does eventually make it down to the surface. Looks like a slow-burn though and at that rate we probably won't start to see the effects until another month or two maybe.
It certainly weakening a lot (as one would expect) as it moves down into the troposphere.
If it’s going to happen, it’s going to happen sooner, rather than later. The +AAO anoms in the upper stratosphere are moving down quite quickly. Probably within the next month, if it’s going to happen.
Here’s one theory on the SSW event manifesting in the tropo:
Let's hope that this is actually it.
It's got all the signs, and nowhere else to go.
Just wondering would a SSW event lead to more cut-off lows and upper lows, cause they can be an absolute boon for drought ravaged areas especially as they hook onto the Pacific Moisture feeds, or would it lead to the general effects of a Negative SAM.
The effects of an SSW event is likely to be felt as a negative SAM scenario which is largely what you’re describing in both outcomes.
It’s a weakening and break down of the PV so there’s an increased likelihood of ‘meridonal flow’ in the form of cut-off lows, meandering cold pools and high amplitude frontal patterns.
Cold pools can be great as they can often induce convective activity – problem is we’re also under the influence of one of the strongest +IOD events, on record – with little to no moisture in our region. So as you point out it can be detrimental to some areas in the form of heat & drought.
Observationally, I have noticed that the LWT has remained quite strong but appears to be quite static in its circulation. To me, this seems to indicate frequently strong systems in the same quadrants of our hemisphere. You only have to look at the lack of frontal systems in SE Aus and frequent, strong systems hitting SW WA during Sep and for the foreseeable to recognize this. This said, the apparent effects of the SSW have not yet been felt at the surface/tropo.
Kind of a dual reality between the lack of much atmospheric momentum (-AAM) and the +AAO. Strong TPV and LWT, but not really going to a -AAO scenario with cold in SE Aus, until we see the SSW drop.
In the meantime, we are starting to see some forecasts on how this tropospheric -AAO event might happen.
Could be better...
It may be a LR prog, but a SL 1030hPa High at 50S South of Tasmania is an extraordinary anom for October.