summer blizzard
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Posts posted by summer blizzard
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4 hours ago, Ladyofthestorm said:
I've seen a few confident tweets mentioned in Amy Butler's feed about colder weather in Northern Hemisphere not requiring a SSW.
I think 2006 was the last time , cold dry Jan and Feb, after a really wet and stormy first half, March and April then was really snowy. It can and does happen.
Winter 2006 was cool and dry throughout after mid-November. Not sure April was snowy either.
You may be thinking more of Winter 2008 which was zonal and then had a cool spring until May.
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2015 and 2012 were the other cool ones (6.2).
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7.4
5.5
2.4 - 2021
7.5
5.7
4.8 - 2018
5.2
5.1
6.2
6.2
4.7 - 2013
6.2
5.2
-0.2 - 2010
Took a look at the first halves to Jan given the cool outlook be that UK High or Scandi High.
Not many cool first halves means it's not difficult to rank well although we are unlikely to surpass 2021.
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Euro tonight has moved to mid-latitude ridging from day 6 onwards. Not entirely surprised and the vortex while weak, will take a while to push down the main thump from the attempted SSW even if it’s failed (tropospheric vortex is much less hostile to weakening than last year so I don’t think it matters that it’s failed - Euro indeed does split to 50hpa).
The combination of downwelling weaker zonal winds and the location of tropical convection could produce an exciting second half.
Moral of the story, we may need more than one bite of the cherry but I think we go from a U.K. high to something better rather than worse.
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1 hour ago, snowray said:
Looking at your list there, can I ask, has there ever been a 7c December?
See the post just above yours, yes.
With 14 out of ~300 years of records it's about once every 25 years.
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32 minutes ago, damianslaw said:
Someone mentioned comparisons with winter 12-13. There was a SSW I think 3 Jan.. a cold spell developed about 13 Jan until 26 Jan , but I don't believe this was attributed to the SSW, but the March cold was?
Just interesting to see thoughts about how the affects of any SSW this time round may impact the UK, given the same timescales.
The Jan spell was almost definitely the SSW response. The timing is about right and you can see even on the European archive that there's a -AO which develops, just not near Greenland as much. We also saw a very blocked February around the UK which is again very common in weeks 3-7 for the UK after a SSW.
The stratosphere was not especially weak during Feb/March which suggests it wasn't directly responsible albeit the tropospheric vortex may well have still been shredded from it.
7 minutes ago, bluearmy said:Can anyone see what may have changed over past 36 hours ? The 00z 26th data led to mean reversal. The data beyond that hasn’t. Given that modelling in the strat is supposed to be more reliable, surely something must have changed in the trop around the 31st ??.
It's not a radical change in the overall forecast, comparing the charts it looks like we've simply lost the very deep SSW forecasts and so the mean has risen a little higher.
We are also seeing the warming right now so it's perhaps a little weaker than expected.
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20 hours ago, SqueakheartLW said:
Maybe the reason winter has gone off the rails with the mild and wet is that the NINO is too strong. We really needed something around +1C to +1.5C, not around +2C which is almost mimicking a Super Nino pattern for December now and with NINO 3 warmer than NINO 4 the EP event isn't helping either.
While not beneficial, it's not the strength that is really an issue currently. Most moderate to strong Nino analogues show a +AO December which flips for Jan-March.
09/10 is a significant anomaly for a Nino of any strength.
We also had convection in the wrong place until about the 20th (feeding through around months end) so we may just have been unlucky in the tropical cycle.
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20DEC2023: Nino3: 2.1 , Nino3.4: 2.0, Nino4: 1.4
On 19/12/2023 at 19:35, Don said:Pretty much a basin wide event now?
Yes.
3.4 is stronger than 1.2 but 1.2 is still +1.6 so its basin wide centered in Nino 3.
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1 hour ago, Eagle Eye said:
Better news away from the Troposphere (up till the potential QTR) to be fair.
Too quick.
A quick response is like a week or so, that's almost symmetrical.
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I'll comfort you all by pointing out that the long run impacts of a SSW are limited and so late winter SSW's are those which are correlated with a cool March and April (the link extends to May as an average but it's a long time since a Feb/March SSW year had a cool May).
Analogues for a SSW between Jan 1st-16th (excluding double SSW years for rarity)..
2021 - Near average March, Cold April and May
2019 - Warm March, near average April and May
2013 - Cold March, April and May
2004 - Near average March, April and May
1985 - Cold March and May, near average April
1977 - Cold March and May, near average April
1970 - Cold March and April, Warm May
1968 - Near average March and April, Cool May.
1960 - Near average March, April and May
4/9 March are cold as are average which is a little above the expected mean. The main signal here is warm March is unlikely.
6/9 April's are near average so clear signal here.
5/9 May,'s are cool interestingly given April's signal.
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Obviously we want to know how many cold Jan and Feb.
Jan - 4/9 at 3.7C or below
Feb - 4/9
So above the mean chance
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1 hour ago, Bullseye said:
If a SSW wasn't to materialise and zonal winds remain weak/very weak (which I would say looks odds on) but not dropping into negative values - does the following tweet feel accurate, meaning that SSW isn't an absolute must if zonal winds do remain weak but SSW isn't triggered?
Yes.
Somebody provided us with the chart earlier but this chart is key to demonstrate.
So basically as you can see here, even without the SSW on the right, the warming earlier in December caused a downwelling weakening of the zonal winds (albeit not enough) which can on its own be enough to produce a significant tropospheric impact. In Jan 12 a failed SSW produced the coldest first half to Feb in some time. Last year, the reduction from 50ms to about 10ms in late Jan was enough to flip the pattern to high pressure even if mild still.
It's hard to tell exactly what mark you need because to some degree it will also depend how hostile the troposphere is so not all events will be the same but our push from about 40ms to about 5ms or below is a good strength push and is likely enough to produce at least a pattern change even if not snowmaggedon.
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2 hours ago, I remember Atlantic 252 said:
tonight low of 13 degrees, now can be colder in summer
talk of cold mid Jan, I'm not having, even past GFS FI, will end up being late Jan, then Feb, then late Feb
While your correct to be skeptical and most people on this forum do get far too giddy about the next Feb 47/March 13 oncoming, in this instance I would suggest that there is a very good chance of the second half of January being the coldest since at least Jan 21. Even if a SSW does not occur, we still have a 30ms+ reduction in zonal winds that will push down the atmosphere from early Jan and we should see convection leave the Indian Ocean around the same time to move into a more favourable tropospheric window even without stratospheric assistance.
So i would not get too excited about February onwards as things stand and it's possible that the pattern change is simply to a cool mid-lattitude high near the UK but at the very least the background drivers don't really support sustaining zonality past the first third of January.
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2 minutes ago, ICE COLD said:
Hi Mike doesn’t the vortex always intensify before a ssw takes place ? I’m sure I’ve read this before ?
Most of the time but not always. It’s simply the vortex being pushed around on this occasion.
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1 hour ago, Mike Poole said:
The initial vortex intensification is almost unanimous now, barring a couple of stragglers. Uncertainty remains on the other side, but solid cluster goes straight for the SSW.
Three SSW clusters in that first third, the mean avoids it but largely due to spread and the strongest SSW is probably the highest plurality.
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On 17/12/2023 at 17:49, SqueakheartLW said:
Bring those negative anomalies down to the trop please
Can't be too much to ask for surely
Just curious where the second U Wind anomoly chart can be sourced.
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13DEC2023: Nino3: 2.1 , Nino3.4: 2.0, Nino4: 1.4
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6 minutes ago, Don said:
Considering the climate has changed somewhat since 2010, I would say you would have to favour 2022 being the closest match?
They were very different years even allowing for warming so I don't think we have to allow a substantial discount to 2022.
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50 minutes ago, Chris Smith said:
I definitely prefer this weather to that currently being endured in Cairns, Queensland. Have we ever had 500mm of rain in 24 hours with a promise of 500mm more?
It's at ~17 Degrees south so very tropical. Basically in Venezuela.
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Modelling currently suggests that we flip from Nino back to Nina.
-QBO is likely to flip towards +QBO by end of year.
-PDO is likely to persist IMO.
2010 and 2022 seem to be the best analogue matches of recent times.
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4 minutes ago, Cheshire Freeze said:
We can’t say that.
We can’t say that because at the moment we’re in unusual territory where the strat vortex is being well displaced from it’s usual territory. On top of that we’ve got weather models that can’t even resolve the MJO properly.
With the strat so weak, literally one bit of amplification in the right place at the right time could lock us into cold.
This isn’t the usual winter scenario where we’ve got a strong strat coupled to the trop with endless strong westerlies above…
As the second chart shows even if we end up with a SSW (we don't on this but it would just be a darker blue), it will still be January when it's reached the troposphere.
Thus we are as you say dependent on tropical convection but since it looks like we will miss the boat on on the late phases. Current convection suggests we might persist somewhat into 2-3 but the Indian Ocean is normally not our friend.
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5 hours ago, Addicks Fan 1981 said:
Wish @summer blizzardwas here as he is probably better at explaining the hovmoller charts than us two and I feel great that I am active here again after what I call myself my own hibernation period.
There are certainly some interesting times ahead and I perceive it as exciting really. It does look potentially like a west based negative NAO set up currently coming up.
Still here.
Tamara knows more than I and summed up the pattern earlier but essentially my take is that tropical convection is in/moving into a position conducive to blocking to our north east and then north west but bar a poor looking northerly attempt it looks like the tropospheric zonal flow is too strong.
We've missed the boat on this tropical cycle I think however it does look like there might be less tropospheric zonal flow and a conducive tropical pattern towards mid January.
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3 hours ago, SqueakheartLW said:
Bring those negative anomalies down to the trop please
Can't be too much to ask for surely
SSW or not (not in this case), it's interesting to see that the weakness does actually propagate down.
Remember that Jan 12 failed to achieve an actual SSW but the hit was enough to give us the first half of Feb 12.
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Autumn & Winter 2023---2024 Stratospheric Polar Vortex. Events, Analysis, Discussions AND Outlooks
in Spring Weather Discussion
Posted
An official SSW just means that the vortex is sufficiently displaced or split to generate mean easterlies.
Essentially we are still getting the thump and enough of one to split the vortex, just not one that will knock the main vortex chunk away enough to count as an official SSW.
So same thing, just technicalities.