Upcoming winter speculation and chat - October edition

[Bristawl Si]

I'm wary of November snow and cold being a precursor to a relatively cold, snowy winter. I think it was mid-late Nov 2005 the South West saw snow, and it was following a long run of virtually snowless Winters here. The rest of Winter 05/06 was fairly mild and hardly any snow here. I stand to be corrected if i've recalled incorrectly.

[Froze were the Days]

'November Ice to bear a duck nothing after but sludge and muck' - I think the saying goes, have to admit haven't seen much of any Ice down here in the last couple of weeks and a few years since I've seen a ponds iced over in November but I know what you mean. 

With the last 2 months looking like they could be below the CET series (which is relatively rare of recent years) it does make you wonder if it might be all a bit too soon before this winter and 'normality' returns but on the other hand with the low solar input and -NAO continuing maybe a run into some uncharted territory since the winters of 2009-2013. Only time will tell.

Edited November 15, 2019 by Froze were the Days

[Sceptical]

4 hours ago, Bristle boy said:

I'm wary of November snow and cold being a precursor to a relatively cold, snowy winter. I think it was mid-late Nov 2005 the South West saw snow, and it was following a long run of virtually snowless Winters here. The rest of Winter 05/06 was fairly mild and hardly any snow here. I stand to be corrected if i've recalled incorrectly.

We had snow November 2018 and winter 2018/19 was noted as mild.

[feb1991blizzard]

4 hours ago, Bristle boy said:

I'm wary of November snow and cold being a precursor to a relatively cold, snowy winter. I think it was mid-late Nov 2005 the South West saw snow, and it was following a long run of virtually snowless Winters here. The rest of Winter 05/06 was fairly mild and hardly any snow here. I stand to be corrected if i've recalled incorrectly.

Yes, decent Novembers have only really gone on to turn into great winters a few times in my life - 95,85 and 2010 although 93-94 was very decent.

[Weather-history]

33 minutes ago, Froze were the Days said:

'November Ice to bear a duck nothing after but sludge and muck' - I think the saying goes, have to admit haven't seen much of any Ice down here in the last couple of weeks and a few years since I've seen a ponds iced over in November but I know what you mean. 

.

Yes that is the problem with that saying and trying to apply that to any snowy or relatively cold spell during November. It hasn't been that cold this November thus far. 

[northwestsnow]

58 minutes ago, Weather-history said:

Yes that is the problem with that saying and trying to apply that to any snowy or relatively cold spell during November. It hasn't been that cold this November thus far. 

Just relentlessly wet.

Absolutely vile, some rain is fair enough in Autumn, this is bordering on the ridiculous now.

[NeilN]

Aside from the hideous rain, but I am thinking is this more like November 2009? That was very wet, and mild - I remember moving into a new house and we didn't put the lovely and warm gas fire on until the first week of December! Perhaps this is a good thing? I just hope we can dry out!! 

[Frost HoIIow]

1 hour ago, feb1991blizzard said:

Yes, decent Novembers have only really gone on to turn into great winters a few times in my life - 95,85 and 2010 although 93-94 was very decent.

Problem with November/December 2010 was Winter practically ended on Boxing day. It was great while it lasted but there was nothing of note for the rest of Winter - January & February being completely forgettable. February especially being very mild. I think Winter 2009/10 was better overall. Had decent snow & cold in all 3 Winter months. 

[feb1991blizzard]

2 minutes ago, Frost HoIIow said:

Problem with November/December 2010 was Winter practically ended on Boxing day. It was great while it lasted but there was nothing of note for the rest of Winter - January & February being completely forgettable. February especially being very mild. I think Winter 2009/10 was better overall. Had decent snow & cold in all 3 Winter months. 

Yes, i was in Salford near Manchester City Centre for 09/10 and here for 10/11 but i wished it would have been reverse to be honest, both were great but Manchester was nearly as good as here in 2010-11 because there was just no marginality it was so brutally cold, where as there were lots of marginal events as well as bitter events in 09/10 and the snow had melted before the next lot in the City, where as here it just mounted up and up and up i have heard culminating in this.

 

[Catacol]

Long post coming….

OK – here’s my winter forecast for 2019/20. My rationale is simple – I want it to be accessible in plain speak but technical enough to tweak some interest. I’m a snow hunter so have written it largely from a snowfall perspective (and make no apologies for that purpose). Finally I do see 2 quite clear possible routes, with the potential direction of travel hinging on the extent of vortex disruption in early January. I am not using any analogs. If you want to see forecasts hinging on analogs there are plenty on sites over in the US at 33andrain. I have become less and less convinced by the relevance of analogs, though acknowledge they make for interesting reading and pattern matching.

 

Drivers

Both via observation and technical paper reading there are clearly core drivers that impact the pattern over the UK. In some kind of approximate hierarchy these are:

1.       ENSO forcing that impacts global momentum budgets and, as a result, likely pressure patterns. Central to this in winter is the extent to which the sub tropical high pressure belt is supported in a northerly direction by circulation at the pacific equator (including convection patterns mapped via the MJO), but also the extent to which surges in momentum can create blocking at higher latitude. The UK sits right on the boundary between the sub tropical (Azores) High and the polar jet, and torque events either over North America or East Asia can have a significant downstream impact on the ridge/trough pattern that leaves us either on the warm or cold side of the flow.

2.       Vortex strength from the top down, but also the extent to which impacts from the bottom up can either disrupt the vortex or alternatively encourage a coupling of the upper and lower layers. Once coupled the vortex is a tough beast to break. The tropospheric vortex naturally strengthens through November and into December before beginning a slow decline through January and more especially through February, and this is an important precondition to keep in mind.

3.       Sea Surface temperature anomalies in the North Atlantic and the extent to which the jet can be affected by this.

4.       Snow cover, ice extent and the issue of arctic variability which can impact on the Siberian High in particular. Perhaps also impacts the vortex in terms of tropospheric ridges in the arctic causing disruption.

5.       Solar variability. Much disagreement here amongst forecasters and interpreters, but the balance of the argument suggests that times of low solar activity encourage higher than average ozone levels in the stratosphere with a greater chance of vortex disruption, but also reduces the overall strength of the jet, encouraging more “wobble”, often described as a more meridional pattern.

6.       Finally its worth acknowledging the natural waxing and waning of the wave pattern, and therefore shifts of wavelength and movements in the peak/trough pattern are inevitable.       Observationally I have come to see these as working in thirds of months, with occasionally a standing wave situation creating less movement. We are in one such standing wave situation now with the trough fixed over the UK for, I would think, two thirds of the month. With such a neutral ENSO background state I wouldn't be surprised to see static periods of wave activity repeat.

 

The Driver Context in 2019/20

1.       ENSO impacts are expected to be minimal this season, with an essentially neutral position currently. The MetOffice forecast sees the weak Nino focused in the central pacific

but a context further to the west of a very positive IOD and cooler waters which, in theory, promotes more of a Nina pattern. Much further to the east the pacific is cool, once again suggestive of Nina impacts. This “Nino Sandwich” is a tricky one to call, but the signature is so close to neutral that impacts will probably not be substantive. However – and this is important – the global atmospheric momentum signature is rising and has been rising for several weeks.

This is indicative of Nino forcing in the pattern (as well as nature's desire to try and return momentum budgets to zero....), and so it looks possible that the tropical cycle through the winter may become more of a factor later on, particularly if GLAAM hits positive values as it rebounds. Given the elastic nature of GLAAM the upwards trend looks likely to continue for at least a few more weeks with a likely peak in January. Whether the upwards trend continues beyond that is a tough call – but more Nino style impacts increase the chances for stronger late winter blocking patterns. More commentary later on this in the monthly descriptors.

2.       The stratospheric vortex is currently strong, but just beginning to feel the impacts of a well known tropospheric combination of low pressure over the Aleutians and High Pressure over Eastern Europe and Scandinavia which encourages warm to be fired into the upper vortex from opposite sides of the globe. This is providing early stress on the vortex, helping prevent the upper and lower layers from properly coupling, and this is a process that may be being enhanced by the background low solar context. Given expected lag times, the impact of this wave 2 attack may take up to 4 weeks to see real tropospheric change given any stretch/split/displacement needs to work its way through the layers (assuming the atmosphere is receptive to frictional downwelling…and we all know that last year it wasn’t…) meaning end of December or early January for maximum downwelling effect. As we move towards December the signs of vortex stress in the modelling are increasing, though these values vary a bit from day to day and model to model. There is broad agreement, however, on an unusual trend towards a weak vortex by end of November and probably beyond.

3.       Sea Surface anomalies currently favour a slightly south of normal jet projection. Warmer than average water around Greenland, if maintained, may help to further support any anomalous ridging in that area, and a jet firing beneath weak heights to the north, and over cooler waters, is a tendency we have already seen this season and one which ocean temperatures suggest may continue. Low solar may also strengthen this signal.

The CFS forecast going forward for the season sees warmer waters to the north, and cooler do the west. To me this strengthen the possible undercut signature with favourable conditions, especially late season, for continental high pressure to nudge west.

4.       Snow cover is high, and ice regrowth on the atlantic and Siberian side has been robust, much more so than around Alaska in the pacific sector. This may well help create a very strong Siberian anomaly for this coming season, and this is a consideration for the second half of winter when atlantic firepower starts to drain away.

5.       The sun is quiet, and looks set to remain quiet. No pepping up of a flat jet is a decent bet for the coming season, and indeed already I think the seasonal models have been blindsided by the angle of the jet as encouraged by the more meridional flow than expected. This is a context that will be with us all season.

 

Monthly specifics

December 

Current patterns have demonstrated a very resilient Scandy/East Euro block that has acted as a solid barrier that any amount of atlantic fury has failed to crack. Watching the first 2 weeks of November carefully has been instructive in this, and for snow lovers the sight of atlantic lows hitting this block is mana from heaven in terms of adding weight to vortex disruption. The MJO pattern through late November is also supportive of blocks at higher latitude. As a result a trough has remained as a semi permanent feature over western Europe, unable to move, dropping copious amounts of rain in England (less so Scotland with the southerly displaced jet) and temperatures have undercut model predictions. However, this pattern looks set to fade. The MJO will reenter the Indian Ocean shortly. In addition, the tropospheric vortex continues to be on an upwards curve seasonally, reinforced in all probability by growing cyclogenesis caused by colder than average temperatures in the US, and into early December a flatter pattern looks likely. A neutral ENSO signature overall is not going to significantly disrupt this seasonal trend. In this scenario the vortex disconnect will remain in force, as tropospheric impacts on the stratosphere disrupt the stratosphere while at the same time the atlantic becomes more dominant tropospherically. +NAO setup will be the end product for the first two thirds with an increasingly +AO in attendance. However, by month’s end downwelling impacts of vortex distress, and possibly even vortex disintegration, will begin to be felt, and the next ENSO cycle will bring the MJO back close to phase 7-8-1 and more support for blocking. A wet first two thirds, with temperatures average to slightly above average will be replaced by a drier final third, greater presence of frost and a pattern shifting towards less mobility.

 

January

Timings tough to pin down here, but two possibilities broadly. Possibility No 1 rests on major vortex distress and a downwelling that impacts significantly. If GLAAM continues in an upwards direction, elastically turning positive on the current upwards curve, then torque events may enhance this phase. Lag time, and likely MJO cycle and associated torque increases, suggests mid month for any potential reversal pattern as the AO drops swiftly, and much will depend on where residual shards of the vortex may land. With the axis of attack sitting between Alaska and Siberia we may expect energy displaced to east Asia and Canada, so a burst of atlantic energy initially via a +NAO followed by a swift reduction and a reversed pattern with a -NAO taking over. Best guess here therefore is for greatest cold impacts mid month, maybe final third. Blocked, cold and snow potential at that point.

Possibility No 2 rests on the vortex resisting the predicted assault, stretching and reforming. This may be assisted by a transition back to a lower GWO (low GLAAM state) as the ENSO signature fades and the MJO returns to the Indian Ocean. In this circumstance again a stormy first third to January, perhaps with a Scandy High in attendance due to vortex stretch, and a slight relaxation into a default westerly regime by mid to late month. A close but no cigar event for snow hunters. Southerly jet predisposition may keep temperatures around average, perhaps marginally below, with rainfall above average. The angle of the jet wont totally rule out snow at times, but widespread and durable cover difficult in this scenario.

 

February

Being honest, if the vortex collapses in January then I think February could turn out very cold. Shortening seasonal wavelengths, as the tropospheric vortex continues its slow decline, encourages retrogression of the wave pattern, and the generally cold and blocked January could lead to a period of significant continental influence as the Siberian High edges west. It is beyond my gift to predict with any reasonable accuracy the likely progress of the month from start to end, but years of observation would suggest that, as the month ends, any cold pattern would begin to relax. First two thirds very cold, final third relaxation as inevitably a degree of late season vortex reforming returns. However the likely passage of the MJO later in the month may help to sustain the blocking throughout, and any relaxation would be relative. Dry overall, with temperatures below average.

If the vortex reforms its shape in January then a second opportunity for cold blocking arrives in the latter half of February as the troposphere makes one final stab at vortex stability. January mobility will produce more wave breaking and another assault on a much weakened vortex, and the knock out blow may arrive with the final ENSO pacific cycle of the season towards the end of February. Chance of late season cold in this scenario – but no guarantee. A non descript first two thirds, certainly drier than January, with temperatures perhaps above average as the Azores High makes an appearance initially, before a colder final third as blocking appears to the north, and intrusion of further cold into March. Temperatures overall around average as the cold end cancels out the relatively mild beginning.

So – there it is. I’m going to plump optimistically for possibility No 1 through January (though possibility 2 definitely remains on the table), and summarise my overall spread as:

December: Broadly +NAO, wet, average temperatures but more blocked final third.

January: Stormy first third under renewed +NAO, then strongly negative -NAO mid to end of month and continental influence. Widespread snow potential. Temperatures overall slightly below average, rainfall overall average.

February: Largely -NAO regime, especially first two thirds. Temperatures below average throughout, relatively dry.

I hope this reads coherently. Bear in mind we all have limits to skill levels, and the truth behind most forecasts is that they are as much hopecasts and guesses as anything else. However I'm interested to see how the season works out in relation to the level of understanding that has created this moment of crystal ball gazing, and ultimately I post for enjoyment more than anything in looking for cold weather patterns. If we get a cold December with snow, and a mild January/February with no ice in sight I won't mind one bit - a cold December would cancel out any disappointment at inaccuracy and, in any case, we are all learning all the time. I'll do a review in Mid March once the winter has lost its edge.

Edited November 15, 2019 by Catacol

[damianslaw]

4 hours ago, feb1991blizzard said:

Yes, decent Novembers have only really gone on to turn into great winters a few times in my life - 95,85 and 2010 although 93-94 was very decent.

I think it depends on how the cold has come about in November. This November has been chilly but nothing especially cold, and the recent colder weather with snow for some has come from cyclonic low pressure system, not deep rooted northerly or easterly airstreams as occurred in 1985 and 2010, which is interesting in itself. I do agree I am always a bit nervous when we have cold spells in November on the back of cold northerly or easterly airstreams, or indeed just cold anticyclonic conditions as has happened in some recent Novembers, short spells around third week 2015 and 2016 for example, 1988 being another classic example. However, I'm not at all concerned when it comes about due to cyclonic conditions.. Nov 96 a good case study in this respect, yes the cold vanished second week January, but we had a preety cold 6 weeks late Nov to early Jan becoming very cold around christmas. I'm taking alot of optimism from the synoptics this November so far, more so than any November probably since 2010, and to an extent 2012.

[damianslaw]

2 hours ago, nn2013 said:

Aside from the hideous rain, but I am thinking is this more like November 2009? That was very wet, and mild - I remember moving into a new house and we didn't put the lovely and warm gas fire on until the first week of December! Perhaps this is a good thing? I just hope we can dry out!! 

Another post from me, yes echos of November 2009 this month so far, in terms of the trough becoming unstuck over the UK, delivering copious rain, coming unstuck against heights to our east, and it was a weak atlantic as well.. difference this month so far, has been the position of the jet much more southerly, and hence it has been much chillier so far than Nov 2009, but agree very very strong similarities.. we had serious flooding in Nov 2009, with a more southerly jet, this has happened about 150 miles further south and east this month.

[Radiating Dendrite]

7 minutes ago, Catacol said:

Long post coming…

Very similar to my thoughts, back loaded winter which gets progressively colder - think March cold be very blocked and chilly. 

Edited November 15, 2019 by Radiating Dendrite

[Don]

3 hours ago, nn2013 said:

Aside from the hideous rain, but I am thinking is this more like November 2009? That was very wet, and mild - I remember moving into a new house and we didn't put the lovely and warm gas fire on until the first week of December! Perhaps this is a good thing? I just hope we can dry out!! 

Whilst I do see certain similarities to November 2009, this month so far has been much colder, albeit not exceptional.  November 2009 had a CET of 8.7C, but the weather saw a big turnaround come mid-December!  However, I think the blocks were building during November that year.  As to what happens this year, it's a bit like the current economic climate - uncertain!

Edited November 15, 2019 by Don

[LightningLover]

@Catacol Exceptional post; Well written, easy to understand, yet full of information. Thank you  

Edited November 16, 2019 by LightningLover

[Catacol]

22 hours ago, LightningLover said:

@Catacol Exceptional post; Well written, easy to understand, yet full of information. Thank you  

Thanks. I probably should have included at least one line on the descending eQBO which by mid January may work to assist any downwelling of disruption given that sensible forecasts see it moving between 30hpa and 50hpa by this point. That is a handy synchronisation of drivers IF (and it remains a big if) the current foundations for vortex misery being built by the November patterns in both atlantic and pacific zones create a substantive hit. The passage of the QBO in January is one reason why I think the pattern pushes towards a greater cold bias as February approaches should that vortex assault bear fruit. If the vortex remains substantially unimpeded then the QBO is probably not a major player in the second half because it remains above the 50hpa level.

[blizzard81]

I remember reading years ago, probably on TWO, that there was a link between cool, wet Novembers in the UK and the following winter being cold. This was especially true with the jet tracking south in November. 

[cheeky_monkey]

On 17/11/2019 at 05:19, Catacol said:

Thanks. I probably should have included at least one line on the descending eQBO which by mid January may work to assist any downwelling of disruption given that sensible forecasts see it moving between 30hpa and 50hpa by this point. That is a handy synchronisation of drivers IF (and it remains a big if) the current foundations for vortex misery being built by the November patterns in both atlantic and pacific zones create a substantive hit. The passage of the QBO in January is one reason why I think the pattern pushes towards a greater cold bias as February approaches should that vortex assault bear fruit. If the vortex remains substantially unimpeded then the QBO is probably not a major player in the second half because it remains above the 50hpa level.

very good synopsis..however there was no mention of the PDO and that big warm blob of the Canadian coast which combined with a neutral ENSO..could produce quite a frigid snowy pattern across much of NA..the result could be a 2013/4 type of pattern across Europe or just maybe a 78/79 pattern which was also a cold winter across NA

[Catacol]

28 minutes ago, cheeky_monkey said:

very good synopsis..however there was no mention of the PDO and that big warm blob of the Canadian coast which combined with a neutral ENSO..could produce quite a frigid snowy pattern across much of NA..the result could be a 2013/4 type of pattern across Europe or just maybe a 78/79 pattern which was also a cold winter across NA

Entirely possible, though 2 things to say there. First of all the warm blob would appear to be fading westwards, and as a result it is possible that the resultant trough through the US may not be as deep as in some years. The second would be that the atlantic profile is supportive of a jet angle that pushes further south than in classic + NAO winters. This doesn’t guarantee that the jet won’t blast through the UK as per 13/14, but it does provide the basis for an argument that sees blocking phases as having some impact, and times through the winter when the air tumbling off the US continent may not encourage the most rapid brand of cyclogenisis.

Only time will tell. Currently the forecasts of jet disruption keep the forecast on track, though Im sure it won’t be long before a spoiler erupts somewhere....

[Matty88]

Despite all the hype that a new SSW might be on the way, there are good reasons to be speculative in my view - as SSW's can mean different outcomes for anywhere in the Northern Hemisphere. My gut feel this time is North America/Canada will be getting it big style while a lot of Europe and including the UK will be jammed in a mobile zonal flow... this outcome can't be ruled out. True it's also possible it can mean we get an easterly block - but it's unlikely in my view, especially given how mild it's been across the continent (at least partially - for mid Europe/Russia where it's been unusually warm). 

Either way the latest charts indicate with some certainty now that the end of Nov/Start of December at least will be dominated by a mild'ish Atlantic flow, with the exception of a cold snap or 2. Eye's then look to mid/end of December for the next evolving pattern. 

By no means is the writing on the wall! Try to avoid getting sucked into the SSW event excitement if possible. 

[Summer Sun]

 

[Griff]

Hi all, 

Long time lurker (well since 2018) but first time posting. Fascinated by how the next few months play-out, especially considering the long range winter forecasts vs recent model runs. I feel like I've learnt so much already but continue to be baffled on a daily if not hourly basis. 

Would love to understand the following terms in no particular order... retrogression, phasing, ridging and short-wave.

Thanks, Griff. 

 

 

[Mike Poole]

42 minutes ago, Griff said:

Hi all, 

Long time lurker (well since 2018) but first time posting. Fascinated by how the next few months play-out, especially considering the long range winter forecasts vs recent model runs. I feel like I've learnt so much already but continue to be baffled on a daily if not hourly basis. 

Would love to understand the following terms in no particular order... retrogression, phasing, ridging and short-wave.

Thanks, Griff. 

 

 

Hi Griff, welcome to netweather, fellow south Oxfordshire resident!

So, retrogression is relating to high pressure blocks - usually weather moves west to east, dictated by the jet stream, but retrogression is the movement of weather systems in the opposite direction, most significant on here is a high pressure block over Scandinavia moving west towards Greenland in the winter. Phasing is two areas of low pressure merging and becoming one.  Ridging is the building of an area of high pressure.  And short-waves, these are basically small areas of low pressure that mess up what we think will happen!  Air circulates round a high clockwise, and a low counter clockwise, so if we think we've got an idea about this on a larger scale dictated by high pressure, a short-wave low pressure cropping up can change the picture altogether.  

[sebastiaan1973]

On November 18, the World Climate Service issued its seasonal forecast and discussion for winter (December-February) 2019-2020 in the U.S. and Europe. WCS seasonal outlooks include an overview of expected climate anomalies, key drivers, and risk factors for the upcoming three-month season, and our forecast document contains detailed discussion of available predictors, including dynamical model forecasts and statistical and analog guidance.

Analog analysis has long been a staple of the WCS methodology for seasonal forecasting, and we invariably rely on diverse sets of analogs derived from numerous aspects of current global climate patterns. Only on rare occasions do we focus on individual analog years, because the climate phase space is rarely a very good match to any previous year in the modern history in more than a few respects; there are nearly always significant differences from any candidate analog year. Moreover, the degrees of freedom in the climate system are too numerous to expect a close correspondence with any past year to continue into the future, and so any search for “the perfect analog” is a fool’s errand (even if the climate were assumed to be unchanging).

Nevertheless, the latest WCS seasonal forecast report discusses a very notable confluence of similarities between the present climate and that of winter 2002-2003. In keeping with usual practice, the WCS winter forecast is not unduly influenced by the 2002-03 analog, but the degree of similarity is so striking that it is worth considering the 2002-03 outcome as a plausible outcome and risk scenario for winter 2019-20. The following list of similarities was presented in the forecast document and is reproduced here:

2002 is the top QBO analog year, based on the 12-month evolution of the 30mb QBO index
The Indian Ocean Dipole was strongly positive in September and October 2002, and tropical convective patterns were similar; 2002 is the third best analog year for 200mb equatorial velocity potential
A region of highly anomalous warmth developed in the northeastern Pacific in late summer 2002 and persisted through autumn, similar to 2019
Arctic sea ice was low in summer 2002 and set a record at the time for low September ice extent
The October Northern Hemisphere circulation was similar in 2002, with Arctic blocking, a trough over northwestern Europe, and a very similar ridge-trough pattern over western North America. The November MSLP pattern was also similar with respect to high pressure north of Scandinavia, low pressure near the British Isles, and low pressure south of the Aleutians.
October 2002 had the highest snow cover on record (1967-present) over North America; October 2019 was the third highest
The 10mb polar vortex was much stronger than usual in the first half of November 2002, but the Arctic Oscillation was negative for November, similar to this year. No other year provides such a close match to this unusual combination, although 2018 is also a good analog.
Remarkably, 2002 is nearly a perfect match to 2019 (better than any other year since 1900) for Central England Temperature in August, September, and October. Perhaps coincidentally, October 2002 England & Wales precipitation was also nearly identical to 2019, and November was also extremely wet (October-December 2002 was the third wettest such period on record).
2002 and 2019 are the only years on record with a strong Southern Hemisphere SSW (Sudden Stratospheric Warming) event; both of these occurred in late austral winter and led to Southern Hemisphere blocking in both October and November.

The most significant difference between 2002 and 2019 is that 2002 had more warmth in the eastern equatorial Pacific and much less in the West Pacific; El Niño was more classical (East Pacific) rather than Modoki-like. There was also much less anomalous warmth in the subtropical and northern North Pacific in 2002.

In view of the extensive and remarkable similarities betweeen 2002 and 2019, it is tempting to conclude that winter 2019-2020 will be closely analogous to 2002-2003, with a strongly blocked pattern, unusual cold in the eastern two-thirds of Europe and the eastern United States, and reduced precipitation and wind in central and northern Europe (see below). However, as noted above, the WCS approach is to treat individual analog years with caution, regardless of how impressive the similarities appear to be. The combined consensus of a large array of dynamical and statistical predictors is a more reliable guide to likely seasonal patterns, and the WCS forecast is constructed accordingly, but the winter of 2002-2003 should be regarded as a plausible alternative scenario. 

Climate Pattern Similarities Between 2002 and 2019 | World Climate Service

WP.WORLDCLIMATESERVICE.COM

---

Discussion of similarities between late autumn conditions in 2002 and 2019

 

[Yarmy]

57 minutes ago, Griff said:

Hi all, 

Long time lurker (well since 2018) but first time posting. Fascinated by how the next few months play-out, especially considering the long range winter forecasts vs recent model runs. I feel like I've learnt so much already but continue to be baffled on a daily if not hourly basis. 

Would love to understand the following terms in no particular order... retrogression, phasing, ridging and short-wave.

Thanks, Griff. 

 

 

@DiagonalRedLine constructed an excellent jargon glossary some time ago here:

 

Keep in mind that often terms are used quite loosely. Abbreviations too, are overloaded, e.g. SW can mean south-westerly, south-west, shortwave, stratospheric warming depending on the context.

Edited November 20, 2019 by Yarmy