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Posted
  • Location: West Yorkshire
  • Location: West Yorkshire
Posted

EC clusters below.

Days 3-4

UK high shifting further east - more of a south-easterly by day 4 turning things colder, especially in the south.

image.thumb.png.e7f4cbe1e58efd6ec6a40d4fa55e364a.png

Days 5-7

Cluster 1 (53%) maintains a south-easterly at days 5 and 6, with high pressure centred east of the UK. Some fairly strong ridging to our north by day 7 around Iceland, but we remain under the south-easterly.

Cluster 2 (47%) has a similar pattern, but the ridging to the north at day 7 is much weaker.

The OP was in Cluster 1.

image.thumb.png.5d6649bd5048249c4f92a8fc6ce36645.png

Days 8-10

Cluster 1 (35%) sets up a strong block to the east of the UK. However, it is a bit too far east for UK cold. Lows are blocked from progressing to our east, resulting in a very wet pattern for the UK as we are trapped under the Atlantic influence. Mild and very unsettled.

Cluster 2 (29%) builds the high to our north into a Scandinavian High. A cold easterly pattern, with the risk of snow.

Cluster 3 (22%) sets up high pressure to our east, but too far to our east. A very Atlantic-driven pattern, with multiple deep areas of low pressure close to the UK. There is a mid-Atlantic ridge, so still fairly cold from the north-west at times.

Cluster 4 (14%) keeps high pressure centred close to or just south of the UK. Some surface cold in the south, but milder in the north where westerly winds blow around the top of the high.

The OP was in Cluster 2.

image.thumb.png.cc341948b0e4cf200dd541869042cae2.png

Days 11-15

There are six clusters here, so I will only deal with each one very briefly.

Cluster 1 (31%) is blocked to our east, but remains mild and Atlantic-driven for the UK.

Cluster 2 (18%) has a battleground between westerlies and easterlies, unsettled.

Cluster 3 (16%) has a textbook easterly with little energy in the Atlantic. Cold or very cold.

Cluster 4 (16%) has some blocking, but the UK stuck with the Atlantic in control. Wet and mild.

Cluster 5 (14%) has high pressure just east of the UK. Mild in the north, some surface cold in the south.

Cluster 6 (6%) has a very cold north-easterly at days 11 and 13, eventually becoming more of a UK high but still cold.

image.thumb.png.eadaa5b2dbd491c28c8d6b7c6513ae01.png

Summary

In the shorter range, we have a UK high gradually progressing to our east over the next few days, fairly non-descript. The key timeframe is around day 7, with the clusters presenting a small but important difference, which is the strength of ridging to our north around Iceland. Stronger scenarios are more favourable than weaker ones. It is virtually a 50-50 split at the moment.

This then informs the options at days 8-10. A strong ridge becomes a textbook easterly as we see on the EC OP (Cluster 2), with about a 30% chance. The other options show how it could go wrong - there is a general principle of blocking, but slight mis-positionings ruin any chances for the UK.

The extended range is not entirely without interest either - a couple of clusters lead to a cold or very cold outcome for the UK. And again, the general principle is there on some of the others, the failures are largely due to the details being wrong, which shows we're at least in with a chance.

I was saying for the past few days that we needed to see some of the clusters really going for it - we have that now. We have a decent 1 in 4 or 1 in 3 shot now on the clusters. It is a case of watching for that to gather support. I would say don't get your hopes up just yet as there are still so many clusters showing how it could all go horribly wrong, with fairly small details. The first of which is the strength of the ridge to the north at day 7.

So far, yesterday's reverse psychology appears to be working. I hope I end up looking like a complete muppet with the prediction of no major cold spell before the end of January. Long way to go though of course!

 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5223519
Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
Posted

Finally, the clusters have updated, here’s T192-T240:

IMG_0031.thumb.png.0a8d9f6b3a354279256fba2ff6dd9229.png

Cluster 1 (18) has the Atlantic hitting a growing Scandi block, but the alignment is bad.  Cluster 2 (15) contains the op, develops a well placed Scandi high and potential easterly, low heights to the south.  Cluster 3 (11) is the -NAO one, weak ridge to the NE, and trough deep to our south.  Cluster 4 (7) inflates a ridge over the UK extending to Scandi.

T264+:

IMG_0033.thumb.png.1647bde91b0a79b57423287054c2203b.png

Huge uncertainty here, but some of these look very promising.  Cluster 3 (8) is potentially award-winning!  A strong block well placed to bring in a potent easterly.  Cluster 2 (9) has a strong block to the NE and easterly.  Cluster 4 (8) has a southerly tracking jet and -NAO but heights to the north are pretty flabby.  

The others are less promising. Cluster 1 (16) has a Scandi block but the connection to the south is not lost and placement is awful.  Cluster 5 (7) maintains high pressure over the UK.  Cluster 6 (3) just looks weird with a rogue Atlantic ridge getting in the way of the evolution, with just 3 members, can probably be discounted. 

Plenty of mileage in this, while the trend continues to be our friend. 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5223514
Posted
  • Location: howth,east dublin city
  • Weather Preferences: extremes
  • Location: howth,east dublin city
Posted

 HarvSlugger Can confirm we get some wonderful streamers from easterlies .Nov/Dec 2010 was epic for Dublin with thunder snow for me here in Howth . 86 / 87 /91/96 09/10 all good for here. The Beast was something else  in Dublin and parts east Wicklow saw a meter or more of level snow but they were snow grains due to the wind. With slack winds in 2010 they were always giant flakes which is why a slack easterly with temps below freezing is wonderful for the convection like in 1986 and also much slower moving showers.


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5223556
Posted
  • Location: Gillingham, Kent
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Gillingham, Kent
Posted

I'm slightly at a loss as to what's driving the current synoptics appearing for late January, albeit it remains a lower likelihood outcome it does seem the signal is very much there. My best guess is that it's down to the MJO passing through phase 1 in a semi-amplified state at the moment (add in the usual lag and end of January seems about right for timing)

EMON_BC.thumb.png.e21d1ed154915fbb760dfad79ee6685a.png

This correlates to the below pattern, very similar to what NWP modelling is suggesting at the moment.

Screenshot2025-01-14at23_12_17.thumb.png.6ea5c0f9b2b6b602925297134a1bd0b4.pngScreenshot2025-01-14at23_12_24.thumb.png.43fbc5fdd2befe2be2d2821a43e05e96.png

In the context of falling AAM you'd expect to see a stronger Atlantic jet, I wonder whether any developing high over Scandinavia could potentially act as a road block and cause the jet to buckle southwards underneath the high, the 18z GFS is an absolute textbook example of that.

Interesting times but feet are very much firmly planted into the ground at the moment. Given the above I think we'd struggle to see any sustained retrogression to Greenland for a prolonged period of cold, we may need a lot of luck for the high & indeed interaction with the jet to be "just right" to produce something. The EPS clusters show how the angle is incredibly important and could easily fall unfavourably for us.

Initial Scandi high, perhaps some attempt at retrogression west before sinking into Europe would be my best guess on the evolution.


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5223636
Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
Posted

The 00z GEFS and EPS don't look very convincing for a cold easterly, the 00z EC det. for London was on the cold side of the ens spread for T2m and the det just brings a SEly, while the GEFS for London was on the cold side of the spread for T850s from Thursday next week and that for a not particularly potent easterly, -10C T850 over the south North Sea at best. I'm sitting on the fence for now, unconvinced a deep cold easterly will come off. But, you never know, the ensembles signal may change colder.

The Scandi high building is strong signal, but getting deep cold air advection from NW Russia to make it to our shores looks an uphill struggle, especially if we don't get sufficient upper troughing / low pressure over central/southern Europe to advect any useful cold air (for snow) our way.


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5223745
  • Like 2
Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
Posted

ECM clusters this morning, T192-T240:

IMG_0039.thumb.png.5485745bf34a1f296526ba35ff9affe6.png

Lots of uncertainty this morning, so things are not really any clearer.

There is a consistent signal to push up a Scandi high of some sort, but focussing on this feature at day 10, the detail varies.  Cluster 1 (16) has a weak feature, but moves to the north of the jet to a -NAO.  Cluster 2 (14) has a stronger high and well positioned to send the jet south and permit an easterly.  Cluster 3 (10) has a weaker feature but retains a connection to heights to the south which prevents an easterly.  Cluster 4 (6) pushes up a big block but poorly orientated retaining heights over the UK.  Cluster 5 (5) is the -NAO one where the high is more to the N or NW, rather weak, and low heights into Iberia.  

T264+:

IMG_0040.thumb.png.25f81fbf87bb90c91d4f76c5d9069ee0.png

No agreement at all about what happens to the Scandi high next.  Cluster 1 (15) retains connection to heights to the south so it is poor.  Cluster 2 (12) likewise, but return of westerlies to the UK.  Cluster 3 (11) looks promising at day 13 but then orients badly.  Cluster 4 (9) looks to have some potential in terms of position and trends to -NAO.  Cluster 5 (4) is the -NAO one, but no high to the north that is relevant to the UK.

More runs needed…


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5223753
Posted
  • Location: Weymouth, Dorset
  • Location: Weymouth, Dorset
Posted

I am struggling to see any longevity, even if we do scrape a half-decent Easterly (definitely possible, if probably unlikely)

After stalling, the MJO has just got going again and in very high amplitude, albeit in phase #1. In terms of overall amplitude it could peak as high as around -2.3, that would put it into one of the highest P#1s recorded for a day in January since 1979.

Looking then at the predicted accelerated scoot of the MJO around to the other side of the globe, this ties in with very constructive interference of the MJO through the Indian Ocean and beyond). What happens next will probably shape the end of winter. Yesterday’s update has supressed the wave compared to yesterday's. 

I think 1993 is a fairly decent simplistic analog, looking at ENSO state and that year’s final coherent MJO DJF wave. Even if we use that, it is reasonable to assume that we may have to endure several near misses but not really near misses (I'm thinking promising ridging/teasing easterlies in FI but ultimately MLBs at best, maybe a fleeting Easterly,) before late Feb / early March, then we could get a chance of the Easterly we have been waiting for.

My only doubt is that the 3rd DJF MJO wave in this base state (which, whilst neutral, is more negative than ‘93) is often (but not always) suppressed and therefore the least invigorated in the Pacific. I believe that to be the case, I may be wrong.

Of course though... no set of circumstances are ever the same, there aren't any real big drivers in isolation, no real sign yet of coupling of the strat and troposphere. So, maybe one more time this winter, we could get things going our way against the odds?


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5223736
Posted
  • Location: Ireland - East Coast
  • Location: Ireland - East Coast
Posted

For a memorable easterly you really need low pressure in southern continental europe, Feb 1986

image.thumb.png.c503f206ac8646a85329a46f16dd1632.pngimage.thumb.png.2d458422e8ebc80ba8c987aaad9dddb3.png

 

A week or so before this event, a lobe of PV moved down over this area, and cut off very quickly setting up blocking to the north and east

image.thumb.png.8f4dec6a18eabfce32baaa571a577e4b.png

3 days later and Bingo. 

image.thumb.png.5173126ebeb3c1384cb938f13996f706.png

 

Rare this, but something to watch out for, a mechanism to sustain or aid an easterly


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5223937
Posted
  • Location: Woodchurch, Kent.
  • Weather Preferences: Storm, drizzle
  • Location: Woodchurch, Kent.
Posted
On 07/01/2025 at 20:26, Eagle Eye said:

What could this lead to longer-term?

Depends on the breakdown of the UK high, the longer the pattern remains in a holding state, the more I suspect that out pattern flatten out. Though the pattern may drive a Ural high to sustain itself and that's a notorious Stratospheric driver which could help with putting pressure on the Stratospheric vortex area and therefore lead to an increase chance of a SSW towards later January. Alternatively, should our pattern amplify and progress towards a Scandi-Greenland dipole then we can have shorter term rewards but that'd be later January or February if it were to happen. Smaller pattern breakdowns may also happen and the NPJ may retrogress and cause more chaos as it'd affect the phase of the EPO and may lead to either a zonal increase as the Canadian jet sets itself up, or it retrogress far enough for another attempt at the Greenland high setup as the northeast American sea board +VE geopotential height can be an avenue for a Greenland high to set itself up. 

Update:

At the moment I'm suggesting that a UK-Scandi high by late January is most likely. The transition to true Scandi or Scandi-Greenland relies on the mid-Atlantic jet being disrupted after a polar vortex displacement over the US. The encouragement of the forced -VE zonal state there displaces the typical jet stream towards an amplified state exiting the US which makes it difficult for Greenland high's to form. However, a regressing Iceland-Euro high may be forced depending on the total strength of the cold air outbreak, if it gets to the normal exit of the US response, then the UK-Scandi high may flatten out eventually. Though I suspect that somewhere in-between that is the true response to this pattern as most modelling prefers a Scandi high solution, with an amplified UK high where the potential for cold sliding down is there, but it's unlikely to truly be UK centred, as a Scandi-Greenland dipole would be. Instead, that may force cold underneath the 500's and will prolong the cold air at the surface with an inversion. Dry solutions long term are therefore slightly more likely. Unless, the cold can undercut the high pressure, which is a possibility if eastward regression occurs. Easteward regression would also increase chances of an upwards stratospheric split, a scenario that's been mentioned many winter's over. Where a wave-2 is forced from a wave-1 intrusion of some sorts because of a Scandi high uppercutting through the tropopause. I say wave-2 due to the fact that the Scandi high tends to also come from some other forcing. In this case it's most likely the downstream effects of the Ural high driving the strat for the next few days. Then the transfer to an Alaskan high is where it may combine for a wave-2 if we're looking for February strat driving. A potential for a SSW mainly comes due to that risk where a Scandi high both helps us short term and long term for  cold risks. Though, it may provide a cold dry risk around the latter part of January, unless it displaces so much that the zonal jet can return. Which is a high possibility during the second half of a La Nina winter.

image.thumb.png.9590b657fb1ae49b20d487a0841c1691.png

GFS run - 20% solution imo with a close cold pool and potential for surface low's for snow.

image.thumb.png.2f9671d10df46f7c6f9acd4b1b97c816.png

GFS ensemble more likely - About 50% likely. With the other solutions making up the rest. UK-Scandi high with the cold and low's further away. May become a Spanish risk and eventually fire up the Atlantic and flatten the high out. Though it may still become a strat driver and SSW risk maker high.

image.thumb.png.1a0aeb4d9ddc640cbf7fe5397112e1a7.png


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5223952
Posted
  • Location: Buckinghamshire
  • Location: Buckinghamshire
Posted

Afternoon, have been able to do an update so here it is.

There are subtle changes to my previous one but a lot of that hasn't changed too much, there's no denying that a battle of sorts is likely to take place between higher pressure moving over then building to our east and/or northeast and Atlantic weather systems gathering to our west for a time, this was anticipated previously, though I will mention what is different shortly, it's important to remember and ofcourse some will know this but whenever there is a significant stand off between two very different possible outcomes over the UK, the models will tend to 'throw' out runs that show either scenario and one in the middle. (Sounds too obvious now thinking about it to point out.)

We can see the GFS/ECM below threw a scenario yesterday where high pressure to our east/northeast 'won' the battle temporarily and we saw east/southeast winds move into all parts from the 22nd then by the 24th bringing some wintry weather and cold temperatures, before a very gradual return to the Atlantic weather systems raising snow risks for many.

GFS yesterday..

EUROPE_TMP850_270_MOB.thumb.jpg.3d86938b16a253a81bce1317fad5ec5b.jpg

EUROPE_OVERVIEW_258_MOB.thumb.jpg.4df5e2fe1cddbb59e5021ff9184b5e66.jpg

EUROPE_TMP850_294_MOB.thumb.jpg.0fa390834a5b56407313bb38dcf0c4e0.jpg

ECM yesterday.

850temp_20250114_12_252.thumb.jpg.15338cb74c06b4c3f1a689b9357d24a1.jpg

850temp_20250114_12_288.thumb.jpg.1b699bdfcc3847b3b496acdc3fff8349.jpg

Icon shows a colder easterly at a similar timeframe, so can't be dismissed atm.

What I think is most likely for the last 9 days of January..

Probability (50+%)

                      ⏬

Higher pressure will probably drift over much or all of the UK on a east/southeast trajectory after the 20th then become slow moving just to our northeast/ east after the 22nd, this has been anticipated for a while but it will prove a little more resilient than first thought.. bringing dry weather initially for many bar perhaps the extreme west, though chilly under rather light winds. ✅ 

                      ⏬

          23rd onwards.. 

Atlantic low pressure systems will initially struggle a bit to cross much of the UK effecting largely the far west at first with dry/drier central and east UK, but these unsettled conditions are still expected begin to make their way slowly across the whole UK west to east by the 24th January onwards (probably), due to the slow progression some places may see longer drier interludes between frontal systems but when a frontal system comes along it could be notably wet. (Not too dissimilar to previous update or two but with the emphasis on a drier start and delay of unsettled/milder weather.)

                         ⏬

Most likely wind direction between 23-29th of January at first southeasterly, southerly then slowly veering south/southwest, this could mean a small window for some precedent sleet/snow in northern/eastern areas (low risk) and mainly on higher ground as we have colder air in situ before the milder and unsettled weather moves slowly east.

So in summary wettest weather largely in the west initially with drier weather east, wet and windy weather effecting most or all shortly after, relatively mild after a chilly start to the period particularly further southeast under a continental flow at first.

29th+ January..⬇️

The final couple of days of January/first week of February, most likely remains unsettled, potentially very wet and very windy at times, low pressure system influences felt further east/south across the northern hemisphere over on our side of the world, higher pressure present over central Europe, temperatures not overly cold in the north but a slight lowering of upper air temperatures are possible and brings the risk of hill snow in the north behind weather systems/perhaps lower levels on the northern flank of any very deep lows, this is quite similar to previous post on an earlier timeframe so yes a slight delay of sorts compared to previous post, less emphasis on a particularly wintry scenario in conjunction with unsettled weather compared to previous post hinting at it as the Jetstream isn't expected to dig as far south at first, could be quite mild in the south by this point.

There are other possibilities though..

Less likely.. approx (40%)

The high retreats quickly east/southeast into central Europe doing little to hold off Atlantic weather systems at all from the 23rd onwards, very unsettled from the get go with risk of gales in places, locally severe gales in the northwest and heavy rain widely with snow on high ground in the north/northwest, and on northern flanks of deep lows, wind direction would be south to then quickly southwest/west, then would plausibly turn colder by months end/very early February with a more widespread risk of wintry weather as Jetstream would likely dive further south, would remain unsettled (that's rather similar to my previous update).

Least likely.. approx (20% or less)

High pressure remains firmly in control for most of the UK throughout the last week of January, a lot of models have shown this as possible recently, keeping things mostly dry bar the extreme west and extreme south on occasion, this would also be where the high would perhaps align in a way to give cold east/southeast winds for a few days bringing occasional snow showers in the southeast/east, but snow also occasionally in the south/southwest as weather fronts attempt to move back in but failing for a time, colder and drier pattern would gradually ease by last couple of days of January/early February with unsettled weather more widespread spreading erratically north, raising significant snow risks along the transition zone before generally turning to rain.

Granted this is my analysis of the outcomes possible and may change but it's reasonable to assume the most likely outcome will occur, it is indicating slow moving patterns to begin with, but this is finely balanced and just a subtle shift in the blocking could flip these scenarios even if deemed unlikely currently, the period of interest regarding any significant wintry weather is certainly the very end of January/early February for now with that potential dive south with the Jetstream, even if a slightly reduced risk.

That's it from me for now, will update if there is a change in thinking. 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224028
Posted

 EML Network ECMWF have written an over view here:

Very good verification at 500mb, not so good for detail (it has a lower resolution). I wonder how best to compare between the AIFS Op and the IFS ensembles .. AIFS has it's own ensembles but I'm not sure what maps are made available.

 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224056
Posted
  • Location: Dorset & Oxfordshire
  • Weather Preferences: Warm and dry, or very cold. See my profile for model trivia
  • Location: Dorset & Oxfordshire
Posted
53 minutes ago, EML Network said:

 Mcconnor8 now THAT is a horrible chart if ever I saw one. Glad thats not a chart for the reliable timeframe.

 

Does the A.I model have any verification stats ?

16 minutes ago, josh-weather said:

Very good verification at 500mb, not so good for detail (it has a lower resolution). I wonder how best to compare between the AIFS Op and the IFS ensembles .. AIFS has it's own ensembles but I'm not sure what maps are made available.

These links may be of interest.

Regular ECM vs. AI models verification scores averaged over three months:

https://charts.ecmwf.int/products/plwww_3m_fc_aimodels_wp_mean?area=Northern Extra-tropics&parameter=Geopotential 500hPa&score=Anomaly correlation

As above, but daily scores throughout those three months:

https://charts.ecmwf.int/products/plwww_3m_fc_aimodels_upper_tis?area=Northern Extra-tropics&day=5&score=Anomaly correlation

ECM AI ensemble meteograms:

https://charts.ecmwf.int/products/aifs_opencharts_meteogram?base_time=202501150000&epsgram=aifs_classical_plume&lat=51.4333&lon=-1.0&station_name=Reading

ECM AI ensemble means:

https://charts.ecmwf.int/products/aifs_medium-t500-mean-spread?base_time=202501150000&projection=opencharts_north_pole&valid_time=202501250000


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224070
  • Insightful 2
Posted
  • Location: Wantage, Oxon
  • Weather Preferences: Hot, cold!
  • Location: Wantage, Oxon
Posted

ECM clusters have narrowed down the uncertainty in the medium term.  Unusually, I’ll run the two later timeframes together, T192+:

IMG_0043.thumb.png.0fef3eb79d75ff2595dfc5eddad8482f.pngIMG_0044.thumb.png.1e2895ec4d87cf0b84eb7062833bf9c9.png

There are two clusters, with perhaps some crossover where the two timeframes join.

Cluster 1 builds and maintains a Scandi high in a decent enough position, that if we were to count this down it could upgrade into something decent from a coldie’s perspective.  

Cluster 2 the blocking evaporates and there is a marked return to zonal +NAO.  Just my guess, taking other info into account, I see a sign of strat/trop coupling in this cluster.

Cluster 1 has 31 members in the T192-T240 and 33 members in the T264+ timeframe. Place your bets, please…


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224239
Posted
  • Location: West Yorkshire
  • Location: West Yorkshire
Posted

 sunnijim  Froze were the Days I think the key point to remember is that all seasonal models are an average anomaly to cover a large amount of time. The same is true of the temperature anomalies.

For example, a winter with a temperature anomaly of +1C, and above average heights to our south and west, could be made up in any number of ways. To give two extreme examples, it could feature a strong height anomaly to the south fairly consistently, with almost entirely westerly winds, but nothing very mild or very cold. It would be remembered as a mild but non-descript winter.

However, you could get there another way. You could have a couple of weeks with a substantial Greenland block and no heights to our south, but then the rest of the winter is dominated by a huge area of high pressure to the south, and low heights to the north. In temperature terms, you might have a two-week period 5C below average, then the rest of the winter averages 2C above average to compensate.

The latter would be remembered as a far better winter than the former because of the two week cold snap, but as far as the seasonals are concerned they're the same.


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224288
  • Like 1
Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .
Posted

Got back into the UK last night so here to share coldies pain !

Originally the low to the sw didn’t look like a big player but that’s become very troublesome.

As you can see from the GEM how it can really shut the door on any cold hopes if it phases unfavourably with the low to the north.

Overall the models are reluctant to build a strong enough high to the north to repel the Atlantic .

So it’s now if the upstream troughing can disrupt sufficiently to send enough energy se .

The ECM tries to eject some shortwave energy se but we don’t manage a clean separation of that with the troughing .

Anytime you get a hang back of that energy it acts to pull the troughing east .

The day 7 into 8 is close but no cigar .

IMG_0111.thumb.PNG.f7a1e6a2388bf997917edce471758c88.PNG
 

You can see that shortwave circled red . If that ejects cleanly it helps to support the wedge to the north as it heads in towards central southern Europe and that then helps to pull some colder air west with the black arrow .

The ECM day 8 shows the issue when that doesn’t happen .

image.thumb.png.49cb666237ae3db2a57262925446c35d.png
 

I should add the ECM is different once again upstream between runs , this morning is an improvement .

At the moment it’s hard to make a case for any sort of proper easterly, the best is a possible initial battle with the Atlantic with the UK the boundary .

There maybe a chance later after this initial skirmish if we can keep the jet running se and heights hang on towards the ne .


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224399
Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
Posted

 Anthony Burden Well, can't rule out some cold enough air being pulled south on the back of the wedge of high pressure that drifts east just to the north of the of the UK later next week, ahead of frontal systems moving in from the Atlantic to bring some snow in the north, like UKMO, but it's a long shot.

UKMHDOPEU00_168_2.thumb.png.c4eb1a6b247c19ca5a72e3796c4c52e1.png

What caught my eye on this morning's EC run is a 850 hPa cold pool that develops over the Bay of Biscay and gets colder as it drifts northeast over the UK on Sunday - not often you see that happen!

cSqmfUleir.thumb.gif.a9fcacd1b2d93d3df26bffe961fce1a4.gif


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224476
Posted
  • Location: Southern England
  • Weather Preferences: Sun, snow, storms etc.
  • Location: Southern England
Posted

I’m not sure why everybody seems so confused about the ECMWF vs GFS differential, because it doesn’t take a lot of research to work out what’s causing it. The GFS is doing the usual zonal-biased claptrap we’re used to seeing from it in patterns like this, because it is rushing the MJO out of phase 1 and exaggerating the amplitude in phase 2. It’s a tale as old as time and I’m really not sure why people are treating outlier GFS runs with much credence as a result. 

IMG_6502.thumb.gif.beeee9f46c3f43d5747607f5ef92427e.gifIMG_6503.thumb.png.1bf66cef312ae396f8ae3e5e97ca1fe3.png

For further reassurance, I’ll attach ACCESS-S2 from the BoM in Australia.

IMG_6504.thumb.png.ddafd43e83271555c60698580ef1eba3.png

This is the January composite anomaly for 500mb heights following a phase 1 - remember there is a lag effect.

IMG_6490.thumb.png.4af8bc23538aed81d88866eecae6f7da.png
Not just higher pressure to our north, over Scandinavia and into the Urals, but also lower pressure into Central & SW Europe. It’s not hard to see imo why the ECMWF is a lot messier like this:

image.thumb.png.c9305f8ac4452b9c6c7fc42151f78350.png

From a cold perspective, the charts are still dire so I understand the frustration, however, technically ICON & UKMO have won the initial battle as all models now slow down the Atlantic by developing this ridge in the first place. Now they’re in agreement over that, it’s about where it lands and how strong it is, which is a phase of play I’d expect ECMWF & ICON to be leading the way. Though the ECMWF has it initially weaker than I’d expect, the upshot is a more blocked setup with a weak Scandinavian High and residual heights around more generally. 

IMG_6509.thumb.png.61cf7335a4189866f46679f2778971f1.png
IMG_6510.thumb.png.79dd257bc0ff75041eeec68ca8638466.png

The cold pool over Scandinavia that the ECMWF entrenches at day 7 is still there at day 14 - even deeper. If you want a deep cold spell, then usually you have to get a series of ingredients in line first. I’d take the ECMWF as in the long run it significantly improved the potential for a Beast From The East™️ - it’s been 7 years since the last. FYI, yesterday’s CFS 12z run started one around February 21st and ended it on March 2nd, which is almost identical dates to 7 years ago. 😅

I still expect mild, wet & windy weather from this setup - though unlike the GFS it can allow for cooler temps to briefly come & go, so not without interest further northeast. There’s still a low chance of a brief cold undercut if the Atlantic is held up long enough, but MJO phase 2 is inevitable & it’ll be pretty ugly for many I’m afraid. Once into phase 3 though, there is potential again, as the pattern correlation is weak for phase 3. GFS has phase 4-5 evolution. ACCESS-S2 4-5-6 evolution.

ECMWF stops at 3 and goes into the COD before aiming to exit around 6-7. ECMWF into February then may show drier (especially to the north and west) and colder outcomes than the GFS in the extended range, people should prepare themselves for this. A pre-established cold pool over Scandinavia, with lower pressure in place over SW Europe, and suddenly it looks as if the battle of the titans has been deferred, rather than cancelled. Bring. It. On.

IMG_6495.thumb.png.8e0ab6b09b871464a2b4ad6bbbe3ce9c.pngIMG_6512.thumb.png.6515cfdd5d9598f11949102ce70b4f83.png


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224573
Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl
Posted

As usual i have been watching developments and although the easterly option was unlikely, given what is lurking upstream with our name on it, i was hoping that the outside bet would prove the background guidance wrong.

Now it looks more likely that we will be facing an eventual Atlantic onslaught as the split jet eventually becomes stronger in the northern arm.

The AO/NAO index reflective of this as we see them both trending positive.

 image.thumb.png.17e7c61708d20948ca969fa04f403d89.pngimage.thumb.png.dc7e6794b98f739e78ae20e2cb6ae38e.png

MJO is now be entering the +ve AO and NAO phases 2 and then quickly into 3 which indicate pretty much the upcoming pattern with some Euro ridging just too far east and the Atlantic winning out with possibly some quite cyclonic conditions near month end.

image.thumb.png.43ac3bde3e89b1ce36faefe5755e09cd.pngimage.thumb.png.74c4f2a758763caa347b350ee672bbc8.png image.thumb.png.1a608772f5a823803789fd1a7e5d7e97.png

We can see the forthcoming evolution of next week by a glance at the following images.

Fax for Sunday then 2 eps 500hPa charts.

image.thumb.png.a629ff4bc40de4dc10ae046daab6b356.png image.thumb.png.8aa1d6c0d2ff4982f00c7ff5591f8289.pngimage.thumb.png.26c3c1ccfc914f72bdcbac1344afeb84.png

The cold air coming off a bitter N.America  next week will create some deep Atlantic lows no doubt.Unfortunately there's no real sign of deep cold here although that very cold air from Canada gets a fair way towards the UK.

With jet driven further south again it doesn't look like a mild pattern so can never rule out some wintry stuff in the the far north at times.

 

image.png


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224576
Posted

^ its worth adding that the NAVGEM whilst low down in the rankings at least illustrates the route to cold from this-

Which is non phasing initially of the 2 lows allowing the one towards iceland to eject eastwards -

As that happens it engages & phases with the cold & energy that has dropped south into Northern Scandi.

8E80FF79-7931-4AB3-8AE4-25DA928D033A.thumb.png.76b33838c6ec74ca39373f1937474322.png

At 180 then the atlantic hasnt made it, & the shape of the high is 'near' perfect.

445204A5-6B72-4021-98BE-2912F65475DD.thumb.png.a925f9e6bdb7552de2208ec820e520fa.png


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224572
Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl
Posted

Brief post - but AAM has tanked

image.thumb.png.78b8dfdf5147654d90876a51d224a069.png

with positive anomalies at 60 north. GWO is on its way down - heading towards Nina phases....which in winter terms mean very difficult conditions for a ridge to gain traction to our north

image.thumb.png.67004fadb2d75f6a669c56c81328ef46.png

..and an SSW looks rather unlikely at the moment. 

image.thumb.png.b6677ded22b00b575641e870d74f4fde.png

 

I have already had more out of this winter than I expected, given a fine line but quite productive mid-November spell and the 10 days that ended just recently on the back of the favourable MJO cycle and negative anomalies that moved poleward. I rather suspect we are done for this winter now, though there is always the curve ball moment that can occur.

An easterly at the end of January would not therefore be supported by the wider drivers. When these drivers are in place we have a change (a chance - not a guarantee) of a cold spell. When they are not in place I believe I am yet to see a cold spell emerge once in my watching years.

I'd love for this to be the first time...but it would be a big surprise to me.


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224708
Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl
Posted

 TEITS

To a point i understand what you are saying in that nwp patterns are prone to change usually beyond the usual 4/5 days.

However the evidence posted today is pretty overwhelming that we will enter a +v AO/NAO phase,not just the background data but the ens. and ops., that early next week the Atlantic moves in as the ridging further east declines.There's is no need for me to tell you what is waiting upstream over N.America. 

Wrt the cold spell just ended,quite a few of us were discussing the possible change pre-Christmas when we were in the middle of the mild spell.

I am certainly more aware these days of the usefulness of the background data,,especially the MJO in it's active stage in Winter and it's affect on the 500 pattern.

 

MJOPhasesannotatedbyMarcoPetagna.webp.80567e77e6051963a33fc080555bfb1b.webpimage.thumb.png.26372319a15968fb7d4bfd7475684632.pngimage.thumb.png.150ca419e66c039e34690b05de9aa438.png

In certain phases it influences the likely state of the AO/NAO if it shows sufficient activity and this is the case currently.This is a recent graph showing it's track record.

image.thumb.png.c589d3f9520132789195cbd2acfef678.png

We are now in phase 2 and will quickly enter 3  and then 4 and with the time lag a change to an Atlantic pattern is difficult to argue against.They are not perfect but what we can say from experience is you are most unlikely to get a cold spell in the  current(warm) phases.  

Believe me Dave i want to see another cold spell before the season is out,whenever it comes,the sooner the better i say.It will be interesting to see how things develop anyway. 

 

image.png


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224863
Posted
  • Location: Central Wales 250m (820ft) ASL
  • Weather Preferences: All
  • Location: Central Wales 250m (820ft) ASL
Posted

There have been substantial changes in the day 8-7-6 range over the last couple of days, which have served to reduce the viability of the block. 

The 12z GEFS charts from Tuesday, yesterday and today for the 22nd, now at day 6, show the combination of events that have undermined it. 

500mb heights:

IMG_4768.thumb.jpeg.a02df7e60326d0ce77215c58f46dedd2.jpeg IMG_4769.thumb.jpeg.cc3fb8e786f995957c06ea37d2cccc42.jpeg IMG_4767.thumb.jpeg.049c0fcb9601f041e6c5fb1271d100f3.jpeg

Ironically, a stronger southern arm to the Atlantic jet stream has led to the deepening of the low off northwest Iberia, from 1014 to 1002 mb. This has been fed by a stronger jet stream through the western Atlantic, so it’s diving south with more energy around to the Canary Islands, strengthening the link between the two ends of the Atlantic trough. 

MSLP:

IMG_4772.thumb.jpeg.db5af0de9218d61b714f6c74f77ab195.jpeg IMG_4771.thumb.jpeg.ac99bd30dcaeaf50d1172c69340d96f8.jpeg IMG_4770.thumb.jpeg.c4149b8be2a63ba336312f6e4e614583.jpeg

A weak trough down through Scandinavia contributes to the lower heights to the southwest, forming a surface low over southeast Finland and northwest Russia, but most importantly, splits the Iceland to Kazakhstan block. This is instrumental in the diminution of its modelled strength thereafter. 

Another paradox, the ridge to the northwest of the UK and Ireland and the heights through Iceland are stronger, holding the low further back at the Labrador coast, with arguably better disruption to the northern part of the trough. 

All this only emphasises further what a finely balanced “disruptive” Atlantic vs block setup this has been for the models to grapple with, and in fairness to the block that was being modelled, it’s taken an elaborate pincer movement to ultimately undo it, if indeed all this transpires in similar vein to how it’s currently being modelled at day 6. We’ll have to see! 

Metaphorically, it’s been hard work for the algorithms and more literally for us in our attempts to interpret them, but as ever, great learning. 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5224881
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