Model discussion highlights

[Cambrian]

With regard to the possibility of the movement of more substantial cold out of the Arctic during the coming weeks, it might be worth noting that the models over the last few weeks have been consistently underestimating the coldness of the air working down from the north at either end of the Atlantic.

T850s - 0z ECM op from 5 days ago for day 10 vs 0z ECM op from today for day 5

 

The models of 5 days ago underestimated the surge of cold moving south into central Canada and the cold air digging in over Scandinavia

And as a result didn’t pick up on the strengthening of the Atlantic jet stream…

 

…and the cyclogenesis over the Hudson Bay / Baffin area and near the UK and Ireland. 

 

This morning’s 0z ECM day 10 chart shows a good push of heights up into Greenland / Iceland, so looking like we’ll get a promising break once we get these storms out of the way, with a quieter spell (not completely dry, but a good deal drier!) around the end of the first week of November, the jet stream fragmenting and moving south again…

 

…the cold air winning through at both ends of the Atlantic, bringing the UK and Ireland into a northerly flow and turning decidedly colder, nicely shown on the T850s anomaly.

 

Have a great day.

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4943363

[johnholmes]

5 days later and what is showing=Saturday 28 October on NOAA and ECMWF outputs

NOAA 6-10 (2-6 Nov) and cold contour heights over the UK, certainly bye early November standards, the whole country is covered by the 5280 DM line with a 5220 DM centre over western Scotland. There is a very large –ve height centred over the UK, at least -300 DM with what looks like an actual max of – 360 DM over the UK!. No actual contour flow over the UK with a strong westerly over western Europe below the extended main trough W-E from NE Canada beneath the Greenland ridge and into the UK trough. An actual contour ridge over eastern Greenland with +ve heights from NE Norway across the Greenland with a +ve max of +150dm west to northern Alaska. I honestly cannot remember seeing this kind of set up in early November, either predicted or actual

So to the ECMWF for a similar period (3-7 Nov). It shows a fairly deep upper centre centred over the UK with the trough down into Iberia. Over the period the trough ends up la bit less marked and slightly east of the UK. Its attendant surface feature over the Scottish Borders given as 967 MB, slowly fills, meandering around to be double centred off southern Sweden and west to the sea just off western Norway. At the same time the 850 MB temperature remains below 5C and falls over the period as the zero C line ends to be shown from N Wales to N Yorkshire.

To me this suggests temperatures will be below normal, possibly even rather cold for areas away from the far south. Also changeable/unsettled, rain or showers at times, windy at first. Snow would be fall, if these charts are correct to lowish levels over Scotland, possibly even parts of far northern England by the period end and for hills as far as the Peak District and N Wales, maybe even hill tops further south.

Of course these charts may well get moderated as we get nearer to the dates given above!

Just had a look at the latest UK Met output 1-3 November and both the 500 and the surface are not that different from ECMWF, so we have models on pretty much the same page. It has happened that all 3 have been too dramatic but not often. I suspect Met O warnings of yellow/amber will be issued early next week.

Anyway time will tell, this time next week we will know the answer!

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

This is the Met O Fax outputs for T+144, not sure what will download, but scroll to the T+144 if it starts with the actual surface chart

UK Met Office Fax Charts - UKMOMSLP Analysis and Prognosis

WWW.WEATHERCHARTS.ORG

---

UK Met Office . . Europe and North Atlantic MSLP analysis and prognosis charts

 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4943375

[Kirkcaldy Weather]

On 26/10/2023 at 21:18, Kirkcaldy Weather said:

I posted the following September 19th 

What could unfold as we go into October?

These are the biggest development dynamical situations I'd be expectant to be occuring. Hazarding a date keep eyes around later of October Week 2 sometime around 10th - 13th

Elongation of European Heights start a gradual movement evolving to Scandinavia---Greenland 

New trough emerging close by most probably a smidge to the East then drifting to the UK 

I'm noticing that trend of low pressures through the United States trends show that eastern coastal Noreaster style as a possible setup

And the following 500hpa animation on 8th of October 

 

New 500hpa sequences following that period which go excellent to my thoughts back in September 

 

'Active West Pacific signals [super typhoon Bolaven]

Californian >> Mexican cyclonic pattern. Major Hurricane Lidia plus Tropical Storm Max. Also the potential next Rossby Wave via Bolaven into new California Cyclonic conditions 

Build of pressure through the UK and Scandinavia which transpires as the Rossby Wave within Atlantic continues its progression further East'

Nothing short of spectacular the manner in which this has really energized the setup pretty much globally 

Using the above JMA phase 7 expectant setups it even gave good indication on the -PNA east American high plus the dual zones over on the western end more on this in a minute 

Really stunning showcase of how a positive PNA swaps to that of a negative phase

"an upper trough trying to align on a negative tilt which might see a severe weather event into the Midwest and west central America as that has the energy from Norma which did indeed move into Baja'

Focusing more at the California Baja >> Mexican troughing this really kicked into life from phase 6 but in particular 7 and 8 we've seen Lidia Max Norma and Otis within like 2 weeks.

Crazy.

Next focus is with the separate trough swinging through the Northwest and Canada the recorded temp differences from AVG are truly incredible already with upto and over 30 DEGREES BELOW AVERAGE

 

 

As the PNA rises this will coincide with these values moving east southeastwards with nearly all of America below average and decently at that, I expect a good number of further minimum temperatures will be at and setting new records particularly in traditional warmer states such as Texas and along the Gulf. Might be some high temp records doing the same within that -PNA high initially however the minimum values really are the main news.

A rare pattern by the very beginning of November in regards to a legit cut off Greenland High, a VERY rare beast bringing back the 09/10 vibes. Note the separation of energy has occurred as our block from Scandi has split with the formation further east connecting through Alaska and the Pacific Northwest with the rest over Greenland as discussed and something I mentioned on October 8th

'I'm eagerly awaiting the approach into Halloween  be looking particularly toward the patterns getting retrogressive in nature with scope for further blocking which looks to have the opportunities of origin towards Scandinavia'

Nice viewing as the composites are starting to show in alignment to the continuing phase 8-1 snailpace MJO movement 

We'll have to keep very alert for week 1 November of the forming CAG with very early signals this has possible connections for the PNA moving once again to positive territory, Florida maybe Gulf states need to be mindful with formation currently signalled by November 4th

This lead up to Guy Fawkes gives another date for cyclone development for us also around 2nd - 6th 

 

On 23/10/2023 at 20:07, Kirkcaldy Weather said:

 

We have two dates to really focus in on which are 27th October and 29th October I expect Sunday 29th will have greater impacts for multiple reasons however Friday shouldn't be completely dismissed.

By the 26th and 27th we will have a main cyclone to the west of Ireland - UK which begins the phase of elongating in structure. Downstream dynamical situations will be a Rossby Wave begin the breaking sequence with Tammy and the High connecting with the -PNA with an upper trough trying to align on a negative tilt which might see a severe weather event into the Midwest and west central America as that has the energy from Norma which did indeed move into Baja 

I've deliberately marked an emerging trough from Canada at that stage as this will be a big factor through the start of the developments for the weekend as it ejects through the Labrador Sea

As the trough energies move on the southern flank of our elongating cyclonic structure the two eventually begin the merge into the weekend 

Another huge reason for rapid deepening and strong cyclogenisis will lie with the next major moon phase with the Hunters Full Moon

"One of the worst hurricanes to ever make landfall in North Carolina was Hurricane Hazel in 1954. It made landfall as a Category 4 with estimated 140 mph winds. Hurricane Hazel arrived in October, making it a fairly late-season hurricane. The full moon at the time caused one of the highest lunar tides of 1954 in North Carolina.

There were also concerns about Hurricane Sandy and whether the full moon was going to make that storm worse for residents all along the East Coast. The storm made landfall on October 29 in New Jersey, and October 29 just happened to be when the moon was waxing to its full phase. Estimates suggested tides along the Eastern Seaboard would be about 20 percent higher than normal.

The full Hunter’s Moon peaks on Saturday, October 28, 2023. As with last month’s full Moon, the Hunter’s Moon rises around the same time for several nights, so start looking for it on Friday, October 27!'

'We'll have to keep very alert for week 1 November of the forming CAG with very early signals this has possible connections for the PNA moving once again to positive territory, Florida maybe Gulf states need to be mindful with formation currently signalled by November 4th

This lead up to Guy Fawkes gives another date for cyclone development for us also around 2nd - 6th'

'We have two dates to really focus in on which are 27th October and 29th October I expect Sunday 29th will have greater impacts for multiple reasons however Friday shouldn't be completely dismissed.'

Very pleased with development fitting really good with the above

I can say with a high degree of certainty there are 2 dates with deep cyclones which will have significant impact for the UK and France particularly Northern France 

1. November 2nd
2. November 4th

Looking in detail how each day develops downstream

The deep cyclonic conditions moving across on the 2nd lies with the snowstorm currently impacting Colorado

 

Even as it exits toward Long Island it already contains an energising Jet streak along its southern flank, same timing sees the wave break I discussed previously in regards to Tammy which splits some energy and generates a new low a few miles to its east, importance within a new low which sets up close to Florida plus the next surge of tropical energy into the far East Pacific 

Ive posted the patterns during phases 8 and 1 during November however this is superb as the trough location ties really great

Halloween ^^^

Note there is an active cyclonic activity through the Labrador Sea which inputs towards our cyclone on November 2nd however less of a contributor than the snowstorm.

More incredible stuff happens on Late Halloween eve and especially November 1st which will see the RARE cut off Greenland High as mentioned above, 

So come Halloween we've the Snowstorm moving into the Atlantic, a high energy upper trough swinging from Canada into the Great Lakes creating the first big Lake Effect event (Tug Hill doing nice from this one i expect) there plus the Labrador Sea cyclone feeds enough energy and forms a cyclone west of Ireland

We begin seeing the Florida low better by then also and these two events will be the key for the cyclogenisis for us into November 4th

November 2nd

Snowstorm undergoing rapid deep cyclogenisis and becomes the main cyclone as the energy merge occurs to the smaller cyclonic centre west of Ireland. Pretty rapid deepening involved with our far East Pacific system also. Floridian trough pairing to the Great Lake upper trough. Beginning development showing into our CAG zone

On 21/10/2023 at 21:18, Kirkcaldy Weather said:

This is likely linking with our configuration into November with further energies from it feeding into further Atlantic RWBs with renewed unsettled and most probable STORMY patterns prevailing 

November 4th

• CAG action kicks into life
• New cyclone crossing a similar path and strong cyclogenisis once more

Entire sequence of activities

 

 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4944237

[Cambrian]

So often over the years we see a situation where a big storm develops in the eastern Atlantic and as it exits east, it seems to suck the energy out of the Atlantic, leading to a quick rise in pressure from the west. 

In these situations though, we normally have lower heights to the north, the jet stream tracking further north over the UK and Ireland, with good penetration into Scandinavia, so the storm makes a quick exit; and due to the jet being further north, the Azores heights are ready to pounce, pushing up a ridge, which can sometimes link up with heights over Greenland to form a solid Atlantic high, that can stick around for a fair few days. 

That isn’t quite what we have here with the storm at day 4 on the 0z ECM ensemble mean with the jet stream having flicked north, but only into France (960 mb on an ensemble mean chart!). 

 

before relaxing back south after the storms at day 8, with the resumption of the southerly tracking jet stream that heads into the Mediterranean, and then fizzles out as it curls up through the Balkans.

  

Any northward build of heights from the Azores is suppressed, and the depression has only moved from the Bristol Channel to the North Sea in 4 days. Here from yesterday’s 12z EPS, the 5-day mean MSLP is 974 mb (say no more).

Even by day 10, the low has only made it to Scandinavia. At that point, despite an effort of heights to pinch through the trough on its western flank, we’re looking west again, and though quieter for now, the core axis of the Atlantic trough is the same as it is at its peak extent at day 2, extending from central North America (Ohio) to Central Europe, hooking up into Scandinavia. 

  

This is the consequence of the maintenance of the same broad setup - northern heights, southerly tracking jet, suppressed Azores high. 

There will by then be a notable difference though, going back to the EPS, the 5-day mean temperature anomaly for the cyclonic period between Halloween and Bonfire Night, very close to average, contrasts with the 5-10 November - temperatures well below average by then. 

 

And as this setup persists, with slow west-east transfer of depressions through the UK and Ireland, cyclonic flows from a northerly quadrant, as indicated here in the EPS mean for 5-9 November and ECM weekly mean for 6-13 November, will be frequent - and as time goes by, moving further into the month, progressively colder. 

 

This has the increasing feel of a slide into a changeable and chilly month.

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4944080

[Catacol]

7 hours ago, IDO said:

Looking at the mean wind, we can see the usual trend of the system(s) being modelled further south as we get nearer the event(s). GFS 06z mean:

Except that this is not what the modelling is showing. ECM is currently very consistent - last 4 runs has the storm entering through the tip of Cornwall with very little deviation. Will be interesting to see whether we get a trend developing. GFS meanwhile is edging ever so slightly north in my interpretation, though it is fine lines for sure at this stage. 

00z Sat

12z Sat

00z Sun

12z Sun

The (in my opinion less reliable) 06z and 18z runs tell the same story, 06z Sat the furthest north

 

If there is a noticeable trend so far it is for the system to stall and fill.  At long range the ECM initially had it quickly losing intensity by Saturday

While GFS by Saturday had it pushing through on a very southerly trajectory into Europe

Both those solutions - which would have lessened the impacts considerably - have now been binned. We have a storm that is growing in strength, looking like it will sit in the jet, propped against higher pressure to the east and fill in a way that will not please those in flood areas. Secondary storm set to hit on Saturday developing out of the same trough sat within the jet streak.

All this means that we are looking at a high impact event that I still think will trend slightly northwards in the coming days. France certain to be hit - southern parts of the UK also.

I'm with Tamara on this one (and we haven't always seen eye to eye!) - current climate impacts sitting on top of developing forecasting techniques is creating a nasty mix. I'm not sure it is possible anymore to rely on seeing average weather. Most of the time developments will sit within the average envelope but the number of times that envelope is being broken is getting more and more frequent, and if this storm develops into one of the nasty global events that are impossible to miss these days then it really isn't good news, even for weather enthusiasts. 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4944361

[Cambrian]

In the mire of a very deep trough this week on the ECM weekly pressure anomalies. It grinds its way through into Europe, bringing us into its cold side by next week - for several days. Early November just a bit early for anything that cold.

 

Things can change quickly though as we push on further through the middle of the month. Heights remain strong to the north. With this kind of Euro low setup, there’s always the chance we’ll begin to pull in some more meaningful cold from the north and east, like here at day 15 on the 0z GEM control. 

  

There’s no quick way back to anything mild from there. 

With the EC46 stratosphere signals for early December getting firmer by the day, 10hPa temperatures anomalously high, zonal winds dropping off - the tropospheric PV is likely to remain uncoupled from it heading into early winter, any episodes of PV-driven Atlantic weather likely to be quite moderate and short-lived. 

  

It might leave us with something like the current slow trough transfer as the default pattern - slack Atlantic (in terms of PV)  pushing through occasional slow moving troughs, the low pressure then getting stuck over Europe.

Not wall-to-wall cold but spells of cyclonic weather, followed by periods of several days of cyclonic but cold, tapping into a progressively colder pool of air to the northeast. If we head into December with anything like this pattern in the offing, it might get very interesting indeed. 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4944511

[Metwatch]

With the above average heights continuing to be present to our north, and the Azores high displaced further south, the strong but southerly tracking jetstream continues this week through the north Atlantic. Perhaps it moves a bit more north next week but little point in analying specifics that far ahead. We may continue to stay in a more cyclonic but cool airmass or also turn less cold if the Azores high and consequently the polar jet shifts to its more usual position, but ensembles keeps things near average temperature wise for most of the country and unsettled.

 

In the closer time frame, a very strong thermal contrast is emerging from the states, which allows an almost 200mph jetstream to race through the north Atlantic, rapidly deepening the low pressure to become our next named storm by Thursday night. I've seen some posts that the jetstream has been analysed as being stronger than what models expected over Canada, which may allow Storm Ciaran to deepen even further, and also track slightly further north, putting more of southern England at risk of some very damaging wind gusts.

Still a great deal of uncertainty, with the latest ECM bringing the low further south compared to ICON, GFS, Arpege and also that is shown with the dalmation plots in the final attachment.

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4944681

[Cambrian]

If we take a closer look at the main models, today’s 66h charts are all very close to the 90h charts from the respective 12z runs from yesterday in terms of the tracking of the centre of the storm.

In descending order from the most northerly solution for 7am on Thursday morning. 

GFS - Devon yesterday, South Wales today, slightly deeper today

  

GEM - Devon yesterday, South Wales today, slightly deeper today

 

UKMO - Dorset / Somerset boundary yesterday and today, big difference though is it’s no longer a two centred complex, so is wrapped a lot tighter, has lower core heights and is 7 mb deeper, at 949 mb

 

ECM - still running along the south coast today as yesterday, still 953 mb, but moving through more a bit earlier. 

 

The track is important alright, but the notably lower central pressure and tighter wrapping into a single centre of the UKMO is perhaps as important a factor as it notably tightens the isobars on the dirty side through the English Channel with a marked impact on the projected gusts, yesterday vs. today along the south coast. 

 

It might sound a bit parochial, and if it does I apologise, but a move like this at this range from the UKMO, of all models, is potentially significant. 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4944761

[summer blizzard]

Interesting tropical profile during October. You can see that we have cycling through Pacific waves with a dead Indian Ocean (loosely, MJO phases 4-5-6-7-8-1) however this has been superimposed with a retrograde standing wave. 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4945155

[Kirkcaldy Weather]

On 21/10/2023 at 21:18, Kirkcaldy Weather said:

There is however an opportunity which could come if a RWB causes a cut off low to go south whilst the blocking to the Northeast connects across Greenland and the Alaskan high 

 

So let's take a look after the stormy spell from the 2nd >>  6th what can be expected after? 

As can be noted above there has been the growing trend for the arch of blocking with output suggesting at least 2 phases with initial attempting by the 7th with cut off low #1, then what is coming in as a stronger go come around Nofember 10th - 11th again cut off low.

 

GEPS really keen on the strengthening with the Atlantic block again especially on attempt number 2

This is excellent for multiple reasons

It's always very exciting as the MJO phases transition into real life 500hpa setups

Using the JMA in November with phase 1 and connecting again into that GEPS chart

As discussed in prior posts these are including some of the most crucial areas through early November plus new patterns

Caribbean / CAG activities increasing which still needs VERY close eyes from the gulf and particularly Florida and Cuba

High builds through the far Southwest USA toward California 

Increasing precip ATMOSPHERIC RIVER(S)? Pacific Northwest 

Very important Arch of Blocking connects from Atlantic up across Greenland plus upstream east of Scandinavia 

Just found this which again is superb and indeed goes perfect  

 

Looking at the actual outputs on the JMA bearing in mind it's at the lower scale of resolution i like what it's showing 

As drawn in the MJO pattern above there will be an opportunity of tapping into a better pool of 850s conducive for wintry weather which should be located to the Northeast roughly

No better time to repost these

I've just seen the part saying ScBL which is Scandinavia Block 3 weeks beforehand ie the setup we've had for a number of weeks now 

We will be looking at the setup labelled c3-2

However the patterns which have occurred throughout October do equate to a great blend of nigh on all of the precursor setups

 

Setting our pieces into place at a relaxing pace ..

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4945222

[Cambrian]

12z GFS op has maritime, then polar maritime, then Arctic air masses for the UK and Ireland.

Day 1-3, the first low travels out of the United States, through Newfoundland to phase with Ciarán. T850s stay around +4 degrees.

 

Day 3-8, two successive lows, of colder origin, move out of the northern Canada lobe of the PV, down the Labrador coast to swing around the low to our northwest. T850s around zero. 

 

Day 8-12, a few days of attempted northward ridges in a standoff with the low heights to the north, lows continuing to be fed out from the Canadian lobe of the PV. T850s oscillating either side of zero. 

 

Day 12-16, the low to the south of Greenland pulls a good chunk of the Canadian lobe itself east through the UK and Ireland, then heights build well north in the North Atlantic and a long track northerly sets in. T850s -4 to -8.

 

Starts with a named storm and ends with a wintry blast - suitably autumnal and a great run for a howler of a November afternoon! 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4945871

[Mucka]

I see some posters have mentioned the potential for blocking toward mid month and I would go with that.

This mornings runs seem to affirm the suggestion we  have seen in various runs prior  for blocking to the N and/or E take hold 2nd week of Nov.

As always though it is very difficult know exactly what that will mean for the UK if it does set up in any meaningful way.

An Easterly flow of some form, at least for a while seems most likely but often the models put out Easterlies when they first sniff out blocking but ultimately have the blocking further W and more Northerly component. 

And of course wherever any blocking sets up just the orientation can make  the difference between cold or relatively mild.

 

GFS mean picking up potential Atlantic ridge day 7

UKMO day 7

 

So it looks as though a Sceuro ridge of some form will  stall the Atlantic trough and force it to dig S with the potential ridging behind.

It takes something exceptional to get proper Arctic cold to our shores in November so a long way to go, but of course we can dream of that record breaking late November cold spell.

 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4946796

[Cambrian]

A few reasons to be a bit more upbeat about the 0z ECM op:

Despite very little overt difference between day 3 and day 10…

 

… the pocket of heights to the north remains throughout, and is beginning to impose itself, pushing the low a bit further south and separating it from the Atlantic low.

Day 5 itself looks half decent! The day 5-10 animation shows the steady west to east progression of the next low after Ciarán, its remnants and the re-complexing. 

  

The next stage would likely see the low continue east into the Baltic, good potential for pulling us into a northeasterly and a reasonable prospect of some influence from all that cold air over Scandinavia, with the foundations to a Eurasian trough in the making and a useful looking schism in the PV running east-west from Siberia to the North Atlantic. 

Looking west, a bit more of a gap emerging after that as the next seaboard low is dropping south rather than moving east out of Newfoundland, it’s eastward movement being arrested by a combination of the northern wedge and Azores heights. It will be interesting to see how the development after that, pushing south through the Labrador Sea is handled. 

It’s increasingly looking for now like this early part of November is one of those situations when we’re looking for the potential for the gaps between systems to turn into something more substantial. In the meantime, a lot of very cold air lurking not at all too far to our north raises the interest during the gaps themselves.

Have a great day. 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4947627

[MattH]

The outlook period, through much of November, carries higher than usual confidence, especially for the week 3 and 4 period. We can link that prediction back to the ongoing developments within the tropics.

The key uncertainty over the last week or so has been where the MJO would emerge, or become more dominant this month. Through October it has been a feature within phases 8 and 1. As we continue to see the combination of +ENSO and +IOD in the tropics, in terms of +ve and -ve VP200 anoms the pattern remains very slow-moving indeed, with the continued subsidence over the Maritimes (phases 4-5-6), while the key areas of rising motion (-ve VP200 anoms) have been over the W Hem and also near the dateline.

It now looks as though the predictions for a more pronounced WWB will come to fruition this month and perhaps with some eastward movement as well. Not only will this aid in another rise in AAM, but will reinforce the oceanic and atmospheric Nino link. What it means is that for much of November, the MJO will often continue to reside in phases 7/8 and 1.

Despite little or no connection between the strat and trop vortices, it is the trop that is currently dominating with clear influence on the N Hem from the tropics. With the above in mind, then it is highly unlikely that the N Atlantic will see anything other than a more troughed pattern with a general dominance of further Atlantic lows for the foreseeable. Any sort of rising pressure will be short-lived, with temporary ridges and the chances of a 'full-blown' anticyclone over the British Isles or in a location that could bring early significant cold is highly unlikely as well.

Whether we are seeing the pattern now settling into the late autumn/early winter regime that is associated with a +NINO/+IOD combination, only time will tell. If, eventually, there is some connection as well between the strat and the trop vortices later in Nov then that really would reinforce the overall early winter expected pattern of something often 'mild, wet and windy' with any colder synoptics following deeper into winter, but that's more long-term than short-term.

The +IOD event, by the way, has now peaked, but its influences are likely to be felt for another 4 to 8 weeks, before a likely breakdown of the subsidence that dominates the E I/O and the Maritimes later in Dec onwards, I would imagine.

In essence, very much standard November patterns looking ahead, but do we really want cold, blocked November synoptics? - IMO the answer is, no...so steady away with typical late autumn weather for now.

Regards, Matt.

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4947991

[Cambrian]

A lot of discussion about a mobile setup for November, all fair enough when we look at today’s charts - not a good starting point!

 

But there is a tremendous difference at this time of year between a strong jet stream-driven mobility with systems crossing from coast to coast within 3 days, and a setup with inbuilt resistances, where they take 5-7 days to get across the ocean. The difference is felt here in better frequency and duration of welcome ridges that allow some drying out, and colder, clearer periods that give the weather a seasonal edge. 

Marked difference between Friday’s day 8’s and today’s day 6’s, the colder air hanging on for longer and a lot more mid Atlantic amplification than was expected only two days ago…

0z ECM ops (Friday / today)

 

…shows the Atlantic slowing down, the base of the trough getting stuck south of Labrador. The first stage of moving towards more interesting synoptics later in November…

…day 6 on the 0z ECM mean anomalies shows the first insertion of meaningful breaks in the trough and a flow that is somewhat more meridional, but it’s a long haul, the day 10 mean remains difficult viewing for now for people in the UK and Ireland looking for something drier. 

 

There are some better signs emerging by that stage though. The ribeye steak of the PV is central but tending to the Siberian side. There is a strong polar trough from it to the Bering Sea and it is elongated usefully towards Northern Europe, hinting at a greater probability of northerly episodes as we head towards late November. 

The 0z controls are at precisely that come day 15 / 16 - ECM control, GEM control. Aleutian low, west Canada ridge, central Canada trough. A long track northerly looking a good possibility, drawing cold air directly south off the pole as the Arctic grows substantially colder. 

  

If you compare this with where we are today, it’s thankfully a world apart, and as a direction of travel towards December, much more seasonally scenic than if we were travelling the other way.

Next few weeks, as winter approaches, I’ll be looking out firstly for a slowing in the mobility, then more breaks and a more meridional pattern, slow but sure west-east transit of the trough, while looking to see the PV get on the Siberian side and more elongated, just as the Arctic gets a lot colder!

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4948443

[Kirkcaldy Weather]

On 04/11/2023 at 16:42, Kirkcaldy Weather said:

So what new developments have and are occuring following on to my previous post?

 

Beginning at the here and now there are a few key zones as two main wave breaks occur

One sees a relatively weak but still very much present cut off low towards Baja this happens as our deep cyclone is present in Britain and the Floridian trough as mentioned 

By midweek we have the UK trough begin a slow weakening phase, this happens because there needs to be some form of activity toward Africa which ties to the MJO path recently. As a rossby wave begins to break in connection with our deep cyclone this creates a separation of energies and resultant cut off low heading into Morocco and the Western Sahara, We also see the trough and connecting Atmospheric river setup shift southwards through the western coastal America and a strengthening into cyclonic developments south of Greenland 

Pretty important synoptic evolutions as we get toward next weekend as we see new signs that the High in the southern end of the Atlantic starts a route into Southwest >>> Northeast alignment via further wave breaks now most probably through Scandinavia and further Northeast which trends show links to a strong Siberian High, Further downstream seems highly likely the west coast trough developments lead into new wave breaking with the Californian cut off low trend yet again showing. GEM somewhat slower however still aligning good

I see the PNA switching on both sides of positive and negative phases however this corresponding to that of a negative 

As I discussed its all occuring at a relaxing pace from my perspective and further nice linkage given phases 8 and 1 continue being prominent

Still a major focal area needs to be developments via the Central American Gyre and the trough signal across the Gulf States which you can see clearly in the above 

GFS 6z quite close to what I'd be expectant of evolving just a matter of timing really.

 

 

 

Long Post incoming by the end you'll possibly be casting a thought to "where did I put that snow shovel"

Patterns for November week 4 through the 1st week of Dec are emerging as the long awaited new MJO cycle[s] start.

This will be accompanied by some other influencing features however I'll begin with the extremely fun 500hpa patterns to emerge in 3.5 - 4 weeks approximately.

We first have to work out the exact route the MJO will be on through the remainder of November , you'll be aware I've been discussing us being on a relaxing pace with regard to the MJO this comes to the fore here, we know for certain we've moved into part of the indian ocean a la phase 2 which in its own right provides good insights to the aforementioned setups 

There are a few dynamics which can be noticed originating with a November phase 2 

Blocking increasing to the Northeast plus Scandi with north Atlantic cyclonic developments taking on a classic \ alignment with some scope of an associated link with trough from the Pacific Northwest and or California. 

Next we have the first part to figure out as this is where the models begin to come in with differing scenarios especiallyin regards with speed. It's fairly reasonable why the MJO is decreasing in amplitude as it attempts to get through to the eastern portion of the indian ocean which is currently being heavily influenced by the likely peak strength of this negative indian ocean dipole 

 

Very useful thoughts by Mr Roundy which is in line with the above 

 

Normally the progress should be in numerical order which we see with the EC and JMA

FOLLOW THE ENS MEAN ABOVE

We will start with this scenario as its the most reasonable 

Phase 3 

Close dynamics which begin in phase 2 and also note the separation from the elongating joined high from phase 8 

Phase 4

This sees retrogression begin to appear 

We'd be keeping close watch on a big cold pool setting in on the Eastern flank of the block 

Putting Ninò into the equation a few tweaks and it's a very wintry situation 

Phase 5

Cross polar high heights 

Deepening of North Atlantic cyclonic developments 

GOLD TIER NOVEMBER PHASE 6

Akin to classic Ninò responses for winter 

With the re emerging journeying across the Pacific this adds up as I'd be expecting some final typhoon signal to end the season. Last nights GFS was rather spectacular with dual major typhoon development which would lead on with eventual feedback upstream [possible blocking enhancing?] As we watched in October after Bolaven.

There's both of the setups I've covered in lots of recent postings the trough into Florida with further wave break cut off low development across California. There has also been a persisting signal between multiple models of high pressure building through the middle of USA centred possibly northern states Dakotas Iowa etc

Already exhibiting the influence of this MJO cycle lovely first trending on CFS 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4949042

[johnholmes]

Well it is now 5 days since I made any notes so let’s see how they look

Tuesday 7 November

NOAA 6-10 Looks almost a westerly through the whole chart, fairly minor trough down western states coast, westerly across n America, similar across the Atlantic after the rounded trough out of the Arctic down over ne Canada, and over the UK into Europe. Still the ridging out of n Norway that seems to have been there for quite a long time, waxing and waning you could say. A very small +ve signal still out of Spain but a westerly across Europe. Contour heights over central England show about 546 DM, quite a bit higher than the last time (5-6 days ago), when I noted them. So temperatures about normal other than the odd cold night under any clear skies. Weather-wise then still a bit on the changeable side but probably no major rainfall issues or problems with the wind. No major change showing in the 8-14 either.

Looking at ECMWF(13-17 inclusive)  and another broad overall westerly with minor troughs/ridges running through the flow; ? a more obvious trough/ridge perhaps setting up by 17th. But little upwind to suggest this doing any more than the previous days. Although the surface pattern does show more rises and falls in pressure working through the flow. Some sign of a more sizeable surface ridge developing north from Iberia perhaps? The 850 MB temperatures starting with the zero C north of Scotland and the +5C in the Channel. By the 16 th the zero C has moved way south and the 17th shows it starting to edge north again. So this supports the 500 mb NOAA heights that temperatures are, in most places, likely to be varying around the early November normal.

Climate Prediction Center - 8-14 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4949082

[minus10]

Yes a tale of the two high pressures and the Atlantic trough developing by day 10...

....key is where the highs lie..10 day ecm0z wants an Azores Scandi link up thus increasing the chances of more settled and cooler conditions with risk of frost and fog..

...whereas 10 day gfs0z is keeping the  two separate highs with the southerly one ensuring a milder and changeable (in the north west) regime ..

..ens both showing general rise in pressure around that period..

...It will come down to whether there is a link up of the two highs ...

..the gfs6z is closer to this..

...position of the jet and strength/orientation of Atlantic trough all important...

 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4949121

[Tamara]

A lot of talk continues about tropical forcing in isolation of the relationship between both the tropics and the extra tropics (as measured by the Global Wind Oscillation).  I auto-repeat so often that total global wind-flow has to be considered if one is to try to gauge how effectively (or otherwise) potential jet stream pattern changing catalysts might propagate through from the tropics to the extra tropics.

A long period of -ve PDO influence has kept reign on the extent that the current El Nino has impacted the atmospheric circulation. There is however no doubt that a tropical convection standing wave signal is rooted in the Pacific, redolent of El Nino, and which has continued to account for an active sub tropical jetstream penetrating across the Atlantic and associated widespread wind and rain high impacts across the greater parts of both north western, central and southern parts of Europe..

However, strongest rises in angular momentum tendency occur when MJO activity creates WWB in the Indian Ocean and these actually intensify as they propagate across the region, without erratic stumbles, to the area of greatest tropical convergence according to the ENSO standing wave. in simple terms, this refers currently to the Pacific. At present there is effectively a cut off along the tropics with WWB in the tropics isolated in the Pacific themselves.  Eastward propagation from upstream is truncated by convection suppression in the Eastern Indian Ocean and lack of widespread presence of eastward progressing WWB across the whole tropics mutes the most robust route to catalyst for downstream amplified poleward pattern change in the extra tropics..  Ergo, the extra tropics are not being subject to the greater potential for rises in angular momentum tendency as the strength of the WWB's in the Pacific might suggest in themselves.

A lot of the MET's on twitter (or X as it is now called) are highly MJO centric and without considering this relationship of both the tropics & extra tropical relationship as one integral forcing - so there is error risk in the calculations (on top of certain bias confirmation processes according to the various weather preferences of where one resides).

This is just one reason, on top of the effects of superimposed climate forcing, why I am more and more sceptical of the reliability of composite forecasting in this way with the over manipulation of them, and indeed over reliance on them.

Perming MJO composites based on a given phase blended with a given ENSO state is prone to error, because as this post tries to explain, the relationship between the tropics and extra tropics can be disconnected (to various degrees) from that base state. Much better to diagnose, by looking at both MJO & GWO budgets & checking the relationship of wind-flow propagation between them.

For some time now, the extra tropical GWO has been neutral or even weakly La Nin-esque negative - an evidential measure of the fact that angular momentum propagation from tropics to extra tropics is muted, as detailed in this post by explanation, and despite the distinct tropical convection signal in the Pacific. The GWO is a calculated measure of wind-flow propagation in both the tropics AND extra tropics, so more attention needs to be paid to its phase state evolution than just the MJO in isolation.

In synoptic terms, the fractured relationship between the tropics & extra tropics means that assumptions made about amplification pathways to influence the high latitudes and the tropopause layers just ahead of the incumbent stratospheric vortex winter, should not be prematurely & automatically expected to create conditions this thread in UK craves for. 

Much can change of course with time, but a greater rossby wave propagation harmony & maximised poleward propagation from tropics > extra tropics > polar field will lead to to this and its worth cautioning that this is not yet in complete harmony. Better to view the situation from a neutral position to observe this.

 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4949175

[Cambrian]

A chilly end to the week in store, with a cyclonic northerly in place for Friday into Saturday at day 2 on the 0z ECM ensemble mean, before clearing east to a good gap that looks like it could give us a pleasant, largely dry weekend, day 3. 

 

We’re seeing Atlantic low pressure systems slowing down, good gaps now appearing - also the lows are quickly filling as they head towards and pass over the UK and Ireland, rather than where we were just last week with them deepening rapidly on approach. 

Then there’s a concerted push of Iberian heights. A build of heights to the south often translates into a prolonged mild spell, particularly if those heights transfer east through the Mediterranean, supporting a Euro high. The UK and Ireland may in this case, however, remain periodically cyclonic and surprisingly quite chilly. 

The first wave of 590 dam heights moves north through Iberia around day 5, but there is little effect on the west / northwesterly sourced flow into the UK and Ireland, still working in at day 7 as the heights through Iberia relax a little. Another wave of heights further west over the Azores serves to force a ridge up through the Atlantic trough, which enhances the northwesterly flow.

 

By day 9, this second wave has reached Iberia and appears to be at the point of maximum influence further north with 560+ dam heights through  the UK and Ireland and the build of the surface high into southwest France squeezes our Atlantic flow around to a mean southwesterly, but critically, an upper trough down through Italy prevents a build of pressure further east over the continent, 

 

so that by day 10, the northward push of heights is subsiding again, as the Atlantic trough once again imposes itself, lining up another low for the UK and Ireland from the northwest. 

The day 8 det nicely shows the balance of the setup - the pocket of heights over Scandinavia and continued low heights over central Europe down into the eastern Mediterranean opening the door to real cold for eastern Europe while serving to steer low pressure systems to track through the UK and Ireland, 

 

in a corridor from south of Greenland to northern Italy, keeping it changeable and more seasonal than the usual take home message of Iberian heights might suggest.

But just as importantly for our longer term interests, also keeping us very much in the game for a surprise later in the month, either by just a slight southward adjustment of the corridor, or by a more organised build in heights to the northeast, both of which, of course, may be entirely consistent with each other.

Have a great day.

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4949634

[Kirkcaldy Weather]

Super positive patterns remain present as the official start of winter 2023 draws nearer 

i'll begin with how the Stratospheric Vortex is as we stand currently

Near record strength 

We see quite classic patterns arriving partly driven by said Vortex strength and combined to phases 3 and 7 [tho not exclusively] of MJO

Some of this feedback creates a high from the Pacific [Northern] into Alaska and Canada with evidence of this generating some Stratospheric warming in these zones and some with the above average area through Siberia

Cut off low toward California. Typhoon threat for Japan. Further intense wave breaks with resultant blocks across the Pacific and Atlantic which move into Greenland at least initially 

As perfect of a setup to begin winter with as can be

Keep trusting with the MJO working it's powers ️ plus other feedback

Anyone who feels inclined can see my first EVER winter outlook which i posted earlier in the week

On 24/09/2023 at 18:57, Kirkcaldy Weather said:

LOOKING INTO THE PATTERNS LINKED TO THE TOP 10 COLDEST MEAN TEMPERATURE VALUES 

composites only available back to 1948 

QBO AND SSW DATA ONLY AVAILABLE BACK TO 1958

ENSO data only dates to 1950

SCOTLAND WINTER RATINGS

• -0.32 1894 - 1895

• -0.06 1962 - 1963 

• 0.36 2009 / 2010 el nino

• 0.40 1978 - 1979

• 0.50 1946 / 1947

• 0.83 1940 - 1941

• 0.88 1950 / 1951

• 0.90 1976 - 1977 el nino

• 0.92 1939- 1940

• 1.05 1935 -  1936

years in the above which are listed as being EQBO

1963

1977-78

joining the above composites and pattern associations to this winters 

 

 

On 24/09/2023 at 22:32, Kirkcaldy Weather said:

WHITE CHRISMAS Stats and synoptic patterns

data I found listing all years 2021 back to 1959 which were classed as white christmases in at least part of the UK. BOLD REPRESENTS AN EL NINO CHRISTMAS

1961, 1962, 1963, 1964, 1965, 1966, 1968, 1970, 1972, 1976, 1978, 1980, 1981, 1984, 1985, 1986, 1988, 1990, 1993, 1994, 1995, 1996, 1999, 2000, 2001, 2004, 2009, 2010, 2014, 2015, 2016, 2017, 2021

1963 CHRISTMAS DAY  DECEMBER COMPLETE 

1965 dec  1965 christmas day 

1972 xmas day  December 1972 entire 

1976 christmas  DEC 

 2014 december xmas day

DEC 2015 I should also note the number of synchronicity to records set this year and 2015 has been present but definitely nowhere close to the number and close representation with years 2009, 2010 and 2012 to name a few as already shown in above posting. Plus checking QBO files the 2015>16 winter was a descending westerly 

 xmas day 2015 

 

I know there was 100% a white christmas in 2022 as an undercut of cold air turned the rain to snow from Northwest Scotland down to around Northwest England

"the Dickensian scene of widespread snow lying on the ground on Christmas Day is much rarer. There has only been a widespread covering of snow on the ground (where more than 40% of stations in the UK reported snow on the ground at 9 am) four times since 1960—in 1981, 1995, 2009 and 2010.”

Christmas Day 1981 December 1981 full month 

Christmas Day 1995 December 1995 entire monthly

2009 Monthly

 

2009  christmas day

2010 Entire DEC  Christmas Day 2010 

 

 

On 11/10/2023 at 22:16, Kirkcaldy Weather said:

Section 2 Kirkcaldy Weathers Official 2023 >>> 2024 Winter Outlook

Most synchronistic winter years connected with 2023 --- 2024

YEARS I BELIEVE ARE GREAT COMPARISONS FOR THIS YEAR 

BOLD ARE THE GREATEST SIMILAR FEATURES

 NUMBER 1 2009-2010. 2008/2009. 1976-1977, 2012-2013, 2010-2011. 1981-1982, 1962-63, 1967-1968, 1946--47

 

On 23/09/2023 at 22:59, Kirkcaldy Weather said:

Kirkcaldy Weathers Official 2023 >>> 2024 Winter Outlook

I'll be conducting this in separate sections which cover the most significant phenomena contributions into winter 2023/2024.

Section 1

ENSO WITH QBO + STRATOSPHERIC WARMING RELATIONSHIPS

Perfect timing as an updated and cleaner laid out format containing excellent info which factors in the above categories has been made by Amy Butler 

• 2023 has seen an increasing El Nino with major similar strength and peak C and time of peak as the 2009 event which rose to +1.7C and peak was around October and November
• The key combos for this coming winter then is Nino plus EQBO

Lets start with the years which contained the same formation as this coming winter Nino and EQBO WHICH FEATURED A SSW

1958/1959

DEC 

 

JANUARY

FEBRUARY

1965/66

This is a fascinating year listed as having dual SSW 

 

DEC 1965 8-Dec-65 16-Dec-65 18-Dec-65 16-Dec-65EE

FEB 1966 24-Feb-66 23-Feb-66 23-Feb-66 22-Feb-66EE

December

January

February

 

1968,69

 

December

jan

Feb

1968 (December):

One of the few 'WHITE CHRISTMASES' of the 20th century; heavy overnight SNOW in the Midlands and Wales had stopped by first light on Christmas morning, leaving a blanket of snow over a foot deep in the Welsh Marches and almost as much in the Cotswolds. SNOW was also reported further south. [ See my Christmas holiday files elsewhere on this site. ]

 1968/69 (Winter):

A notably COLD spell across the Denmark Strait / Iceland region (ICE reached north & east coastal Iceland by late winter - not known in recent/early 21st century years), coincided with the 'Cod War' between Iceland and the UK, when Iceland attempted to protect their fishing grounds from UK trawlers. Several British trawlers capsized due to superstructure ICING - which made the small ships unstable. A trawler support vessel [MV 'Miranda'] was stationed in the area, funded by the UK government, with an on-board meteorologist. [ At the time I was an Assistant in the Central Forecast Office, Bracknell - we had to plot special charts to support the forecasts for the fishing fleet and the Miranda. ]

 1969 (February):

On 7th February, 1969 the highest GUST (up to that time, beaten in 1989) at a low level station in Great Britain was recorded at Kirkwall in the Orkney's, 118 knots.
SEVERE BLIZZARD across the northern Isles, as a polar low slipping southeast across Britain on the 7th gave rise to exceptionally severe, near BLIZZARD conditions across the Midlands and East Anglia, along with parts of southern England.
On the 19th, south Devon was hit by a SEVERE GALE (easterly), causing considerable DAMAGE; at the same time, there was a good deal of DRIFTING SNOW over southern Britain.

1972 -- 1973

 

The Massive South Carolina Blizzard Of February 1973 Will Never Be Forgotten

WWW.ONLYINYOURSTATE.COM

---

The Blizzard of 1973 wreaked havoc on South Carolina's roadways and structures, causing untold millions in damage.

 

Dec

January

february

JAN 1977****9-Jan-77 9-Jan-77 9-Jan-77 EE

Dec 1976

January 1977

February 1977

1979/80

Dec 

January

FEB

FEB 1980 29-Feb-80 29-Feb-80 29-Feb-80 29-Feb-80 29-Feb-80 29-Feb-80EE

 

On 08/11/2023 at 16:45, Kirkcaldy Weather said:

Kirkcaldy Weather's Winter 2023--->24 Full summary ️🌨

I expect to see both rainfall and particularly Snowfall records at high risk of being broken given the water vapour a residual effect from Hunga Tonga still at incredibly significant amounts at nigh on all stratospheric height levels, interesting that a previous similar trend of that was there during 2012---13

I sent the following to @Mike Poole in DMs all the way in May

Amazingly and I'm extremely happy seeing the latest SST output supporting this with that Warm Cold Warm like anomaly which I believe was active in 2010

OK let's see the style I'm expectant of evolving through December January and February

Starting with the progress of the El Ninò event we see this is at the stage of peak strength from October into January 

There is just the one region which is likely to see at least some warming from here on in which is the 3.4 zone

OK let's look at the scenarios heading into Winter, taking some of the monthly data 

December 

First we need to look at patterns currently in play and my views on how December develops.

I believe a key area continues being the strong high across the Pacific through Alaska 

In the next few weeks we should see low pressure toward Greenland with high pressure still highly active over the area above 

However once influences from the emerging cycle of MJO from the Indian Ocean to Pacific develop within future pattern evolution I believe a switching will begin 

Can already watch the Ninò begin to show and as January comes in the atypical Ninò 500hpa sets in 

Combined to teleconnective influence of the MJO,PNA AND NAO this will feed in strengthening Blocking whilst the Ninò Jet leads to an elongating Atlantic trough 

I expect January through a significant amount of February really sees the above increase 

 

The setup I see being dominant especially from Jan onward

 

Hope everyone enjoys reading my views, certainly seems I picked a cracking winter for my first EVER go at a winter outlook 🗯

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4950577

[Mike Poole]

There’s an awful lot of uncertainty in the ensembles at the moment, here’s the spread on the EPS at T240:

The whole of the ‘left’ side of the NH seemingly up for grabs.  Here’s the clusters at T192-T240:

There certainly could be an Atlantic ridge or Greenland ridge (clusters 1 and 2), but many other possibilities.  Skipping to T360, and the clusters look like this:

You’d hardly credit that these were run from (approximately) the same starting point, they are so different!  All four border colours represented.  But there are some very interesting individual members in the mix by T360:

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4950602

[Cambrian]

Interesting trend over the last few days on the ECM extended range regimes towards a much stronger Atlantic ridge signal - charts from 8th, 9th and yesterday, albeit in the context of a still dominant NAO+ signal. It’s worth noting that the ‘flip’ happened as close as day 7, with the progressive slowing of the Atlantic that we’ve been watching across the models.

  

It wouldn’t be a surprise if this becomes a more prevalent and enduring signal over the next few days.

The 0z EPS 500 chart clearly shows the ridging in the heights contours over mid-Atlantic at day 10, with the UK and Ireland in a developing northerly on the cold side of a trough extending from northern Scandinavia to the North Sea. 

The EPS is slower than the ops and controls in clearing the ex-Iberian heights out through the Mediterranean, here at day 15, but the cold trough to the northeast, that is underpinning the more spectacular solutions of today’s control runs in particular, is very much a feature.

The trough might actually be easing back a bit further west between days 10 and 15 and if that’s the case, rather cold and cyclonic could well be the order of the day for the UK and Ireland during week 2. 

The positive anomalous heights between Greenland and Iceland remain, with a ridge still in evidence there in the contours - it’s likely that it is this emerging signal that is supporting the enhanced showing of the Atlantic ridge in the extended range regimes forecasts.

If this is the setup that we’re heading towards, it supports the idea of it continuing changeable but become increasingly colder as we move towards the end of the month, with more Arctic air more regularly in the mix.

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4950361

[TSNWK]

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4950583

[Cambrian]

The models have been working up to this, teasing with signals, for a fair few weeks. However, it is today’s 0z ECM that is the most indicative yet for getting notably cold air into the UK and Ireland. 

We’ve spoken a lot of late about the stubborn heights to the north, all those wedges, but their sister has been the resilient upper trough from Arctic Siberia to Scandinavia, which though it has undermined the prospects of development of a Scandinavian high, has been the backbone of the delivery of some very cold air into Scandinavia. As this trough deepens, it opens up opportunities for moving the cold air further southwest towards the UK and Ireland.

The day 8 ensemble mean is a telling chart in this regard. A surface low at the base of the trough bringing the flow to the north around to the northeast. The mean anomaly chart for day 9 holds the trough in place. 

 

The det at day 10 has the makings of quite a sharp cold spell as the trough extends southwestward towards Spain and the western Mediterranean. 

  

There’s also a potentially very useful low pressure system over the Azores, propping up the Atlantic high and a pocket of heights over Svalbard, linking back to a surface high over the Kara Sea. 

The Baltic trough supports a surface low in Central Europe. If it sets up like this, it might prove to be very slow moving from there.

It is intermittent, but there is a signal for Atlantic ridging showing now  from day 3 to day 12 on the latest ECM extended range regimes forecast, which are based on yesterday’s 12z runs. This signal has emerged over the last few days, 8th vs. 11th here. Plenty more surprises to come.

 

It’s always such a somber time of the year, getting darker as it does by the day. Following the charts, particularly this November, has been a great solace. Have a great day.

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4950647