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Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks
Posted

Sun 19 Jan 2025 and another look at the 500 mb anomaly charts

Looking at the 6-10 500 anomaly shows the very strong flow from nw America round the main trough and towards the UK, also on the 8-14 shows no sign over the last 4+days of decreasing. There remains some degree of divergence in the flow around 20W so deep lows close to nw UK or indeed clipping the northern half Scotland seem probable over the next

 7-10 days in my view.

The Met raw shows a sharpening upper trough in its 144-168 hour charts with similar heights on the charts to 6-10 day . It and NOAA both show that air arriving over western UK originates quite well north over Alaska and northern Russia. So on the cold side at 500mb.

A fairly disturbed spell of weather seems likely. Both GFS and ECMWF take both main storms well into northern Scandinavia. The 6-10 and the 8-14 NOAA keep the +ve heights and ridging so which model will end up with a more accurate handle remains to be seen.

I’m assuming that the 2nd deepening low shown off Newfoundland as the second storm.

image.thumb.png.ef53bf94708e93097b982e51f862482a.pngimage.thumb.png.4effc2f637587c94796b1ee58e7d0346.png


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5226296
  • Like 1
Posted
  • Location: Nuneaton,Warks. 128m asl
  • Weather Preferences: Snow then clear and frosty.
  • Location: Nuneaton,Warks. 128m asl
Posted

 Daydream Boy

Mobile indeed

If GFS is anywhere near to what will happen i counted 5 lows coming across the Atlantic,counting a possible secondary low,within 10 days.

It all kicks off Thurs into Friday.

overview_20250119_12_114.jpg

That would be a notable stormy spell by any standards,hopefully with time we see successive lows trending further north ,but in this volatile pattern who can forecast that.

One other event of note is over on the southern states,around the gulf coast

image.thumb.png.272ff2ae9adf330a35839166e5f822e4.png

snow modeled right on the doorstep of the Caribbean,rarely we see that.


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5226388
Posted
  • Location: West Yorkshire
  • Location: West Yorkshire
Posted

 Mcconnor8 

The wind out to sea is insane on the first storm, not sure I've seen one quite that strong before. A max of 170km/h (106mph) sustained, which is 106mph. Gusts to 226km/h (140mph).

To put that in context, the sustained winds out to sea are equivalent to a high-end Category 2 hurricane! Fortunately it weakens on approach and isn't a direct hit for the UK.

image.thumb.png.c31c08def1a6a485577cf2da9a3ca121.pngimage.thumb.png.8e44820800df3032ef942e42e13e5cad.png

The second one has a max of 140km/h (87mph) sustained, a mid to high end Category 1 equivalent. Gusts to 183km/h (114mph).

image.thumb.png.1488ba253b48880125415dffe5b155f6.pngimage.thumb.png.d4fc8e1d52ed0ae3281a236e95e65f71.png

Of course, impacts from the second are higher, with higher gusts inland if it came off, simply because it passes closer to the UK. The first storm generates stronger winds though.

Just to be clear - if ever comparing wind speeds between our storms and hurricanes, it is the sustained winds that should be compared, though even there it's not an exact science, so the above comparisons are just a rough guide.

A storm of the sort of strength we see on the first set of charts above is definitely the sort of thing you want to see turning out to sea. We can marvel at it meteorologically, but I don't think anybody would want to be directly impacted by the worst of it!

 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5226433
  • Like 1
Posted
  • Location: Ski Amade / Pongau Region. Sometimes UK
  • Weather Preferences: Northeasterly Blizzard and sub zero temperatures.
  • Location: Ski Amade / Pongau Region. Sometimes UK
Posted

 Cold Winter Night  GFS control run showing this build of pressure to start Feb. Some of the smaller Euro Central European models in their longer term outputs have been indicating for a few days now a strong North Russian High for early Feb. Some of the outputs have shown extreme heights of 1070mb  over Northern Scandinavia. Good to see one of the Super Global models now lending some support in its longer term outputs. However, that is still a long way off . If it were to verify, would be a remarkably swing to the other end of the pressure spectrum from what is about to be delivered by the end of this coming week across The British Isles.

C

GFSC00EU12_384_1.png


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5226452
  • Like 1
Posted
  • Location: West Yorkshire
  • Location: West Yorkshire
Posted

For a bit of a longer term look, here are the EC clusters.

Days 3-4

Low pressure moving in initially from the Azores.

image.thumb.png.ded27160ffcc7eb7a5625a92de6fadfb.png

Days 5-7

Cluster 1 (25%) has a deep low running right through the UK at day 5, then remaining generally unsettled. Another deep low possibly a threat at day 7.

Cluster 2 (24%) swings the first deep low further north, grazing Ireland and Scotland. Remaining generally unsettled thereafter, with a deep low off to the south-west by day 7.

Cluster 3 (16%) has more of a direct hit with the low at day 5, but makes less of the next one at day 7.

Cluster 4 (16%) also grazes Ireland and Scotland with the day 5 low. Deep low pressure to the west at day 7.

Cluster 5 (10%) is a near miss with the day 5 low, but the second low at day 7 is a potential threat to our south-west.

Cluster 6 (10%) is also a near miss with the day 5 low, again a potential threat at day 7 from a deep low to the west.

The OP was in Cluster 1.

image.thumb.png.9d710a602de06f0152178644731d4949.png

Days 8-10

Cluster 1 (63%) tracks another deep low through the UK at day 8 with stormy conditions, then more generally unsettled to day 10.

Cluster 2 (20%) is a near miss with the worst of any stormy conditions at day 8. A west-east split for conditions - mildest and wettest further west, drier but somewhat cooler with a continental flow to the east.

Cluster 3 (18%) is somewhere in between. Deep low pressure affecting Scotland, and then a generally unsettled pattern to day 10.

The OP was in Cluster 1.

image.thumb.png.f9c7044f8d9393f88b1eaa9e596d6bc1.png

Days 11-15

Cluster 1 (69%) starts with low pressure over the UK at day 11. Fairly cold but quiet conditions at day 13 with a mid-latitude high, then more of a west-east split  (milder and more unsettled in the west, drier and colder in the east) by day 15.

Cluster 2 (31%) has low pressure to the north and high pressure to the south. A long-fetch westerly or south-westerly. Mild and unsettled.

image.thumb.png.a5613e21e3a9cbcb2abd10bbc90a398a.png

Summary

A very disturbed period of weather coming up generally in the North Atlantic. The final outcome remains uncertain for now, so it is best to talk probabilities.

The first period of interest is at day 5, with roughly a 20/40/40 split. 20% of the ensemble is a near miss, a very deep low missing most of the UK. 40% is a grazing hit, most impacts for Scotland, Ireland, and some exposed western coasts of England and Wales. 40% is more of a direct hit, which would be a significant and notable storm if it verified. Beyond that, a generally wet and windy pattern up to day 7, fairly mild but not overly so.

Beyond that, at day 8 another potential deep low threatens the UK. This time, a rough 20/20/60 split (near miss / grazing hit / direct hit). Once more, this could bring the risk of impactful weather with stormy conditions. More generally, an unsettled pattern is favoured to continue beyond that up to day 10.

In the extended range, there are signs that high pressure may play more of a role. The clear majority cluster develops a mid-latitude high, which would bring at least a brief quieter period. However, a minority cluster develops the high further south, which would be much milder and remain unsettled.

No sign of any significant cold, the main interest for the next 10 days will be the risk of stormy weather.


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5226470
Posted
  • Location: Buckinghamshire
  • Location: Buckinghamshire
Posted

I would take more notice of the UKMO on this storm for Friday, more especially with the centre track once it's to the northwest of Ireland, the GFS is very likely just too far east for Scotland, on a bigger scale these differences are small but ofcourse locally it makes the difference between damaging/possibly destructive winds and your more typical windy/very windy spell.

Ofcourse very strong winds will probably be in northwest areas and parts of Ireland from a brush past, but the worst probably stays just about away, but despite this being most likely, ofcourse this may not be correct and we could see something more significant just less likely.

The central belt of Scotland would get some particularly strong winds according to the GFS.

gustmph_20250120_06_105.thumb.jpg.70d5476044e41335f49120b38b96a208.jpg

The GFS is often quite poor with modelling many inland gusts especially those a fair way from coasts, they tend to be upto 10-15mph lower more widely inland, particularly with a gradually weakening storm/low pressure system, it's localised inland spots that can reach them, coastal spots are closer to the projections and in some isolated locations exceed it. Ofcourse the GFS being a global model won't be able to necessarily pick out smaller land details/interaction that realistically alter wind patterns and that's partly the reason for it.

So when the GFS in this case blankets a swathe of inland areas with 70-80mph gusts, the reality in a weakening system/ windfield will most likely be..

55-65mph widely inland, locally 70mph especially/most likely inland areas relatively close to the coast within say 50 miles from where the wind is coming from with a more limited land interaction and providing it's not an overly sheltered location. Exposed coastal spots 70-80mph, possible isolated 80+mph.

In a strengthening system/windfield, something a little more closely towards the modelled gusts would prove more accurate more often.. GFS modelling 70-80mph gusts widely inland..

Reality would probably be.. Inland 60-70mph, locally 70+mph especially again those inland areas relatively close to the coast within say 50 miles from where the wind is coming from with more limited land interaction, exposed coastal spots 75-85mph locally 90mph.

This ofcourse isn't always the case, In uncommon instances especially particularly severe systems/very rapidly developing systems, the inland speeds can widely exceed the GFS and more definitively in coastal spots.

Most of the models including to a generally lesser extent high res models have a similar overestimate problem with less intense windfields and a similar thing can usually generally be applied but the high Res models are usually at least a bit better, especially with picking out those isolated peaks that occur.

So in summary..

Models generally do better modelling inland gusts with a strengthening low pressure system, in those cases, gusts usually more closely match projections and in some cases inland can exceed them, especially with intense storms, exposed coastal spots can exceed them more often, as similarly mentioned above.

So in other words the stronger the storm the better the models will tend to be with the expected winds.

There is more of a widespread snow risk with the GFS from this storm on Friday, but I would be cautious with it.

overview_20250120_06_090.thumb.jpg.64ae09a07a5955dfb0b2ee1d0fb3b677.jpg

overview_20250120_06_093.thumb.jpg.3f124fcf26848a1690abe370b9e8a4f9.jpg

overview_20250120_06_096.thumb.jpg.003ca5d5a4691215d518954bf2557a7c.jpg

The wraparound also gives more wintry precipitation into western Scotland.

overview_20250120_06_108.thumb.jpg.9a0d98c50e4627f7e2976d48dce7d33e.jpg

A little disturbance behind it brings some more snow in the north.

overview_20250120_06_117.thumb.jpg.1eb214811bf80ec02d21aa00467a6c45.jpg

overview_20250120_06_120.thumb.jpg.bad4a66c8906676f2bedd5667ddbfb94.jpg

overview_20250120_06_126.thumb.jpg.482246c5fdd9fa795c6bcf748436e4f8.jpg

The Icon also has the smaller feature..

06_117_ukpreciptype.thumb.png.4c1721e41e6f8d9f500dc0e9b5bccd56.png

Icon closer* to most likely track/intensity and any snow extent than the GFS with the storm.

06_93_ukpreciptype.thumb.png.479ba0ad3e6cb6117b34c9216362d736.png

06_96_ukpreciptype.thumb.png.894a7924b9d7f05f87fdc67a50cf45d3.png

06_102_ukpreciptype.webp.thumb.png.fa9f38dd62a5d7e5e6ab7f892e225b72.png

06_105_ukwindvector_gust.thumb.webp.3a5a0a2138ff269b0cc2081855e016d4.webp

but even this model seems just a bit too far east with the very strongest wind placement in the west of Scotland/western Isles, those are ferocious, 80-90mph for the western Isles. Despite being less likely, it is a reasonable worst case scenario.

Here's the mean wind speed in knots from the Icon.. highest is 68 knots which is (78mph) so hurricane force offshore.

sfcwind_mslp.uk(3).thumb.png.8bdcae548aa4a9d96a3cce41835ba177.png

sfcwind_mslp.uk(2).thumb.png.58672f48bd6152678591a77b39ae2bb8.png

Gusts are 123mph offshore..

Friday's storm..

Most likely:

The worst most powerful winds missing just to the west/northwest but not by much, very strong winds for western Isles, western Scotland /northwest Ireland and possibly northern Ireland, northern Scotland, in fact very much like the UK met office warning that I've just had a look at with gusts of atleast 50-60mph locally 70-80mph along those western/northwestern coastal spots there and you wouldn't rule a isolated coastal spots seeing a tad more in the far northwest corner. 🙂

Less likely: worst of the winds from this fierce storm brushing western Isles/possibly northwest Ireland too with gusts inland of 70-85mph, isolated slightly more in coastal spots.

Least likely but still something to consider just in case, storm centre over central Scotland strongest winds further southeast, much more of the UK away from the south at risk of damaging winds of 60-80mph.

And @Mcconnor8

If the low pressure system on Monday is weaker* and/or more complex (disorganised/ lopsided centre) then probably expect a more southerly track as that lopsided centre could govern a track differing from the dominant flow, a stronger/more compact storm will generally most likely be further northwest and that is most likely for now, the very unsettled weather is going to be more widespread through the first half of next week I suspect though anyway and that's been highlighted for some time, with one or two stormy spells quite likely either close by or in the northwest especially, but very windy at times elsewhere with heavy rain at times, wintriness in precipitation in the north more-so on higher ground a continued possibility.

We do need to watch for potential lows spawning along frontal systems, I noticed a couple of people earlier also highlighted this, that is what would increase the chance if they occured of a brief more southerly stormy spell for England and Wales, and this would also give a higher risk of snow in the north on the peripheral north/northwest of the precipitation, especially the higher ground. 🙂

Anyway..

29+ January onwards into early days of February the outlook spoke about a few days ago remains largely the same with conditions remaining somewhat unsettled in the northwest in particular but an even stronger trend for generally drier and less unsettled / more settled conditions to move over southern/southeastern half of the UK, with higher pressure to our south/southeast for a time, there is perhaps increased chance once again (from previous lowering of confidence) on a tendency for heights to build again to our east by this point or shortly after, so slow moving frontal systems in the northwest could be more problematic as we sit in a relatively mild air mass by this point perhaps.

GFS also gives some indication of this, though I suspect too far north with frontal systems, ofcourse this is a long way out so it could change, though I'm sure by much.

EUROPE_OVERVIEW_348_MOB.thumb.jpg.70d0712454029c09f3b0d82d571667ba.jpg

EUROPE_OVERVIEW_366_MOB(1).thumb.jpg.98a0006634e59dd18bf4cf147abf9361.jpg

The GEFS mean representation more realistic..

mslp_20250120_06_336.thumb.jpg.7b60560e13b4edc4c52b8a1a3438f94d.jpg

Though doesn't pick out those heights rising to our east atm. But it's not certain that will occur for now.

Those possible renewed height rises to our east are what I thought could potentially allow the jet stream to dive southeast over more of Europe favouring slightly colder conditions by the start of February but that is unlikely and has been that way since my thinking at one or two occasions several days ago.


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5226691
Posted
  • Location: West Yorkshire
  • Location: West Yorkshire
Posted

Here are tonight's EC clusters.

Days 3-4

Deep low pressure close to the UK by day 4. Cluster 1 (35%) has the system further NW, Cluster 2 (35%) is a little further east with slightly greater impacts. Cluster 3 (29%) looks like a reasonable worst-case, with a particularly tightly wound low.

image.thumb.png.2269feee275b61c916adc4ef38cc9e05.png

Days 5-7

Cluster 1 (41%) remains unsettled, and swings a second very deep and potentially stormy area of low pressure close to the west of the UK at day 7.

Cluster 2 (37%) has a further east and/or faster progression, with the low directly over the UK. Potentially quite a severe storm.

Cluster 3 (22%) has the low further to the west of the UK at day 7, this is either a near-miss or a slower progression.

The OP was in Cluster 1.

image.thumb.png.32417e5c71efa22eab408e347b6bd247.png

Days 8-10

Cluster 1 (27%) remains generally unsettled, with another deep low NW of the UK at day 10, though possibly more of a near-miss.

Cluster 2 (22%) remains unsettled at days 8 and 9, then a bit more equivocal by day 10, with no real signal.

Cluster 3 (20%) is unsettled throughout, with a threat from a further deep low at day 10.

Cluster 4 (18%) is generally unsettled, but no threat from deep lows, so just wet and windy.

Cluster 5 (14%) is generally unsettled. Perhaps a bit colder than some other options with slight height rises in the Atlantic, a hint of a north-westerly at times. Some near misses from storms but no direct impacts in this timeframe.

 

image.thumb.png.ad3af9349bf5c72eba140c17daf3c6f6.png

Days 11-15

Cluster 1 (65%) builds heights to the south, still low pressure to the north. A N/S split for conditions, driest in the south. Mild everywhere, perhaps very mild at times.

Cluster 2 (35%) stalls low pressure to the west at day 11. Remaining mild but settling down with ridging from the Azores through the UK at day 13. Colder by day 15 with more of a continental flow from the south-east, and the mild feed from the Azores cut off. Still not that cold though with that wind direction.

image.thumb.png.122f2adf8f150ae3aed6dac17a48730f.png

Summary

Still nothing from a cold perspective. Up to day 10, the low pressure just keeps on coming. At least one storm very likely later this week, and potential for further direct impacts (though of course not guaranteed) at both days 5-7 and days 8-10. Regardless of further storm impacts, remaining unsettled to day 10.

In the extended range, some sign of things settling down a little, with the Atlantic train slowing down, allowing some height rises. Very little sign of anything conducive for cold though. Similar conditions to the next couple of days would be likely - fairly cold and damp conditions with not much wintriness involved, even if we do get the mid-latitude high. The more likely option on Cluster 1 needs no further commentary.

Overall, storm interest goes on for a while yet. For significant cold, the rest of January is almost certainly a write-off.


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5227004
  • Like 1
Posted
  • Location: Irlam
  • Location: Irlam
Posted

Keep an eye on any little features that may appear in the chilly flow following the storm.  They could give surprise snowfalls for some parts.

GFS 0z  has one over NI  and one over the far SE

image.thumb.png.f62755f954e2eabdb62808d33a74a45f.png

12z and 18z across the Midlands

image.thumb.png.d1a312507287b0d6d0bb2dda602639b0.pngimage.thumb.png.bc1a0bf5f7d66053dace425958098b7f.png


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5227159
  • Like 1
Posted
  • Location: Caldercruix, North Lanarkshire - 188m asl
  • Location: Caldercruix, North Lanarkshire - 188m asl
Posted

 Penrith Snow I agree broadly with what you're getting at however February 2021 was not muted. There were some extremely low minima and in terms of snowfall, I had my biggest 48 hour accumulation of my life, and many places in the east had significant snow that lasted the week due to the extremely low temperatures that followed the intial snow: 

Screenshot_20250121_122459_Gallery.thumb.jpg.8a8887b17847212860c0edfe7011bee7.jpg

Screenshot_20250121_123054_Gallery.thumb.jpg.d1930cdc3c9b10918873efedd95ae8e7.jpg

Screenshot_20250121_122920_Gallery.thumb.jpg.9c1045936b0164bd28177705376a4897.jpg

Screenshot_20250121_122856_Gallery.thumb.jpg.3c29d25eddb480c4fb391960636bedbb.jpg

Screenshot_20250121_122944_Gallery.thumb.jpg.c3e6e1ba6438f20f281dd4dbed21bfce.jpg

What was more muted I'd say was the synoptics for it. It wasn't you're classic powerhouse easterly and indeed the majority of Europe was under low pressure. 

To bring some relevance back to the post, the above snow unfolded between the 8th and 9th of February.

The MJO is being mentioned often enough again however if you take February 2021 as the example, it sat in the COD having dropped into it from low amplitude phase 4 until 21st of January before emerging into a mid amplitude phase 6 at this point and meandered in phase 6 right up til the event started. Phase 7 was not entered until the event was under way and phases 8 and 1 were never in the frame:

Screenshot_20250121_124552_SamsungInternet.thumb.jpg.e24c4f0a2a4704e52f59043223cd4a6d.jpg

 

Looking at the BOM forecast moving forward from now, we're projected to be mid amplitude phase 6 in around 11 days time. There is tentative signs of another rise in pressure over northern Europe in the extended and an emerging potential wave 2 pattern. I would be reluctant to throw the towel in for February just yet. 

Screenshot_20250121_125657_Samsung Internet.jpg


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5227379
  • Like 1
Posted
  • Location: Buckinghamshire
  • Location: Buckinghamshire
Posted

Late post tonight but here's the GFS 18z ensemble mean on wind gusts for Friday's storm, not to take too literally ofcourse.

sfcgust-mean-met_uk.thumb.png.55dfb663c90d9d935be11c7f4abc09b8.png

sfcgust-mean-met.uk(1).thumb.png.8993e83bf543d92721fe76116cfa0b3e.png

sfcgust-mean-met.uk(2).thumb.png.0a320651ddae288e08b7f6c0793f6172.png

 

Now the ensemble mean track/central pressure along with it's ensemble members on the charts below, the red pressure reading is the ensemble mean and the smaller number and placements of them are where other members have the centre for that particular timeframe with slightly different intensity with the pressure..

They are generally deeper than the 12z, with a stronger storm.

12z

sfcmslp-meanmem_uk.thumb.png.1c064c26c305352fe1f235994b6903ad.png

sfcmslp-meanmem.uk(1).thumb.png.b9ba7d930bb808177f965bbb62c9919e.png

sfcmslp-meanmem.uk(2).thumb.png.bceb41b9a8fac74fb5cbf98328ea4e4f.png

Now the updated 18z.. pretty vicious system

sfcmslp-meanmem.uk(3).thumb.png.7fb61930ff974e0cf40d1b64f8a6d6b8.png

sfcmslp-meanmem.uk(4).thumb.png.85aa1798cff4f51d0f48768a5613f061.png

sfcmslp-meanmem.uk(5).thumb.png.ddb82cbe8148d40def3d67f183246881.png

The central track of the mean aligns quite closely with what my thoughts have been since Monday afternoon with it going northeast just to the west then northwest of Republic of Ireland through western mainland of Scotland then into northern Scotland. Monday morning and the preceding few days before my thoughts where a track 100 or so miles further west/northwest with the worst just staying offshore, that's ofcourse not going to happen.

Variations exist ofcourse amongst the ensemble as you can see with depth and the exact track but not too much now, a lessening of the strongest winds by the time it reaches north/northeast Scotland is the consistency albeit it's very gradual weakening.

Here's the Jetstream below, it is the GEFS mean so may not exact.., but you can see an intensification for the timeframe the storm arrives, this is what could cause the storm to deepen later and as it first arrives instead of notably further southwest weakening before a hit, more likely it will develop and peak just very shortly before it hits then very gradually weaken whilst it's crossing northeast through parts of Scotland, (a slight strengthening of the windfield may occur over the northern isles with 70-80mph possible there).

Speed in (Knots)

300wh-mean.uk(2).thumb.png.6c97c9d7e16a108c1db42baa6acf4649.png

300wh-mean.uk(3).thumb.png.fe1e1df109b07ebe495a74e99a9e5416.png

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300wh-mean.uk(5).thumb.png.021f8de439e8415cc3a05aa9eab010a5.png

Even with the later development, this doesn't necessarily equate to more severe winds overall necessarily ofcourse as other models that develop it earlier although weaken the windfield on the southern/southwestern side of the storm after initial extreme development to our southwest still show much stronger winds impacting Ireland compared to others that develop it slightly later, the modelled gusts look to more closely match for when they effect Ireland, the gusts shown vary slightly depending on what model you view but that's expected for 2 days out.

However despite the above,this Jetstream profile and the fact the storm develops so close is important to bare in mind when looking at the wind gust prediction I give below as there is the smaller risk of even stronger winds in the worst effected areas.

There isn't too much difference now between the models overall but enough still present that it does make a difference to how strong and potentially damaging the winds may be in certain areas of the north of England for example and western Scotland with the most of any uncertainty in these two regions but they do look to be not quite as badly effected as some other places.

Most likely scenario re winds I think.. the strongest winds from this powerful storm move into western parts of the republic of Ireland then spread northeast through northern Ireland then into central, southern Scotland with severe gales or storm force winds inland for western Ireland with gusts reaching between 70-80mph for a time, but possibly locally 85mph too, with isolated 90mph possible in the most exposed location most likely along the immediate coast there. Wind direction ↗️ ➡️↘️

Western and especially northern Scotland, most likely inland gusts of 55-65mph, locally a bit more perhaps in exposed places, but the less likely risk remains of 70-80mph in western Scotland/western Isles if the track either shifts a little further northwest or the swathe of winds are slightly more in reality when the centre reaches the north of Scotland but again that isn't as likely.. wind direction ↗️➡️↘️

Central belt of Scotland, southern Scotland/northern Ireland, severe gales with 60-70mph gusts widely inland, locally slightly more than 70mph inland possible, particularly closer to the coast, and especially on immediate exposed coastal spots where they could get close to 80mph in or two spots. Wind direction ↗️➡️↘️

For northern England and possibly north Wales, very strong winds with gales, quite widely inland gusts of between 45-60mph, upto around 65mph locally inland possible, but particularly the Pennines and exposed west facing exposed coasts which would be northwest coast of England, possibly northwest coast of Wales where they could be close 70mph, the far north of northern England, might see comparable gusts to the above mentioned southern Scotland.

The lesser potential is there for 60-70mph widely inland in many areas of northern England/north Wales), with 75mph for the Pennines/ exposed west facing coasts which as just mentioned would be northwest coast of England and northwest coasts of Wales. Wind direction ↗️➡️↘️ so potentially disruptive and in some places perhaps damaging for those areas, these two regions are as I mentioned one of the places with most uncertainty with even the most likely outcome above possibly changing to the slightly lesser likely outcome so keep an eye on met office warnings.

South/southeastward of here so for the Midlands and further south, gusts markedly lower but still strong with widely gusts of 35-50mph, though locally slightly more is possible in a few inland spots, but more particularly on the exposed south/southwest coast where they may reach upto 55-60mph, the strongest winds in these areas from the frontal band of rain moving through which will be quite heavy for a time in places and will be heavy quite widely across the UK.

A spell of snow, some of it quite heavy on higher ground for possibly parts of northern Ireland, perhaps briefly northern half of the republic of Ireland, some spots of northern England, briefly perhaps the tops of the hills for north Wales and especially more widely into Scotland, where there could be a more significant amount of snow probably on higher ground mainly.

Here's the GEFS mean accumulated snow depth for the higher ground, assuming a rain to snow ratio of 1mm equating to 1cm of snow.

sn10_acc-mean-met.uk(1).thumb.png.b30d4a893f5ecda4d424033a1d1a103d.png

Ofcourse the details may change a bit/meaning slight changes in potential wind strength but this shouldn't be too far off.

Regarding the low pressure system possible this upcoming Sunday, remember when I mentioned on Monday morning about the ECM AI showing a southerly tracking primary low pressure over the centre of the UK may be due to it getting 'confused' with the possibility of development of a secondary low spawning off the frontal system further south of the parent low which was most likely expected to be further northwest? 

Well the GFS does show that a secondary low pressure develops to the south/southwest of the main low, swinging northwards as it reaches the UK..

EUROPE_OVERVIEW_114_MOB(1).thumb.jpg.a35f2a37fa76b20a2d81a6ed950923d1.jpg

EUROPE_OVERVIEW_144_MOB(3).thumb.jpg.5ad7605cdbab924175dd419012146d06.jpg

EUROPE_GUST_144_MOB(2).thumb.jpg.a59590af44ce4328181a15d977497e46.jpg

admittedly shows a more southern primary low than thought for now but it's still shows the point well.. but it's not certain that will even occur as it was low risk a couple of days ago, but certainly possible, the main low may look like the current GFS but I suspect it will be just slightly north by the time the day comes round, probably not stormy over the UK from this, but more typical wet and windy weather, with most of the development more likely over the Atlantic before filling somewhat close to/over the UK (could ofcourse change)

secondary lows if they do develop along the frontal band of rain or entirely separate but merging will be a tad more potent with heavier rain and slightly stronger winds moving in from the south/southwest, pattern looks to stagnate a little more by then with slight height rise to our southeast evident at this point perhaps.

 

But back to the shorter term, a powerful storm that is likely to cause some damage and disruption for quite a few it looks like, especially for republic of Ireland which wouldn't suprise me if they issue a red warning for western half of there if this certainty of a dangerous storm continues. For the UK the potential for Amber warnings for parts of northern UK , northern Ireland at greatest risk it seems, but also central/southern Scotland, we'll see what tomorrow brings with any updates as that's not certain.

Take care everyone and stay safe, will update if any changes, I understand many don't like windstorms for understandable reasons because no one enjoys the problems and damage that come along with them, so I do understand that some may not like it and hopefully any damage and disruption can be minimised 🙂 but for those that do enjoy a powerful storm and are in the risk areas, then enjoy the power of nature safely and don't feel bad for doing so!  💨🍃🙂

Goodnight 💤 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5227898
Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl
Posted

 LRD Expectations from here need to be kept very low if it is cold that is being hoped for. The end of the cold spell recently was never going to lead to another quickly - all the drivers that provide background context for potential height rises to our north were pointing in the opposite direction despite what NWP suggested regarding heights rising over Scandy, and they will generally continue to point in the wrong direction for the rest of the season as far as I am concerned.

The one small window that might open is the second half of February when we would expect to see some favourable lagged forcing from the next cycle of the MJO through the Maritimes and out into the Pacific. It is, however, going to be operating against a vortex that looks odds on to be in roaringly strong form and an embedded context where the near continent is mild. And we know that CC has strengthened sub tropical high pressure tendency, so keeping the Azores High or Euro High from being dominant is less and less easy. And Nina winters tend to be mild second halves. But hope springs eternal, and it is the case that the November and January cold phases we have had were delivered from a context that was not loaded cold on the probability dice....so possibilities always remain. 

In the meantime knuckle down for an extended phase of westerly, windy, wet and probably average/mild most of the time. 

 

 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5227239
Posted
  • Location: Lincolnshire - 15m asl
  • Weather Preferences: Frost and snow. A quiet autumn day is also good.
  • Location: Lincolnshire - 15m asl
Posted

 bluearmy Think it is unlikely this season. We aren't seeing such a preponderance of high pressure over central Europe, the azores ridge setting up further west, and therefore much depends on wave 1 activity driven more from the pacific side. I'm seeing a strong vortex from here that lasts the winter, a generally mobile February perhaps benign for the South at times with perhaps a chance of some transient blocking further north in the last third of February - last hurrah for winter hopes? - and then a March which for once will see Spring arrive on time, or maybe early. 

With the impacts of global climate change in full swing, and CO2 increasing at record speed - with a cooling stratosphere enhancing vortex strength generally - I continue to think that the best chance for the UK to experience a really sustained spell of seasonal winter cold lies with a shattered and split vortex ala 2018. That year it all happened a bit too late to be absolutely perfect, but it demonstrated that deep cold can still reach our shores if we can negate the driving force of westerly vortex-driven winter winds. We will get cold from atlantic wave breaking events and Greenland or Scandy blocks pulling air in from the N or NE, but the source of this air is now much warmer than it used to be, and our oceans keep us balmy and the azores high or euro high are generally further north and more dominant than in the 20th century. For proper deep, midwinter cold we need a vortex split in late December very early January with a swift downwelling and a total depowering of the westerly regime. By its very nature this is a rare sort of event, and so deep midwinter cold of the 1980s style is going to be very infrequent. And it wont be this year.

Bar needs setting much lower. +NAO broadly from here. Later in Feb for that last gasp hope of something white to lower levels.


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5229598
Posted
  • Location: Central Wales 250m (820ft) ASL
  • Weather Preferences: All
  • Location: Central Wales 250m (820ft) ASL
Posted

Though particularly intense, more signs that the wild burst from the Atlantic looks like it will be a relatively short one, though there is very little signal for another cold spell any time soon.

6z GFS ensembles for Belmullet, County Mayo, in the northwest of Ireland, show the exceptional overland barometric pressure that storm Eowyn will bring, around 950mb. It will be lower still over Achill, the Mullet peninsula and parts of Donegal. Monday’s storm is currently modelled in the 960’s for Belmullet town. These are very deep depressions to be experiencing one after the other in such a short timeframe.

IMG_4853.thumb.png.b62c5c8fa84f71b64d6b261fe7d733ac.png IMG_4852.thumb.png.246e1a22722dd9d71b516fef462a82cc.png

This contrasts with Birmingham, where the second storm will be deeper despite a similar track to Eowyn. Potential for greater impacts further south and east with Monday’s storm. 

Both charts show a steady rise in pressure thereafter, to around 1020mb for Erris and around 1028mb for central England. These are decently strong signals on the mean.

0z EPS is happy with this, firming up on the beginning of the heights rise around day 8, compared with yesterday’s 0z for day 9 (left), with a bigger build north of the Azores. This has been a growing feature of recent days. 

IMG_4841.thumb.jpeg.591ba43436511fc83197666013face88.jpeg IMG_4842.thumb.jpeg.a11732c28c25d17b49f703e7954a2658.jpeg

EPS at day 10 shows the continuation of the build before it begins to wane around day 12 as the North Atlantic trough regathers. There’s no real scope for a sustained build in high pressure in an advantageous location for cold to the UK and Ireland from these charts at the current time.

IMG_4846.thumb.jpeg.7f79d3f8564121aeaf01c4d1cc844e71.jpeg IMG_4847.thumb.jpeg.b160c236579ebf966fc52095098e8c49.jpeg

The PV is anchored to the Labrador Sea and heights remain consistently firm through continental Europe, so the UK and Ireland probably not escaping the return of a more active zonal flow later in week 2, the GFS ensemble means perhaps picking up on the beginning of a falling back in pressure, particularly further south where it has built more. 

Wintry interest for the time being is restricted to back edge events and cold sector features in the back-sweep of passing systems, like these on the 6z GFS op.

IMG_4849.thumb.png.b5b854a6405577ed6ab7d417f164ace8.png IMG_4850.thumb.png.1411751462e7d22ff0f666fed45f81e2.png

Persistent positive NAO index from the GEFS combined with a blocking signal from the ECM, but especially one in fairly good balance with NAO+ members, smacks of waxing and waning Greenland-Iceland low / Euro high for the foreseeable. 

IMG_4851.thumb.png.0d9302547af0f794b5a022618270108e.png IMG_4848.thumb.png.f5fdeb9e363463b17ab05c30565d9f32.png

The beginnings of a signal for an Atlantic ridge later on the ECM46 signal for later in February is worth watching to see if it gains firmer footing.

In the nearer term, after experiencing at first hand the severe disruption and danger of storm Darragh earlier in the winter - these storms are harrowing - my thoughts are with so many good friends in the west of Ireland, a beautiful part of the world for which it appears that Eowyn will be truly exceptional. 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5229515
  • Like 1
Posted
  • Location: Southern England
  • Weather Preferences: Sun, snow, storms etc.
  • Location: Southern England
Posted

Struggling to understand the fatalistic longer-term murmurings amongst some on here, particularly this morning. The medium range outlook really isn’t looking that bad atm - and it’s certainly far from settled. These are the NH 500mb height anomaly flowcharts for days 7-10 on the midnight suite. ECMWF & GFS Operationals have a split jet stream that gradually reforms in a way that these models have a flat westerly flow. Euro High & Siberian High keep their distance as well. GEM in contrast has these two linking up, and the low to our south is fully cut off, the mild southwesterlies are to our north and it’d be colder and drier. There is a clear path available to a potential Scandinavian Blocking High in that evolution.

IMG_4761.thumb.jpeg.28937b897d9f0093c340362b3cbdacd7.jpeg
 
Then I look at the far from overwhelming ensemble support for the GFS & ECMWF

IMG_4763.thumb.jpeg.7a66665e86c00304e24231933432fcb6.jpegIMG_4764.thumb.jpeg.f7cc21956b0b363f8c1776c29a2c887b.jpeg

The GEFS mean has the two highs combining over days 8-9, so most evolutions are settling us all down overall, not just the south. But what about the ECMWF ensembles? 

IMG_4765.thumb.jpeg.e9e794188528ea8067daeab1162797ae.jpegIMG_4766.thumb.jpeg.791b2acf213ccf85bc140a566a39318c.jpeg

Well, there are 2 clusters of zonal-based weather. There are 13 (including the ECMWF Operational & Control) in the drier & milder one, and 8 in the unsettled & cooler option. There are another 2 clusters (again 13 and 8 perturbations) with properly settled weather & likely surface cold - maybe even upper air cold into the southeast on the 13-member scenario. There’s also 9 that are cool and unsettled with an ongoing split jet scenario. There’s a virtual 50-50 split in the ensembles as to where we go in two weeks’ time between zonality vs other options. It’s 15 vs 11 in favour of the cooler & wetter scenario this time with the zonal camp. It’s 14 vs 11 in favour of the Scandinavian Blocking High taking over in the alternative options camp - as opposed to a UK-centred high.

So looking at this, I’d say the direction we go in is wide open - in relation to temperature and precipitation alike (although the south is mainly dry with most ensemble members). GEM had ICON & UKMO Operational backup earlier as well, so personally I would be looking for a drier and colder first week to February. It is one of the weather’s classic periods of climatological stability - look back at the reanalysis and the weather regime is often on the move to or from higher pressure. Northerly & easterly outbreaks are also fairly frequent. I’ll conclude with the ECMWF day 10 Operational contours (faint dashed lines & two low centres), cluster mean contours (thick black lines & black text for labelling), and standard distribution (coloured fill). It looks like the ECMWF has limited support for its very flat profile. Note too how the biggest MSLP uncertainty area is greatest to our northeast. It’s too early to be calling anything.

IMG_4767.thumb.jpeg.0c77e2b1995602d50b9a1895b40980d7.jpeg


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5229889
Posted
  • Location: West Yorkshire
  • Location: West Yorkshire
Posted

EC clusters below.

Days 3-4

After Eowyn, another potential storm approaches by Sunday or Monday.

image.thumb.png.810542a7a22eb12ad81baeabbb5a30ec.png

Days 5-7

Cluster 1 (53%) builds a mid-Atlantic ridge. A short-lived cold snap from the north-west or north before it topples into the UK. Generally unsettled.

Cluster 2 (27%) fails to build any ridge at all, remaining mild and westerly.

Cluster 3 (20%) is somewhere in between Cluster 1 and Cluster 2. A ridge does build but it topples more quickly than in Cluster 1, perhaps only the briefest of cold snaps.

The OP was in Cluster 1.

image.thumb.png.aab0203a0664314e381faa126266367b.png

Days 8-10

Cluster 1 (27%) ridges high pressure in from the south very strongly from Iberia through the UK and across much of Europe. Mild and dry.

Cluster 2 (24%) has high pressure ridging slightly further north. More of a mid-latitude high. Winds from the south-east, fairly cold but dry.

Cluster 3 (22%) has high pressure to the north of the UK. Winds from the east. Potentially cold, though the coldest air may be blocked by another high further east.

Cluster 4 (18%) has the UK under the centre of a large area of high pressure. Non-descript and dry.

Cluster 5 (10%) maintains a more unsettled pattern from the west or north-west. Potentially quite stormy again at day 8.

The OP was in Cluster 4.

image.thumb.png.0720d7dce177c7e980f46b9c31376e7e.png

Days 11-15

Cluster 1 (27%) has high pressure to the north. Cold with winds from the east.

Cluster 2 (24%) has fairly weak signals close to the UK. Very mixed conditions. 

Cluster 3 (16%) has winds from the south-east initially, fairly cold and dry. Becoming more of a UK high by day 15.

Cluster 4 (16%) has a mainly westerly pattern and fairly unsettled, varying from south-westerly to north-westerly.

Cluster 5 (12%) is mild at day 11 with high pressure to the south, then a cold snap from the NW or N with a mid-Atlantic ridge.

Cluster 6 (6%) has a UK high at first, fairly non-descript. Eventually it ridges further north, allowing the wind direction to switch to the north-east.

image.thumb.png.0f4cdc48c26b245613f16100c289b632.png

Summary

Overall, after a strongly zonal period up to around day 7, increasing signs of a change thereafter.

At days 8-10, the vast majority of the ensemble has much more high pressure influence. The key question is where. At this timeframe it doesn't look too conducive for cold, with some mild high pressure setups, and some mid-latitude highs, with a low chance of any high-latitude blocking.

However, beyond day 10, perhaps the first signs of at least some interest in the models. I count two good easterly clusters (Cluster 1 and Cluster 6), and one decent northerly cluster (Cluster 5). Between them, perhaps about 40% of the ensemble offers a chance. The rest of it looks much less promising, though.

Far from guaranteed of course, but perhaps a chance that in the next few days we might at least see a few more promising OP runs. We will need quite a lot longer though before it comes into anything approaching the reliable timeframe.

Not enough to really pique my interest yet, would want to see a much stronger signal. But enough to be worth keeping an eye on.

 

 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5230156
  • Insightful 1
Posted
  • Location: st albans
  • Location: st albans
Posted

My optimism is growing for 2 weeks time.  I’m encouraged by the fact that we appear to be in a good place to get low heights into the med. at the least we could well avoid high heights to our south. 
 

The stamps look pretty decent hemispherically with lots of amplification but the again, they did around 7/10 days ago for day 15 and that hasn’t verified. 
 

One step at a time - hopefully the next couple days of ens don’t remove this amplification in week 2 and the chances of a proper cold ‘easterly’ flow. 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5230456
  • Like 2
Posted
  • Location: Manchester Deansgate. Elevation : Garbage
  • Weather Preferences: Heavy disruptive snowfall.
  • Location: Manchester Deansgate. Elevation : Garbage
Posted
  • Location: Central Wales 250m (820ft) ASL
  • Weather Preferences: All
  • Location: Central Wales 250m (820ft) ASL
Posted

A profound turnabout on the way as the Arctic oscillation (GEFS) drops sharply over the next week, and the jet stream abruptly weakens.

IMG_4857.thumb.png.037a1a710e62b836b1990afcdc073851.png

12z ECM op raises the pressure 55mb over three days between day 5 and 8.

IMG_4862.thumb.png.403fdae212c9b864ae46cdafa28cdb43.png IMG_4863.thumb.png.7106bf0cd1cd9b6124a4a79378c0d645.png

However, by day 10, as on the GFS op, the high struggles to get far enough north and west to advect cold west into the UK and Ireland.

IMG_4864.thumb.png.44dc93b366a124b489a5723cf3f16651.png IMG_4865.thumb.png.e290a05224e473691e11a557d18e1f66.png

There is though some support from the 12z GEFS at day 10 for more northward potential, especially compared to yesterday’s at day 11 (left). 

IMG_4860.thumb.jpeg.e488cf649b8b3e2907a4c8294f45fbfb.jpeg IMG_4861.thumb.jpeg.88f6e8354c5cf1e242cf84e4f7e97a94.jpeg

The contours show an upper level ridge building into southern Scandinavia and there are positive heights appearing further north and west through Svalbard and across the pole, despite a firming up of the Siberian lobe of the PV, so the amplification is being driven more by the Atlantic trough digging deeper towards the Azores.

It’s notable too that the trough is pushed back further east at the northern end over Greenland and has lost its positive tilt. The Atlantic is much closer to being more meaningfully stalled with this profile. These creeping trends can often prove to be of material significance down the line.

12z EPS at day 10 with similar ridge and build north. Not so stalled with more energy going over the top. On the flip side, it maintains better propping up by the low heights over southern Iberia. Again, a stronger ridge than yesterday’s chart for day 11 (left) and the pattern backing up west.

IMG_4867.thumb.jpeg.e1ba1678f5eb5dac17ffdc6a59b909e2.jpeg IMG_4866.thumb.jpeg.3ef69c37ccf5718a80894cf129848f0e.jpeg

So perhaps we either get better scope for a more durable UK and Ireland high with ultimately more opportunity for building a surface cold pool (EPS) or a pop at a firmer build north through Scandinavia (GEFS), with a proper continental feed.

A long way off for now, but these are modest though interesting trends at a good timeframe for further enhancement and provide a lot more scope and options than the charts of recent days.


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5231997
Posted
  • Location: st albans
  • Location: st albans
Posted

Those of you becoming interested in events very high up - it remains trop led. so with some very amplified NH solutions on offer across some ops and also ens we are going to see some v interesting strat charts.  But being trop led, they don’t hold the same value as would usually be the case. 
 

until we can get to a point where we see that amplified pattern set within a week, it’s not worth over analysis of the upper strat.   The question as to whether a reversal wave would head down quickly is a good one.  I’d suspect the answer is yes but depending on whether an ssw was split or displaced that may not be of much value to us. (re existing trop pattern) 

 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5232303
  • Like 1
Posted
  • Location: Central Wales 250m (820ft) ASL
  • Weather Preferences: All
  • Location: Central Wales 250m (820ft) ASL
Posted

Though there are clearly some very interesting indications at times, not only is a SSW on current modelling not that likely overall, at this stage of the winter looking forward to several weeks before it might happen, it might be a bit of a red herring in any case in terms of potential for a cold spell. 

Firstly, it’s difficult for me to set too much store in the ECM46 10hPa zonal wind charts heralding anything of note regarding an SSW at this juncture, including:

IMG_4868.thumb.png.2da9b446877901dd1842c616e3eb96a8.png

1 This massing of outliers at the lower end has happened more than once already this winter, only to disappear in the outputs very quickly. (This is similar to the signals in the later stages of the GFS ops - there for a few runs but overall, can equally seemingly be a case of “now you see it, now you don’t”.)

2 The drop in the mean is 4 weeks away and by then, it’s getting late in the season.

3 Like the previous occasions we saw this trend, there is a similar number of members in the upper tenth percentiles as in the lower tenth.

 

Then the (in less kindly put words) “Strat split? So what” points:

1 At the best of times, SSWs always have a “hit and miss” relationship with subsequent cold spells in NW Europe. This year, there are sensible grounds for a tad more scepticism than usual that a good linkage would ensue.

2 The trop has in any case been acting as two halves for most of the winter with the separation frequently running well up into the strat - up to 50mb or higher. In effect, we might well have had our “SSW effects” in instalments throughout the winter, with a lot of the cold spillage already over the North American continent. Compared with previous years, there isn’t near as much usable deep Arctic cold to break out of the high Arctic. 

0z EPS T850 anomaly at day 15.

IMG_4873.thumb.jpeg.fb79a90efc6ba3bc5d6039ad609716d6.jpeg

3 The strat and trop have coupled only briefly throughout the whole season. At week 4, it appears that they will again be uncoupled, with a re-stretching of the trop PV, from week 1 to week 4 

IMG_4869.thumb.webp.a688c84109af07c987354b5504fbbd98.webp IMG_4870.thumb.webp.96267ce2ff2c978ec9ae063fcfb3c605.webp IMG_4871.thumb.webp.d81c43f5bafa9c1b3caaded5b38b8fc0.webp

By then, the strat core PV is around Svalbard with a warming near Alaska. We had one very similar to this a few weeks ago at the same time as the zonal wind charts showed some outliers, starting over eastern Siberia and working around to Alaska. 

That indeed appears to be the overriding feature of this winter - a stretched PV with a “disconnect” between the strat and trop, with the trop invariably “leading” the strat. Brief bursts of zonal flow before a resumption of solid mid-latitude blocking.

I took it upon myself to learn some more about it this year, but I admit to still being on a very steep learning curve in the strat area - some of you guys are brilliant and I really enjoy your posts - and though I still have an open mind on this year, to me however this just doesn’t fit with the typical ingredients for a big cold hit from a SSW - we just haven’t seen several weeks of unfettered zonal flow with massing of Arctic cold. The elastic band has never got stretched enough to truly look like snapping.

I’ve read of the massive downwellings that can happen that actually flush cold air down from the strat, but I’m continually struck by the staggering warmth of the Arctic troposphere this winter. It looks like there would be much dilution before it reaches us in the mid latitudes. 

Moreover, despite keenly keeping an eye on equally waxing and waning potential for sympathetic orientation of high pressure, I think that the most likely setup for a further cold spell will be more in keeping with the previous cold spells this winter, when the Arctic fluxing allows the dominant lobe of the PV to move back through the pole and we get lower heights through Europe, perhaps but not necessarily in concert with the favourable phases of the MJO

As would be expected, not much sign of this in the models as yet, though the second half of February is still set well to bring plenty of scope for one more good cold spell. 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5232442
Posted
  • Location: Southern England
  • Weather Preferences: Sun, snow, storms etc.
  • Location: Southern England
Posted

IMG_6617.thumb.gif.ebe9111a8354ebc276cc5f560e47288d.gifIMG_6616.thumb.gif.e3520acffe4cd9662d8653d8fb4369ec.gif

If this trend accelerates it could be the saviour of our late-winter period. It’s well-known how La Niña often causes a milder and wetter spell in mid-to-late winter - particularly when central-based as opposed to eastern-based. Well, the trend over recent weeks has been a warming one - with the eastern portion already above average as a result. If we can shake off the La Niña signature quickly, it could help with winding down the Atlantic & improving the MJO situation. The SOI being reflective of El Niño-like atmospheric conditions is shown by negative numbers, which we had through most of our January cold spell. It’s been positive since then - I think it’s another index that needs a closer eye than it sometimes gets. 


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5232947
Posted
  • Location: Peterborough N.Cambridgeshire
  • Location: Peterborough N.Cambridgeshire
Posted

Well a big change in the model output compared with yesterday's 0Zs which I thought were dreadful. Seems the E,ly via a Scandi high cannot be ruled out. 

When I looked at the ensembles yesterday I noticed huge uncertainty relatively early on. Well this is down to the usual suspect called a shortwave and it depends  if it tracks SE and how far E this goes before tracking SE. A simple way of describing this is if the shortwave tracks SE into Scandinavia and then Germany/Poland it's going to be marginal if the developing Scandi HP thereafter can extend towards the UK. This might occur eventually but no guarantees. Now if this shortwave tracked SE much earlier i.e UK into France then a much better chance of the following developing Scandi HP to reach our shores.

We are far away from me being excited yet. Firstly I want to see if this shortwave tracks SE and where, secondly if a Scandi HP does develop then how it orientates itself is important. The ideal situation is a Scandi HP being aligned N-S before rotating E-W. This ensures a pool of colder air from the Arctic is established prior to bringing the E,ly this way.

Many hurdles to jump and im not sure if we can join the race yet?


Original post: https://community.netweather.tv/topic/101097-mid-winter-forecast-and-model-discussion-commentary/?do=findComment&comment=5233007
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