nick sussex

NOAA criticized both the GFS 00 and 06hrs runs as out of sync with the rest by next Monday. Additionally given teleconnections the GFS seems to be ejecting the eastern CONUS troughing too quickly. They do expect troughing to last there till at least next Thursday supported by high pressure near Baja California. This doesn't mean we can expect any miracles but the ejection of the troughing does effect the downstream pattern. You'll note the UKMO at T144hrs looks like holding the troughing there for longer.

Although theres not that much excitement on offer for most of the UK upto T144hrs. For northern Scotland theres the chance for something wintry. Several shortwaves run east in the UKMO and theres colder air just to the north there so one of these might engage that and bring some snow more especially to higher ground. Its finely balanced especially with these shortwaves which the models are having a hard time pinning down.

The UKMO at T120hrs isn't that bad but then implodes at T144hrs. The GFS goes from hero to zero in 12hrs. The models are still making a drama over the shortwaves and so although the towel is being readied I wouldn't throw it in just yet. We best wait till tonights ECM run.

I think the chances of the GFS 06hrs run verifying are low against the ECM and UKMO which resolutely want to phase energy to the nw of the UK at T144hrs. I’d be shocked if anything like the GFS 00hrs run made a return given even the 06hrs has latched onto more shortwave issues in the Atlantic. Anyway as ever us coldies will keep hoping for a last gasp miracle which needs to start tonight. Because of the complex behaviour of shortwaves and timing issues as to when phasing takes place there might still be some room for changes but best to lower expectations for the timebeing .

On one hand great to see this GFS run develop some festive spirit but it’s really up against the ECM and tomorrow mornings viewing will be from behind the sofa!

Not a bad GFS 18 hrs run so far and quite a bit different from the ECM horror show. Heights building strongly towards sw Greenland and shortwave energy aligned more favourably to the west .

In a nutshell the ECM delivers one phasing tragedy after another. That bulge you see sw of Iceland at T120rs is waiting to engage energy from the ne You either want no initial shortwave ejection and for that to become completely absorbed in the next upstream low or for it to eject early like the UKMO which gives you a chance . The ECM does neither and leaves the worst halfway house. The GFS although delivering some interest eventually is really not to be trusted because it’s evolution is so fragile with shortwave energy flying all over the place .

What drama! I don’t want to open Pandora’s box with the issue of data coverage in some key areas but this can be a factor . You can read that from the horses mouth and tonight’s NOAA extended discussion. They mention upper energy in data sparse regions north of Alaska and Russia and they do sometimes allude to data problems in previous discussions I’ve read . The issue we’re seeing is the exact orientation of blocking and height seepage , that’s my new term for this winter ! Lol As I mentioned earlier today we want the blocking boxed in and not allowed to seep towards Canada because this then puts less forcing on energy in the Atlantic . Effectively we want the main block to remain as far east as possible so to avoid the dreaded west neg NAO.

Still too much uncertainty in the models to throw the towel in for some colder weather. The situation is finely balanced because the UK is at the weak end of the blocking , this often means low pressure will want to head ne from the sw at that point. And if you’re on the wrong side of that you’re in the milder air which is what we’ve seen shown in quite a few outputs At present it looks like it’s a close but no cigar outcome but I think we’d need a few more runs to see whether the block might get edged further east . Upstream we want to see the high boxed in and not allowed to seep heights into Canada , that way we see more forcing on the pattern in the Atlantic .

As much as I'd like to find a few positive crumbs in tonights outputs I think the prognosis for a decent spell of colder weather isn't looking good. The big problem is the block is too far west and not orientated favourably with low pressure deepening to the sw as it engages energy from the ne. Of the 3 the GFS is by far the worst in terms of salvageable by T120hrs the games up as the shortwave is much further north than the ECM/UKMO. The UKMO is the pick of the big 3 with a stronger block and less energy to the ne with the shortwave cutting ese towards the Low Countries. The ECM at least cuts the shortwave east further south than the GFS but then we see it hit the buffers after that. We're still waiting to see what the UKMO at T168hrs shows but the only feasible way to see an improvement in the outputs is to see some energy from this shortwave circled to disrupt quickly towards Iberia this means your engagement point as the energy heads sw from the ne is further se.

OMG why GFS! Here a parcel of low heights run sw from near Iceland which the helps to energize the low to the sw. I think the issue continues to be the core of heights being too far west, the eastern end of the block is like swimming with sharks. This run continues to ferment my absolute disgust for west based negative NAOs. Vile, useless waste of blocking. Wheres the brandy!

Think of that shortwave running into the UK from T120hrs as the Millenium Falcon trying to escape the Death Star with secret plans to deliver some cold to the UK! The Death Star tractor beam is that trail of energy to the Millenium Falcon. Once the MF can escape and detach itself it can deliver the plan. That nose of high pressure just mentioned by SM is the tractor beam about to be disengaged. We need the shortwave to escape the tractor beam as early as possible run into the UK and then allow ridging to the north to exert pressure sw wards.

Overall some possible interest moving forward but its one of those set ups that's finely balanced. The ECM is actually more progressive with low pressure over the US at T168hrs but then salvages the situation by holding troughing over ne Canada and this shoots off a couple of shortwaves in towards the UK. Theres not a great depth of cold though at this stage, its possible with a few tweaks northern areas in particular could see a shortwave run se into some colder air so a chance there for something wintry. Indeed the one that pops up earlier at T144hrs could produce something on its northern flank, if its a shallow feature this would help and much depends on the track, currently it looks a bit too far north but a southwards correction could bring some interest to Scotland higher ground.

Hard to have too much faith in this ECM run given its a complete departure from its 00hrs run. Although its following a similar GFS trend the matter of needing two shortwaves to decide if they're going to behave should give cause for concern for coldies. We really need a southwards correction in the outputs as everything is too finely balanced.

Its like a drama that never ends. Now the GFS after not delivering with the first shortwave now manages to fall over the line with the second one but that's well out past the more reliable timeframe and given whats happened over the last few days I'd refrain from ordering the ear muffs and ice scraper! The UKMO having been the least interested looks a bit better at T144hrs with an important gap in energy and detachment between the second shortwave upstream and the one over the UK. In this set up your shortwave is in a sense your marker in terms of either increases or decreasing chances for cold, the further south this crosses the UK the better chance.

It’s a bit of a mess this morning with a game of model musical chairs . The UKMO is an improvement at T144hrs with a more favourable looking shortwave to the west. The GFS again has problems ejecting the upstream shortwave cleanly and this now becomes absorbed by the main low which isn’t good. The ECM has now moved a little towards the GFS/UKMO , it’s not as sharp upstream and is now thinking of ejecting a shortwave at T144hrs. Overall still no resolution as to what to expect, the ECM at least doesn’t deliver the dreaded west based negative NAO. The key time frame is around T144hrs to T168hrs , if that falls kindly then a decent spell of colder weather is possible, but it’s trying to overcome those shortwave problems that’s turned into a big hurdle.

Some good news there for us downstream in Europe from US forecasters at NOAA. This is from New York state for next Friday to Sunday, I've picked out the bits more pertinent to us in terms of the downstream pattern: "Before we get to the day to day specifics...its worth pointing out that the preferred guidance for this time frame is the ECMWF. The GFS has been notably faster than other packages for several runs now...and this fact has not been lost with the modeling experts at the Weather Prediction Center...who also favor a blend of ECMWF solutions for this period. As we open this period on Friday...the aforementioned energy crossing the Intermountain west will encourage a broad downstream ridge to amplify somewhat over the Lower Great Lakes." So at least some positives that the ECM is preferred upstream, the amplification of that ridge should help to sharpen up the troughing ahead of it which does help us. The differences upstream start appearing quite early with the ECM and UKMO disagreeing at T96hrs, this has a huge impact moving forward. To put some detail on this take a look at the different views of shortwave energy off the eastern seaboard of the USA. ECM UKMO

No PV over east Canada or Greenland and the weather Gods managed to dish up this tripe on the GFS 18 hrs run. This is more disappointing than my last look at the weighing scales !

The shortwave you see running towards the UK needs to separate more quickly from the parent low upstream. The longer it keeps a train of energy back to that the worse the outcome because you need it get a move on to allow ridging to the north to force the pattern further south . The next low moving in needs to disrupt if you’re to salvage the situation but another problem is the main height rise to the north is towards west Greenland. Positively this doesn’t support the UKMO but you can see here how this run could easily have gone completely pear shaped given the issues with shortwave energy to the west .

What just last year it’s been the same since I can remember ! Lol The UKMO sucks big time , if that verifies I’ll be hitting the bottle ! It looks like a west based negative NAO which I detest even more than the limpet Azores high! Anyway let’s keep the faith , the UKMO has been woeful all week and has been late to the party although at this stage we’re not sure which is the correct one, the ECM or the GFS. I see you’re new in here so welcome to NW and if you like cold weather and snow you’re in the right place with lots of fellow coldies.

Actually having seen the UKMO T168hrs chart I’m going to go further than my original it’s crud comment regarding the T144hrs , it’s utterly vile and needs to never darken this thread again !

I'd be more worried about the UKMO if its recent performance was good. It has in the past though dealt a blow to hopes so of course we'd like to see it move either to the ECM or GFS. I'd prefer the ECM because that won't have coldies nerves shredded! The high at day ten shouldn't sink which means we could see a decent spell of colder weather.

The sinking high is in relation to the earlier timeframe at T144hrs. If the upstream trough is going to eject a shortwave towards the UK then you want the high flattened, then you rely on height rises near Iceland and south Greenland to develop. If the ECM is correct you want that trough upstream to amplify and not eject a shortwave towards the UK. You don't want a middle ground solution as that looks something like the crud delivered by the UKMO.

Yes a less traumatic route to something colder without a shortwave drama. We need either this or the GFS solution. We don't want a middle ground solution so either the clean more amplified troughing upstream at the key timeframe like the ECM or a quick sinking of the high and shortwave running se per the GFS.

The ECM now planning a different route! Different handling of upstream trough energy which leaves us none the wiser this evening as to whats going to happen.