nick sussex

No the ECM is garbage, I don’t care what it shows past T168hrs. It’s also taken the PV further east because the troughing is given a tow by the upstream calamity . Its now going to tease but I’m past caring !

Game over sadly , as soon as that shortwave energy phased to the nw and amplifies at T96 hrs the effect is to bloat the high over the UK ahead of it. We want that shortwave energy to the sw to remain flat. So FI begins at T96 hrs , one output is going to look very silly tomorrow.

My mood is about to hit the buffers , the ECM at T96 hours throwing another curveball into the mix. It will take a miracle to retrieve the situation now with a phasing from hell and a poor T120hrs chart. You want the high over the UK flattened its of no use now , any ridge has to build from the nw over the low.

The reason for my surprisingly upbeat post which I know seems strange given some of my mood swings in here is the scope for improvements if we can overcome the first hurdle. The first hurdle is between T120 and around T150hrs: The split of that energy to the sw with one separate shortwave low ejecting cleanly, then as the troughing in the east USA sets up it forces a lobe of high pressure east. In the medium term the next attack point will come from the nw, you'd want a weaker low than what the GFS shows later and the question is whether we could see positive heights holding on towards the ne around that purple area. If we get over the first hurdle then its whether the UK can remain in cold air with a shortwave low ejecting se with snow on its eastern flank.

Not bad and not great. Its neither a Little Chef special or a Michelin starred dinner but with some tweeks could be a good night out! At least we have model agreement which has been lacking so the shortwave energy splits so that's one hurdle the outputs get over. The GFS in its later output keeps the positive PNA so that's good, if the troughing in the east USA keeps the main PV stuck in Canada then the energy coming off the eastern USA could track more ese and theres still a chance we'll see that track favourably to engage colder air near the UK. Overall given what could have happened the outputs so far have enough scope to improve without needing a dose of fiction or a Hollywood writing team. The main thing is the shortwave energy splits and the shortwave low getting east of the UK with the ridge building in from the nw, that's still not a given so I think before looking too far ahead we need that in the T96hrs timeframe.

I thought you were going to say me! I have been known to become quite melodramatic at times. Normally the film analogies get wheeled out when the outputs are beginning to get on my nerves !

I'm wondering whether we're seeing a result of the re-invigorated MJO. It's interesting that this has come just as the La Nina is weakening which normally allows for less interference. For those that followed the very in depth discussion from New Hampshire state forecast last night the forecaster is becoming quite melodramatic today and does touch on the MJO. Its a long read but worth it if you like a mix of techno babble and some Hollywood type over the topness! Winter is coming. Step back to the present, deep exchange ongoing over the N Atlantic and W Europe. Highly amplified, a wall is in place. Nothing abating upstream, the Pacific jet continues to pump mid-level energy across the CONUS through the zonal flow. Bottling up, one after another, across the Central N Atlantic, the blocking wall retrogrades from 30W to 60W longitude over the weekend into early next week. Slowed to stopped flow upstream, no where to go, the pattern amplifies, energy becomes displaced around the N pole, especially as mid-level disturbances jam up across E Canada. S draw of Arctic air magnified via S shear courtesy of amplified H5 ridging over Western N America, aided perhaps via MJO contributions. The jam up over E Canada, going into the following weekend, attention will be needed upon additional mid-level disturbances as they rotate through the amplified ridge-trof flow spread across the CONUS. Looking for sub-tropical connections coincident with strong dynamics and robust curvature associated with any trof amplification across regions of baroclinicity that`ll aid in storm development, this as Arctic air continues to spill S rearward, especially over the N Central CONUS. It`s behind the cold front that undoubtedly the NE CONUS finds itself on the cold and dry side of the envelope towards late week with a potential brush of winter-weather outcomes well N/W as low pressure develops and deepens over E Canada. Bottled up, we must watch for additional energy rotating through the amplified pattern, if there are any storm implications for our region. However, in evaluating mean ensemble guidance, it`s possible the plug is pulled across the N Atlantic allowing zonal "escape" flow E by the weekend, the downstream wall potentially having broken open. Not sold on the late period 30.0z EC just yet. Considerable spread in ensemble guidance and a lot of moving parts that are 6 to 10 days out, low confidence in the forecast further out in time. So a lot of uncertainty there, the zonal escape flow suggests we might see more mobility by next weekend but the issue is the jet track into the UK. The AO is expected to stay negative which means a better chance the jet will track more south. NOAA update their December forecast tonight so it will be interesting to see their thoughts as that will effect us in Europe.

It really is painful. I just wish the outputs could just agree and deliver a decision! The GFS run is perfectly possible but so is me going on a diet which never happens! It really is crunch time though. If the shortwave energy splits to the sw with one running east then a good chance of snow, if not its unlikely. And if by some miracle that does happen then it means the block is stronger and better orientated which will then have a knock on effect as the PV over Canada shoots some more energy across later. It's possible the jet track will be se into the UK with colder air close by to engage those. So not to be too melodramatic but the messenger your shortwave to the sw will be your bellwether. The crucial timeframe is between T144hrs and T168hrs. We're running out of time before the Death Star nukes Planet Coldie! We need action tonight and no more waffling from the outputs!

All the outputs were wrong last night not just the ECM, all show a delay to the cold heading south which isn't great news. Its now become even more complicated with more shortwave trauma than previously. Still a chance of a battle ground scenario and it still looks like positive PNA upstream so the PV shouldn't set up over Greenland. At least the models are generally agreed that between T144 and T168hrs will be the make or break moment. Shortwave energy to the sw splits in both the ECM and GFS, one shortwave low moves east. That needs to happen.

The issue with the ECM was not till post T168hrs. The PV is not expected to eject to Greenland but remain over ne Canada and this is what NOAA think will happen with it also shuffling a bit more to the nw. This means energy will shoot east off that and run to the UK, they also expect the Greenland heights to remain which will take the jet on a more southerly track. The ECM would look like tonights GFS upto T240hrs although we'd expect to see some better ridging to the north. You can't have a positive PNA with a rampant PV stuck over Greenland so that's why a positive PNA often comes with positive heights over Greenland. This type of set up can produce some good snow. Its of course risky but can produce so lets hope things fall kindly for the UK.

The GFS 18hrs run shows what should have happened to the ECM before it started tripping. This is a good match for the expected upstream pattern, PV retrograding, ridge over Greenland, energy heading east on a southerly track and a positive PNA. Could be some major snow as those shortwaves run east. It gets a bit messy later but overall not a bad run, I expect the ECM will look more like this tomorrow.

Oh that's setting me up for a fall! I'm just a humble model anorak! Anyway in terms of the ECM the eps aren't covered till much later, normally the state forecasts do a further update at around 8-9 pm eastern time. The issue isn't really upto T144hrs that's where the ECM has trended towards the GFS/UKMO. Its after that where the issues arise, but a positive PNA normally has a dig of cold in the east with the PV pulled towards northern Canada. Without amplitude in the jet upstream you can't get that dig of cold in the eastern USA. The New Hampshire forecast suggests we're going to see the PV revolving around the trough engaging shortwave energy and spitting out some energy into the Atlantic but with blocking near Greenland. The ECM wants to flatten things out and take the PV over Greenland which is very dubious. All will be revealed in the morning , I'm not saying the GFS and UKMO have got the solution nailed down but the ECM looks very much like an outlier past day 7.

Yes I'd bin it for now because its far too progressive. And then it takes the PV and sticks it over Greenland.

I've decided to put this out from New Hampshire state forecast. I have to say this is one of the most in depth discussions I've seen and I'd advise everyone to give it a good read as it impacts us in Europe. Pattern shift emerging towards mid-December per ensemble guidance. Interrogating, persistence of low pressure across the N Pacific as the present phase 4 MJO transitions towards phase 5/6 yields an increasing pump of warm-moist air across the NE Pacific into NW N America. Subsequent ridging, Arctic air is dislodged and sheared southward towards Central and E N America, hence -EPO/+PNA trends, along with Pacific energy being cut-off over the SW CONUS from the mid-latitude flow. Meanwhile over the N Atlantic, a bit more complicated. Persistent warm-moist pump towards the poles across the Davis Straight and Greenland lends to blocking mechanisms that make E/SE Canada a favorable region for storm development at times. However, the associated polar low wobbles back N/W, retrograding as it reloads, at which time additional Pacific energy through the mid-latitudes becomes cut-off into the N Central Atlantic by upstream ridging, gumming up the downstream zonal flow, hence a persistent -AO trend and an inconsistent NAO trend. US forecasters refer to the PV as the polar low, and that's supposed to go nw not be ejected east, you'll also note the persistent negative AO. In terms of the warm moist air heading into the pole from the Davis strait, a southerly there means the block centred further to the ne. The storm track suggests energy firing east out of se Canada but with a block in place that should be on a southerly track. In terms of the upstream pattern this from New York state forecast: A more significant shortwave is developing for Tuesday into Wednesday as a shortwave moves onshore of the Pacific northwest Saturday night into Sunday. This wave eventually amplifies into a full latitude trough. A full latitude trough in the US is one which digs right down towards the Gulf of Mexico, you wont have that if the pattern flattens out upstream.

I am currently compiling evidence from upstream that the ECM is wrong! This will be passed to the prosecution to be heard by a jury drawn from irate nw members ! The charges against the ECM are as follows: Emotional abuse of nw members. Child cruelty , Little Jimmy was promised sledging in the snow and has now been told instead he’s going to one of those naff fake Lapland parks. A collapse in the share price of Ear Muffs and Scarves RUs. Evidence to be heard a bit later after my operatives in the USA have compiled a full dossier of evidence .

Before the ECM started tripping it had actually moved towards the UKMO and the GFS. If the ECM had been on the money in recent days I would be throwing my toys out of the pram however it’s been poor with its modeling towards the ne USA. Its of course disappointing that it’s still not on board but to put complete faith in its output given its recent form is like backing a steeplechaser after a couple of wins but has fallen and refused in its last two starts , tonight it looks like it’s also slipped and unseated it’s rider on the run in !

The difference between the ECM 12hrs run and 00 hrs in the later stages is unbelievable . Upstream it’s all over the place. Then it ejects the main trough from the eastern USA which means it’s completely lost the plot . Stick it’s later output in the cat litter tray.

The ECM goes a bit AWOL later on but earlier it’s an improvement and it’s hardly covered itself in glory over the last few days. Even this run delivers a snow event to the north with a slow moving front.

The ECM is better than this mornings output . Trigger shortwave now forming off the upstream low, it’s all about the upstream phasing now to sharpen up the pattern to the west and send that shortwave se.

Two outputs out of the way and no major dramas! There are some differences upstream between the GFS and UKMO but positively these don't make much difference to the northerly post T144hrs. The GFS then develops a shortwave running ese with snow on the northern flank. As long as we don't get derailed before the block sets up the amplifying upstream troughing gives us a good chance to extend the cold. In terms of tonights ECM the UKMO solves the irritation of the shortwave in ne Canada by taking this east not se. That shortwave on the ECM phases with the ne USA low and then a further shortwave ejects east which this morning blew up and run towards the UK. You don't want this but that shortwave energy running east. Both had this feature this morning and its a complication, given the UKMO still refuses to follow the ECM and doesn't make a drama out of it lets hope the ECM follows that and doesn't cause a forum meltdown!

And so the longwinded saga has been given a second series today! They obviously saw the NW viewing figures and decided there was demand so today we have a complete mess with dismal continuity from the ECM! The UKMO and ECM are closer upstream with the placement of key features and the former has a similar shortwave to the ECM over ne Canada, but you end up with two different scenarios at T168hrs. We don't have the full UKMO view but from what we can see shortwave energy is absorbed into the main low and doesn't eject as a separate shortwave low. The trouble area and which is causing big problems is here: ECM UKMO NOAA had this to say about todays outputs: IF ANYTHING, NEW 00Z GUIDANCE THUS FAR ADDS EVEN MORE UNCERTAINTY. THERE NOW SEEMS TO BE A BIT OF A FASTER ADJUSTMENT WITH THE TROUGH AS IT ARRIVES. THEN THE GFS/UKMET CLOSE OFF A COMPACT UPPER LOW ALONG THE CENTRAL CA COAST BY LATE MON WHILE THE CMC SHOWS A PROGRESSIVE UPPER LOW WHOSE ENERGY REACHES UP TO THE MS VALLEY BY DAY 7 WED. Positively this points to a window of opportunity for the UK downstream: THE MOST AGREEABLE ASPECT OF THE MEDIUM RANGE FORECAST IS THE TRANSITION OF THE MEAN PATTERN FROM ONE OF LOW AMPLITUDE AND PROGRESSION TOWARD A HIGH AMPLITUDE/PERSISTENT REGIME. THE END RESULT BY DAY 7 WED SHOULD BE A STRONG RIDGE ORIENTED NORTH-SOUTH NEAR THE WEST COAST WITH A DOWNSTREAM TROUGH EXTENDING SOUTHWEST FROM THE UPPER MS VALLEY/GREAT LAKES. The problem at the moment is exactly how this translates downstream which as we've seen is far from being resolved. I personally don't like the ECM because its ridiculously deep trigger low tracks unfavourably and will take time to fill, you want a low se into the continent and not dropping south, even with that it just throws another curveball into proceedings. With cold synoptics in the UK the cleanest and quickest solution is best because more time more chance of another variable popping up.

Okay now that everyone’s beginning to calm down after the GFS thriller there are some things to bear in mind here. Unfortunately the track of the shortwave low won’t please everyone because the snow on the northern flank can’t hit the whole UK, although luckily because of the depth of cold some backedge snow is also likely which broadens the area . I’m hoping things could get shared out , so if you miss the main snow you get snow showers. I would like nothing more than to put a Code White ! But don’t bank on the low even hitting the UK , the main hurdle to get the northerly in is still not a done deal. If the low does hit treat it as a bonus and think of what you might have been happy with after this mornings outputs. Anyway that’s my sensible eat your greens post for today!

No not yet! If it came off it would be very rare, maybe a weaker low is more likely. The track and how far north the low gets is often not nailed down till within T72 hrs .

If you factor in GFS bias I doubt the low would deepen that rapidly . This means it’s track won’t pull ne as much. It’s quite rare to see this type of set up. Just a word of caution re track, at this range it’s very difficult to pin down so favoured areas are likely to chop and change between runs.

Wow another good GFS run! Barring the ECM which although an improvement is still being a bit stingy it’s been a very positive evening for coldies. It would be great to usher in the northerly with a snow event for some lucky part of the UK.