nick sussex

Thanks. The longwave gives us the bigger picture but as we know in the UK it’s often at the periphery of the cold , small changes have often bigger effects . When we see for example a Scandi trough and high to the west the big picture doesn’t show whether the UK had a direct hit of cold or whether it’s too far east. Globally a few hundred miles isn’t much in terms of the longwave pattern but has huge effects on the weather on the ground for the UK.

Thanks , yes of course without a good longwave pattern you’ve got no chance but here we’re talking of a tiny difference in terms of angle upstream within T144 hrs . The longwave patterns of the big 3 are very close , so we can see here at T144hrs hrs that the butterfly might be playing a role . This mornings spoiler shortwave highlights how sensitive the evolution is. I think I’m going to coin a new term Longwave Sensitivity.

Both are of course connected however if you look at the outputs this evening the main key features haven't changed within T144hrs, as in the longwave pattern is similar to this morning but amongst that these small features can play a role. Take for example the spoiler shortwave this morning. Lorenzs original view of the butterfly effect, yes one effects the other but the initial small change can manifest itself into bigger changes down the line.

Okay I promise this is the last crayon job this evening. Mucka just mentioned phasing and heres where this on the face of it tiny feature plays a part. The two lows circled will phase, the shortwave develops into a low as its fed low heights this then also phases and drags the phased systems further east and tilted more unfavourably. The shortwave also stops a bit more WAA feeding nw and also effects the tilt of the low se of Newfoundland. So the ECM basically delivers a chain of events timed to perfection for maximum irritation and downstream effects, at this point we should ask it the Euromillions winning numbers! The odds of this chain of events occurring on its 00hrs are minimal. Because of this tonights ECM from T144hrs is given the first SSO (Suspicious Synoptic Outcome) award of the season.

Heres the aforementioned subject of my irritation: This stops better ridging into Greenland, it also then puts on its shades and relaxes in its sun lounger waiting to complicate the phasing action of the upstream lows one over the ne USA and the other further upstream. The damn thing is still sitting there at T168hrs!

I’ve found another shortwave which complicates the ECM and results in less ridging north . Its that small kink north east Canada at T144hrs hrs, this effects the ridge near Greenland and the phasing action of both upstream lows . So room for improvements .

Quite amazing turn of events today . For this reason I think we need tomorrow mornings outputs to solidify that the spoiler shortwave has finally been exorcised ! There are some differences , the GFS has the better chance of a snow event as it had a shortwave running east but that does come with higher risks and then it edges towards a west based neg NAO. The ECM fails to build on its early better trend but at this point there are bound to be more changes . The main thing is we don’t have the shortwave spoiler , because that’s crucial in having any chance of developing some interest .

What do you mean sane I thought we’d all passed the point of no return ! Spending hours observing model outputs and obsessing over the direction of a shortwave could be seen by others as a bit strange ! My friends who know all about my obsession call us the snow people! But I don’t care, I find people strange if they don’t like snow ! I cant get my head around that, who couldn’t love snow . I’m just as excited now to see snow falling as I was when I was a kid. Anyway in a desperate attempt to move back on topic, the minutes seem to be taking ages to count down to the ECM run!

NOAA have just called the ECM 00hrs run outlandish ! They have serious doubts over this mornings op run which is good news because it was dreadful from a cold perspective!

Which one are you talking about? I was talking about the Greenland high further east because the attack point is taken further east after the initial shortwave . If you’re talking about the high near the UK before the fun and games start then yes that one further west.

It wouldn’t be the same without me moaning about something ! The block needs to be further east, but given the morning horror show it’s a step in the right direction.

Great stuff from the GFS so far with the cold air undercuttng the precip. The UKMO has also improved so after a traumatic morning sighs of relief all round however it’s not a done deal and still a few hurdles to overcome. I’d prefer to see the block centered a bit further east but that’s a way out so could change.

The newly named corridor of hope is shown here! You must maintain a clean flow not interrupted by shortwave energy. I've circled the key features, black shortwaves, the purple is the Pacific troughing moving east. As you can see from the differences between the GFS 00hrs run to T138 hrs and the new GFS 06hrs run to T132hrs, the latter has the clean flow and also a bit more amplitude to the Pacific troughing. Events over ne Canada are crucial because as the upstream flow amplifies it phases the low in the west Atlantic with that shortwave over sw Greenland both then head east and you're caught on the wrong side of that amplified wave. Just having the clean flow won't by itself deliver the northerly within a reasonable timeframe, you'll still need a little bit of luck but theres zero hope if the shortwave shows up to the sw of Greenland.

All is well the NAVGEM 06hrs run keeps the corridor of hope open! Clean flow and no shortwave spoiler at the crucial timeframe. This has been an emergency Code Red desperation use of an output that we normally ignore!

The doctors have detected a pulse! Typical just as the priest was called the GFS 06 hrs revives hopes! This occurs because of a slight change over Artic Canada with a more amplified pattern which stops the shortwave appearing to the nw which is now becoming the make or break of the current long winded saga. You must maintain a clear flow from the UK ridge back towards ne Canada. If you don’t as the upstream amplification works east it amplifies the pattern to the west of the UK which takes shortwave energy to the nw. In terms of meangate I agree with Weathizard, the mean is not very useful in this set up because the evolution with or without spoiler shortwave is completely different.

The wheels have really come off this morning with a spawn of satan shortwave blocking the clean flow from the ridge developing ahead of the eastern moving Pacific troughing over Canada across to Iceland. Its this which stopped an earlier calamity. The amplification arrives too late by which time the UK is stuck on the wrong side of the jet. Very disappointing to see yet another sorry episode of a northerly imploding. The GFS is least worst this morning as it eventually pushes the pattern se, the ECM really finds the worst phasing point and delivers a pile of crud at day 10. I can't imagine the ECM could plot such vile output again tonight!

This is the state of play ! The set up is one which could deliver because the high to the nw is likely to be forced east as the next wave of amplification pushes a trough towards the ne USA. The shortwave track is likely to change but if and of course big if there’s a chance this could disrupt close to the UK. At the same time engaging colder air from the north could deliver snow on the northern flank. As long as the high is boxed in by low heights over the east USA and Canada it won’t seep west and give a victory to the mild dross to the south . The GFS is similar to tonights ECM in trend . Key things the shortwave detaches and doesn’t remain attached to the second one behind it. This improves chances , it’s about time the UK had some luck here. I have everything crossed for tomorrow morning .

You're in denial! Its currently evolving in a very complicated tiresome way. Someone might get lucky if the pattern gets edged south as the shortwaves decide what they want to do. Lots of cold to the north ready to engage and deliver a snow event if by some miracle the weather Gods play nice!

Its painful to watch. A battle between the bloated blob to the south the cold to the north and whether that vile shortwave will detach head east and cut itself off from upstream energy. The blob to the south needs to do one pronto, so that's it the outputs are determined to wring every last bit of drama out of this. What a surprise, I should know better its been the same thing for years!

In relation to Knockers post talking about the Pacific amplification. There seems to be two bouts coming up the first is whats causing the initial divergences, as the first one takes place between T144 and T168hrs it sharpens up high pressure over the east USA which in turn sharpens up low pressure in the west Atlantic. The reason I haven't thrown my toys out of the pram this evening is I can't see the hideous west neg NAO setting up and hanging around because any high pressure lobe should be forced east. The second bout is what the ECM shows at T240hrs with that digging trough in the eastern USA, now in these situations the amplitude there will dictate our ridge to the nw. Its always difficult this far out to determine how amplified that will be, the shortwaves messing around in the Atlantic are an issue and until that gets sorted we won't know how quickly a northerly flow could get far enough south. Amidst all this is the chance that some one could get lucky with a shortwave cutting east and hitting the cold air heading south before the northerly clears south. So a lot going on but really if the UK can't get something out of this it will be very disappointing.

Thanks SWH and thanks also to Northwest Snow. Great username by the way , shortwave traumas are part and parcel of this thread !

I can’t seem to find the forecast on their site? Do you have the link?

MJO on the move in the GEFS probably helped by the weakening La Niña signal. The 3.4 region has shown a warming in recent weeks .

Before the NW counselling unit gets over run there is little chance of a west based neg NAO setting up because of the expected upstream pattern which is likely to force any high pressure lobe east. The issue is timing and phasing point of shortwave energy to the sw of the UK. And it’s possible a lucky area could see a snow event if you can edge the pattern south, a shortwave could run east and engage colder air to the north. I’d be more worried if the dreaded west neg NAO was seeming the end point and as we’ve seen from the UKMO those shortwaves can cause huge changes in the outputs. From zero to hero in 12 hours !

The ECM is saved because we don’t see a west based neg NAO , the high cell is forced east which helps force the pattern se. I hope tonight’s ECM goes some way to explain why regardless of earlier outputs the CSAC Cold Synoptics Action Committee unanimously voted to keep a Code Red advisory in action !