Ian Brown

To say that we should not be worrying about the GIN (corridor of death) area is unbelievable Steve, pre-2009 or not, cyclogenesis in this area is the well established quick fire route to end a Northerly. The most important thing to remember here is that shortwaves developing at the Eastern end of the jet streak will not be picked up until this is around T120 on the NWP. The GFS has a better formation of pressure rise in the first place than the ECM, and there will be changes to come from both models as this comes into the higher resolution but remember when LP has broken the link between HP in the Atlantic and Greenland OR when lower heights have crossed the Greenland plateau, it’s game over for our Northerlies.

There should be no party based on the output, but yes there is every chance of that.

If it lasts 3 days it will bring snow showers much further South than that. Hopefully we will see some firming up from the NWP as events start to come within T168, we are of course relying on the corridor of death area for any decent Northerly, and there are lots of similar set-ups that have gone wrong or been over before they have begun in the past.

I would disagree, I would think any northerly next week will be the last such cold shot for some time, we have a poor set-up but have avoided full on zonality for a couple of weeks through low heights over Europe and some amplification in the Pacific. You would bet against that sustaining and as someone said earlier 'the big purple blob' should soon be settled over Southern Greenland with the attendant height rise over Europe.

Glenn, you have been around a long enough to know how many let downs there have been over the years, we have even had the ECM at T96-120 showing bitter cold easterlies that have never materialised. If we are in a cold/average set-up and the models show mild at T120-T144 we know its virtually in the bag. Of course recent years have seen some of theses cold synoptics verify, but we only have to look back at last December for one of the biggest failures of all, a double whammy of no easterly and then the Atlantic returning within a couple of days of when the easterly should have been happening. Even the northerly early last week totally changed from what the NWP was showing at T144-T168, so we can expect further changes. Of course prior to 2009, I could look at the models and think where can this go wrong ? Or look at a particular run and see the chink in the armour, and that is what would end up happening. Not sure why people place any faith in the GEM.

Glenn, that is because mild synoptics have a huge margin for error. Cold ones, especially easterlies but northerlies also, do not have that margin for error.

Of course we don't need HLB for a decent North/North Westerly blast, but the synoptics being shown are 200 hours away plus and that should lead to extreme caution especially given how quickly these synoptics can fizzle out to the cold blast missing us to the East etc..

With regards to Steve's post, I don't agree that it is poor form to go for a return to mild after any initial Northerly, unless we are looking at a Dec 81 scenario, which we are not, Gibby and whoever else are going with by far the most likely solution, particularly as we see nothing to suggest HLB in the NWP.

Of course this hasn't actually happened yet and any plunge of cold air is subject to the timing of Seaboard depressions and the usual complications associated with getting polar air across the UK.

http://www.meteociel.fr/modeles/ecmwf.php?ech=216&mode=1&map=0&archive=0 This looks a decent blast from the ECM.

Well its T240 and another variation on the theme, hard to say what would happen from there.

Northerlies are not really Steve's thing, besides which however we look at the charts, any cold shots will be transient.

The ECM goes on to show what would be a brief cold snap at T240. Its about timing really and if there is a long enough gap between systems coming off the Seaboard then you get the best case scenario of the GFS run for any northerly. Still all a fair way off but the general pattern is there, and as Mucka says nothing in the models to suggest anything long lasting in the way of HLB.

Yes, the pattern simply looks to fluid to sustain HP between the Atlantic and Greenland to get anything other than transient NWrlies.

No it doesn't ?

Yes, as long as HP is around us or to the West there is always that chance that it could pull back NW, I don't think it will at least for any length of time but if we have a zonal reset that means the High slipping into Europe from our present position and if there is one set-up that can last a helluva while, it's that one !

Yes, still at the stage where more runs are needed but it wouldn’t surprise to see a change in the METO update to average to above average certainly in Southern areas for early December.

I don't agree - for me there is nothing to suggest HLB, for sure the chances of brief NWerley incursions, but I don't see anything in the output that deviates from the METO outlooks for early December.

Frosty, I wouldn't pay much to the attention to the GEM. there is nothing really to suggest a transfer of the core of heights from the Atlantic to Greenland. North Westerlies at times for sure, but nothing to suggest any HLB. The ECM T240 chart would be particular poor for cold fans going forward.

Yes it's a very poor set-up going forward with both the GFS and ECM hinting later on at pressure rising over Europe as the PV deepens to the NW.

Lol, well we were talking about something that was at day 8 plus anyway and is subject to the usual caveats at those timeframes. The ECM tonight ends up back at square one and what I said last month about taking HLB for granted after the change of the last few winters is relevant, though of course very early days yet.

Well Steve what will be verifying is a million miles from what the ECM was showing at the beginning of the week. GFS has been closer to the mark and correct not to build heights at Northern latitudes.

Come on Chiono, the weather forums are littered with epic failures - especially of the easterly type. Next time we see an easterly, say agreed by 2 of the 3 big models, I will lay you appropriate odds on it actually verifying. Then when Uncle Barty is on the horizon at day 6, you can reciprocate !

I wouldn't rule out the Bartlett scenario at all Shaun - continual depressions coming off the Seaboard can easily lead to a tramsferring of the core of heights from the Azores to mainland Europe.

I think what the GFS shows is the best we can get out of the situation; a brief northerly toppler before the jet rides over the top again. ECM is less keen to have any core of heights shift from the anchor to the West.