bluearmy

Yep at least with the strong reversal below 60N, you’re more likely to get the swipe of cold far enough south to engulf the whole country. It’s frustrating to watch it head across to our north into the north Atlantic basin

I think too much emphasis is placed on the reversal at 10hpa/60N regarding consequences. if we had a strong sustained reversal at 65N then we would expect some positive consequences for the mid latitudes over the following month (with downwelling waves if they propagate ). A tech ssw isnt a magic bullet. we’ve seen repeated notable reversals above 70N last two weeks and these continue up till around the 21st. Would be amazing if these didn’t have consequences in feb but our worry is that they mean the wintry patterns don’t get far enough south. think west based neg NAO as an example. how many times have we seen the retrogression take the blocking west at a latitude that’s no good for nw europe ? hence my earlier comment about feb possible being a v frustrating month,

Heights into Greenland for more than a fleeting ridge at best look troublesome to me within the next 16 days. unless we see the Canadian vortex relaxing itself markedly across the end week 2 ens, then i think we could be looking towards week 4 approaching mid feb to get that to stick. It really wouldn’t surprise me to see the nwp trying to repeat the last couple weeks with a mlb that eases north to Orkney ish latitude and then retrogresses slowly. if upstream plays ball then we can then get a griceland high to follow. If split flow plays ball then we can possibly advect something notable around the south of an Orkney high.

Agree substantively with this Mike but I would add that we’ve seen repeated warmings since the back end of December and actual strong reversals above 70N through the first half of jan. These look to be done by 21st. you would expect those reversals to drive repeating waves over the next six weeks. I appreciate that the quick downwelling of these seen at high latitudes with a weak strat to resist may mean that there are less of these through feb than might be expected. But my point is that we should expect negative flow support for the trop from the strat at some points over the next month above 70N. On its own that perhaps wouldn’t help bring deep cold far enough south across the NH (re our latitude) but it may push some cold pools far enough south to interact with blocking that may not be able to gain quite the traction that we’d look for. We should be aware that feb could easily end up quite frustrating for us.

18z looks closer to the 12z ecm than the 12z gfs still amplified to our east but not as sharp as the 12z gfs V reasonable continuity

Too much upstream forcing for the time being but there must be a few members that aren’t far from the gfs op

I wouldn’t disagree Phil but seeing as we get to see the cross sectional that goes with op run, we may as well have a gander

It could be a downwelling wave from the warming at the end dec into Jan. three to four weeks wouldn’t be outside the expected range. The cross sectional of the atmosphere later may show how the weaker flow comes about through the run. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5015409

It could be a downwelling wave from the warming at the end dec into Jan. three to four weeks wouldn’t be outside the expected range. The cross sectional of the atmosphere later may show how the weaker flow comes about through the run.

Not quite as ridiculous as it looks but gfs op definitely over doing the signal at this time. Something to follow in fi for a few runs to see how long we have to wait for it to repeat

Sod’s Law innit! the tech ssw is merely the end point of the reversals that have been ongoing since Jan 2nd above 70N. The fact that they actually get to 60N 10hpa is merely a technicality. You could say that the mild and zonal renews as the warmings and reversals end. We will have had almost two weeks of blocking by this point. Sadly, not quite in the right place for our small island. We saw late nov and into December that the warmings then took a pretty strong flow high up and brought it below average. There are those that would say the past two weeks of blocking are down to that warming with a month delay on the downwelling wave. Not sure about that. we can expect ramifications through feb and possibly march on the back of this past two weeks of reversals in the higher latitudes. Whether that’s enough to deliver at our latitude would be the question. as for the next couple of weeks, it looks like an MJO imprint phases 4 and 5 with a week or so lag. And the strat vortex segments rejoining together to our north is never a good sign for the northern arm. Put together it’s no surprise to see the Atlantic in full flow for at least a week.

The gefs are showing a renewed slowdown later week 2 the cfsv2 is all in on a marked reversal in feb The ec46 found a small cluster yesterday that looked to headed back down again so watching that later we are seeing modelling showing a new ural ridge upcoming and some Aleutian troughing so if that verifies the I wouldn’t expect the spv to survive the warmings that are generated by that. of course we can expect downwelling waves in February anyway from the warmings and reversals seen in first half jan - we run the risk of a neg AO from a downwelling wave either being interfered with by a new tech reversal ssw or not downwelling because of interference. I think we can guess how this might play out !

was all related - petered out now. The low is going to track as expected

I think the confusion is over two areas John. The overnight Cheshire gap type precip extending into the e midlands which is ahead of the warm front but is likely connected to it as an extension se of the instability. This area wasn’t shown on the fax chart as being likely to delivery anything and has caught some unaware as not everyone is looking at the light precip flickering in and out as each model run is produced. As has been mentioned over the past week, small areas of unexpected precip will crop up. Unlikely to be of any real consequence but a dusting is nice to look at. (Especially if unexpected)

Ec op 12z showed something along these lines. Doesn’t look like it’s part of the main system which is due to head se on its intended path Isle of Arran in and n Humber out It showed the light snowfall through the Cheshire gap in the early hours and extending into the e midlands before petering out away from a line n of stoke - derby - Lincoln as the shortwave system moves across during the day I would assume other higher res models picked this up aswell as for Chelmsford - that’s very isolated looking at the radar !

I’m astonished that a pro like Marco is making such a big deal of the ssw. It barely gets across 60N 10hpa and and by day 6 we’re here if feb sees downwelling waves which deliver a strong neg AO and perhaps wintry conditions then it won’t be anything to do with the next couple of days in the strat but the last couple of weeks that have seen repeated negative flow above 70N down to the trop and which culminate with the next few days which squeezes a tech ssw. Perhaps one of the weakest and shortest tech ssw’s we will have ever seen ? and one for @Mike Poole - showing the positve flow headed up through the strat as opposed to what we’d expect which is the strat influencing the trop over time Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5013582

it’s still showing HLB - just not quite where we’d want to see it still time for these to evolve to a better place - if there were no high anoms then you’d be more worried

I’m astonished that a pro like Marco is making such a big deal of the ssw. It barely gets across 60N 10hpa and and by day 6 we’re here if feb sees downwelling waves which deliver a strong neg AO and perhaps wintry conditions then it won’t be anything to do with the next couple of days in the strat but the last couple of weeks that have seen repeated negative flow above 70N down to the trop and which culminate with the next few days which squeezes a tech ssw. Perhaps one of the weakest and shortest tech ssw’s we will have ever seen ? and one for @Mike Poole - showing the positve flow headed up through the strat as opposed to what we’d expect which is the strat influencing the trop over time

Possibly seeing a destination and evolution for two weeks time Every chance that in week two we see an amplification of the euro ridge north but likely on a positive tilt of the northern arm to our west. This is well advertised on the gefs in week 2. Nwp then trends to a notable Alaskan ridge which drives a downstream trough and takes the ne canadian vortex axis away from the Labrador Sea and into e Canada. Gefs and geps are then flattening the sceuro ridge with a weak areas of low anoms headed towards n scandi. These two evolutions could allow the sceuro ridge to then retrogress into the Atlantic and some WAA driven by the upstream trough could deliver enough amplitude to bring colder air south across nw Europe this isn’t a prediction but it is a way of putting some of the jigsaw pieces together which fit telecon expectations for early feb (and seasonals ). shame we can’t see ec46 week 3 clusters. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5012993

Possibly seeing a destination and evolution for two weeks time Every chance that in week two we see an amplification of the euro ridge north but likely on a positive tilt of the northern arm to our west. This is well advertised on the gefs in week 2. Nwp then trends to a notable Alaskan ridge which drives a downstream trough and takes the ne canadian vortex axis away from the Labrador Sea and into e Canada. Gefs and geps are then flattening the sceuro ridge with a weak areas of low anoms headed towards n scandi. These two evolutions could allow the sceuro ridge to then retrogress into the Atlantic and some WAA driven by the upstream trough could deliver enough amplitude to bring colder air south across nw Europe this isn’t a prediction but it is a way of putting some of the jigsaw pieces together which fit telecon expectations for early feb (and seasonals ). shame we can’t see ec46 week 3 clusters.

Jules - your MJO composites are Jan for 7 and feb for 6.

There are enough jigsaw pieces late on in week 2 and certainly for week 3 But it looks tough to see how you’d arrange for them to bring winter to nw europe. mind you, I could barely manage one side of a Rubik cube so I’m not your man anyway !

18z ec suite is the strongest south coast clipper of past four runs possible 3cms on the sw moors and up to 2 cms along the coastal 20 miles strip - amount increases a little as you head east taking the eps into account.

It’s been consistent with its placement of the low but that’s pretty much been through n France and only skirting the se coast on some runs That remains the message good spot about the consistency of graphcast btw

Imdeed - The flattening of the Atlantic has been a consistent week 2 cross model ens agreement for some time I assume that the assumption that the nwp was wrong has affected expectations