stodge

Evening all While this evening's output has undoubtedly disappointed a few, it's often a case of "no pain no gain" in the pursuit of more wintry synoptics. As I've often said, the route to very cold usually starts from very mild and I note the continued and persistent Wave 1 assaults on the PV. These are not ideal for our point of view as the attacks from the Siberian side tend to knock the PV back over to Canada/Greenland yet as we move into February the PV looks in continued distress and the zonal winds are clearly weakening all of this offers possibilities for amplification. Plenty of time for lying snow in February and March and while we may have to endure a 7-14 day Atlantic based regime, the next pattern change after that may be of more "interest".

Evening all Well, I think I'm going to leave Mrs Stodge and run off with the GEM 12Z OP - especially the T+240 chart: That's about as good as it gets if you're a fan of the Greenland HP scenario. The truth is GEM makes the join and JMA just about gets there albeit briefly but neither ECM nor GFS is able to (at least in their OP runs) as there remains just too much energy in the northern arm of the jet to allow for full retrogression. Without it, we're stuck in a mid-Atlantic block with occasional "backdoor" drifts of colder continental air. These are still pretty potent (plenty of -8 850s). The 10 HPA charts continue to interest inasmuch as we know zonal winds are falling off and that should allow for amplification. I have no clue what's going to happen - I'll simply offer the very fact we have charts like this at this stage of winter and the very fact we are speculating about an SSW (a mixed blessing as we know) puts up well up on many other years. I'm enjoying the ride - we've come a long way since we were going back to mild SW'lies a few days ago. Where we end up, as I've say, I've no real idea.

No, I didn't. I said the Control had a large Scandinavian HP which it does but the OP keeps a stronger jet and we end up with a mid-latitude feature. Perhaps the sunspot activity is driving all this.

Evening all Three to four chilly if not cold days may be the best next week has to offer - we'll see. There seems general cross-model agreement on the heights building back into western Europe from around T+180 and in a sense we're back to square one. GFS 12Z Control builds a huge Scandinavian HP in far FI but with little or no cold air. The 10 HPA temperatures show the stratosphere still under strong pressure but all that's happening is the PV is staying in its usual place and the northern arm of the jet is too strong to allow heights to build into Scandinavia leaving us in a mild Atlantic-driven flow to the end of the month. Plenty of winter yet of course.

Evening all Certainly some more interesting eye candy in the output than at this time last week. I thought we might have several more weeks of Atlantic-driven weather because of the repeated Wave 1 attacks from the Siberian side which keep the PV in the Canada/Greenland area. However, my reading of the 10 HPA charts is that assault isn't as strong as expected (though right at the end of FI it's very powerful) and perhaps we can catch a break again. GEM was my favourite tonight - a week long northerly. Other output has a longer or shorter colder interlude. Again, I'm hoping we can catch that break to allow the Scandinavian heights to set up as there is some very cold air far out to the east. This is my chart of the evening:

The very wet summer in NZ continues with the arrival of ex-Cyclone Hale: https://www.stuff.co.nz/national/weather-news/300780108/live-huge-slip-trees-down-creeks-overflowing-as-cyclone-hale-hits-great-barrier-island In the video at the very end a bit of our old mate, Dan Corbett, in more serious mode than usual. The GFS 12Z OP has the storm over North Island. In wind terms, nothing unusual but the ex-Cyclone, which formed over New Caledonia, moved first south east then is turning sharply south to be over Auckland by Tuesday morning (Local) before moving SE to be out over Hawkes Bay by the end of the day. Needless to say, very large rainfall totals expected - 120-150mm widely and up to 300mm in some areas and this on ground saturated from a deluge last week. These tropical storms can have +20 850 air embedded within them so it's little surprise the rainfall totals are huge.

Mrs Stodge's mother reports from Hawke's Bay it's been a very wet summer so far especially for the North Island. It seems HP has become blocked to the east and south east and that's allowing sub-tropical air and LP to drop south from the tropics down over North Island in particular while the South has generally enjoyed fine weather. Illustrated by the current GFS chart with an E'ly or ENE'ly bringing humid and wet conditions to the North Island. It's the season for tropical cyclones to head south and affect the Bay of Plenty or clip the east coast near Gisborne.

Evening all Once again a lot of Wave 1 pressure indicated on the 12Z GFS - I've hung my hat (for what little it's worth) on the current pattern continuing until mid-February but that will be the point we catch a break or two in terms of amplification and we bookend this winter with cold spells with the majority of the season mild, wet and windy.

My "educated guess" is this pattern will continue to mid-February (yes, another six weeks of this at least, cue pictures of spring flowers and the like) but then we'll get a major pattern shift to cold to end the winter - another two week spell of below average temperatures and snow. That may continue into early March before the thaw sets in,

Evening all Plenty of interest this evening in the 12Z suite. It looks as though we will move from a briefly fairly benign spell into a more unsettled and colder spell (nothing remarkable in that) with PM domination over the weekend. GFS OP backed off on that a little but ECM has tantalised with height rises to the NE and the possibility of the trough aligning slightly negative through northern Europe. GFS OP in FI will have piqued interest - there were LRFs which offered a more anticyclonic spell in mid to late January so kudos if it proves accurate. The Wave 1 and 2 pressure on the PV looks considerable to mid month and the synoptic charts in far FI - while not offering much for snow fans - are showing -8 850s which would be cold. In the more immediate, the rain continues albeit perhaps less intense than it has been: No real surprises there with North Wales due for nearly 6 inches in old money but higher numbers through southern counties suggesting, as we've seen, secondary LP features and troughs running along the Channel coast.

Evening all First, Happy New Year to all on here whether regular contributor, occasional commenter or lurker. Thanks also to the Team for keeping the road on the show. As for tonight's output, fairly broad concensus around a continuation of unsettled, Atlantic-driven weather to start 2023. Next weekend it looks as though a strong trough will develop to the south of Greenland and this will align negatively into Europe temporarily displacing the heights over Iberia back into the Atlantic and allowing for PM air to work across the British Isles and North West Europe. Snow for some and certainly for those with elevation further north likelihood of more than perhaps transient snowfall. Beyond that, well, the first point is attempts to build heights into Scandinavia are so far getting flattened by the strong jet - we need the displaced PV to end up more over central Canada and less over NE Canada/Greenland. The 06Z 10 HPA charts on GFS OP were very impressive but the 12z less so if I'm being honest. I'm not huge on Wave 1 warming from the Siberian side as it simply sends the displaced vortex back over to Canada/Greenland but if we can get Wave 2 attacks as well so much the better. It looks as though we will move into a short period of PM influenced weather through next weekend but whether the pattern resets with heights returning to Iberia and a positive re-alignment of the pressure systems or whether heights rise enough to form a mid-latitude block is to be resolved. I don't currently see the kind of cold and snowy weather many on here would like but nor so I see relentless zonality for weeks on end. There's clearly a lot going on and a lot to be resolved.

Evening all We've been here before many times and we'll be here again many times. This is traditional North West European winter weather - Atlantic based but with HP to the south. After what was for many (though not all) a decent December cold spell (and if you get 14 memorable days out of 90 you're doing well) we are back to normal. It may get even milder if the HP ends up over Iberia and we get a more South South Westerly feed. The rainfall figures scream positive alignment: A deluge for anywhere facing south west otherwise not too bad and temperatures above average. How do we break out of this? Not easily - attempts to build heights into Scandinavia are thwarted by the strength in the jet which flattens any heights and turns a possible high latitude block into a classic mid-latitude. Maybe we'll get a bit of help with some negative alignment of the trough if the HP pulls back into the Atlantic but that will be transient. Continued warming on the Siberian side serves only to keep the PV on the Canadian side and as @CreweColdhas opined, we may well be into proper coupling of the strat and trop before too long. We could get an SSW but there doesn't seem much prospect currently though it may look different in a couple of weeks. The other possibility is we may have had our cold and snow this winter and the next time it'll get cold is when we'll all be clamouring for spring warmth - the weather's like that, capricious at times.

Afternoon all An extraordinary event as said and the warm up next week will also be considerable - Cincinnati at -10F now will be +60F by the end of the week. Looking at the charts over North America, I do see some parallels with the events of 17-18 December 2010 over here. Between a very large and strong HP over Greenland, a blast of very cold Arctic air headed south and south west across north west Europe and especially the British Isles. A cold LP developed in the flow over Scandinavia and migrated to be over the British Isles during the 18th and that brought heavy snow to many areas and temperatures below freezing for many. Presumably, the sea passage mitigated the strength of the air flow in a way it doesn't over North America as the frigid ait travels south across the Canadian Prairies and into the Midwest and just as our coldest and deepest N'lies can reach right down to Iberia so this blast has reached the Gulf of Mexico. The rapidly deepening LP looked to head north or even north-north west which is a track we've observed with hurricanes and only now has it begun to fill and move back NE. The HP has also declined and cut off the air flow from the Arctic for now.

Evening all Thought I'd reference the accumulated rainfall numbers from GFS 12Z OP: A lot of rain (nearly 8 inches in old money) for western Scotland but note the high numbers through the Straits of Dover and just clipping the far south east suggesting some of these frontal systems and secondary LP might pack a bit of a punch. Overall, pretty unsettled and wet for many if not all. The other observation is one I often make - the route to very cold starts from very mild. We often need a very mild synoptic evolution to begin the process of amplification toward something different or a change in the pattern. As others have noticed, heights to the south can, if the jet slows sufficiently, build into a mid-latitude block if not better. We have in my view 14-21 days of mild weather, initially unsettled but becoming very mild and more settled around New Year before we see another pattern change.

Evening all Well, if you're after storm force easterlies and -20 850s you're going to be out of luck - indeed, you usually are. What I'm NOT seeing in tonight's output is traditional Atlantic driven positively tilted systems offering transient PM flows. Instead, it's more about the transient TM airflows and the preponderance of PM sourced air which while not offering a lot for lowland southern Britain provides plenty of interest for those with altitude and especially those further north. I'm not sure if I would call it "cool zonality" either but what I would call it is very unsettled. Lots of rain and snow for the usual suspects - western coasts of Scotland , England and Ireland but also high rain totals through the Channel and southern counties of England suggesting a number of secondary features moving along or close to the Channel. Once again, I'm struck by the core of the PV continuing over Siberia with the strongest of the zonal winds. It doesn't help us now and probably precludes a Scandinavian HP.

Evening all As an aside and it may be no significance at all but I do like t follow the 10 HPA charts and the zonal winds. Most years, the "attacks" on the PV have come from the Siberian side and what they tend to do is knock the core of the PV back over to the Canadian/North American side firing up the jet and putting us back into the Atlantic dominated westerly regime. By the way, I think that's what did for our recent cold spell. The odd thing this winter so far the bulk of the warmer 10 HPA temperatures are on the North American and European side and, as you might expect, this has the effect of sending the core of the PV back over to Siberia enabling our Greenland HP. Tonight's 12Z GFS OP (hideous outlier as it no doubt is) illustrates this and what it also shows is, contrary to the normal pattern, the strongest zonal wind pattern is over the Siberian/Eurasian side - the storms are there while under the lighter zonal winds, the Greenland HP is able to survive and occasionally exert its influence leaving the Atlantic its less than zonal stuff and keeping the real storms well away. Just an observation, may mean nothing. Original post: https://community.netweather.tv/topic/98132-model-output-discussion-the-run-up-to-christmas/?do=findComment&comment=4774281

Evening all As an aside and it may be no significance at all but I do like t follow the 10 HPA charts and the zonal winds. Most years, the "attacks" on the PV have come from the Siberian side and what they tend to do is knock the core of the PV back over to the Canadian/North American side firing up the jet and putting us back into the Atlantic dominated westerly regime. By the way, I think that's what did for our recent cold spell. The odd thing this winter so far the bulk of the warmer 10 HPA temperatures are on the North American and European side and, as you might expect, this has the effect of sending the core of the PV back over to Siberia enabling our Greenland HP. Tonight's 12Z GFS OP (hideous outlier as it no doubt is) illustrates this and what it also shows is, contrary to the normal pattern, the strongest zonal wind pattern is over the Siberian/Eurasian side - the storms are there while under the lighter zonal winds, the Greenland HP is able to survive and occasionally exert its influence leaving the Atlantic its less than zonal stuff and keeping the real storms well away. Just an observation, may mean nothing.

Evening all To be fair, time was called on the current cold spell earlier in the week and a rapid transition to milder weather will now happen in the second half of the weekend. As to the lead up to Christmas, there still remains a small window but tonight's runs have trapped most fingers in the window frame with the troughs phasing and keeping the milder airflow. I didn't think ECM 12Z OP was too bad - the T+240 looks a very good chart in terms of the direction of travel: A nice disrupting trough and heights to the north west - may not amount to anything but I've seen a lot worse. No clue as to the New Year - the disconnect between the stratosphere and the troposphere keeps things interesting.

Evening all Certainly looks as though we will see a pattern change back to something more "normal" for a UK winter. To get a 10 day spell of well below average temperatures and a decent snow fall has been excellent and in the 90 day period of our winter, while not exceptional, certainly more than the past few years have delivered. As the late week Atlantic LP winds up, heights get pulled across Europe and the SW'lies return with much milder air - again, not an unusual development. GFS has hinted at Scandinavian heights in far FI for a while and we'll se if it goes anywhere but I think the Eurasian warming at 10 HPA was always going to give the PV over Canada/Greenland a boost though the GFS OP hints at an unusual orientation - stretched across Canada - so it may be this is what is driving the building heights to our north east. We still have a few days of cold and the evolution up to Christmas remains far from clear or resolved.

Evening all An interesting day weather wise here in downtown East London. The temperature has hovered around or just above freezing all day. The snow pack has been reduced through sublimation rather than melting - it's drying out rather than converting to liquid. The footpaths are drying as are the roads. Not a breath of wind but delightful to see the wet snow which had clung to every surface slowly drop. I don't know if we'll freeze tonight or not. An excellent snow event - well up to 2009 or 2013 in its extent and longevity. It goes to show you don't need really deep cold - the more marginal events can also deliver.

Yes, some comparisons with the Feb 2009 event which came up from the south and was quite marginal - that delivered six inches to East Ham. December 2010 was different - that came from the north and put down four and a half inches of lying snow. About four inches now here and I suspect we've had most of it - comparable to early 2013 but clearly the best snowfall event for several years in my part of the world.

Evening all The first snow in East Ham since the last time. A good couple of inches based on my dustbin lid measurement so about as unscientific as it gets. One or two children from the carol concert at the nearby church marvelling at the flakes. It will be interesting to see if this freezes over night or whether the heat island initiates a slow thaw. It did the former in December 2010 but in the suburbs it doesn't usually linger.

Evening all While I'm now hopelessly smitten with JMA after tonight's run, the fact remains beyond T+120, as I said last night, nothing is resolved. Tonight's T+144 charts from UKM, GFS OP, ECM, GEM and JMA reflect the uncertainty modelling heights to the north west, west and south west. Clearly, those looking for the continuation of cold will not want to see heights to the south and an LP forming to the north west but at this stage it's all very unclear.

Evening all With the notable exception of the GEM OP, an other excellent evening of 12Z OP output for fans of cold with the current air mass likely to be in charge for some more days. Something different from me tonight - today's ECM +0 chart from T+240 via T+168 and T+96 first the 850s This was well called 10 days ago on the 12Z - those looking at all the other runs need to remember to look at the equivalent suite each day. I only look at the 12Z runs - if you only want to look at the 00Z output, no problem. Looking at the 500s, the chart was resolved at T+96. That's my experience - T+96 or sometimes T+120 is the outer limit of reliability - beyond that is speculation and watching for trends. If it's in at T+96 it's probably going to happen at macro level. So, if you look at T+168 charts, it's in the world of speculation, of "guesstimating" or looking for trends but as tools for reliable forecasts, I'm less convinced. However, waste not, want not so here's tonight's guesstimates from GFS OP, ECM, GEM and JMA

Evening all Another very solid set of evening output for fans of cold this evening with both ECM and GFS producing the kind of charts to get any winter fan excited. Hints and suggestions of a breakdown but at least a week away and given some were seeing a breakdown this Saturday a few days ago not to be taken too seriously as yet. Out to T+168 and a selection of the good, the bad and the downright ugly - GFS, ECM, GEM and JMA from the 12Z suite Sub -5 850s everywhere so very decent for cold fans. Night time minima not spectacularly low but daytime maxima really struggling (how much better this would be with a deep snow covering in place?) so frost will linger in sheltered areas. Not much prospect of snow in my part of the world in the reliable. As to whether January could see a repeating pattern of Scandinavian heights, it's hinted at in far FI in GFS OP while Control briefly rebuilds the PV in its usual place before sending it spinning into central Canada.