stodge

Evening all Well, I'm none the wiser - it does seem as though we'll have notable colder incursions midweek and perhaps next weekend. From there, GFS OP starts promising with the height rises over Scandinavia but the 850s are uninspiring further into FI. Control and GEM take us quickly back to a more conventional Atlantic onslaught. The signal for heights to the north and east is there but I remain unconvinced for the moment.

Evening all Tonight's ECM at T+240 is a million miles removed from last evening's so it's a healthy dollop of caution from me at this time. The continuing inability of the Azores HP to either positively align or move fully into Europe is the take-away from tonight's output. It seems we have another week of the NW-SE alignment of systems with LP moving SE across or near the British Isles. The tease of a following height rise in Scandinavia (ECM and GFS OP) is often a chimera, let's be fair. We do need the PV to be well across northern Canada and for the zonal winds to be reduced for that height rise to take hold and be maintained. All too often there is too much residual energy in the northern arm of the jet and the HP sinks to the more comforting mid-latitudes. IF we can get the very cold air advected into southern and eastern England, we'll get a classic temperature inversion across the British Isles but that's of no comfort for fans of snow - this is likely to be very dry, cold, crisp air so frost and fog the main items and let's not forget ice days are perfectly possible in December with inversion - it's not all about DPs and snow if you like it cold.

Evening all A lot going on tonight and I hope everyone is keeping safe. As for the 12Z output, GFS Control is very good and there's not much wrong with ECM to this observer. As for GFS OP, yes, it does set up a huge Russian HP which begins to intensify west but the PV looks too close to NE Canada in far FI. JMA is decent for cold fans while GEM is great for storm enthusiasts - particularly those who like rapid cyclogenesis from secondary depressions.

Evening all Have to say on a quick canter through the 12Z output, I'm really pleased. The cold spell, far from clearing out on Sunday, now looks set to continue through much of next week and of course that takes us into the wilds of FI. GFS Control tantalises with Scandinavian height rises in a way GFS OP doesn't. JMA is also well worth a look out into FI for continuation of the negative alignment theme. It might just be me but a couple of steps forward tonight, I think.

Evening all After this weekend's fun and games, what's in store for early December? It's often a period of mild or very mild conditions (17c has I think been recorded in North Wales under Foehn conditions). Not much sign of that currently - the two options on the table seem to be a continuation of the negative alignment scenario with LP systems moving SE into Europe between heights to the SW and NE and a more anticyclonic evolution with heights through the British Isles and to the east. What strikes me from the 12Z GFS OP is the Atlantic and the jet stream are still a long way removed from the zonal monster we expect. This enables amplification to be attempted into Scandinavia and the flattening of that into deep FI is unconvincing. However, Control offers a more active Atlantic and that encourages continued negative alignment.

Excellent post from @Uncertainy and plenty to mull over. The notion of strong heights to the east and north east has been mentioned more than once - the classic stand off charts between continental cold and oceanic mild airmasses leaves the UK in an often benign S'ly airflow. We can expect heights to wax and wane and when they are closest and strongest we can advect some continental cold. An even rarer phenomenon these days seems to be the UK anticyclone. One of these mid winter can bring ice days thanks to significant inversion and it's not to be sniffed at if you want cold though not much hope for snow. The key then to what looks an increasingly dry winter is the position and orientation of any HP. Will we be looking east and if so how far?

Evening all Well, yes, some understandable excitement though I'm often reminded the happiness of a Sunday evening model output is all too often crushed by the dank reality of a Monday morning set of zonals. Chin up, all of them, as Mrs Stodge would say. The key to this observer is the small Atlantic LP which approaches the Azores at T+144 as shown on both the ECM and GFS 12Z OP runs. This forces the HP more north and east which in turn amplifies the Atlantic and leads to the shot of WAA up the west coast of Greenland and the downstream retrogression. Once the pieces are in place, the whole thing is a joy to behold. GFS OP tantalises with a Scandinavian HP at the far reaches of FI - I prefer the Control offering but then living in East London I would. That's -8 uppers on a NE'ly which works for me if you want snow at the end of November I would guess. Just a bit of fun of course at this time. Always worth saying, we ain't there yet. If the LP fails to develop and the HP remains further south the Atlantic will block off any retrogression. We need the HP to build as far north as possible to begin the process.

I'm also wondering if this winter is going to be persistently chilly - never stunning cold but plenty of cool/chilly spells. Perhaps we all look for those remarkable 7-10 days out of 90 and forget the other 80-83. Indeed, to get one good month (Dec 2010) means forgetting the other two which were unremarkable. Frequent spells of slightly below average temperatures might not be remarkable and indeed the whole winter would be written off by many but in their own way would be interesting. An extended period for example of negative alignment would bring chilly and cold conditions especially to north and east but not the snowfest to which many on here aspire. This isn't a winter forecast by any stretch - just an observation of some of the possibilities.

Well, to no great surprise, the GFS 12Z OP and Control runs generated plenty of comment. A classic retrogression evolution with heights over Scandinavia heading west through the British Isles and then north-west into Greenland allowing the trough to drop south into Scandinavia and Central Europe. It's a classic pattern for cold and if we were in January and this were at T+6 (despite some claiming it could still go wrong etc), it would be a wonderful scenario for those wanting snow especially across Eastern Britain. Unfortunately, other models aren't anywhere near as enthusiastic - given it's all in FI I certainly wouldn't expect model unanimity at this stage - indeed, GFS might itself drop the scenario by tomorrow. We will see a build of heights over Scandinavia but the other possibility is the heights will sink quietly south and leave western Europe in a mild WSW'ly airflow or decline away east which might be more helpful for cold fans. I wonder if the GEM evolution might be where we end up - no retrogression and a half way house of the trough dropping into Scandinavia but too much energy in the Atlantic to allow heights to build north and west.

A colder outlook in the final third of November isn't wholly unusual - there's often been a colder snap around the 20th-21st of the month and it's often been a northerly. It doesn't start and the start of December tends to be very mild with a long fetch SW'ly. The cycle of colder spells and milder spells is the feature of the transition from autumn into winter. There have been forecasts of a "front loaded" winter and of course 2010-11 was a prime example - everyone remembers December 2010 but who remembers January 2011 and February 2011? It's all nice to look at for now - a lot depends, it seems to me, on the position of next weekend's HP and that small LP coming up close to the Azores which encourages the ridge northward.

Evening all I applaud the enthusiasts who can get so much from tonight's 12Z output. The GFS OP is very typically anticyclonic late autumnal fare - the interesting thing is the shift of core heights from the south west more towards the east and we get a situation we often see with a large mid-latitude block over the east of Europe deflecting the jet up and over Scandinavia. It either means mild or very mild SW'lies or just possibly a cooler continental feed but nothing too dramatic. I do wonder if heights to the east will play more of a role this early season - that would be indicative of a weaker than usual PV giving a chance of some heights building into Scandinavia.

Evening all I can imagine the end to the GFS 12Z OP will have got quite a few salivating - the classic stand off between the Scandinavian HP and the undercutting Atlantic trough - happy days. In the shorter term, it does look as though as the trough finally digs south to the east, we'll lose the balmy (or barmy) SW'lies and revert to a much cooler NW'ly flow for a few days. T+192 for the 12Z suite from GFS Control, OP, GEM and ECM The interplay between the Atlantic HP and the sub-tropical LP looks key to how this will play out. GEM creates a significant LP to the west of the Azores which means more of an Atlantic ridge and a more defined N'ly. Others keep the trough much closer in the North Sea - either way, it's much cooler and more unsettled than what we are currently enjoying. ECM ends with a lovely chilly November NE'ly - yes, I'm not convinced either.

Evening all Well now, of little import to the UK but this is a very cold run for Scandinavia and that's a decent little cold wave pushing through Finland and Sweden. Nearer to home, the heights to the NE promoting negative alignment of the trough sending LP ESE through the British Isles into Europe. Interesting to see if this trend continues or develops later in the month.

Fair to say benign continues on the 12Z GFS OP - Control is rather more interesting if you fancy something colder from the north. GEM goes strongly unsettled - a return of Greenland heights by T+240. Plenty of options as you would expect - I wouldn't rule out a brief colder incursion which wouldn't be unusual and some early snow for the Scottish mountains.

Lokað til austurs á Hellisheiði WWW.MBL.IS Lokað er til austurs á veginum um Hellisheiði um óákveðinn tíma vegna veðurs. Að sögn Vegagerðarinnar er ökumönnum bent á hjáleið um Þrengsli. A hint of winter perhaps....

Evening all What I take from tonight's modelling is a progressive change to a more "traditional" and seasonal pattern as we move into and beyond the middle of the month. The extended period of LP over the Continent looks to be easing as, at long last, the Azores HP builds NE through France instead of being forced to the north of the British Isles. This may be due to more energy over Greenland (perhaps the result of ex-Hurricane Larry) which finally fires up the long-dormant jet forcing heights back just to the south as a more typical autumnal SW'ly sets up later in the month.

Evening all I'm struggling to see much clarity as we move into September. ECM and GEM keep northern blocking which allows Atlantic LP to roll in to the British Isles on a southerly jet. GFS and JMA are much better keeping HP close to or over the British Isles - I'm interested to see GFS introducing ex-hurricanes though as always with these modelling their exact trajectories seems an inexact science at best. One seems to move NE, NW and then NE round the Azores HP - GFS Control has an ex-tropical feature moving in towards NW Europe.

Evening all Again, just a quick glance at the evening output but the Greenland heights are hugely influential keeping the jet (as it is) to the south and suppressing any push of Azores HP. However, as you might expect, a lot of options on the table in the mid to long range - T+216 500s: ECM, JMA, GEM, GFS OP and GFS Control from the 12Z output. You pays your money....etc. We spoke about the possible breakdown the other evening - just some of the possibilities.

Very true - up to a fortnight more of E'ly or NE'ly winds for downtown East London from the 12Z outputs - extraordinary for any time of year. Breakdown? Some thoughts - one possibility is from the south with the European LP encroaching north as the HP declines - the E'ly flows continues but becomes increasingly unstable. Another option (probably the favourite) is the HP sinks south, probably to the south west and allows Atlantic systems to encroach from the north-west. An outsider would be proper retrogression and a Scandinavian trough with LP moving down the North Sea bringing rain, showers and cool conditions. That's my three on first thoughts.

Getting true retrogression is difficult enough any time of year, whether summer or winter. It's not just getting the heights in the right place - you also need the trough to drop nicely over Scandinavia to bring the N'ly down over the British Isles. Note the small LP over the Norwegian Sea which would extend SSW towards the North Sea as the HP retreated NW.

Evening all Yes, a chilly NE'ly already present here in east London but it's a fine and glorious evening. It may not be full-fledged retrogression but with HP sitting to the north or north-west for a few days a steady ENE for most parts so, as they used to say, "go west" if you want the best of the weather but still decent further south and east. As to the longer term, as you might expect, the tendency is for the HP to slip back south or south west. No sign on GFS at any rate of any ex-hurricanes to bring some energy forward - GEM suggests otherwise.

Evening all In contrast to many other late Augusts, not one to sit out in the north-facing back garden this evening. A distinctly chilly NE'ly setting up and I suspect we'll have it for several days in this part of the world. Fine and sunny and otherwise glorious - I suppose I could always sit in the front garden and mumble at people as they walk past......

Evening all With this morning's Daily Star telling me it's going to be 31c by the end of the month, I'm looking for those +20 850s on this evening's charts. Let's see what we do have at T+216 in terms of 850s from this evening's 12z output. T+216 is Wednesday August 25th Respectively GFS OP, GFS Control, GEM, JMA and ECM Once again, GEM is the slight outlier keeping heat closer while all the others, frankly, don't. Now, let's not get carried away - the prevailing synoptic is to develop strong HP to the north of the British isles which means an E or NE flow so for the west it's going to be very good indeed with plenty of warm sunshine and hopefully any low cloud will burn back to the coasts early further east. It's what I call "San Diego" weather in reverse and frankly it's my favourite type of weather - low humidity, pleasant sunshine etc. I'd much prefer it to stifling heat and high humidity. GEM and to an extent JMA have more of an ESE so draws off warmer air with a short fetch across the cooler water. Entirely possible and oddly enough in midwinter, my favourite scenario for cold for the south east. Other models build the HP more to the north than north-east so the flow is more across the North Sea with a longer fetch. All in all, I like what I'm seeing tonight - if GFS in particular verifies, it's going to be very amenable weather. Glancing out to the end of the month for a bit of fun GFS OP and Control at T+360. One of the things I've observed this summer has been the persistence of LP over North Africa feeding into southern Europe. This has left heights further north than normal and has left Europe and southern Britain facing more thundery outbreaks. If you were to posit a shift of synoptic patterns north in response to a warmer world, this might be what you would see. The heat build up over North Africa manifests with heat LP as we see over desert southern California and pre-monsoon India. The HP response is to sit further north or west - it's most evident on GFS Control when the LP waxes north and creates instability over western and north western Europe - the outcome is heat and storms. You see the same in Southern California, Nevada and Arizona when humid unstable air moves up from Mexico - heat and storms. This is aided and abetted by a moribund Atlantic and a lack of energy to move the synoptic pattern.

Evening all Fans of heat were starting to get excited last evening as the very real possibility of a classic "plume" of hot air advected from Iberia heaved into view. Let's see where we are tonight with the T+216 850s from the main models: Respectively, GFS OP, GFS Control, GEM, JMA and ECM: GEM looks the outlier with all the others showing hot air building from the south by Monday 23rd. JMA shows the plume already easing away to the east so may be progressive but GFS OP and Control and ECM all look very close. Five days on and for both GFS OP and Control, the heat has moved away. The problem for heat fans is the HP builds right over the top of the British Isles into FI cutting off the flow of hot air. It will be fine and settled and warm or very warm but really hot - perhaps briefly in the south but a the HP eases west or north west, a NE moves in and chases the heat away. I'm not currently seeing a prolonged hot spell - I do think 2-3 days of heat (daytime maxima above 30c) are very likely for the south just before the Bank Holiday before the cooler air returns. One thing I do see is a prolonged spell of settled conditions with little rain and hopefully some fine and sunny days.

Late afternoon all After a bright and breezy start and middle to the day here in lowland East London, it's gone downhill rapidly in the past two hours as the shower/squall line has edged SE and now lies right through central London almost on the line of the Thames. A succession if heavy showers merging into a more continuous spell of moderate rain currently. The NW radar "suggests" the shower line is edging further SE so the worst may be over for us in the next hour or so.