stodge

Evening all A mild week once we get rid of the weekend's LP - a long trough aligned positively from mid Atlantic to Scandinavia feeds a flow of TM air from the south west so above average temperatures but rain for western and north western parts through the week. Hints next weekend heights from the north will elongate the trough more to the east as the jet is pushed south so the unsettled conditions spread to eastern and southern areas but beyond that far from clear. Obviously, 12Z GFS OP has plenty of interest but Control is more mundane so we'll have to see if it is an outlier or the start of a new trend to a pattern change. The ongoing SSW doesn't seem to have an immediate impact - my thought it might be a final warming not correct but the "recovery" in the jet from a reversal is nowhere that we saw in mid January - the zonal winds move back slightly westerly but it looks more like the proverbial dead cat bounce.

Evening all The pattern for next week has resolved. The collapse of heights to the north east aided by residual energy in the Atlantic allows heights to rise over Iberia and consequently a long positively aligned trough ushers in a run of south west TM air. The one thing that won't bring is a prolonged dry spell - indeed, more soaking rain forecast over the next 7-10 days for the south west of England, Wales and especially the north west of England - the usual suspects. Beyond that, some idea the trough will finally clear through to the north east ushering in a colder spell with perhaps heights building to the west. The 10 HPA vortex temperature profile looks like final warming to me but little sign of a tropospheric impact in tonight's charts - again, as some have argued, the impacts of the SSW may be far from clear as yet. Longer range CFS charts play with northern blocking around Easter - nothing desperately unusual in that, April can be prone to E'ly or blocked evolutions.

Evening all Starting to firm up the early part of next week and despite the main LP crossing northern France over the weekend, enough residual energy remains in the Atlantic to spawn new LP and keep a broadly unsettled theme going up to midweek. Those hoping for renewed cold look like being disappointed while those looking for early warmth likewise. A little respite for the south and east in terms of further rainfall but more soakings for western and especially north western parts. No sign of the SSW having a significant impact as yet but as it often the case in late March, northern blocking starts to show its hand to an extent. Hard to get the detail as yet but a southerly tracking jet obviously leaves southern Britain more vulnerable to further rainfall.

Just glancing at the 12Z CFS - if northern blocking is your thing, you're going to enjoy April this year.

Evening all A far from spring like weekend approaching with a fairly deep LP scheduled to be close to southern Britain by Friday and moving only slowly east into the early part of next week. The removal of heights from Scandinavia means there's nothing to stop the next LP aligning positively and with heights building back into the western Mediterranean it looks as though it will turn milder next week but not really settled with rain never too far away especially from western and southern areas. Signs of another trough disruption later in the month but little sign so far of a tropospheric response to the SSW. 12Z GFS Control is perhaps the most interesting in terms of keeping the PV over Siberia - other models try to feed the very cold air back across the Pole. I'm not sure the post-weekend evolution is anywhere near resolved as yet but the disruption of the trough to the south looks to be within the reliable.

Evening all Without worrying too much about the medium term or FI this evening, the initia 96-120 hours seems to be falling into place with the Atlantic trough disrupting SE towards Iberia thus confirming some form of Easterly flow for the British Isles. Next weekend could be another washout for southern areas in particular. The heights to the NE don't look robust enough to hold and after a brief col, the Atlantic trundles in agsin but it's a very slow process commensurate with a very weak jet. Plenty to be resolved yet.

Evening all Another fascinating batch of 12Z output. To be fair, far from all the models are in the "cold" camp - JMA being a good example. The key seems to be getting the Scandinavian HP to orient west and then north west to set up a more direct E'ly feed which in turn encourages the Atlantic trough to move into Europe and offer "interest" and "potential" to southern areas. We're a long way from getting the detail of next weekend resolved - we will have an LP close to the south west on Monday and the first manifestation of the strengthening Scandinavian block will be a shift to a SE'ly air flow (still mild) while the trough seeks a way under the evolving block from midweek onward. The risk comes if the trough fails to get into Europe before pressure rises over Iberia which would maintain the SW flow - it is a risk and not one to ignore.

WYorksWeather That's not how it works though. If you have 10 of something at +10 and 10 of something at -10, the mean would be zero but there is no actual instance of zero. I look at those two diagrams and I see a lot of cold options balanced out by a lot of mild options. That doesn't mean "nothing to see here" - what it actually means is there are a number of warmer and colder evolutions in the mix as you would expect in March which is typically a time when warmer and colder airmasses meet and co-exist close to the British Isles. At the moment, the number ans strength of the former and the latter are roughly in balance. That means uncertainty and a lot to be resolved both in the near term and especially so in FI.

IDO I'm much less convinced by "certainty" at Day 10 than I would be certainty at Day 4. This winter has been a fine example of the best laid plans of Day 10 forecasts not surviving to the "reliable". Let's see where we are this time next week.

IDO Tonight's party-pooper. After last night's GEM 12Z OP, it is interesting to see the evolution even on the table let alone from the OP run. As with last night's GEM, the key to the evolution is having the Scandinavian HP even further north which pulls the very cold air over from NW Russia though the airmass itself is of Arctic origin. The cold airmass flows WSW over Scandinavia and phases with the energy over southern Britain.

Evening all Well, it's good to have some interesting synoptics in March (and not unusual in all honesty). The journey from the weekend seems to be settling - the LP sends enough energy back west into the Atlantic to spin another vigorous little LP towards the south west on Monday but and we might get a brief S'ly flow midweek but the Scandinavian HP intensifies and the LP begins to disrupt south leaving the British Isles in a SE'ly or ESE'ly flow by the end of next week. Plenty of hints in FI we could get a more E'ly flow but nowhere near the reliable currently. The European warming continues to feature strongly on the 10 HPA charts - it's unusual to my eye but likely to keep the synoptic interest going.

What GEM 12Z OP does is develop the core of heights not over Scandinavia but north of Norway (up around Svalbard) which allows a pulse of cold air to extend south west from a small LP over western Russia and that flow of cold air eventually makes it to the British Isles. The vast majority of other output keeps the heights over Scandinavia so any colder air is steered toward south eastern Europe.

Met4Cast You really are a party pooper aren't you? I thought this deserved another airing - yes, I know it won't verify etc, etc. On a more serious level, still a lot of uncertainty about next week - the more immediate concern would be yet more rainfall early next week as a quite vigorous LP approaches from the south west re-enforced with the energy from the coming weekend's LP as it deflects back west. We could be looking at a standoff next week between the residual Atlantic trough to the west and heights to the east which would leave the British Isles in a mild or very mild S'ly feed. The question though is whether, as per JMA, the trough will be close enough to keep the British Isles unsettled with periodic secondary LP in the flow. OTOH, 12Z ECM OP has the Scandinavian HP in charge by this time next week while 12Z GFS OP has a couple of very mild days before the Atlantic LP disrupts south as heights build from Scandinavia to Greenland. At the moment, a lot of options are on the table (as you'd expect). One of the problems with this winter has been what is perceived as the persistent "failure" of the models to accurately predict what happens. My honest view is until it comes within T+96 you simply can't rely on it. Looking at the 10 HPA chart from GFS OP, it looks a sorry vortex by mid month with the next big warming coming from Europe - I'd assume a European warming would push the PV over to North America leaving the possibility of heights over Scandinavia but with residual energy over western Siberia, I just wonder if we might see the block over us. All speculation at this time of course.

raz.org.rain I can certainly believe warmer for a while especially if we get into a stand off between the Atlantic LP and the Scandinavian block and we get a S'ly feed but the models don't show that last ing long and unlike most of these "battles", the Atlantic loses as the trough weakens and is forced south by heights bulilding toward Greenland.

Evening all Certainly some interesting charts in tonight's 12Z suite albeit a very long off but nice to look at for now. There's still uncertainty over the more immediate developments with the LP disrupting south on Friday but enough energy phasing back into the Atlantic over the weekend to maintain an unsettled theme but at the same time the Scandinavian block is intensifying and this causes an initial stand off with the British Isles in a mild to very mild S'ly flow but with the heights building to Greenland, the LP is forced south and a SE'ly regime sets up across the British Isles with 12Z GFS OP offering a real tease in far FI of some colder air (-8 850s in March anyone?) moving in. The 12Z OP 10 HPA shows a strong European based warming which you don't see every day of the week suggesting further amplification. Let's be fair - northern blocking in March isn't unusual and for those looking for an early spring the orientation of such a block is crucial as the difference between a warm-sourced SE'ly and a cold-sourced E'ly will be considerable. It should also be noted 12Z GFS Control isn't interested and some keep northern blocking but the trough much closer to or over the British Isles. That's the thing with spring heights - if you want dry, you don't want the heights to be too far north and angled too directly east-west as that traps the trough over us but a stronger Scandinavian block keeps the trough more to the south west or south.

Evening all A lot of uncertainty across the 12Z suite this evening. The LP later this week is the first problem - the negative alignment drops the trough south on Friday which could be quite an unpleasant wet, cold day but beyond that will we see a clean ejection of that energy south? It seems not as in the face of blocking to the east the LP eases back west and re-enforces the Atlantic trough leaving the British Isles in a mild, very mild or even warm stand off by the end of the week after next. One option would be for northern blocking to extend from Scandinavia to Greenland dragging the trough south and introducing a mild ESE'ly flow (again far from unusual in early spring). 12Z CFS is by contrast a nirvana for cold and snow fans but I suspect this won't happen.

Evening all Some very interesting output this evening from the 12Z suite. Having been the first to moot the idea of next weekend's LP disrupting to the south, both GFS and ECM have moved on having the likes of GEM and JMA looking they are 24 hours off the pace. Neither GFS nor ECM have a "clean" disruption of energy to the south allowing the ridge to build through the mid Atlantic and into Scandinavia. Instead some energy heads back west to the Atlantic and restarts the mobile pattern. GFS has a third attempt at dropping the trough through the British Isles in the second week of March and for those hoping for some respite from rain down in the south, this is the nightmare scenario as the cut off LP takes up residence close to southern Britain keeping unsettled conditions going for a while. Presumably due to the weakness of the PV and the decrease in zonal winds we see the jet weaken and amplify into March with the trough stalling or dipping south with heights extending towards Greenland - again, nothing unusual in and of itself though perhaps a month or so then we often see so it ends up an April synoptic pattern. KSA 12Z has a pretty good take on it though I've seen no verification stats for the South Korean model.

Evening all The rest of February looks to be set. Once the LP which crosses southern England into Sunday migrates to France on Monday (leaving a raw chilly day for the south east I suspect) HP builds back and with postive re-alignment a couple of quieter days before the pattern repeats at the very end of the month as the Azores HP is aligned negatively allowing the trough to sink over the British Isles. The start of March seems to have two options - I spoke last night about a clean phasing o energy from next week's LP and both GFS and ECM OP (and KMA) runs have this allowing a strong build of heights to the north east. Other models aren't so keen - those building the Scandinavian HP keep the core of the displaced PV over western Siberia so the air flow is more ESE or SE than pure E or NE. The coldest air dives over western Russia (-16 850s) but could still advect west by mid month. The 10 HPA FI charts continue to show the PV in shreds - caution last night with hints the reversal might not be as drastic as some hoped. We'll have to see where we are today. The possibility of northern blocking won't help southern areas yearning for a drier spell as LP could be close to or over southwestern areas.

Here's the thing - looking at the 10 HPA from the GFS 12Z OP we see repeated warmings from the European and Siberian side. Now, as the strat warms on one side, it cools in response on the other and I suspect we see an increase in zonal winds between the cold and warm areas. We actually need to see an end to the warmings because that tends to equalise the 10 HPA temperatures across the northern hemisphere and would also lead, I suspect, to a slackening of zonal winds. That's how I see it - I'm doubtless wrong.

Evening all After we get through this weekend's fun and games and both Sunday and Monday look particularly unpleasant in the south with the LP over southern counties on Sunday and easing SE into France on Monday leaving us in a short lived NE'ly. Normal service tries to resume but by Thursday another trough is digging south over the British Isles - 12Z GFS OP disrupts this splitting the energy and allowing heights to build in the col. Other models are less keen to split the energy and keep the cold trough over us through into early March. From there, who knows? KMA might be some people's idea of the answer but I remain to be convinced though it's nice to look at. As for the 10 HPA, repeated warmings keep the PV unstable but intact promoting cooling in response. How this will play out as we go through March I'm not sure - there have been plenty of forecasts suggesting a zonal wind reversal so we'll see. I like March and April - interesting synoptics especially if we can get some serious northern blocking and a contest between the colder and warmer air masses - we know who wins every year but the battles can be interesting.

damianslaw Indeed, the Iberian HP retreats west into mid-Atlantic allowing the trough to drop down through the British Isles ushering in a cooler and more unsettled phase with plenty of rain and wind and for higher ground as the PM air digs in, snow. That's basically a week on from now but beyond that, plenty of evolutions and no real clue. The negative alignment prompts a strong pressure rise in mid Atlantic but will that translate into anything favourable for UK cold? Another option is the souward jet will encourage more LP from the Atlantic to move in from the west and of course we could see HP try to move back into Europe to reset the mild pattern. All up for grabs at the moment.

Evening all The key event, while not yet in the reliable but supported across all models, is the HP withdrawing from Iberia west into mid-Atlantic which allows the trough to negatively align and offer a spell of PM-dominated unsettled conditions with potentially large amounts of rain (snow for higher ground) at the end of next week. Exact positions of the trough are far from resolved but it would be quite a shock after this week's exceptionally mild conditions. Beyond that, it may be the Atlantic pattern will quickly re-assert (GFS Control) or it may be an opening for a more meaningful mid-Atlantic ridge offering a transient N'ly which again would be a shock to the system for all though any snow would likely be limited to high ground (not perhaps in the far north of Scotland or the Highlands and Islands). Another option well touted in model FI is the continuation of negative alignment and a second LP moving NW-SE through the British Isles at month end. Far too early to be thinking about March - the state of the 10 HPA vortex at the very end of FI on the GFS 12Z OP continues to suggest slower zonal wind speeds and opportunities for amplification which in March usually means northern blocking and a stand off between colder air to the north and east and warmer air from the south west.

I don't think a "major" SSW was ever on the cards. What we are likely to see is another hint of a split but this time a less dramatic recovery - the zonal wind speeds forecast (15 m/s) are still on the low side of average - and this seems confirmed by the briefest of breaks in the Atlantic dominance in the last week of the month. March continues to show a prolonged further weakening back towards zero so you'd expect the Atlantic train to slow again with more opportunities for heights to build and amplification to occur. We could end up with a warm early spring or we might not. As we see, the response to a strong Wave 1 is to re-strengthen the vortex so the signs are March will see a gradual weakening which might be more conducive to blocking on our side of the globe.

Met4Cast Yes, I am firmly of the view Wave 1 warmings from Siberia (far more common than Canadian warmings) have regularly affected British winters for decades if not centuries. The PV is sent back to Canada/Greenland and we all know what happens then. This process of PV development, displacement via Wave 1 and eventual split either via an SSW or final warming has, I suspect, been the pattern for hundreds of years. As to why there are nuances - some winters see much less Wave 1 activity than others, I don't know. I don't know if there has been any study into how the polar vortex behaved 100, 500 or 1000 years ago. As to how it will behave in a warming world, I don't know either. A warmer atmosphere suggests more energy and more volatility so you'd expect more warmings but would it be weaker longer term?

Evening all A lot of negativity on here tonight and it's not hard to see why. However, we do have, based on GFS OP and Control, an "interesting" storm set to move over us at the end of next week which would doubtless be named whatever the next name is. Other models not so keen on the storm coming as far to the south but the Atlantic train rolls on into the last week of the month with yet more rain and wind as the jet edges back south. The vortex does continue to look weak with another strong warming later in the month so far too early to be negative about March and the seasons take little notice of the arbitrary definitions of when season should begin and end. There's also the not unjustifiable thought we might get our most favourable winter synoptics in spring - cold Easter anyone?