stodge

Evening all Well, the 12Z ECM OP has awakened some interest on here and no surprise. The way it handles the weekend HP is very different from GFS 12Z OP which builds a strong HP but then has it retreat fairly quickly SW before moving ESE into Europe and keeping the UK in a mild flow. With ECM the HP hangs on and then splits at T+192 with part going SE into Europe and part SW into the Atlantic. Neither remaining cell is strong enough to resist the trough sinking south into the UK with the colder air following. Worth noting UKMO has a much more intense LP over the south of Iberia than ECM or GFS.

Afternoon all Midway through the winter cycle today (my birthday) and, as has been the case for most of my years on this Earth, wet and windy rather than cold and snowy is the outcome. Looking forward, an impressive build of HP from Sunday from the Azores but, slightly surprisingly, it only lasts 3-4 days before declining back SW and allowing a more mobile and unsettled pattern to return. Yes, we may see some frosts and perhaps some fog which will be a shade of winter albeit not what many on here want to see. The problem with the 06Z OP FI is the HP then heads back into Europe and we're back in a mild SW'ly pattern. A number of the GEFS Members handle that evolution differently with some taking the HP further west and allowing a quite potent N'ly to develop (coinciding with the MJO move into 7-8 I would think). Other drop the HP south or SE. If you want some real eye candy, the current CFS monthly run for mid-February would please many. How might we get there? Interestingly, the repeated builds of HP do have a cumulative effect in terms of amplifying and slowing the Atlantic - I also note signs of a new warming on the GFS OP for later in the month which might, with all the caveats at my command and given the lag time, suggest mid-February onward (as others have suggested in their LRFs) will be the start of a wintry phase. Of course, so much can and probably will go wrong.

It would also depend on whether a) the Siberian lobe was stronger than the Canadian and whether b) the Canadian lobe set up far enough west to encourage ridging into Scandinavia.

Afternoon all The 06Z OP tantalises with a small level warming from the North American side which weakens the TPV, sends a lobe over to Siberia and that in turn encourages height rises to the NE. It might be our way out of the current mild and benign rut but we need a lot to drop right and for some consistency as we approach mid month. I'm fractionally less pessimistic than I was yesterday.

I agree there's nothing much for the actual winter period on offer - the best we can hope for is a well-positioned MLB which could advect some colder air into southern areas. I do think March and April will be much more interesting and exciting - I think from mid-March onwards we could be looking at some really interesting synoptics as the PV starts to break down.

So the question then becomes when and how this intense TPV gets shifted or distorted? I suspect even an SSW won't achieve a full split now so we're looking beyond the confines of winter to March and April. I suspect the annual battle between colder and warmer air masses will be more interesting in 2020.

Evening all Just back from two and a half weeks (including Christmas) on Tenerife in the Canary Islands. You might think the weather in the Canary Islands is pretty uninteresting but you'd be wrong - there's a lot going on and it's not always straightforward. The principal influence for the Islands is the Sub-Tropical HP (we call it "The Azores HP") which is normally, and not surprisingly, near the Azores. To the SE of the HP cell and especially if the HP is ridging toward the British Isles, there is a fetch of NE winds (known as the "trades"). These bring cool maritime air across the islands and prevent them being as hot as you might expect given their latitude (28 degrees North). It's not always that straight forward of course - when we arrived on Thursday December 12th and for several days after, the jet tracking well to the south of the British Isles and the suppression of the Azores HP further south-west left the islands vulnerable to a NW flow and occasional showers especially for the north facing coasts. The winds were often quite gusty though nothing like the storm force gusts over Galicia and Asturias in the week leading up to Christmas. Despite the cooler breeze, daytime maxima were still 21-23C with largely clear skies with occasional cloud coming over the mountains from the north of the island. Another way the status quo can be disrupted is if the Azores HP transfers into southern Europe. This occurred just before Christmas and introduced a feed of E'ly winds from Africa. This was a clear flow on Christmas Eve allowing temperatures to hit 29c but much cloudier (more like a dust haze) on Christmas Day though still warm. It didn't happen on this visit but if the Azores HP displaces far enough east or NE, pressure can fall over the Islands either with an LP forming near the Azores (possibly as the Atlantic trough digs south and creates a cut-off feature) or an equatorial LP moving up the African coast. Both can bring rain or showers and much cooler temperatures to the Canaries. It's a wonderful winter location for northern Europeans but 29c on Christmas Eve just didn't seem right.

Evening all A bit early for me to get interested in the winter modelling but it looks an increasingly disturbed outlook through mid month with the jet close to or just to the south of the British isles and a strong flow out of North America. The main LP centres won't be the problem but embedded secondary features which would enhance rain/showers/wind as they zip from west to east across southern areas. In terms of accumulations, the usual suspects to the north and north west catching the bulk of the rain as you'd expect with the south and east not faring too badly. The question then becomes how we break out of the pattern - not immediately would be my thought. The signal for height rises to the east remains in a number of the GEFS members and the scenario of a "battleground" isn't wholly far-fetched but whether it would be SE'ly winds and slider LPs or a more conventional S'ly flow with deep LP moving NNE to the west of Ireland remains to be seen.

Evening all I try to learn without bothering the experts but this one is puzzling me - the "warming" being shown at the 10 HPA level on the GFS/FV3 charts I understand but it seems within the belt of warmer stratospheric temperatures is an increase in wind speed. First, the wind speed chart: The contrasting temperature chart: It looks to me as though the warming strat relates in some way to a corresponding wind speed increase so as the block displaces it strengthens. Therefore a warming from the Eurasian side leads to the block re-forming on the Canadian side but with a stronger if smaller core. This temperature chart is from the Control at the same time and is, I think, much more interesting: Not suggesting any of this will verify but the Control almost splits the warming and leaves the PV much weaker than the OP run.

Afternoon all :) I fear I'm a novice at this as well and I don't understand the optimism of some on here. To me, we are seeing (and still in FI) a strong warming from the Eurasian side - all that will do is displace the PV back to Canada where it will strengthen and re-form in situ and inevitably the trop and strat vortices will connect and the jet will fire up. We need two or three of these to weaken the PV enough to dislodge it further west and encourage blocking either over Scandinavia or perhaps Greenland. I accept there may be a lot else going on at different levels and at different ways but I wonder if this is where the UKMET's mild winter forecast originates - a powerful displacement which doesn't split the stratospheric PV but sends it back to Canada where it strengthens and locks us into a zonal Atlantic spell.

Evening all Well, it's still a couple of months before I get interested in the winter model output so just an observation or two. Back in the spring of 2013, the GFS would constantly show FI with milder "zonal" conditions returning to break the cold spell but they didn't verify for weeks. Now we are seeing a lot of output (12Z Control) showing a more conventional zonal aspect returning in far FI but the 12Z OP is much less certain tonight. GEM and ECM out to T+240 keep the southerly tracking jet in play as well. I don't know and the model output reflects a lack of a clear signal. I follow the Stratosphere thread as a novice and am in awe of the knowledge of many on there - I fear a displacement from the Eurasian side will simply knock the PV back to Canada and fire up a 10-14 day Atlantic spell. As others have said, keeping the PV over Siberia (and the trop-strat disconnect) helps those looking for cold. Would the displaced PV be weak enough to encourage Scandinavian HP?

Yes, probably only been like this since the end of the last Ice Age so nothing new there. The only saving grace so far has been the wedge of heights into Scandinavia which has forced the trough to align negatively. As Tamara opined, that's not going to last forever and we may have to enjoy/endure a prolonged spell of Atlantic zonality - again, pretty much as has happened every winter since the end of the last Ice Age. That in turn will end somehow (SSW?) and it's that we need to hope will lead to a 7-10 day spell of severe winter weather which will make the winter of 2019-20 in any way "memorable".

Evening all Signs of more settled and warmer conditions later in the month which is something we often see in the UK. Having a look at the Northern Hemisphere profile from the GFS 12Z, it seems the heights over Greenland are broken down quickly by what seems to be an ex-Pacific typhoon which heads through the Bering Strait and its energy invigorates the formation of LP across the very north of Canada and NW Greenland which brings colder air across Greenland and triggers a drop in heights allowing ridging from the Azores to trend NE across western Europe. This is one aspect of how tropical weather systems influence weather patterns at higher latitudes. We see it with Atlantic hurricanes but I've long thought extratropical systems from the Pacific moving into cooler waters must also have an impact. I think this explains why we often get decent weather in September and early October because the tropical systems are at their strongest, the PV has not yet formed and the jet is often weak or prone to amplification.

Morning all Not quite sure what others are seeing but 00Z ECM fairly uninspiring in the short term. That wouldn't be a pleasant summer's day but very welcome rain for the south and east. The question for next week is whether the LP will retreat far enough west to allow a brief Azores HP ridge to nose in from the SW. Well, yes. but ECM suggests it's only a transient feature with the Atlantic re-asserting into the following week. UKM this morning isn't pleasant for those wanting settled and fine conditions. GFS 00Z OP follows ECM at the end of next week: Eventually, as with ECM, the ridge collapses and the trough moves back in and it's a typical disappointing August. My summation, a much more unsettled and wet spell coming up over the next 3-4 days with some welcome rain for many, From the middle of next week, however, signs of a ridge from the SW leading to more settled conditions especially in the south but more widely by the weekend and a 4-5 day decent spell, nowhere near as hot as it has been but certainly pleasantly warm. Thereafter, clear signs for the ridge to collapse and a more unsettled spell moving fully into August with a much stronger Atlantic influence.

Morning all Didn't sleep too badly - tepid shower before bed generally works. The flow remains SSE to NNW with bursts of thundery rain coming off the continent across London and heading into the east midlands. Incredibly, East Ham missed everything last evening - we had a storm to the west and one to the east and the later evening action was about 30-40 miles east of us over the estuary and into Essex and Suffolk. It looks as though we'll catch something from this morning with some heavy rain over SE London heading our way. Still warm and it'll take some days for the sturdy London brick to give up its heat but a sense the worst is over for now.

Afternoon all To the east of London we're at 35c but as always a slight breeze from the Thames Estuary takes the top off the temperature and while a little cloud has amounted to nothing the breeze means we never reach the values recorded to the north and west of the city. Good luck to those tilting at records this afternoon - I do think today might be the hottest day of the year (or it might not). It will be the hottest day in July I think.

Evening all As to the "then what" question, UKM and ECM producing very similar output out to T+144 tonight. Both show the pool of hot air moving into Scandinavia and inflating a significant anticyclone which then pushes the residual warm air west toward Greenland. The British isles are left under the trough so a very different week next week with plenty of rain but some hope as the LP retreats back west of a new push of heights from the SW. GFS 12Z OP goes down that route with the LP never really getting in and the ridge keeping the south not too bad - obviously a deal cooler than now but still in the warm category. Control follows the UKM/ECM route but Legacy holds HP in charge until early August when rising heights over Greenland send the trough over us and it's June 2019 Part 2.

Evening all A hot or very hot ECM 12Z for the south and south east with 72 hours of 850s above 20c and the 24c line flirting with the south coast. The problem is of course we don't know how much cloud there will be and that will have a big impact as we saw last month. High 850s under cloudy skies with thunder mean sticky humidity but no heat records. The key, as we saw on 29/6, was to get the clear skies and sunshine from dawn to dusk. Other shave noted it's likely to be an outlier - doesn't mean it won't verify but it does mean, as we see with easterlies in midwinter, the rollercoaster ride will be open for business over the next few days.

Morning all The ECM this morning was uninspiring with a day of heat before a much more unsettled end to next week. GFS 06Z Legacy has got one or two people hot under the collar and we'd be looking at a solid 48 hours of hot conditions across the south east with a rather shorter spell elsewhere and to be fair OP doesn't even manage that. As the HP transits east and tries to form a discrete cell to the east we do get a SSE flow but it's either quickly filled by the trough from the west so more cloud, storms and not as hot but very humid or the HP quickly moves off into Scandinavia and the trough takes over from the south (more of a classic plume). Plenty of time for more attempts from the Azores HP to ridge NE but that pattern will always keep the hot air to the south - as the ridge advances and recedes there's no opportunity for the hot air to move up.

Morning all Some warmth in the output charts this morning but no real heat mercifully. 850s remain where you'd expect them to be and with HP building from the west the airflow keeps the heat pinned well to the south. GFS continues to show some uninspiring charts for mid month with LP moving closer as the Azores HP retreats south west. It's perfectly possible last Saturday might have been the warmest day of 2019.

fter yesterday's stifling heat here in lowland East London, a much more agreeable day today. Looking ahead, generally settled though the GFS 12Z does offer a brief N'ly but mercifully none of those silly +20 850s on the horizon which should mean 25c and decent humidity levels which we can all enjoy. That will get us into mid July so one of the big heat periods will have been survived - the beginning of August is the other time when we can see some serious heat. The good news is for a change the Azores HP looks less of a force after this week so a more Atlantic-dominated outlook. Decent enough for southern and south western parts as you would expect - indeed, the whole chart series screams typical summer weather.

Evening all Looks like it will be a much warmer if not hot week next week possibly lasting all week if the 12Z GFS is to be believed. For the south, though, increasingly thundery and for those who like that sort of thing it could be a memorable few days. No sign though this is anything more than a transient development and the medium to longer term continues to suggest a return to Atlantic conditions with heights to the NE and SW meaning the trough sits more or less through the British isles. Looking at next week's projected temperatures off the GFS 12z in all honesty nothing too remarkable - two or three days at or around 30c for London and the south east but perhaps the lack of established heat is going to hold the higher temperatures back coupled with cloud and storms.

Afternoon all A lot of uncertainty in the medium to longer term, I'd argue, from the models this morning. The question is how do you keep the E'ly going? Basically, two approaches - one is to maintain northern blocking by keeping the HP over Scandinavia or hint at some form of retrogression. The second is to expand and develop the trough north toward the British Isles which maintains an E'ly flow even if heights are absent further north. I'm far from convinced a return to warmth is going to mean a return to settled conditions for all though I do think the north and north west (as they often do at this time of year) will do well. Further south and south west, the risk of thundery showers coming up from the south is present as well as more prolonged and heavy rain if the Atlantic LP tries to approach. As for the PV and the strat playing their part, the zonal winds are forecast to return to a more normal speed having been very high for late in the season and it may well be the speed of the wind drop is exacerbating blocking tendencies but if we get a wave 1 warming it would only re-strengthen the PV on the Canadian side and force a return of Atlantic conditions into May.

The 06Z changes little - even the Parallel joins in with some serious retrogression. Had that LP to the west of Norway come SSE rather than SE it would have been perfect for some late April snow. The OP conversely ends pleasant as we get an increasingly SE flow off a warming continent while Control in low-res shifts the block far enough north to allow the trough to take over the British Isles so a changeable end after a settled spell.

Morning all An interesting start to the week - having looked as though the E'ly might not last too long the main outputs are much more bullish this morning about a continuation into next week and perhaps beyond. It seems as though an intensifying Scandinavian HP will hold off the Atlantic LP which will then fragment ESE maintaining the E'ly flow. GFS 00Z OP is a thing of beauty in low-res with a Greenland HP setting up and a good old fashioned late winter cold blast incoming from the NNE - almost perfect, Parallel beings back a westerly flow while I note GEM also teases retrogression at T+240. ECM and UKM are fairly close at T+144 but UKM maintains a stronger Atlantic profile so it all looks very precarious for E'ly fans. ECM keeps a strong Scandinavian HP with a ridge through to Greenland but it's a warmer SE'ly over the UK by T+240 so much more pleasant. Taking the ECM and UKM evolutions, I'd have a look at the 00Z GFS Control and see if that's where ECM might be heading after T+240.