Man With Beard

Continuing my look at the Bank Holiday weekend then - Not a great deal of change overall compared with yesterday. By T240, about 60% of GEFS members on the 00Z still stalling a low far enough to the west of Ireland to encourage southerlies for most, with significant enough similarity to take seriously as a cluster. The ECM mean at this range, like yesterday, a little further east with the pattern - but the means are similar enough really: So a betting man would still be putting money on above average temperatures, though a 50/50 call on whether that be hot and dry, or warm with frontal interruptions (the chances of frontal activity increase quickly as one heads west) All rather similar to the NOAA outlook from last night: The ECM op this morning should not be taken too literally in my opinion. It's a bit of a freak that England/Wales is the only spot under a tiny continual cold pool within 1000 miles in any direction! And at the timeframes involved, you'd hope we'd have a decent chance of seeing the warmer air around us instead, seeing that in general, there isn't too much cold air around.

The GEFS this morning has caught my eye. Looking at the GFS op at T240, which suddenly plucks out a stalled trough off the west of Ireland dragging up a southerly, you could think just one of those things that happens in FI: .. until you study the whole GEFS ensemble set, with 15 out of 21 members stalling a significant trough in a very similar place at the same timeframe - I could post any of them but for space sake I'll just post this one: Note the 850s mean gets close to 10C around that time for London, and not masses of rain (you need to click the link below to see): http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=306&y=141&ville=Londres ECM mean not as dramatic but clearly favouring an Atlantic trough too, more low pressure influence on this one but could easily go the same way afterwards: Given the recent tendency for the models not to see the full strength of the Atlantic until a nearer timeframe, more runs are certainly needed - but as far as we can see right now, heatwave conditions are definitely one of the options for the Bank Holiday weekend. If it's still looking like this by Saturday, get the suncream and the BBQ prepared.

Vorticity - yes that has been on my mind too What we've seen in the past few days is on absolutely typical example of what the models often do. How many times have we seen this over the years? In the mid-long range, the models pick up on the macro-signal to push heights from the Azores towards the UK. Look at ECM archive charts below at T240/T216 for the coming Saturday: Then, around D6-D8, the models pick up on micro-signals, usually being extra disturbances coming from the Atlantic and, with heights being too weak to withstand, we see a turnaround - BBQ charts replaced with umbrella ones. As shown on the ECM at T192/T168/T144 below: But there's often one last twist in the tale, and this is the one I don't really get - just before the point of no return, the models decide that there was actually some merit in the macro-signal after all and there is a slight backtrack on the dominance of the Atlantic. And hey presto - here's today's ECM for Saturday - now at T120 - the bump of heights towards NW Europe is back: I reckon that the T120 result is what happens 70% of the time when the T240-T144 pattern shown beforehand occurs i.e. when a decent pattern in the long range gets overridden in the mid-range, there seems to be a small bounce-back to the original pattern just before FI ends. OK - in this case, the implications are small - areas to the south and east of London may get two decent, warmish days on Friday/Saturday, but apart from that it's pretty wet - time has gone for a big enough correction to allow more areas escape the unsettled weather. But when the weather seems on an Atlantic knife-edge, where it could go either way, I would suggest looking back at what the signals were in the T200-T300 range - more often than not, the weather will nudge back in that direction slightly, especially when there was a big turnaround between T150-T200. Doesn't always work but if you look for this over the summer I think you'll find this idea is right more than wrong.

Indeed knocker. The problem I see though is that the models are only building in weaker positive anomalies in the long term. These almost always seem to get eroded in the D6-8 period, perhaps because of a very slight prior underestimation of the Atlantic. I suspect we may have to go through another a full unsettled week after next weekend.

Huge turnaround this morning in the T192+ range, which of course can happen at this range. GEFS now has 12 out of 22 members with low pressure slap bang on top of us by next Sunday, all pretty similar to the op: However, eight members remaining with a stalled trough to the west so not a dead duck at all. The first one below would need a pretty dramatic turnaround. The second is a bit more typical of the cluster: Will be interesting to see where the ECM mean goes this morning, as last night it was much more like the last GEFS member shown above.

A lot of toasty runs appearing for next weekend - this morning's are not the first. Long way off but one to watch:

So confidence growing on a nice period Sunday - Tuesday next week with temperatures rising - probably back into the very low 20s (warmer runs now harder to come by). Midweek onwards though, models now firming up on a typical Atlantic trough centred to the NW, bringing changeable conditions for the south and probably unsettled weather for the north, as the ECM means at D8/D10 show: The GEFS is a bit of a mixture for the end of next week - either changeable as heights battle against troughing to the north - or more unsettled for all as the Atlantic trough makes a more decisive move south. Most options fall somewhere between these two: As Summer Sun points out though, many ens members show improvements once again as we get further out.

ECM and GFS parallel with plenty of cheer for summerites. Cut Saturday out (and Friday in the north) and they are excellent runs, especially GFS(P). The Azores High builds in nicely from Sunday and quickly warms us up - back up into the 20s by Monday, and 22-25C for midweek on the parallel. Less settled on the ECM by D10 for NW areas but that's way off.

Good to see you on here again CS Well the Scandi trough was the outlier solution a couple of days ago, and now it's the form horse. Recent summers have often seen low pressure in that location a little further NE by T0 - I'm tempted to expect the same this time, which would lead to more of a glancing brush on the cooler conditions for the east, but something fairly decent for the west, especially SW. By next Sunday, something like 10C on the east coast and Scotland, 15C for central areas and 17C or 18C for southern facing coasts, particularly in the SW. Mainly dry for all. Warming up a little into the second week.

Afternoon all By D10, a weak Scandi ridge seems favoured - the mean doesn't tell the whole story as the values are massively suppressed by a couple of outliers which have a deep low over Scandi - 16 out of 20 ens members have better ridging centred over Denmark than is shown by the mean below: Makes you wonder if the same has happened on the ECM ens, except with the whole pattern shifted slightly further west, and a few better troughs over E Europe So by next weekend, settled/warm weather just about the favourite for the UK, but a number of possibilties for a breakdown, particularly a trough to the S moving up, and trough dropping into Scandi. Probably not as warm as the upcoming weekend, but keep that t-shirt handy.

Perhaps because the UKMO is sufficiently different - the unsettled stuff to the W/SW is a good 200-300 miles further away (not necessarily correct, of course!!) By Monday there's a big variance - very warm on the UKMO, becoming unsettled on the GFS away from the north

That's not a bad chart. That low to the SW looks stuck there for a while. Continental air for most of next week on that.

But knock, can you ever recall a summer trough to our SW that doesn't eventually find its way to us? It's a 3 hot days and a thunderstorm style set-up for me. The benefit of the orientation I suppose is that more warm weather might follow on behind.

This is a serious tease... http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php Looking slightly above 50% chance now of a ridge setting up to favour warm (hot?) southerlies in the middle third of the month. But that trough to the SW will surely interfere at some point. Might be some big winners and big losers out of this (heat/sun/thunder wise). I would suggest a shock 80F is not out of reach as a best case scenario. But some sort of 70F plus looks a good bet in places.

Yes have to go even warmer - please up mine to 12.4

12.0 seems good to me. A battle between Atlantic troughing and occasional European influence coming up, so a bit up and down. Possibility of pressure rising mid-month - in summary for the mornth a little better than the recent average seems a good punt right now

We saw a lot of charts like these last summer: In your heart of hearts, you know they're going to be on the wetter and cooler side than you want, but they just dangle that bit of hope for a July 1st style southerly if the pattern shifts slightly west. Such a fine line between warm (hot?) / sunny, and cool / rainy. Germans will need to be readying their sun-cream for sure. Very nice charts for thunder lovers though - prospect of cold fronts moving into continental air. At last the never-ending winter looks to be ... ending

Yes, Bluearmy is onto something here - going to be worth studying the D10-D15 ensemble output in the next few days, as a height rise of some sort towards central/eastern Europe looks likely : if anyone looks further at the individual ens members, they will see that this idea of a SW-based Azores ridge / trough to W Ireland / ridge in C Europe is a very common theme. Question is, where will the boundaries lie between the trough and the ridge? Very difficult to call yet, and I'm surprised some are already nailing their colours to the mast for early May with such confidence. To me, some sort of warm S/SEly is a 30% chance going by the charts we can see today (which in turn means a 70% chance of just being under the trough and wet, of course)

Excellent posts above but to add a little focus on the "potential" change at around D9: several models now throwing a trough into the Atlantic at this time, cutting off the cold northerly feed. Whether that leads to warm/sunny or cool/showery/westerly is debated: Caveats being the usual - big pattern changes in FI often get modified as they move through D7 / D6 / D5, and along those lines, the GFS Parallel demonstrates a quite likely variation with a portion of heights surviving in the mid-Atlantic leading to the following: although interestingly we've reached the seasonal tipping point for easterlies, and the result is increasingly warmer weather: the lesson being, the continuation of northern heights may no longer be such a bad thing for spring weather if the Scandi trough is removed (EAST COAST EXCEPTED!!) Either way, I do not see the beginning of May being significantly below average, leaving aside the first couple of days.

Quote from original post 4th February: "There is a strong likelihood of biting cold Arctic winds sweeping south over Britain at the end of April or the start of May 2016". Ian, you've done it again! Well done!!

A bit fresh this weekend?

The key for me is that Scandi low. It looks stuck with nothing to push it on. I do recall the GEFS being very keen on northern blocking in the D10-D15 stage at the start of this month, so credit there.

A highly messy period for the models goes on. The early part of next week looks better resolved now from a general modelling point of view, but still extremely mixed in terms of surface conditions - not particularly cold if one can miss the showers, but no great confidence that any dry conditions will stick around for long. Further out, and it now seems the ideas of a pressure build from the SW are gone, and indeed it looks increasingly like low pressure is going to be forced south on a regular basis. Still waiting for this forecast pressure rise in the north Atlantic, any hints still beyond D8, been waiting since the beginning of February! Maybe this time the hints will be right.

8.1 for me. I note that the majority of GEFS runs today have northern blocking in D10-D15 range, leading to a Northerly or Easterly component. Even at this time of the year, this would be sure to push the CET down a little. A slow-starting spring this year I think, might be some time before the t-shirts come out.

GFS pushes the Atlantic away by T144, with very little rain around. ECM gets it in much more with wet weather, particularly in the west Then, seeming agreement to push the Azores High towards us, but in proportion to the T144 charts So looking warmer and settled for the south by the middle of next week - but the north will be hoping the GFS is correct in order to join in.