Leaderboard

Hi - yes, some very relevant points made A favourite period of the year for me with the long hours of daylight. Autumnal weather set in comparatively early in September last year (no summer extension on this occasion) so the recurrent warm spells arriving following a cold and wet first half of the Spring have been especially welcome in my opinion with natural hopes of plenty more to come in the many weeks ahead of us. These warm spells are a good point to begin the starting analysis. Why have they happened, and why is it important that the factors behind them sustain to allow seasonal wavelengths to augment them, rather than increasingly detract from them as happened last summer for example? The tropics have been active in respect of MJO convection for several months. Everyone knows of the spectacular tropical cycle which helped engineer the SSW in February - but what has happened since. This is a layered profile of the atmosphere from top to bottom for the opening months of 2018 - which tells the story well. The classic down-welling series of the negative zonal anomalies evident from the stratosphere to the tropopause layers as triggered by the massive SSW - a series of higher latitude easterlies which persisted into the first half of April. Rather accounting for the weather type seen through the first half of the Spring with a supressed Jetstream and persistent -AO/-NAO pattern A change quite suddenly appeared in the middle of April with the polar field switching +ve in tandem with the Atlantic profile to +NAO. If we take a look at the trends of total and relative atmospheric angular momentum we can see a pattern reflective of the changes across the polar field and the tropospheric pattern. Seasonal wavelength changes heading into Spring in tandem with falling atmospheric angular momentum following the SSW locked in the longwave pattern to -AO/-NAO . However, during this time with the tropics remaining active, a series of +AAM anomalies propagated poleward over time in accordance with this activity and c/o co-operation in the extra-tropics in the form of repeated +ve mountain torques over Asia creating a jet extension across the Pacific and adding westerly winds to the global atmospheric circulation. (Notice also the corresponding peak in +AAM tendency in the plot above in the second half of April along with the recovery in GLAAM reflecting those additions of westerly winds). These westerlies aided a recovery in atmospheric angular momentum tendency and the poleward +AAM wave train eddies manifested anti-cyclonic wave breaking with anomalous mid latitude ridges bubbling up downstream which have assisted the jet stream north and warm air advection patterns replacing the dominant cold air advection and troughing of the supressed jet stream -veAAM/SSW legacy. Another way of looking at the attempted ocean/atmosphere steer away from La Nina type forcing is the -ve trending of the Southern Oscillation Index (SOI) downwards from persistent +ve numbers in March (signifying a Nina-ish tendency) to much more neutral figures in the last few weeks https://www.longpaddock.qld.gov.au/soi/ So, we have continued to reap the benefits of the lagged effects of these westerly additions through the much better surface conditions (overall) in this second half of Spring - the periodicity (timeline recurrence) of the MJO has shown its influence in this respect of large contribution towards determining longer range weather patterns, and the possibility of using these intra seasonal phenomena for assisting longer range prediction. This overview of the seasonal evolution since the end of the winter, provides us with clues as to trends to look for ahead as another summer rapidly approaches. We also have the La Nina legacy hanging over us in terms of how things evolved from this time last year, which after all also provided some early season warmth and sunshine before, ultimately going downhill by mid summer as easterly trade winds surged repeatedly and retrogressed the fine warm anticyclonic early pattern into an Atlantic height and downstream UK trough anomaly. The standing wave pattern of La Nina which has dominated everything for the last 2 yrs, (despite a few notable "destructively acting" disconnects of relatively higher AAM such as in February this yr leading up to the SSW) really needs to be unshackled over the coming 4 to 6 weeks to ensure that a reasonable chance that the jet stream shift seen since mid April and the presently highly enjoyable fine weather continues. As of the here and now, we see westerlies being scrubbed from the atmospheric circulation as easterly trade winds increase in response to kelvin wave activity in the I/O These easterlies propagating across the Pacific and with both total and relative tendency of atmospheric angular momentum snapping backwards. The Global Wind Oscillation, which is a plot depiction of total wind-flows in the tropics and extra tropics, has largely been orbiting between Phases 0/4 ( signal for downstream mid latitude ridging) since mid April and is falling back into La Nina territory Phases 1/2 in reflection of the tropical signal rooted in the Western Hemisphere At the moment, being still in Spring, the significance of easterlies being added upstream amplifying the Pacific pattern and decelerating the jet downstream remains a benign enough one ( @Singularity analysis is very good here). However, (assuming for just one moment the atmospheric circulation remains close to where we are at present in light of latest drop backwards) seasonal wavelength changes heading into the summer which is fast approaching increasingly suggest a retrogressive pull of the long wave pattern with the spectre of that Atlantic ridge and downstream trough returning if the ocean/atmosphere relationship cannot fully break down the legacy of the La Nina standing wave. This (in this scenario) would mean that despite the ENSO regime "technically" returning more neutral in association with many forecasted expectations - there would still be a -ve adjustment/disconnect to the atmosphere which inclines the AAM budget within the atmosphere being pre-disposed towards greater easterly wind-flow inertia and hence high pressure in both the Pacific and Atlantic - rather than a longwave more Nino-ish pattern of, the reverse profile, of Pacific and Atlantic troughs and respective downstream ridges. The trough in our locale under summer type +AAM/El Nino type forcing being repeatedly focussed/re-set to our west in the Atlantic and the ridges over Western Europe and Scandinavia. There is of course every possibility that this latter hoped for scenario prevails to underpin some of the promising seasonal modelling indications. If we take a look at the above copied GWO spider graph of the on-going low AAM phase of the tropical/extra tropical cycle , the Phase 1,2 orbit of the GWO is thus discernibly shallower than that of 6 weeks back. This reflects the overall grip that La Nina has relaxed on the atmosphere - though clearly not yet gone completely. Its important that we see a willingness of persisting MJO tropical activity supporting further bounces in +ve AAM anomaly wave trains, but more important still an eastward shift of the locale of this tropical activity from the Western Hemisphere Such an eastward shift in the location of tropical activity seeking cooperation from the extra tropics in form of more +ve torque mechanisms adding further westerly winds to the atmosphere to prevent the sort of deja vu of a La Nina type summer and instead keep building downstream ridges and reinforcing the trough in the Atlantic (and not the UK and Europe). This type of persisting +AAM anomaly trade between tropics and extra tropics would see the GWO orbit more sustainably keeping away from the La Nina Phases 1,2 and 3. The present atmospheric profile, as shown at the start of this post, is conducive to a +AO profile, which even with a de-coupled -NAO would clearly be very good for warm/plume advection - though its still early in this respect and there is time for things to change if a persisting lower angular momentum regime in tandem with eQBO gained ascendency and increases heights across the pole and encourages blocking in the North Atlantic and supressed temperatures as the tropospheric pattern retrogresses. 30mb zonally averaged winds at the equator. -ve QBO phase in italics and April figure in bold. 2017 14.92 14.78 14.35 13.88 8.01 -3.18 -10.48 -14.42 -15.28 -16.79 -17.20 -18.12 2018 -19.02 -19.37 -19.77 -21.41 http://www.esrl.noaa.gov/psd/data/correlation/qbo.data Aside from any La Nina disconnect considerations as part of any downside analysis, should we evolve on the upside towards a more El Nino type circulation or even a weak Modoki El Nino state during the later summer and then further on into the autumn (i.e the eastern most Pacific zone remains relatively cool and convergence winds in both the eastern and western Equatorial Pacific focus a tropical convection signal as well as help upwell warming sub waters in the Central Pacific) then there are examples such as 1990, 1994 and 2004 to draw on. These years have all displayed the virtuous cycle nature of repeated downstream ridging at least at some stage in the heart of those summers in our locale - and bringing very warm/hot conditions (and with the exception of 1990) a fair amount of thundery activity (c/o temporary trough intrusion overspreading and destabilising the heat) for the weather enthusiast who likes some added interest to blue skies and hot sunshine as well Lets hope that this early season promise leads on to more, and not less, for a change

12z UKMO keeps the high with us into next week it doesn't look like it will be going anytime soon

Really starting to look like we'll do well out of a combination of enhanced subtropical ridging (last, but remarkably strong breath of La Nina influence?) and anomalously high heights across Scandinavia that appear tied to a combination of MJO forcing, the Arctic sea ice pattern and some particularly well-established blocking that can fend off the sluggish Atlantic. Typically, such a pattern will be tested by early June as the thermal gradient between the continent and N. Atlantic increases further, giving the jet a bit more oomph. Sometimes, though, that stronger jet just gets sent north of the ridging and can actually reinforce it further - but the question then becomes how far north the ridge is when that happens, as it takes on a flatter, west-east orientation. Recent GFS runs have been exploring outcomes that keep the ridging unusually far north, with interesting results as heat to the east wafts across. For what it's worth, I expect the 2 m temps these runs show are likely being underestimated by a number of degrees.

I loved the Ecm 00z and I'm also loving the GEFS 12z mean too which is going the same way as the 6z with a scandi / azores high link up and a prolonged spell of very summery weather nationwide!

Here's the first half of the GFS 12z, high pressure never wandering far from the UK and continuing the generally fine and warm weather: Later more of the same, here T300: Sets us up nice for summer. And thanks for that fantastic post @Tamara

Fantastic as always Tamara! Very informative and as much scope for a good summer as not it would seem. A friendly reminder to everyone, please don't feel the need to quote her entire post. It's a real pain when reading from a phone!

Just popped in to say how much I the Ecm 00z, especially towards the end!

Very much like the Ecm 00z ensemble mean, hopefully a recurring pattern for the next four months or so!

Brilliant from Tamara as always The modelling as a whole is shouting for the low momentum situation to lock-in for quite some time with some impressive positive GPH anomalies afoot, but if you look at the latest CFSv2 weekly maps, you can see some suggestion of a retrogressive tendency as we go into June. On the other hand, the long-range modelling in general indicates settled conditions to predominate this summer with below average rainfall and ridges tending to locate to our N and NE. Partly this appears influenced by the huge deficit in Arctic sea ice to the north of Scandinavia, but I expect some push of the atmosphere away from the La Nina imprint is also being developed behind the scenes. I personally believe that if the atmosphere fully breaks free and heads into weakly positive NINO territory by late June or early July, we'll be unlucky not to see a summer to rival some of the all-time greats. Last year did however demonstrate that the atmosphere is capable of hanging on to a La Nina imprint even with the SST anomalies venturing away from a La Nina pattern, as Tamara has very rightly reminded us. So it feels like we're being given a second shot at achieving what we almost did last summer. I too am pleased that we are in such a position .

Really nice 12z ECM high pressure dominates & very pleasant temps Long may it continue

As others are pointing out, that Azores High / Scandi High linking has once again taken hold in the models, and the EC clusters at D10 are no different: those oranges/reds to the NE and SW indicating the positive anomalies: The control cluster looks pretty awesome for spring half-term (D15), and the other two aren't shabby either: The question will remain then - will there be enough energy in the Atlantic to drive between them? Most of the last four weeks has been a cateoric "no" but the potential remains. So I wouldn't say a hot end of May is set in stone just yet. But the balance is in that favour right at the moment.

Today will dawn bright and clear for most areas and will continue in this vein leading to many having a very warm day. The slight exception being the eastern and and far west coastal areas where the overnight fog and low cloud, courtesy of two decaying fronts, may linger and thus depress the temps. Also today sees the transition to a colder airmass and the cold front responsible for this is over Ireland and the Western Isles this morning and the band of patchy rain associated with it will track slowly south east down the country through today, decaying as it goes, introducing the clearer but cooler air in it's wake. Overnight and through Wednesday the front will continue on it's travels but fizzling out as it goes resulting in a much cloudier day in central and southern areas with the cooler clearer air behind and thus a much cooler day all round from today as the high pressure builds to the west Particularly in eastern areas which will be subject to a light N/NE drift. By Thursday the high cell is safely nestled over the UK leading to another generally sunny day, albeit not as warm as now, usual caveats vis coastal areas, and also a fair diurnal temp range range resulting in some quite cold night's with ground frost, and possibly even an air frost, in some areas. A similar story on Friday but some pressure on the block is being exerted by the energy swinging south of the intense upper trough situated around the southern tip of Greenland and a decaying front is attempting to push into western Ireland. By Saturday this impressive upper low has deepened over the Denmark strait with the deep surface low associated with it south of Iceland, all of which is putting pressure on the very resilient block resulting in the high cell shifting a tad east and possibly some cloud from the associated front just about impinging on the north west. otherwise another dry and sunny day after a chilly start.

Switching to long range models, the May GloSea5 charts are out for Jun, Jul, Aug, check these out! 500mb heights: 2m temperature outer quintiles, I think this is the strongest signal for a good summer I have seen on these since I started watching them. Precipitation outer quintiles, signal less strong, but pointing towards drier.

Very good Ecm 12z with high pressure / strong ridging dominating most of the uk with just the far NW very occasionally being a tad more unsettled / breezy...for most it's looking very pleasant with largely dry and warm conditions with variable cloud and good spells of sunshine.

Why did you have to quote Tamara's (excellent) long post eh but add nothing to it?.....I scrolled through with bated breath only to hear a ping on my phone with the dreaded notification from o2 to say that I've gone over my data allowance thanks to you, and my next bill will have far too many zero's....thanks a bunch .....I'll fetch me coat ...... nice model outputs so far today, a settled spell in the offing for many parts, with temps hovering around the 70F mark for my locale......lovely!

Things do seem a bit different this year after the SSW....I can’t pretend to know one percent of what @Tamara does, but love reading the posts. I can just about make out that we have a better shot at a decent summer this year with everything stirred up since the SSW. Let’s play eh waiting game....but things look ok for now.

Fantastic ECM run this morning - increasingly settled, dry and warm as high pressure builds. The sight (nearly) everyone wants to see during the summer....low pressure all over the north pole. Stay there please! We should exercise some caution. A few days ago the ECM was showing a massive polar high for this Saturday: That isn't going to verify. Keep those eyes peeled.

Well on the 18z ICON at the end of the (short) run,there's some kind of Great Crested Jet Stream Demon creature by T 120, here: But it won't deprive us of our high pressure and start of summer:

Loving this weather at the moment , 18-22c, warm sun, blue skies, not too hot Perfect early summer weather !

This May is shaping up to be a very good month after what seemed like a very dull March and April. A whole 360 turn much cooler tomorrow, but then there seems a gradual warming trend.

A quiet outlook, with little in the way of unsettled weather - in a word 'dry' - not unusual for May though, this is as I keep saying the time of year when the atlantic is in slumber and we are far more likely to see sustained dry conditions, indeed a predominantly wet unsettled outlook is more unusual. Not much to discuss, high pressure ridging through the UK, could be some stubborn cloud though as it has an atlantic cool source, and it doesn't look like we will inject any continental influence into it for some time at least keeping temps near average, no significant heat in the offing, but under clear skies and sunshine and light winds by mid May it always feels much warmer than the temps suggest, indeed the sun is more powerful now than in late July - even though that is when we see yearly average means reach their peak. The current synoptics on offer at the kind of synoptics that have given rise to some of the classic summers of years gone by, the azores-scandi high link up with the jet tracking far to the north, it can be a recurring stuck pattern - but, seeing such conditions in mid May by no means they will last for the next 3 months, the summer rarely settles into its groove until late June, and its then you want to see such synoptics occur (think 1995), as there is often a tendancy for a switch to occur around then, the base state flips and settles in for the summer haul..

If we count the first half as the 1st to the 15th and second half as 16th to 31st then it's happened 45 times in the record, so roughly once every 5 years. More often than I would have guesses! The most recent was 2016, with a first half of and a second half of 12.7C and a second half of 12.4C. The biggest difference was in 1898, with a first half of 10.94C and second half of 8.16C, giving a difference of 2.8C. More recently, 2008 was quite notable. First half of 14.6C (2nd warmest first half on record), second half of 12.2C, difference of 2.4C!

...You make me proud to live in Hastings. exceptional post as always!

Here's the forecast based on the 06z GFS Rolling CET... Anomaly to 81-10 rolling avg (Daily Avg: Anomaly to 81-10 daily avg) 12.1C to the 15th... +1.2 (13.8: +2.0) 12.2C to the 16th... +1.2 (12.7: +1.3) 12.0C to the 17th... +1.0 (9.6: -1.7) 11.9C to the 18th... +0.9 (10.0: -1.4) 12.0C to the 19th... +0.9 (13.1: +1.3) 12.1C to the 20th... +0.9 (14.1: +1.8) 12.3C to the 21st... +1.1 (15.9: +3.8) 12.4C to the 22nd... +1.1 (14.4: +2.2) 12.5C to the 23rd... +1.2 (15.4: +2.6) 12.5C to the 24th... +1.1 (13.1: -0.2) Some ups and downs in the coming week but relatively stable overall, a warm final week could leave us above 13C, or into the 20 warmest Mays on record, while a cool final week could see us drop below 12C, or close to the 81-10 average (11.7C).

The GFS was excellent too. High pressure dominating from start to finish.

These charts at the moment could make a grown man cry

The chance of some surface based thunderstorms in the far southeast, moving north east- south west. With up to 450kj/g there are more likely to be pulse storms rather than organised, but the isolated stronger cell can’t be ruled out. Only a 50% chance of lightning today though. I really hope convective weather pick up on this for today’s small chance of seeing the first thunderstorm in the southeast. As being in Essex missed the last storms from the last heatwave. Also funnily enough I have never seen estofex issue a forecast and not convective weather. Maybe the chief forecaster is busy this week!

Lovely day, unbroken sunshine with light winds and a high of 19C - more of the same please!

Just to add to the good news tonight. Given which it seems unusually quiet in here. Here's the last four CFS runs for June, Z500 anomalies, 0z first: Taken with the GloSea5 charts posted earlier, I think we can say 'Roll on summer!'

Fabulous afternoon here too with long sunny periods and a very light sea breeze from the north.A high of 20c.Last of cows and calves out to small shelterd late growing grass field. Swift squadrons screeming round the house all afternoon. Real high summer.

Absolutely fine!

Well, it is that time again ... LONG RANGE OUTLOOK for SUMMER 2018 In general terms, I am expecting a very warm summer for the U.K. and Ireland although trending more towards normal values in western Ireland and Scotland. There is likely to be a strong continental influence especially for southeast England, probably extending to south central England and the Midlands, Yorkshire and possibly parts of eastern Scotland too. Even parts of Ireland will benefit from this influence. My reasoning for this is based on two separate factors. One is that my research model indicates higher than average index values for isolated analogue components in about three quarters of the set that I have developed. The other factor is more immediate, blocking has continued to be a fairly prominent player ever since the notable cold outbreaks of late February into March, and as many suspected, that tendency would not remain cold far into the spring but would increasingly favour warmth (also turning from northeast to southeast dominant wind flow helps with the warming effects). I suspect that the summer may rank well up there among the top all-time summers for warmth, so I will go with some relatively conservative forecasts for the three monthly CET values of 16, 18 and 17, expecting that perhaps one of these will be too low, if not more. If that verified the summer would average 17.0 and be ranked tied 9th warmest with 1933, and marginally warmer than the currently tied 10th warmest summers of 1911 and 1781 (16.97) with only these summers warmer: __ 1947 (17.03), 1983 (17.07), 1846 (17.10), 2006 (17.23), 2003 (17.33), 1995 (17.37), 1826 (17.60) and 1976 (17.77) __ Some of the summers with good reputations finished as low as 16.5 so I would certainly expect 2018 to go higher than that. With that general set-up, the chances are high that rainfall would be below average in many southern and eastern districts, and closer to normal in western portions and in the north. The most likely zone for severe or heavy thunderstorm outbreaks would be near the average position of the polar front which separates tropical from modified Atlantic air masses, and that would likely be (on average) in southwest England, Wales, portions of southeast Ireland, northwest England and east-central Scotland but at times shifting closer to a Bristol to Newcastle line. This does not of course rule out some good thunderstorms in the warmer zone and it always seems like late June is a good time frame for Channel storm developments that last overnight and rumble across southeast England. With a suitable energy peak around 30 June this is perhaps even more possible. It is unlikely that this good summer weather regime will be permanent from start to finish and if you look at the list of similar or warmer summers, some have a bias towards later warmth and some go earlier, while a few distribute well throughout. With this blocking tendency already well established I imagine that this implies either an early bias like 1846, 2006 or 1976 or a constant warmth. It can be noted that my prediction would make this the warmest summer of years ending in 8. Summers ending in six have done very well in the past (four of the top six). The current warmest summer ending in 8 would be 14th ranked 1868 (16.87) which might prove a bit of a challenge. The futility mark is that of summers ending in zero (tied 49th warmest 1730,, followed by the fours (1794 was tied 36th). Lack of solar activity is correlated with blocking and it does not seem to be an impediment to hot summers, for example 1826 in a very inactive solar regime, 13th place going to 1899 in a low solar period and even the Maunder managed to produce 15th place 1676. The hot summers in more active solar intervals are generally near solar minima also, the only one with high solar activity would be 1947 although others are shoulder years in terms of solar cycles. I find solar indices to be more useful for winter forecasting when Atlantic storminess is more of a factor. No doubt in long intervals of low solar activity, there can be runs of dismal summers due to a depressed jet stream and colder ocean temperatures, but this year does not seem to fit that scenario (yet). As to tropical activity, I would look for a very active season with perhaps 20 named storms and 12 to 14 of those being hurricanes, 5 to 7 becoming major hurricanes. In North America, I am predicting a very hot summer in the west, and also across the southeastern U.S., with a gradient towards more normal temperatures northward into the Great Lakes and northeastern U.S., leading to very frequent thunderstorm activity near oscillating frontal bands running from Alberta southeast into the Dakotas and then east-south-east into the lower Great Lakes and inland northeastern U.S. ... these regions may have some severe storms and flooding episodes as a result. The inland west may have a scorcher of a summer and widespread wildfire problems (hope I'm wrong about this, but it's 31 C outside my house right now, normal would be 19 C).

ECM ensemble mean looks really good at T240, that high pressure nosing in, I think a prolonged settled period is likely: Further support for a decent early summer, where we go thereafter needs more runs.

GEM late to the party today, but here it is in its entirety: Its the picture we've been seeing for a while now, with repeated areas of high pressure over the UK as the systems move SW to NE with slightly less settled conditions interspersed. But this run seems to end with a very continental outlook, optimism for summer good, and increasing the more models I look at.

Good evening to my neighbours in the next door region. I'm posting here because i'm done with the thread that covers my region It's been a cracking good day here with plenty of sunshine and temperatures around 23c. I've managed to get a fair bit done in the garden and currently sitting outside enjoying a beer and the evening warmth. Long may it last.

GEFs Not the most unusual pattern for late Spring where winds from the east could dominate over a large part of the country with high pressure solidly in place to our north east, this puts western areas in the firing line for the best weather when the high pressure asserts full control whilst the east is always at risk of cooler and cloudier conditions. To be honest the extended ranage looks like more of the same, perhaps the high retrogressing towards the UK during week 2. At the moment I don't see any major heat, but it does look warm in the sunnier spots with mid/perhaps high twenties possible in the west at times.

Except in west London where it's probably been the dullest in a century? In all seriousness, May has been a cracking month so far.

With charts like these I wont be surprised if May comes off as one for the books regarding sunshine hours. Still looking very dry and pleasant, ECM 00z could certainly deliver the first 30C of the year over the BHW if it comes off

Only 14 here at the moment, and it's going to get even cooler tomorrow. Just take each goat has it comes, I suppose?

Met longer range and charts going for the usual fare well into June.Generally very good summery weather down here in south with the odd thunderstorm. Unsettled midlands northwards with the usual rainy spells and average temperatures. Could it be yet another bust summer midlands northwards? Very possible imo.

Big event this Saturday and I hope the weather plays ball for this massive even, yes we are having a BBQ No will be harmed in the making of it.

12.0 to the 14th 1.5 above the 61 to 90 average 1.1 above the 81 to 10 average

Absolutely dream charts as a summer lover. Would you say this current Azores/Scandinavian high link up pattern is reminiscent of (dare I say it) '76?

Next time you're back in Peebles, come home via the back road.. At the eastern end of the main street in Innerleithen, turn off to the left to Heriot - the B709. That's my back yard! Fab scenery of hills and more hills, wee twisty road but with good long straights. Wee burns and sheepies in them. Buzzards and short eared owls and hares. It's like the highlands in minature lol, and far easier to get to

The 0500 UTC surface analysis showing the fog/low cloud/drizzle along western coasts. I can confirm that is the case here at the moment

SUN

NAO seems to be heading towards a more negative phase. Not a good sign heading into June as it increases the chance of high pressure development near Greenland. http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao_index.html

Absolutely beautiful day today. The fresh breeze makes all the difference. So much better when everyone can enjoy the conditions and not just those that like it akin to a turkish bath.

Maybe the heat from this discussion melted all the ice?

and you calling for mods to intervene is also unreasonable