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Showing content with the highest reputation since 18/05/18 in all areas

  1. 28 points
    The first and most important thing to say is to enjoy the spoils of some excellent weather in the 7 to 10 day period. After a warm week ahead, it could feel quite tropical by the Bank Holiday weekend with hot sunshine for many and some thundery downpours for some....then clearing to let hot sunshine out again. Rinse and repeat for a few days The last post gave some background as to how the early season warm spells have evolved since mid April. The highlighted sections of the above extracts from that post last week then went on to try to anticipate a likely crossroads ahead. This crossroads now broken down into basic suggested pathway scenarios : Changing seasonal wavelengths from Spring to Summer > leading to either, Low atmospheric angular momentum retrogression of the wavelength - North Atlantic/Greenland ridge and downstream trough or, High(er) angular momentum greater retention of downstream Scandinavian/European ridging and a troughing profile in the Atlantic to our west or, There is actually a third scenario that involves a lapse around the 12 to 15 day period into the Option 1 but a bounce (and likely a sustained cyclical bounce) back to Option 2 thereafter. That is I freely admit, covering all options *and sounding like a lot of back covering on her part* but two things here: The aim is, and has never been to give long range predictive forecasts - there are plenty of guru's around who like to do that anyway without adding any more. Secondly, the balance of factors, as I see them, are very finely balanced, so it seems eminently sensible to pitch any summary suggestions to embrace all the spectre of possibilities within that envelope. So I have my own little ensemble suite most of the time, which seems to work for me anyway Speaking of ensembles, NWP has indeed started to take the suggested pathways under the radar as we start the new week. The retrogression spectre started to appear in some low resolution GFS output late last week and now the EPS clusters have started to pick up on this signal. However, the background signals in relation to the tropics, extra tropics and subsequent consequences for atmospheric angular momentum remain uncertain. Based on some more recent historical precedence (and also a seemingly increasingly inherent longer term climate trend, but that is not for this thread) it would be easy to see start of summer and yet another collapsing angular momentum regime as somewhat predictable with a string of summers in the last 10 yrs following this same pattern.... Spring warmth leading to another indifferent cool and damp summer.... But back to basics - where are we with things this since time last week? GLAAM has slumped back below average, losing the gains of the recovery earned since mid April However, as likely commented to be the case last week, relative angular momentum tendency has been holding higher again in the present low cycle ebb than the previous low tide marks in the global wind-flow cycles of mid March and then early April. The inference of this, extrapolated longer term, is that the atmosphere is trying to resurrect itself longer term from the La Nina state that has, mostly, been in evidence for the last two years. Convection in the tropics in reflection of this, is continuing to imprint the active periodicity (recurrence) cycle of the last 90 days. As bolded in the captioned post above, what is very important as we hit June is that we see clear signals that MJO forcing wants to embrace eastward shift to the Pacific as represented by an evolution to Phases 6,7 and 8. This, as demonstration that the upcoming cycle represents a further move away from La Nina with accelerating westerly wind inertia in the atmospheric circulation sustaining the priming of downstream summer warm ridges rather than sustained lapse into downstream summer chilly trough. The deterministic tropical convection forecasts have been proving, not unusually, a bit too progressive with trying to break down amplitude of the latest cycle. There is a conceivable chance this time around that modelling may overcook -ve AAM downside, and hence any blocking in the North Atlantic and/or Greenland may be overblown. Either that, or of it does verify, it does not sustain. Just this side of the Spring/Summer wavelength changes, in the short term the recent fall back of AAM has done no harm at all. Indeed, the upstream deceleration of the jet has/is helping our downstream ridge hold sway with a moribund Atlantic. The deceleration and amplification of the jet upstream in the Pacific clearly represented here by the -ve mountain torque over Asia - with the consequent vacuum created to fill as momentum is lost from atmospheric wind-flows Such a negative AAM regime, however, not recovering as we arrive at imminent changing seasonal wavelengths also assists further retrogression of the longwave pattern and is not desirable longer term. So its important that momentum upstream has some impetus heading into the new month so that any retrogressed ridge to the W or NW (should it evolve) is shunted back east by the jet stream increasing from upstream and as a consequence LP being re-set in the Atlantic. This scenario would suggest a pre-cursor to some further, sustained warmth into the meat and bones of official summer - even if the initial burst of momemtum flattens the ridging initially and allows a (likely brief) more unsettled westerly pattern for a time. Some of our best summers have displayed this sequence of events in early season, so the retrogression scenario of the extended period, should it come about, should not be treated as "summer is over before its officially begun" . It could well prove to be the opposite. On that basis, the present and upcoming spell of weather may well be just a taste of what is to come. So best not fret, just yet anyway, about the new month (and new season) breaking the weather down - it might not be for too long if it does happen Have a lovely week and Bank Holiday weekend
  2. 16 points
  3. 14 points
    In a nutshell for this morning, if an endless plume is not your thing, Look away now! Absolute convective paradise for the storm lovers, pretty much right throughout the entire run. What a year this could be shaping up to be, both for coldies earlier in March and for the thunderheads! Or even better if you’re like me and do both!
  4. 11 points
    And it is two weeks away... always easy to point out a cool, wet chart when you get into FI eh? The GFS is fantastic in the closer range and it will be interesting to see how widespread the storms will get on Tuesday. The disparity in the output from this morning comes with the strength of the high pressure to our north which emerges next week. With a lot of cold air bottled up in the North Atlantic there is a chance the Atlantic jet could wake up a bit more and push things further east. The GFS has been very persistent though in forecasting that not to happen. If it doesn't we are looking at a lengthy warm spell. In fact, using the GFS to calculate forecast CET, I have it at 13.5C to end the month. Given the GFS tends to underestimate maxima it wouldn't surprise me if we saw a CET of around 13.8C at the end if the 06z came off. That would make it the warmest May since 1848.
  5. 11 points
    Lovely 00z runs with HP generally in charge.. looks like ukmo has shifted a bit to the GFS this morning.
  6. 10 points
    Back home after a great couple of days walking around northern Loch Lomond. As Catch has posted very settled looking outlook. Reporting in for Haar watch duty though!
  7. 9 points
    This mornings runs....WOW!! Growing support for a plume into the bank holiday. I mean look at this ridiculous ECM 168 chart today: http://www.meteociel.fr/modeles/ecmwf/runs/2018052100/ECM0-168.GIF?21-12 Nearly the entire UK bathed in +12c uppers, touching +14c in places. Unreal for late May, and could be the third very hot spell of weather for 2018 already, and we're not even in the summer months yet. Superb.
  8. 9 points
    Superb ECM - may the early start to summer keep on rolling!!
  9. 9 points
    The lack of energy in the Atlantic is quite something to behold on this mornings charts! Not sure I've ever seen it so blocked in summer. Now you know me, not one to ramp but it is pattern like this which is step 1 towards a 1976 style period. It can only happen with total Atlantic shut out. Step 2 would be to get the high oriented in a way to give a continental drift rather than Scandi/Baltic. Step 3 = lock-in. We aren't quite at step 2. But not impossible, and step 3 could follow!!
  10. 9 points
    A brief summary from me about tonight's Ecm 12z ensemble mean which, in a nutshell looks...summery
  11. 9 points
    Really happy with what the Ecm 12z is showing this evening..even more happy if it verifies, plenty of summery weather on these charts..nationwide..with power to add beyond T+240 hours!
  12. 9 points
    ECM upgrading the high this evening on the 12z It could be a long time until this high loses its grip over the UK
  13. 8 points
    Yes, what a fantastic post by my Sussex Girl neighbour Tamara. Certainly take what we have now and enjoy. What wonderful weather here in Cheshire. Just timed my Blighty break at the right time. Must be 23c and the Cheshire countryside looks stunning and ever so green.Pint or two this evening in one of my old watering Holes, the lovely "The Bells of Peover " pub ( below ). C
  14. 8 points
    Looks like potential is growing for some very warm/hot weather developing into the next bank holiday weekend. Long way off at the mo, but it’s appeared a few times now and needs watching. Great 12z again, this May has been fantastic on the whole!
  15. 8 points
    Fabulous mid / late May according to the Ecm 12z..in summary, it's summery
  16. 8 points
    More great output this morning! ECM on board now with the warmth lasting the whole week. The only question is now how much in the way of thunderstorms will there be? Comparing the Cape levels of the GFS and ECM (available from weather.us) GFS ECM Today Minimal None Sunday Minimal None Monday Moderate Light Tuesday Light Moderate Wednesday Light Moderate Thursday High Moderate Friday Very high Light GFS tends to overestimate Cape and has backtracked from the really high values we saw forecast for Tuesday. However Midweek ECM sees pockets of quite decent CAPE around midweek so there could be a helping of storms, mainly across eastern and southern areas of the UK.
  17. 8 points
    My apologies to everyone, I seem to have inadvertently posted the T0 chart from the ECM in the post above. Here's the actual T240: In rude health, you might say. Moving on, here's the UKMO 0z at T144: Peachy! And GFS at T180: Just a thought, is 2018 going down as the year of the easterly?
  18. 7 points
    Today marks the transition to the next phase of this fine spell of weather (not forgetting that this hasn't, and isn't the case, in N. Ireland and north west Scotland). as the amplifying north east of the Atlantic ridge disrupts the main trough and forges a corridor to the Scandinavian high pressure. This essentially sets the pattern for the next few days and through the holiday weekend with high pressure to the north and north east dominating proceedings and with an unstable low pressure area to the south an easterly regime over the UK is set in motion with the Atlantic trough relegated to the west by the aforementioned corridor. The detail for the next few days. Today - The front and band of rain is still affecting N. Ireland ans western Scotland and will continue to do so through the day and evening with some heavy pulses traveling along it whilst elsewhere after a clear night another warm, very warm, day beckons once fog and low cloud has receded from eastern coastal areas although it will still be a tad cooler here. But cloud will bubble up in central southern and western areas that could lead to isolated thunderstorms. By Tuesday there is a new high cell north of Scotland where the decaying front is still lingering albeit the rain has died out but temps around the region remain depressed Elsewhere Another very warm sunny day with again the chance of thunderstorms in the south. The usual caveat vis temps along coasts, particularly the east coast with the onshore wind. By Wednesday the center of the high has shifted northeast and whilst warm and sunny conditions continue to dominate in many areas with again the risk of thundery outbreaks, temps in northern Scotland and eastern coastal areas decidedly cooler in comparison. On Thursday the aforementioned 'corridor' to the west is in full swing and with the low pressure to the south pushing north a trough does likewise bringing more concentrated convective outbreaks to the south and west in the freshening easterly wind. A similar story on Friday vis the risk of thundery outbreaks in the south and again another warm day but with a definite westerly bias and cooler in the eastern half of the country with possible some low cloud and mist along the coast. The rainfall distribution reflects the above - hopefuly
  19. 7 points
    Been a while since I've written in this thread, or indeed anywhere on the forum, such has the weather had little of note worth talking about. But as it looks like there is a risk of storms, albeit isolated, most days in the south and west this week, I'm back and with a Netweather Thunderstorm Outlook for Monday. Storm & Convective Forecast Issued 2018-05-20 21:46:39 Valid: 21/05/2018 0600Z - 22/05/2018 0600Z THUNDERSTORM OUTLOOK - DAY 1 (MONDAY 21ST MAY 2018) Synopsis A broad upper trough covers the far N Atlantic with an upper ridge centred over Scandinavia/Baltic Sea. A weak upper low with cooler air aloft over near continent will drift westward across England and Wales in next 24 hours which, combined with diurnal heating of increasingly moist surface flow, will be the catalyst for isolated thunderstorms to develop across southern and western areas on Monday. … S, CENTRAL AND W ENGLAND + WALES … Weak and diffuse upper low/trough drifting west across Sern Britain will introduce subtle cooling aloft in the mid-levels atop moistening weak low-mid level flow from the east overnight and through Monday … this will steepen lapse rates … initially bringing some weak mid-level instability to E/SE England early Monday, which may produce spotty showers. Diurnal surface heating will then increase surface instability into the afternoon, as sunshine warms a moistening airmass (dew points in low-mid teens C) beneath mid-levels cooling from the east, resulting in around 500-1000 j/kg CAPE. This environment should promote the development of isolated thunderstorms across S England, perhaps a little more numerous across W England and E Wales – where weak surface convergence is indicated. Weak vertical shear will limit potential of severe weather from any storm to a low risk, though hail is possible given predicted CAPE and an isolated incidence of large can’t be ruled out … localised flooding may be a greater risk given slow-moving nature of any storms. Storms will generally die out after dark as heating wanes, though there is a risk of elevated instability/convection returning to the SE Monday night, which may bring isolated lightning. Forecast here as well: https://www.netweather.tv/weather-forecasts/uk/convective
  20. 7 points
    Lovely day here today, and it's quiet in here and I can see why, looking at individual runs won't tell us much we don't know about the next week, and longer term where the high heads is still open to question. Quite happy if it evolves like the ICON 12z though:
  21. 7 points
    Turning out to be one of the finest Mays in recent memories! Absolutely stunning. I will note however that we are never too far away from some impressive instability over the near continent, which could bring some real ground shakers in terms of storms to the south at times more towards the end of the week as it stands! Very much reminiscent of late May 1999.
  22. 7 points
  23. 7 points
    The weekend will be warm and sunny with some exceptions. Today after a chilly start it will warm up quickly with plenty of sunshine. It may be a little filtered still in north west Scotland where the front is still adjacent and low cloud and mist will still be a feature along the south east coasts so temps down here. As they will be a tad in other coastal areas as the sea breeze kicks in. The low cloud and mist may become more extensive through the evening and overnight which again will be quite cool under clear skies. But by 00 Sunday cloud and rain with a freshening wind will encroach N. Ireland and western Scotland as fronts associated with the low over Iceland track east. Through Sunday the front tracks a little further south east thus continuing patchy rain with cooler temps and quite breezy in the north west whilst elsewhere the ridge continues to dominate and another warm and sunny day will unfold with the same caveat vis low cloud in the east and sea breezes. Monday will be another very warm and sunny day for most, the exception being the west of N. Ireland and the Western Isles where the front is still loitering. But changes are afoot to the west. Another cut off upper low has formed west of Iberia, courtesy of renewed ridging north east of the Atlantic high pressure, which invigorates the low pressure to the south which moves north introducing an easterly and perhaps some convective activity.in the south as the ridge is pushed north east. By Tuesday this has resulted in a high cell north of the UK and with the aforementioned low pressure safely ensconced to the south there is a light easterly over the UK leading to another very warm day, apart from the north of Scotland where the front is still lingering. Still a risk of some thundery outbreaks over central England and Wales. A not dissimilar story on Wednesday except the high pressure has shifted north east over Scandinavia albeit still maintaining the easterly over the UK and still the possibility of convective activity in the south in what will be another warm and sunny day for everyone. According to the gfs around now is rather a key time as the upper trough to the south gets a further boost which tends to establish an anticyclonic/low pressure north south split but which will prevail?
  24. 7 points
    Cracking ecm - warm air hanging around all week, temps Into the mid twenties, and the chance of some hefty storms in places if that floats your boat. Lovely stuff!
  25. 6 points
    UKMO/GFS look lovely with plenty of warmth and high pressure on offer, EC looks similar out to 192 were we have this chart- One of the best Mays i can remember looks odds on to finish beautiful.
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