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Gordon Webb

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  1. Forecast Details Upper trough will slowly lift NE across the UK on Friday, with surface low centred over the north of Ireland at 06z moving NE across Scotland during the day, centred over the North Sea between Scotland and Norway by midnight. A moist airmass prevails across the UK on Friday, characterised by dew points of 15-17C. Surface heating in sunny spells of this moist airmass is forecast to yield around 300-600 j/kg this afternoon across large parts of the UK. This instability will support more widespread development of increasingly heavy showers through the morning and into the afternoon, amongst these some thunderstorms too. Storms most likely to develop along lines of breeze convergence developing and also along one or two shortwave troughs moving NE. With PWAT (Precipitable Water) values of 30-33mm forecast, locally intense rainfall from storms may lead to some flash-flooding. Hail, cloud-to-ground lightning and strong wind gusts may also accompany storms. Areas least likely to see thunderstorms appear to be the far SW of England, S Ireland, southern and western coasts. Storms should fade after dark as diurnal heating wanes. Issued by: Nick Finnis
  2. Day 1 Convective Outlook VALID 06:00 UTC Fri 10 Sep 2021 - 05:59 UTC Sat 11 Sep 2021 ISSUED 06:38 UTC Fri 10 Sep 2021 ISSUED BY: Dan Upper trough over the UK/Ireland on Friday will relax northeastwards, but still overhead during the day to provide the potential for showers. As was the case on Thursday, this will be complicated somewhat by areas of cloud and showery rain which could both inhibit surface heating at times, but also likely break up into scattered showers as the day progresses. In either case, cool air aloft with surface heating will likely yield 300-700 J/kg MLCAPE with the potential for numerous showers to develop across central/eastern/northern portions of both Britain and Ireland in particular. The steepest mid-level lapse rates will be over eastern Britain at midday, eventually shifting to the North Sea through the afternoon, but nonetheless a few thunderstorms will be possible - especially from the Pennines across to the E / NE England. Shear for the most part will be rather weak, and so showers/storms may tend to be pulse-type in nature but could still produce some local surface water flooding, alongside gusty winds and some hail. Activity will tend to decay during the evening hours.
  3. Dan makes a mention of it in his update this morning but again I think some are expecting more than what might actually occur , a tempering of expectations might be required
  4. Day 1 Convective Outlook VALID 06:00 UTC Wed 08 Sep 2021 - 05:59 UTC Thu 09 Sep 2021 ISSUED 06:41 UTC Wed 08 Sep 2021 ISSUED BY: Dan An upper low over the Celtic Sea will lift slowly northeastwards through Wednesday. On the leading edge, a narrow tongue of relatively high Theta-W will be the main focus for potential lightning activity along an instability axis, and this will gradually migrate northeastwards with time. Initially, the main focus will be over Ireland, SW England and the Channel Islands, moving eastwards across Cen S Eng and S Wales through the day and towards SE England / Midlands during the evening. There is a large amount of uncertainty as to how much lightning activity will occur vs just pockets of showery rain, and this adds difficulty in determining the threat levels to introduce and where. Realistically, there could be a few odd lightning strikes almost anywhere from various pulses of showery rain during this forecast period. Current thinking is one cluster of heavy rain and elevated thunderstorms will affect the Channel Islands and SW England (especially Devon) during the morning, but possibly weakening (in terms of lightning) towards midday. Another wave may develop over northern France (initially surface-based potentially) and drift across the English Channel towards S / SE England during the afternoon and evening hours, but again perhaps weakening as it tracks further north - however, there could be an uptick of activity inland over the Home Counties late evening/overnight. Elsewhere, there is a small chance of isolated surface-based showers/thunderstorms developing over SW Midlands, SW England (especially N Devon/W Somerset), central Scotland and western Ireland - but in most cases this will be capped and heavily dependent on sufficient surface heating. my opinion - not very hopeful for storm fans at least on widespread scale , bet they wish this was happening in June / July
  5. update from another site 11Z Nottingham ascent indicates Sig CAPE has formed over the Midlands , Eastern England & Northern England. Thunderstorms have become heavy across Northern England in the left exit region of the strong Jet across the South. Maximum 300-500mb divergence is across Northern England aloft. This is allowing for greatest outflow of air, allowing for Tops to easily reach 26,000 or -40C Storms across parts of N England showing active C/G Lightning and Hail and torrential rain. Further South Shear is greater but instability and CAPE is lower due to weaker low to mid level lapse rates. Still an area across the East Midlands, Lincs, parts of East Anglia and Eastern England where the greater instability and higher shear overlap which generates a slight risk of a severe Thunderstorm and marginal Tornado Threat through the rest of the afternoon. Prob area around the Wash is still a possible area for a more intense Thunderstorm later today with risk of Hail, Possible Tornado. Paul Blight Bournemouth, Dorset, UK twitter @PaulBlight6 if this post is not allowed due to rules there or here please let me know
  6. that'll be very tight but I think it'll pass just to your south but you'll know shortly , there not dawdling
  7. Day 1 Convective Outlook VALID 06:00 UTC Tue 27 Jul 2021 - 05:59 UTC Wed 28 Jul 2021 ISSUED 06:13 UTC Tue 27 Jul 2021 ISSUED BY: Chris An upper trough will be situated across Britain on Tuesday with a reinforcing sharper upper trough approaching Ireland from the northwest later in the day and overnight into Wednesday. Scattered to numerous heavy showers and thunderstorms are expected to develop across northeastern Wales through much of England (apart from far western areas) and into southern and eastern Scotland by late morning and through the early evening. Much like previous days surface convergence will be the focal point for shower development, and this is particularly the case for showers that develop from N Wales across to eastern England and northwards into southeastern Scotland during the afternoon and early evening. The shortwave trough axis and associated PVA will drift eastwards across S/Cen England towards western parts of E Anglia during the late afternoon and early evening perhaps giving a slight uptick in lightning potential in these areas later in the afternoon. CAPE amounts of 500-800 J/kg will develop widely in the SLGT area by midday and into the afternoon. This combined with PWAT values of around 30mm and surface dewpoints of around 15-16C indicate humid air in place and due to the slow-moving nature of the convergence driven convection, some localised spots could see 50-70mm of rain in a short period leading to the risk of flash flooding. There is little to no shear present so updrafts may be relatively short-lived, although outflow from developed storms combined with further convergence may help to develop daughter cells in the vicinity mature storms. Severe weather will be limited mostly to flash flooding, although some small hail may be possible in the tallest thunderstorms. There may also be the risk of some funnels or a brief tornado in the early stages of more vigorous convection during early afternoon. looks like places North of the Midlands see the heavier showers today not that other areas won't see showers
  8. 2nd attempt Convective Outlook - Tuesday 27th July 2021 Issued Monday 26th July 2021 Valid 10:00 BST to 23:00 BST Tuesday 27th July Headline High Risk of a very showery day across many Central & Northern parts of the UK. Low to moderate risk of Surface Based Thunderstorms developing across parts of Wales, Central England, Midlands, Northern England, inland parts of Scotland. General Situation Broad Upper trough will cover the UK, Areas of High Positive Vorticity (spin) will move NE across the UK during the day. Fairly Slack surface pressure covers the UK with convergence zones expected to develop across parts of Wales, West Midlands, Northern England, SW Scotland, Central Scotland during the day and propagate slowly NE Wards during the afternoon. During the evening a rearward sloping active shortwave 500/300mb upper trough will increase ascent across Wales, SW Scotland Northern England. This will come with increased SE Shear and increased Vorticity. Thunderstorms may linger well into the evening and will continue to produce significant threat of torrential Rain and increasing threat of Hail. Detail Broad upper trough will cover the UK during the next 2 days. A broken occlusion moving into Ireland & SW England overnight into Tuesday will mean that Tuesday starts with frequent showers and isolated thunder across Ireland, SW Wales, SW England and the Channel Islands. A Drier start across Central & Northern Parts. During the day as the occlusion moves NE it will decay and break down, but as the upper 300-500mb trough gains more potency to the North and daytime heating occurs we can expect convection to fairly rapidly develop. The Surface Pressure pattern will be quite slack inside this broad trough with surface convergence zones developing during the late morning and into the afternoon especially across Wales, Northern England, parts of the Midlands, Northern Ireland and a broad one stretching from the Pennines to Southern Uplands into the Highlands. Thunderstorms will break out given the steepening low to mid level lapse rates . During the Afternoon a weak surface low is expected to develop over parts of N England with Light Easterly winds across NE England, West to NW Winds into NW England and SW Winds converging into the Midlands. A light Easterly into Eastern Scotland will meet a converging westerly wind across parts of W Scotland. Thunderstorms will continue through the afternoon becoming quite heavy in places. Models suggest a fairly high moisture content will remain in place so storms may not be hugely electrical but do offer the scope for significant downpours and leading to some torrential rainfall rates in places. Risk of Hail increases later in the day in places too. Storms will also be aided by topographical uplift across the Pennines and Uplands and Highlands of Scotland. During the evening an active rearward sloping upper trough with significant 500mb Positive Vorticity and increased Vertical ascent will move into N Ireland and DLS will increase across SW Scotland then into Central Scotland. This increase in synoptic scale energy and forcing combined with a further steepening of Mid level lapse rates as 300-600mb temperatures cool further will allow for Heavy Showers and Thunderstorms to persist well into the evening across Scotland. Suggest 30-50mm could occur in places where persistent convergence develops and isolated higher amounts in places. Main Difference to Sunday is the Convergence zone is likely to propagate or move during the day therefore the very large amounts which were registered across parts of London and East Anglia should not be repeated. However torrential downpours could produce some local issues. Primary Risks - Heavy , possibly torrential rain in places, Hail, C/G Lightning and local flooding. Fig 1 - GFS 500mb flow and vorticity showing the main upper trough over the UK and a rearward sloping shortwave and focussed vorticity on its ascending side Fig 2 - EURO4 - Convergence zones which highlight multiple areas from Midlands north to Scotland. Paul Blight midlands Northwards looks more favoured tomorrow and seems to get better as day goes on , may explain why no met office warning for south issued
  9. there's a lot of exceptions to this anywhere forecast isn't there
  10. rather more detail Areas affected Parts of southern England Parts of SW England Parts of S Wales Hazards Isolated brief tornadoes Heavy rain CG lightning Gusty winds Discussion Cloud is breaking to allow spells of sunshine to develop across southern Britain. This should allow several hundred J/Kg of CAPE to develop, perhaps 700-800 J/Kg in a few places. One or more low-level convergence zones should develop, mainly due to sea breeze boundaries. With low cloud bases and decent low-level convergence, any showers or thunderstorms which develop along or close to these boundaries will have a chance of producing a few funnel clouds, and perhaps one or two brief/weak tornadoes. Gusty winds and locally heavy rain will be possible, with a few thunderstorms possible too bringing CG lightning. Activity should wane through the evening. Last updated by RPK at 15:45 BST Saturday 24th July 2021
  11. latest from Convective Weather Cut-off upper low continues to linger near the Brest peninsula on Sunday, with lobes of PVA rotating anticlockwise up from France and into southern Britain. The steering flow along its eastern and northern flank will allow advection of a relatively high Theta-W airmass from France into southern Britain in close proximity to a frontal boundary and within a zone of broad divergence aloft. As such, outbreaks of heavy rain are expected to spread gradually northwards across S/SW England on Sunday morning, extending into SE England around/after midday and then into the S Midlands / S East Anglia / S Wales later in the day. Embedded elevated convection will enhance rainfall rates, as was the case on 18th June for example, leading to some locally high rainfall totals and the risk of surface water flooding. Very moist profiles and generally skinny CAPE suggests lightning will probably be rather limited, with perhaps the exception of the eastern English Channel and adjacent areas. Ahead of this band of rain, some early elevated convection / showers will be possible over East Anglia and the East Midlands. Assuming sufficient cloud breaks can occur by late morning and into the afternoon, surface heating could lift 2m temperatures to 21-22C with dewpoints of 16-17C possible. A strengthening northeasterly wind will allow advection of this warm, moist low-level air west/southwestwards towards the northern Home Counties and south Midlands/M4 corridor, where an area of enhanced convergence may evolve by the afternoon hours. If all ingredients come together, surface-based thunderstorms could develop just ahead of the main rain band, perhaps also aided by some modest orographic forcing in the area. Forecast profiles exhibit fairly unidirectional winds, although some backing of the low-level winds will be possible. Speed shear is fairly low due to similar strengths at most levels, but stronger flow in the upper troposphere is available if deep convection can grow tall enough. Overall, this setup bears a resemblance to 16th August 2020 which produced some extreme rainfall totals due to very moist profiles (with a large proportion of the cloud layer below the freezing level) and persistent back-building - and a similar situation could evolve over the south Midlands / M4 corridor, albeit with a shorter window of potential (so probably not as much rain!). Current NWP guidance suggests anywhere from 50-70mm to as much as 100mm may be possible very locally, with hourly accumulations of 20-30mm. A SVR has been issued primarily for the risk of exceptionally high rainfall totals and associated flash flooding, but this will be fairly localised and not affect the whole area highlighted. If surface-based convection can develop, then low cloud bases and vorticity stretching near convergence zone could produce an isolated tornado. However, the situation is very finely-balanced, and insufficient surface heating or a faster northward motion of the rain will probably eradicate this potential. Also, depending on quickly rain can clear from Cen S / SE England (and indeed how extensive such rain/cloud is in the first place), there may be scope for surface heating here later in the afternoon that could foster surface-based convection too. In some ways, faster motion of rain northwards decreases the potential in S Midlands but increases it in SE England, and vice versa. Any thunderstorms will probably weaken eventually towards mid/late evening, but a new wave of rain with embedded elevated convection will likely push out of France towards southern England during the overnight period as the next PVA lobe rotates around the main upper low. Again, lightning may be rather infrequent/isolated given moist profiles and skinny CAPE.
  12. well London and the SE have little reason to grumble if this comes off but from midlands north where severity looks less intense judging by charts but have to wait and see (can hear the SE now , well you were spoiled last year)
  13. never mind , I won't send you North of the Wall , can't speak for others though
  14. amazing what poor charts do to forum participation , well it was a short read this morning
  15. even those high temps on Wednesday of 29c are really only the for the more SE quadrant not that the picture for the rest of England is cool by any means , well until you get into NW parts that is
  16. Midlands is a pretty big place so i doubt everywhere will see them but reading forecasts from as early as this morning would have told you what the expected weather would be Netweather - it'll be a trough which will serve to trigger some hefty downpours. Not just in central parts, but some will also potentially develop either side of it as well Metcheck - A mid level low pressure system will move Northeast across England and Wales on Sunday. Some decent instability for mid to upper levels with the risk of thunderstorms developing initially across high ground of Wales on Sunday afternoon and these moving Northeast into the Midlands and later East and Northeastern areas in the evening and overnight. and last but not least the Met Office - Cloudy for much of England and Wales with patchy rain followed by afternoon showers, some heavy and thundery. Mostly dry with sunny spells across Northern Ireland and other western parts
  17. not sure what peoples expectations of today were but they seem to be much higher than what the reality was ever going to be , no forecast gave any indication of anything severe or widespread , a little perspective is required to avoid the disappointment that is about to come for some
  18. the mass of rain to our south looks the most likely to affect us but it doesn't look very active and any cloud ahead will probably reduce temps and so forth and so on
  19. Is that a F F S I can hear from the SE (had to space out the letters as a filter seemed to dislike it it and replaced it with abc) LOL
  20. quite right but charts that are been posted here for POTENTIALLY thundery weather are at least 3 days off and 6 days off in same cases and should not be taken as gospel or over hyped , the things can and probably will change or might not even happen at all
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