Nick F

Blog looking at why we are only seeing brief one day bouts of heat this summer, despite some recent tabloid headlines of a 'Heatwave For Two Weeks' on the way. View the full blog here

GFS and ECMF, over last few runs, have been hinting at a southerly plume of very warm, humid and potentially unstable air beginning early next week as an upper trough stalls to the west. Long way off though and subject to downgrades ...

Blog look at the weather outlook for Europe over the next 7 days. Southern Europe typically hot throughout, northern Europe cooling down next week after warming up this weekend. View the full blog here

Storm & Convective Forecast Issued 2016-08-04 08:38:39 Valid: 04/08/2016 0600z to 05/08/2016 0600z CONVECTIVE/STORM FORECAST - THURS 4TH-AUG-2016 Synopsis Upper and collocated surface low close to E Scotland will move NE toward Norway, while a shortwave upper trough to the W of Ireland moves SE into France embedded in strong cyclonic Wly veering NWly flow. Wly/NWly polar maritime flow will become unstable to surface heating across England, Wales and S Scotland on Thursday. … S SCOTLAND, N ENGLAND, E WALES, MIDLANDS and E ENGLAND … Cooling mid-level temperatures spreading from the NW and W in association with upper low over N Sea and shortwave trough glancing SW UK will create steep lapse rates as surface heating increases with sunny spells … yielding 200-500 j/kg CAPE. Showers already across the west this morning will spread/develop further east into the afternoon and become increasingly heavy with a risk of thunder as surface heating reaches its peak this afternoon. Vertical shear will be rather weak, so any storms will struggle to organise, with no severe weather anticipated as a result. Issued by: Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2016-08-04 08:38:39 Valid: 04/08/2016 0600z to 05/08/2016 0600z CONVECTIVE/STORM FORECAST - THURS 4TH-AUG-2016 Click here for the full forecastCheck the full storm forecast here

Looks like it was lively in the early hours just north and west of the central lowlands of Scotland. A few more storms expected today embedded in convective bands swirling in across Scotland around a low moving in from the west later. Storm & Convective Forecast Issued 2016-08-03 08:41:04 Valid: 03/08/2016 0000z to 04/08/2016 0000z CONVECTIVE/STORM OUTLOOK - WEDS 03RD-AUGUST-2016 Synopsis Upper low and collocated surface low will drift east across Scotland on Wednesday, bands of heavy rain and thunderstorms will swirl around this low pressure system as it moves across Scotland. … SCOTLAND … Upper low and associated cool mid-levels will create steep lapse rates across Scotland, steepest toward Nern Scotland. This combined with large scale ascent of moist airmass from upper trough and forced ascent in areas along bands of strong positive vorticity swirling around low moving in from the west will allow convective bands of heavy rain, accompanied by thunder and lightning locally, to move east through the day. Vertical wind shear will be weak/unidirectional – so no severe weather is anticipated, though heavy downpours in the convective bands could produce an inch or more over a few hours so could lead to localised flooding. Issued by: Nick Finnis Tomorrow Sunshine and showers for many, some heavy with hail and thunder across Midlands, southern and eastern England

UK Severe Convective & Storm Forecast - Issued 2016-08-03 08:41:04 Valid: 03/08/2016 0000z to 04/08/2016 0000z CONVECTIVE/STORM OUTLOOK - WEDS 03RD-AUGUST-2016 Click here for the full forecastCheck the full storm forecast here

Wondering why UK summer 2016 seems to be so changeable, with any proper warmth or heat fleeting? Blame it on the jet stream, it just won't leave us alone. View the full blog here

Risk of some isolated post frontal storms developing across Wales, Midlands and parts of southern and eastern England tomorrow, a fairly narrow zone of instability moving through ... Storm & Convective Forecast Issued 2016-07-27 21:21:27 Valid: 28/07/2016 0600z to 29/07/2016 0600z CONVECTIVE/STORM FORECAST - THURS 28TH-JULY-2016 Synopsis Upper low persists to the north of the UK centred over the Norwegian Sea, driving a deeply cyclonic westerly flow across the UK. A shortwave trough and associated jet max, originating from far NW Atlantic/NE Canada will moves east across Nern UK on Thursday beneath the upper low to the north. A surface low will cross N. Ireland late morning, then across N England in the afternoon/early evening. Attendant warm sector will move across England and Wales late morning and afternoon, cold front clearing E England by early evening. … WALES, MIDLANDS, S and E ENGLAND … A shallow layer of quite moist air will persist across the above areas into the afternoon during peak heating post cold front clearance. This warmed moist surface layer combined with steepening lapse rates as shortwave trough glances as it moves across Nern UK will yield a narrow pool of around 300-700 j/kg CAPE that will follow near/ behind the cold front clearing east. This unstable zone should support the development of isolated or scattered thunderstorms for a time across the above areas. Strong westerly jet streak aloft and veering winds as low moves through is indicated to yield 30-40 knots of Deep layer shear and 15-20 knots of low-level shear ... which is sufficient for organisation of any storms that develop. So there is a small risk of hail, strong wind gusts and torrential rain leading to flash-flooding. Low LCL/cloud base and locally enhanced low-level shear means funnel clouds or even brief/weak tornadoes can’t be ruled out too. However, with what looks like an isolated/uncertain risk of strong thunderstorms – have refrained from issuing severe probabilities. Issued by: Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2016-07-27 21:21:27 Valid: 28/07/2016 0600z to 29/07/2016 0600z CONVECTIVE/STORM FORECAST - THURS 28TH-JULY-2016 Click here for the full forecastCheck the full storm forecast here

Shallow Moist Zone

Bit of a quiet period we're in storm-wise thanks to cool westerly and northwesterly winds over the coming days, but not without some risk. Today A small risk of catching a storm or at least a heavy shower across SE England and E Anglia this afternoon as skies brighten following clearance of morning cloud and rain. Storm & Convective Forecast Issued 2016-07-27 07:55:29 Valid: 27/07/2016 0600z to 28/07/2016 0600z CONVECTIVE/STORM OUTLOOK - WEDS 27TH-JULY-2016 Synopsis Upper low persists to the north of the UK centred over the Norwegian Sea, driving a deeply cyclonic westerly flow across the UK. Surface low crossing southern Scotland overnight is now moving east across the North Sea, trailing frontal system bringing cloud and rain across England and Wales will slowly clear this afternoon, the SEward-moving cold front clearing Kent this evening. ... SE ENGLAND and E ANGLIA ... Residual surface moisture following clearance of cold front, clearing skies allowing insolation and dry mid-levels will create some modest instability (100-300 j/kg CAPE) to develop this afternoon across the above areas in sunny spells that develop. Therefore there is a risk of heavy showers and a few thunderstorms developing. Vertical shear will be weak and CAPE modest, so no severe weather is anticipated. Tomorrow Surface low moves east across the far north of England during Thursday afternoon, GFS shows several 100 j/kg CAPE developing across N, central and E England, ascent created in vicinity of triple point and cold front combined with lift of shortwave moving east aloft, dry air intrusion across S/central England enhancing instabilty. Strong wetserly jet streak aloft and veering winds as low moves through indicated to yield 30-40 knts of DLS and 15-20 knts of LLS ... which maybe sufficient for organisation of storms. Lightning wizard shows a STP (significant tornado parameter) across N and E England. Friday BBC/Met Office forecast indicates potential for heavy and perhaps thundery showers for SE UK, though GFS not highlighting sufficient CAPE away from eastern Scotland atm.

UK Severe Convective & Storm Forecast - Issued 2016-07-27 07:55:29 Valid: 27/07/2016 0600z to 28/07/2016 0600z CONVECTIVE/STORM OUTLOOK - WEDS 27TH-JULY-2016 Click here for the full forecastCheck the full storm forecast here

Storm & Convective Forecast Issued 2016-07-22 09:16:18 Valid: 22/06/2016 0600z to 23/06/2016 0600z CONVECTIVE/STORM FORECAST - FRI 22ND-JULY-2016 Synopsis An upper trough will slide east across the UK and western Europe as an extension of upper low complex over the far North Atlantic, a slack but moist surface airmass across the UK will become unstable to surface heating this afternoon ahead of an occluded front moving across the west today, with heavy showers and thunderstorms developing in places. ... ENGLAND, WALES and ERN SCOTLAND ... The slack/weak surface flow across much of the UK will feature several convergence zones across the above areas, which will tend to strengthen as the day goes on due to surface heating inland creating strengthening sea breezes to spread inland. A moist airmass, (characterised by dew points of 15-17C) and surface heating into the low to mid 20s deg C will generate around 300-600 j/kg CAPE. Lapse rates don't look particularly steep on GFS progs, which will prevent greater instability generally, so thunderstorms will tend to be confined to convergenze zones where strongest updrafts will establish. Given high moisture content of the atmosphere across the above areas (PWAT values of 27-30mm) and weak upper winds, slow-moving torrential downpours leading to localised flash-flooding will be the main threat from any storms. Have issued a MARGINAL risk for flooding for SW England, parts of central S and SE England, E Midlands and parts of E England - as strongest convergence/storms seem most likely here this afternoon. Any hail will tend to be isolated and small given modest CAPE, weak winds aloft and surface convergence will favour the development of a few funnel clouds. Issued by: Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2016-07-22 09:16:18 Valid: 22/06/2016 0600z to 23/06/2016 0600z CONVECTIVE/STORM FORECAST - FRI 22ND-JULY-2016 Click here for the full forecastCheck the full storm forecast here

Not often you see a UK radiosonde ascent show 1000+ j/kg CAPE, strongly unstable atmosphere today by UK standards, this is the noon ascent for Nottingham. The wind profiles were all wrong to produce a tornado, with a westerly flow at the surface and winds backing Sly aloft (should be other way round). Nonetheless, 1300+ CAPE was enough to produce strong updrafts sufficient to make large hail and also produce frequent lightning. This water vapour loop for this afternoon/evening shows mid-level trough and associated dry air (dark stripe) and its positive vorticity swing east which enhanced lift to create the storms from the Midlands down to E Anglia, surface cold front marking back edge of this dry air intrusion. http://brunnur.vedur.is/myndir/seviri/2016/07/20/seviri_eurnat_wv6-2.html

Storm & Convective Forecast Issued 2016-07-20 07:46:47 Valid: 20/07/16 0600 to 21/07/16 0600z DAY 1 CONVECTIVE / STORM FORECAST - WEDS 20-JULY-2016 Synopsis Upper ridge across western Europe including the UK continues to decline southeastward to allow the edge of upper trough over the Atlantic to move in across the far west of British Isles. A hot and humid plume across much of the UK has become unstable across the north and west overnight, as the upper trough edges in from the west. Forcing for ascent of hot and humid air by approaching upper trough, shortwave trough ejecting NE and developing surface low moving NE ahead of a surface cold front moving in from the west will lead to an increasing extent of thunderstorms across northern and central areas on Wednesday, some of these storms may be severe given favourable convective parameters. … N WALES, MIDLANDS, N and E ENGLAND and SCOTLAND … Overnight storms across northern Scotland will gradually clear this morning, but another area of storms, a MCS (Mesoscale Convective System) is ongoing to start the day across N Wales, NW England and SW Scotland. This MCS will shift NE this morning across NW England and Scotland and will continue to affect eastern Scotland through the afternoon. The main risk from these storms this morning will be torrential rain leading to flash flooding and frequent cloud-to-ground lightning. Fresher and more stable conditions across EIRE and N. Ireland this morning will arrive across western Scotland, Wales and SW England this afternoon, with risk of storms diminishing here, as cold front moves in from the west. However, ahead of the cold front, storms may re-develop across SE Scotland, N England, parts of the Midlands and perhaps eastern England (where they will be more isolated) as temperatures rise combined with increased forcing for ascent from approaching upper trough, shortwave moving NE and surface low across SW UK in the morning moving NE. Despite modest deep layer shear (20-30knts) – fairly strong low-level shear combined with 1000-1500 j/kg CAPE across N England, Midlands and E England may favour the development of strong and perhaps severe thunderstorms capable of producing large hail (2 to 3cm in diameter), damaging wind gusts, frequent lightning and flash-flooding. Given backed SEly flow initially across N Sea coasts, high CAPE and low LCLs (cloud base) … there is a small risk of a tornado or waterspout across NE England and SE Scotland. Have issued a MODERATE for severe storms across SE Scotland and N England for the risk of large hail, damaging winds, flash flooding and small risk of a tornado. A SLIGHT risk covers elsewhere across northern Britain for the risk of large hail, flooding and damaging winds. Issued by: Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2016-07-20 07:46:47 Valid: 20/07/16 0600 to 21/07/16 0600z DAY 1 CONVECTIVE / STORM FORECAST - WEDS 20-JULY-2016 Click here for the full forecastCheck the full storm forecast here

Storm & Convective Forecast Issued 2016-07-19 09:04:37 Valid: 19/07/16 1800z to 21/07/16 0600z DAYS 1 & 2 CONVECTIVE FORECAST - TUES 19TH and WEDS 20TH JULY Synopsis Upper ridge across western Europe including the UK begins to decline southeastward to allow the edge of upper trough over the Atlantic to move in across the far west of British Isles. A hot and humid plume spreading north across much of the UK will become increasingly unstable across the north and west as the upper trough edges in from the west over the next 24-36 hours. Forcing for ascent of hot and humid air by approaching upper trough and developing surface low moving NE ahead of a surface cold front moving in from the west will lead to an increasing extent of thunderstorms across northern and western areas from Tuesday evening through to Wednesday evening, some of these storms may be severe given favourable convective parameters. DAY 1 CONVECTIVE FORECAST – TUES 19TH-JULY-2016 Valid 19/07/16 1800 to 20/07/16 0600z … EIRE, N. IRELAND, N WALES, N ENGLAND and SCOTLAND … Hot and humid plume spreading north across the UK over the last 24hrs will yield quite large amounts of CAPE (by UK standards) today with surface heating, GFS indicates 1000-2000 j/kg CAPE across large areas of the UK and EIRE this afternoon. This potential energy will be strongly capped by upper ridge, but heights will weaken across the NW this evening with approaching upper trough from the west as ridge declines. Increasing large scale ascent this evening across EIRE, N. Ireland into western Scotland created by approaching upper trough and additional ascent from shortwave trough rounding the upper trough to the west and moving NE will likely trigger scattered thunderstorms. Storms increasing in coverage and extending NE to affect more of Scotland and also north Wales and northern England. Given the large CAPE values forecast, 30-40 knots of deep-layer shear and surface winds backed SEly from SWly flow aloft … any storms that form are likely to organise into multicell clusters, a few supercells can’t be ruled out initially before storms tend line out into clusters. As storms will tend to be elevated, main severe threat from storms this evening and overnight will be excessive rainfall (30-40mm per hour or up to 50mm over a few hours) which may lead to flash-flooding locally. Strong and perhaps isolated damaging wind gusts are also possible. Given high CAPE values – isolated large hail (2 to 3cm diameter) can’t be ruled out with evening storms before hail risk subsides. Frequent lightning will also be a hazard. Therefore have issued a SLIGHT risk of severe weather for the above areas. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ DAY 2 CONVECTIVE FORECAST – WEDS 20TH-JULY-2016 Valid 20/07/16 0600 to 21/07/16 0600z … N WALES, MIDLANDS, N ENGLAND and SCOTLAND … Thunderstorms, perhaps locally severe, will be ongoing to start the day across EIRE, N. Ireland, N Wales, N England and Scotland. These storms may wane through the morning across these areas, before drier and fresher conditions spread across EIRE, N. Ireland and western Scotland in the afternoon and Wales in the evening, as cold front moves in from the west. Storms re-developing across eastern Scotland, N England, N Wales and parts of the Midlands ahead of cold front as temperatures rise combined with increased forcing for ascent from approaching upper trough and as surface low across SW UK in the morning moves NE and deepens slightly. Despite modest deep layer shear (20-30knts) – fairly strong low-level shear combined with 1000-1500 j/kg CAPE across Midlands, N England and S Scotland may favour the development of strong and perhaps severe thunderstorms capable of producing large hail (2 to 3cm in diameter), damaging wind gusts, frequent lightning and flash-flooding. Given backed SEly flow initially across N Sea coasts, high CAPE and low LCLs (cloud base) … there is a small risk of a tornado or waterspout across NE England and SE Scotland. Have issued a SLIGHT risk for now, but may upgrade to MODERATE risk if severe storms look to be more extensive. Issued by: Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2016-07-19 09:04:37 Valid: 19/07/16 1800z to 21/07/16 0600z DAYS 1 & 2 CONVECTIVE FORECAST - TUES 19TH and WEDS 20TH JULY Click here for the full forecastCheck the full storm forecast here

Not had chance to do a proper storm forecast for next few days, though have mentioned in my blog Brief Heatwave & Thunderstorms - What To Expect the potential for severe storms from the Midlands/S Wales nothward from late Tuesday through to late Wednesday before a surface cold front sweeps the very unstable, hot and humid air away eastward from the UK Wednesday night

A blog looking at the brief heatwave peaking on Tuesday across the UK, before a thundery breakdown spreads from the west across northern and western areas on Wednesday, then cooler and fresher conditions return Thursday. View the full blog here

Risk of a few isolated heavy thundery showers developing across southern counties this afternoon looking at morning models, probably result of a sea breeze front developing inland as warmth builds inland and pressure falls to allow sea breeze to develop. Does look like northern and western areas will be prime areas for storms as the breakdown starts from the west later on Tuesday. Thunderstorms developing across EIRE, N. Ireland, NW England and SW England during Tuesday evening, before these storms rumble northeast across Scotland Tuesday night. Thunderstorms ongoing or reveloping across northern and western areas on Wednesday, further south across Wales and SW England too, perhaps some severe storms developing from SE Wales, NE across the Midlands to E and NE England too, looking at 00z ECMWF, as an area of low pressure moves NE along the cold front. Detail subject to change at this range though.

Back from being away with a storm forecast for today, given light winds aloft main threat will be flash-flooding from slow-moving storms training along wind shift zone shifting SE across SE England and E Anglia. Storm & Convective Forecast Issued 2016-07-12 09:28:53 Valid: 12/07/2016 06z 13/07/2016 06z CONVECTIVE / STORM FORECAST - TUES 12TH-JULY-2016 Synopsis Upper trough extends south to Iberia from upper low centred south of Iceland, with deeply cyclonic westerly flow across the UK. Coldest mid-level temperatures and thus steepest lapse rates will be towards SE Britain on Tuesday, so central and eastern counties of England will see the greatest risk of thunderstorms today. ... MIDLANDS, SE ENGLAND and EAST ANGLIA ... A combination of highest moisture (dew points of 12-13C), highest temperatures (18-20C) and coldest mid-level temperatures will produce greatest instability across the above areas - with 300-600 j/kg forecast to develop this afternoon with surface heating. As a result, heavy showers and thunderstorms will likely develop. Despite lack of vertical wind shear, a wind shift/convergence zone shifting southeast across Thames Valley/E Anglia will organise bands of storms which will be slow-moving given light winds aloft ... so there is risk of prolonged torrential downpours leading to flash-flooding in some places. Therefore have issued a MARGINAL risk for SE England and E Anglia. A few storms and more heavy showers will continue across the SE and E Anglia into the night, perhaps merging into a longer spell of heavy rain, bringing a continued risk of localised flooding, before rain clears away eastward first thing on Wednesday morning Issued by: Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2016-07-12 09:28:53 Valid: 12/07/2016 06z 13/07/2016 06z CONVECTIVE / STORM FORECAST - TUES 12TH-JULY-2016 Click here for the full forecastCheck the full storm forecast here