Nick F
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Posts posted by Nick F
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Storm & Convective Forecast
Issued 2017-08-17 08:16:18
Valid: Thurs 17th Aug 6AM to Fri 18th Aug 6AMDay 1 Storm / Convective Forecast
Synopsis
Upper trough over the Atlantic will approach western UK today, before the trough axis slides in across northern and western Britain overnight. A strong cyclonic SWly flow aloft with 100 mph+ jet stream across S England will lie atop a moist and unstable SWly flow at the surface. 3 areas of convective/storm focus potential likely: 1. Sern UK this morning/early afternoon + far SE tonight; 2: W Scotland , W Ireland and N Ireland today; 3. Scotland, NW England and W Ireland today and tonight.
1 ... S ENGLAND, E WALES, MIDLANDS and E ANGLIA …
In wake of morning rain clearing the east coast, sunny spells developing will generate modest instability of up to 300-600 j/kg across the above areas – to coincide with mid-upper dry air intrusion with steeper lapse rates pushing in from the west on northern edge of jet across far S of England. As a result, convection may attain enough depth for a few thunderstorms amongst a swathe of showers developing from SW England/E Wales NEwards across Midlands, central S England towards Nern Home Counties and E Anglia this morning and early afternoon … before models indicate instability subsiding eastward through the afternoon. With 30-40 knts of DL shear … some organisation into clusters of shower/weak storms is possible – capable of producing localised flooding. Also hail and gusty winds may accompany showers/storms. No severe weather expected.
There is a risk (albeit below 30% risk) of some isolated lightning embedded in heavy perhaps convective rainfall clipping far SE of England (Sussex & Kent) tonight, as a frontal wave moves NE through the English Channel.
2 … SCOTLAND, W IRELAND and N. IRELAND …
Lapse rates will steepen through the day with approach of upper trough over the Atlantic to support heavy showers which may become weakly electrified with the addition of surface heating overland. Showers/storms maybe accompanied by hail and gusty winds, but no severe weather expected.
3 … W SCOTLAND, NW ENGLAND, W WALES and W IRELAND tonight …
Heavy showers with some thunderstorms amongst them look to continue overnight across coastal areas and moving inland as increasingly cold air spreads in aloft with arrival of upper trough from the W atop seasonally warm SSTs – creating instability over the sea. Fairly strong flow aloft may organise showers/storms into linear clusters capable of brief intense rainfall leading to localised flooding along with strong wind gusts and hail may accompany stronger convection.
Issued by: Nick Finnis
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UK Severe Convective & Storm Forecast - Issued 2017-08-17 08:16:18Valid: Thurs 17th Aug 6AM to Fri 18th Aug 6AMClick here for the full forecast
Day 1 Storm / Convective Forecast -
Chance of a few rumbles of thunder in the heavy pulses of rain spreading N and E across northern UK tonight, then later in the night a risk of some elevated storms spreading NE across parts of SE England.
The overnight thundery rain clearing first thing to sunshine and showers for Tuesday, greatest chance for thunder likely to be Scotland along with northern and eastern parts of England.
My latest storm forecast below. Day 1 covers tonight until 6am, day 2 cover Tuesday 6am until Wednesday 6am.
Storm & Convective Forecast
Issued 2017-08-14 22:07:17
Valid: DAY 1: 14/08/17 22z to 15/08/17 06z. DAY 2: 15/08/17 06z to 16/08/17 06zDays 1 & 2 Convective / Storm Forecast
Synopsis
Monday (Day 1): Upper trough slides in from the west across western Britain on Monday, with an area of low pressure to the West of Scotland driving a cold slowly east across northern and western areas. Heavy showers with isolated thunder will affect Ireland and N. Ireland along the cold front, then later waves moving NE along the cold front further east may produce some isolated thunder embedded in pulses of heavy rain moving NE across Wales, N England and Scotland overnight. Towards SE England, a seperate area of heavy rain and embedded thunderstorms may develop and spread NE ahead of cold front moving east.
Tuesday (Day 2): Following cold front clearing eastern areas in the morning will be followed by an unstable W to SWly flow as upper trough begins to move in across the UK aloft. So scattered heavy showers and some thunderstorms are likely - more especially across northern and western areas.
DAY 1 DISCUSSION ... UNTIL 6AM TUESDAY 15TH AUG
... IRELAND and N. IRELAND, SW ENGLAND, WALES, N ENGLAND, SCOTLAND ...
Conveyor of warm moist air ahead of cold front and steepening lapse rates from the west with approaching upper trough will allow embedded convection near or along cold front moving in from west where lift will be enhanced by waves developing and moving NE along it. Convection may become deep enough to produce isolated thunder and locally high enough rainfall to produce localised flooding.
... SE ENGLAND ...
Plume of richer moisture over France, characterised by steep lapse rates and advecting NE, may produce deep enough convection for some isolated thunder and heavy rain leading to localised flooding tonight, as mid-level warm moist air advection destabilises with approach of upper trough from the west.
DAY 2 DISCUSSION ... 6AM TUES 15TH AUG UNTIL 6AM WEDS 16TH AUG
... SCOTLAND, N and E ENGLAND ...
Models indicate lapse rates will be steepest across northern and eastern UK - where coldest mid-level temperatures of the trough axis moving east will be during peak heating in the afternoon. Surface heating in the sunny spells and cold temperatures aloft will support the development of scattered heavy showers and some thunderstorms. No severe weather is anticipated, given weak vertical shear and modest temperatures/moisture profiles ... any storms may produce small hail and a localised risk of minor flooding. Showers/storms should quickly fade after dark, as surface heating wanes.
Issued by: Nick Finnis
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UK Severe Convective & Storm Forecast - Issued 2017-08-14 22:07:17Valid: DAY 1: 14/08/17 22z to 15/08/17 06z. DAY 2: 15/08/17 06z to 16/08/17 06zClick here for the full forecast
Days 1 & 2 Convective / Storm Forecast -
UK Severe Convective & Storm Forecast - Issued 2017-08-14 11:58:05Valid: 14/08/2017 06z to 15/08/2017 06zClick here for the full forecast
Convective / Storm Forecast - Monday 14th August 2017 -
Storm & Convective Forecast
Issued 2017-08-07 22:04:31
Valid: 08/08/2017 00z to 09/08/2017 00zCONVECTIVE / STORM FORECAST - TUESDAY 8TH AUGUST 2017
Synopsis
A deep upper trough will slide east and amplify across NW Europe during Tuesday, a potent shortwave trough moving SE across Ireland towards NW France into the base of the upper trough will aid in the deepening of a low pressure system drifting north across the near continent on the forward side of the upper trough. Thunderstorms will spread NE across France Monday night and through Tuesday, with a risk of storms developing across SE UK too, while a frontal wave further north and west will bring outbreaks of heavy and perhaps thundery rain.
… SE ENGLAND and EAST ANGLIA …
Plume of warm, humid and unstable air spreading northeast across France with low pressure system moving north ahead of approaching upper trough to the west looks to clip SE UK on Tuesday. Thunderstorms spreading northeast across France Monday night into Tuesday morning may spread across the eastern English Channel to affect SE England and parts of E Anglia, though 'home-grown' storms may also develop aong breeze convergence too. Storms will likely be hit and miss and with weak deep layer shear, unlikely to produce widespread severe weather … though models indicate rainfall totals that warrant a MARGINAL risk of torrential downpours leading to surface water flooding. Also light winds aloft, surface convergence and fairly low cloud bases will be ideal conditions for funnel clouds or even brief weak tornadoes/waterspouts.
… CENTRAL S ENGLAND, MIDLANDS, YORKS and LINCS …
Slow-moving frontal wave edging north across the above areas on Tuesday will bring outbreaks of heavy rain, waves rippling along the front may produce deep enough convection for a few embedded thunderstorms along the front which will move NE, particularly during Tuesday morning. A low risk of localised flooding may occur where convective torrential downpours develop along the front.
... IRELAND, SW ENGLAND and WALES ...
Shortwave trough moving SE will create steep lapse rates with surface heating in expected sunny spells and create lift of cool but moist airmass ... which will support heavy showers and a few scattered thunderstorms which maybe accompanied by hail, gusty winds and locally torrential rain.
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UK Severe Convective & Storm Forecast - Issued 2017-08-07 22:04:31Valid: 08/08/2017 00z to 09/08/2017 00zClick here for the full forecast
CONVECTIVE / STORM FORECAST - TUESDAY 8TH AUGUST 2017 -
Heatwave 'Lucifer', which has brought record heat to Italy, eases here, but continues for The Balkans and Greece. Meanwhile, heavy rain with a risk of flooding to affect NW Europe.
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Heatwave 'Lucifer', which has brought record heat to Italy, eases here, but continues for The Balkans and Greece. Meanwhile, heavy rain with a risk of flooding to affect NW Europe.
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Heatwave 'Lucifer', which has brought record heat to Italy, eases here, but continues for The Balkans and Greece. Meanwhile, heavy rain with a risk of flooding to affect NW Europe.
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Heavy downpours with occasional thunder here near Croydon after a sunny morning with towers building all around
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Already been some thunder across parts of Wales and SW England, more recently over Gloucestershire/south Worcs/west Oxon
Storm & Convective Forecast
Issued 2017-08-05 06:47:51
Valid: 05/08/2017 06z to 06/08/2017 06zCONVECTIVE / STORM FORECAST - SATURDAY 5TH AUGUST 2017
Synopsis
A strong belt of upper westerlies will cover northern Europe on Saturday, with an upper trough embedded in this flow crossing west to east across the UK. An unstable showery airmass will cover the UK, with a risk of scattered non-severe thunderstorms across southern Britain.
... E IRELAND, WALES, CENTRAL and SOUTHERN ENGLAND ...
Diurnal surface heating beneath increasingly cold mid-level temperatures associated with upper trough moving east will create steep lapse rates and a modestly unstable airmass across the above areas - yielding around 300-500 j/kg CAPE. As a result, scattered showers this morning will turn increasingly heavy and more widespread across central and southern areas of England and Wales through the day, as lift from upper trough combined with increasing surface temperatures increases instability. Hail and occasional thunder is likely to accompany heaviest showers spreading east. Across S England - 30-40knts of deep layer shear towards strong jet stream and local wind convergence may organise showers/storms into clusters that may bring an isolated risk of surface water flooding. However, no severe weather is anticipated, given modest instability / shear.
... SE/E SCOTLAND ...
Heavy showers developing or moving in across here may turn thundery this afternoon, with a risk of hail and localised flooding. Weak vertical shear will mean severe weather is unlikely
Issued by: Nick Finnis
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UK Severe Convective & Storm Forecast - Issued 2017-08-05 06:47:51Valid: 05/08/2017 06z to 06/08/2017 06zClick here for the full forecast
CONVECTIVE / STORM FORECAST - SATURDAY 5TH AUGUST 2017 -
Looks like there will be a large swathe of severe storms over the next few days stretching from the Pyrenees NE across France, Germany and into Poland along a slow-moving boundary that separates hot and humid conditions over southern Europe and the cool and changeable conditions over NW/N Europe. Would love to be in these areas to watch supercells roll through, though could be some nasty conditions.
Back home, more benign showery weather thanks to the cool conditions, but nonetheless, we could see non-severe storms today, mostly Scotland, N. Ireland and parts of N England - where lapse rates will be steepest. Chance of seeing a brief tornado / waterspout in the NW - where surface wind convergence and plenty of LL instability combined with light winds aloft will be ideal conditions for them.
Storm & Convective Forecast
Issued 2017-07-31 09:11:19
Valid: 31/07/2017 06z to 01/08/2017 06zCONVECTIVE / STORM FORECAST - MONDAY 31ST JULY 2017
Synopsis
Upper low and collocated surface low pressure system will be parked off the west coast of Scotland during Monday. A cool and unstable showery southwesterly flow will cover the UK, surface heating will allow numerous showers become widespread away from SE UK, thunderstorms most likely for Scotland and N. Ireland.
... SCOTLAND, N. IRELAND & N ENGLAND ...
An upper cold pool across northern British Isles associated with upper low centred west of Scotland will create steepest lapse rates across Scotland, N. Ireland and N England ... so here will see the greatest risk of thunderstorms developing with surface heating in sunny spells. Vertical shear will be generally weak across these areas with stronger instability, though surface wind convergence along with troughs in the flow combined with lighter upper winds may bring slow-moving lines of showers/storms that could bring a risk of localised flooding. Any storms maybe accompanied by hail and gusty winds too.
Across the Western Isles, western Scotland and northern side of N. Ireland - likely local surface breeze convergence, low LCLs (cloud bases), light winds aloft and strong low-level instability will be ideal conditions for rotating non-mesocyclone updrafts, so potential for some brief tornado or waterspout sightnings here.
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UK Severe Convective & Storm Forecast - Issued 2017-07-31 09:11:19Valid: 31/07/2017 06z to 01/08/2017 06zClick here for the full forecast
CONVECTIVE / STORM FORECAST - MONDAY 31ST JULY 2017 -
Wondering why the hot weather, that teased us earlier this summer, is reluctant to return? Blame an unusually southerly tracking jet stream.
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Wondering why the hot weather, that teased us earlier this summer, is reluctant to return? Blame an unusually southerly tracking jet stream.
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Wondering why the hot weather, that teased us earlier this summer, is reluctant to return? Blame an unusually southerly tracking jet stream.
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UK Severe Convective & Storm Forecast - Issued 2017-07-27 09:47:12Valid: 27/07/2017 06z to 28/07/2017 06zClick here for the full forecast
CONVECTIVE / STORM FORECAST - THURSDAY 27TH JULY 2017 -
Notable shortwave visible as dark stripe in WV imagery approaching NW Britain and Ireland likely to support development of heavy showers and thunderstorms in this area this afternoon
Storm & Convective Forecast
Issued 2017-07-26 09:21:36
Valid: 26/07/2017 06z to 27/07/2017 06zCONVECTIVE / STORM FORECAST - WEDNESDAY 26TH JULY 2017
Synopsis
Upper low and collocated surface low pressure system close to the west of Scotland today will drive a band of rain along a frontal system eastwards across the UK this morning. Post frontal airmass will become unstable across Scotland, Ireland and N. Ireland through the afternoon, supporting heavy showers / thunderstorms.
… SCOTLAND, IRELAND + N. IRELAND …
Water vapour imagery shows a marked shortwave trough in a belt of strong upper westerlies moving east towards NW Britain this morning in wake of frontal rain currently across much of mainland UK. This shortwave trough will steepen lapse rates and create forced ascent which will support the development of heavy showers and thunderstorms. Strong westerly winds aloft and backing of winds towards the surface with approach of shortwave will create fairly strong deep layer shear in the order of 30-50 knts … which will help organise heavy shower/storms into clusters and line segments. These may produce isolated strong wind gusts and also some hail. An isolated brief/weak tornado or waterspout can’t be ruled out with stronger convection which co-incides with an enhancement of low-level shear with approach of shortwave.
Issued by: Nick Finnis
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UK Severe Convective & Storm Forecast - Issued 2017-07-26 09:21:36Valid: 26/07/2017 06z to 27/07/2017 06zClick here for the full forecast
CONVECTIVE / STORM FORECAST - WEDNESDAY 26TH JULY 2017 -
A very intense shower just clearing here at my parents just SW of Ashford in Kent
Before (looking north) with radar
Following a kind of 'whales mouth' below looking south had torrential rain but no thunder
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More funnel sightings today, this may even a weak tornado over the New Forest
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Storm & Convective Forecast
Issued 2017-07-23 05:59:56
Valid: 23/07/2017 06z to 24/07/2017 06zCONVECTIVE / STORM FORECAST - SUNDAY 23RD JULY 2017
Synopsis
Upper and collocated surface lows across eastern England will slowly drift east across the N Sea during the evening. An unstable Wly veerying NWly to Nly flow will cover England and Wales.
… ENGLAND and WALES …
Cold mid-level temperatures of upper low atop moist diurnally heated surface airmass will create steep lapse rates which will support the re-development of scattered heavy showers and thunderstorms today. A zone of wind convergence shifting southeast across England and Wales during the day could be the focus for storms to organise and train along, bringing a threat of localised flooding where they do organise. Otherwise weak vertical shear will mean showers and storms that develop will be dis-organised and pulse-type and will limit the potential for severe weather. Any showers/storms may produce hail and, like yesterday, there could be a few funnels or even brief weak tornadoes / waterspouts – especially where surface convergence combines with buoyant and strong updrafts.
Issued by Nick Finnis
Also on Netweather here: http://www.netweather.tv/index.cgi?action=convective;sess=
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Convective/Storm Discussion Thread - 1st August onwards
in Storms & Severe Weather
Posted
Looks like it was quite a lively night across parts of west Wales but especially N England.
Didn't expect thunder to be so prolific across N England! Was quite an active (split) cold front ...
Here was my storm forecast for yesterday: