Nick F

UK Severe Convective & Storm Forecast - Issued 2016-06-16 09:09:38 Valid: 16/06/2016 06z to 17/06/2016 06z CONVECTIVE / STORM FORECAST - THURS 16TH-JUNE-2016 Click here for the full forecastCheck the full storm forecast here

Interesting lowering from a storm over the Black Country earlier. Haven't heard any thunder since last week here in south London, few more days left before the thunder risk dies off over the weekend.

Just hung my washing out in the garden, which will mean the rain will now arrive after a dry day so far. Still waiting for my first thunder of the week, not heard any since last week!

UK Severe Convective & Storm Forecast - Issued 2016-06-15 12:56:46 Valid: 15/06/2016 12z to 16/06/2016 06z CONVECTIVE / STORM FORECAST - WEDS 15TH-JUNE-2016 Click here for the full forecastCheck the full storm forecast here

Looks like parts of north North Wales could see some flooding issues, a lot of slow-moving heavy downpours there in last few hours.

Pretty much agree with what Brick mentions above, bit more of a head start with insolation here in London this morning compared to yesterday, though sunny spells are brief -so modest surface heating at best today with a lot of cloud for my liking. Still - should be some storms around, and N Wales, N Midlands to Lincs /Norfolk could be prime spot for funnels or even brief/weak tornadoes due to convergence between E/NE and SW winds here. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Storm & Convective Forecast Issued 2016-06-14 08:53:44 Valid: 14/06/2016 06z 15/06/2016 06z CONVECTIVE / STORM FORECAST TUES 14TH-JUNE-2016 Synopsis Upper low that has been to the west of the UK over recent days finally shifts across the UK by the end of Tuesday. At the surface, area of low pressure centred over N Wales this morning will shift slowly east to be centred off the north Norfolk coast by midnight. A showery circulation around this low will cover England and Wales, with increased surface heating triggering scattered thunderstorms. ... ENGLAND, WALES and EIRE ... Airmass covering UK will be cooler than recent days, but still moisture rich with dew points of 12-14C typical. Cloud breaks should allow modest surface heating of the moist surface airmass to yield 300-600 j/kg CAPE beneath increasingly steep lapse rates as cooler air edges in aloft with arrival of upper low from the west. As a result, scattered heavy showers and thunderstorms will develop. Like recent days, unidirectional winds from the surface to upper levels and little increase aloft means weak vertical shear with little organisation of storms likely. However, storms will likely be slow-moving across central, northern and eastern parts of England where winds are weak aloft - so have highlighted a MARGINAL risk for flash-flooding here. Additionally, models indicate a zone of winds convergence from N Wales to Norfolk this afternoon between E/NE winds to the N and SW winds to the south - which may allow storms to train along this zone increasing risk of localised flooding ... Also weak winds aloft, fairly low LCLs (Lifted Condensation Level) around 600-800m and surface convergence may allow funnel clouds or even a few brief/weak tornadoes to develop in the Marginal risk area. Storms will move through quicker in the south - with faster mid-level steering winds. Issued by: Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2016-06-14 08:53:44 Valid: 14/06/2016 06z 15/06/2016 06z CONVECTIVE / STORM FORECAST TUES 14TH-JUNE-2016 Click here for the full forecastCheck the full storm forecast here

It appears extensive cloud cover and consequent lack of sunshine, compared to Sunday, has suppressed strong convection today resulting in a distinct dearth of storms so far. Tomorrow looks more promising though, with less frontal interference as low pressure moves over the UK plus more CAPE showing on both ECMWF and GFS.

Storm & Convective Forecast Issued 2016-06-13 08:59:38 Valid: 13/06/2016 06z to 14/06/2016 06z CONVECTIVE / STORM FORECAST - MON 13TH-JUNE-2016 Synopsis A slack cyclonic westerly flow upper flow covers the UK on Monday between an upper low over the mid-N Atlantic and upper low over NE Europe. A broad surface low pressure system extends from the mid-N Atlantic across UK/EIRE and east across Benelux and N Germany, low pressure circulations within this system moving east, one slowly-moving across Ireland today. ... EIRE/N. IRELAND, E WALES, S ENGLAND, E ANGLIA, MIDLANDS, N ENGLAND and SW SCOTLAND... Like Sunday, Monday morning will see extensive cloud cover and showery dynamic rainfall from a frontal system moving through NEward. Following clearance of the front, cloud breaks will develop to allow surface heating of fairly moist airmass (PWAT values of around an inch) ... yielding 300-800 j/kg CAPE across the above areas. Water vapour imagery indicates a shortwave trough with associated drier mid-level air (darker stripe) and lobe of vorticity moving east across Ireland and SW UK this morning ... large scale ascent and steepening lapse rates from this feature combined with localised surface convergence and surface heating this afternoon should trigger scattered heavy showers and some thunderstorms. Vertical wind shear looks to be rather weak again (20knts or less), so storms will struggle to organise and have much longevity. However, during the more stronger stages of storms, large rainfall totals in a short space of time are possible (15-25mm per/hr) ... leading to a risk of flash flooding ... particularly across northern and eastern parts of the area depicted for thunderstorms in the forecast map - where have highlighted a MARGINAL risk for severe weather, because storms will likely be slow-moving here .. with lighter winds aloft. Storms may also produce hail, gusty winds and occasionally frequent cloud-to-ground lightning. Storms will be diurnally-driven, so should fade by late evening. Issued by: Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2016-06-13 08:59:38 Valid: 13/06/2016 06z to 14/06/2016 06z CONVECTIVE / STORM FORECAST - MON 13TH-JUNE-2016 Click here for the full forecastCheck the full storm forecast here

Stunning skies around London looking from my 10th floor office in west London, this is a cell that went up over central London, apologies for not so great quality: Skies over north London

Skies clearing out nicely here in west London, with growing patches of blue skies, should spark some good storms in a few hours hopefully.

Storm & Convective Forecast Issued 2016-06-12 06:17:10 Valid: 12/06/2016 06z to 13/06/2016 06z DAY 1 CONVECTIVE FORECAST - SUN 12TH-JUNE-2016 Synopsis The UK and EIRE will be under the cyclonic influence on the eastern edge of an upper low out west over the mid-N Atlantic, Thunderstorms are again likely in places on Sunday where pockets of surface heating combine with large scale ascent in vicinity of an upper shortwave trough and surface convergence ahead of fronts moving NE across the UK ahead of upper/surface low to west of Ireland. ... S ENGLAND, E ANGLIA, MIDLANDS, E WALES, N ENGLAND ... A rather complicated picture once again with regards to where will most likely see thunderstorms develop. Storms will be generally dependent on where instability will be greatest and where forcing for ascent will be strongest - which is not always forecast well in slack flow regimes with alot of cloud cover and rainfall already present from weak frontal systems passing through. Where sunshine does break through expected widespread morning cloudiness, pockets of surface heating of the warm moist airmass still present across central, southern and eastern UK, characterised by dew points of 13-15C, could yield CAPE values in the order of 300-900 j/kg during the afternoon. A number of fronts are indicated to move NE over the UK on Sunday, which are producing a lot of cloud cover and dynamic rainfall this morning - which makes forecasting where cloud breaks occur tricky. Storms will likely develop on Sunday as the combination of instability generated by localised surface heating where sun breaks through, large scale upper ascent ahead of shortwave upper trough edging NE and low-level ascent near surface convergence ahead of frontal boundaries. A broad area has been depicted as having a MARGINAL risk of severe weather - mainly for threat of flash-flooding given moist profiles indicated by models - with up to 20-40mm falling locally from storms. A little more wind veer and increase in speed with height than recent days across the south of UK suggests some loose storm organisation in multicell clusters is possible - which may enhance rainfall totals ... pusle-type storms further north with weaker shear away from convergence zones. Some storms may also be occasionally be quite electrically active too, given CAPE values forecast, with frequent lightning an additional hazard. A few funnel clouds or even a brief/weak tornado can't be ruled with stronger storm updrafts above convergence zones. Issued by: Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2016-06-12 06:17:10 Valid: 12/06/2016 06z to 13/06/2016 06z DAY 1 CONVECTIVE FORECAST - SUN 12TH-JUNE-2016 Click here for the full forecastCheck the full storm forecast here

Menacing skies just south of Gatwick airport currently... can feel cold outflow from it.

Have heavy showers and storms to the NE, E, SE and S of me here at work at Gatwick Airport, though nothing heading my direction for now. Warm and very oppressive in the sun.

Haven't watched the whole lot, but some good footage there 20 minutes or so onwards with a few cgs and continuous rumbling ... similar to the storms we had roll through south London that day. Have you ever been or ever considered chasing in the U.S,A in May or early June? On another level compared to the crowded roads and generallynon-severe storms of the UK ... with generally not much problems with traffic in U.S.A. other than chaser convergence when there's only one dominant storm for miles, but you get vast vistas in the Plains, amazing structures - lots of CGs, very large hail and, of course, tornadoes. Back to home, milky sunshine and feeling oppressive here in south London.

Storm & Convective Forecast Issued 2016-06-11 08:17:28 Valid: 11/06/2016 06z to 12/06/2016 06z DAY 1 CONVECTIVE FORECAST - SAT 11TH-JUNE-2016 Synopsis The UK and Ireland will be on the edge of cyclonic upper flow ahead of upper low over the N Atlantic, a shortwave trough ejecting E and NE ahead of this upper low will cross the UK today, with a trailing surface cold front also moving NE into western areas by midnight. Warm moist surface airmass will likely destablise as upper trough passes through, with a risk of thunderstorms developing across central and southern Britain on Saturday. ... EIRE/N. IRELAND, E WALES, S ENGLAND, MIDLANDS, N ENGLAND ... A warm and moist airmass, characterised by PWAT (Precipitable Water) values of 1.1/ to 1.5 inches resides across much of the UK and Nern EIRE away from the far SW UK and S Ireland. Despite a lot of mid-level cloud cover, pockets of hazy sunny spells, already evident across some southern areas, will generate modest surface heating to yield 300-900 j/kg CAPE by mid-afternoon across the above areas. The combination of increasing large scale upper ascent and surface convergence ahead of approaching shortwave trough moving in from the W/SW will create enough forcing to produce scattered heavy showers and thunderstorms from late morning through to late evening across the above areas. Vertical shear will be rather weak, but given light mid-level steering winds, storms will be slow-moving and may back-build along surface convergence lines to produce locally high rainfall totals (15-30mm) within a short space of time - leading to flash flooding - particularly across inland northern, central and southern areas of England. Therefore, have issued a MARGINAL risk of severe weather. Storms may also be accompanied by frequent cloud-to-ground lightning, hail and gusty winds. Issued by Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2016-06-11 08:17:28 Valid: 11/06/2016 06z to 12/06/2016 06z DAY 1 CONVECTIVE FORECAST - SAT 11TH-JUNE-2016 Click here for the full forecastCheck the full storm forecast here

Storm to the north me over central London, distant rumbles roughly every minute or so, though not as active as yesterdays storm that trundled north through south London with near constant thunder... Think it will miss me and pass west and I get some rainy dregs Looking north to central London.

Can see the heavy showers on the outskirts of north London / M25 and they appear to be headed my way but not electrified yet though. Much better visuals on these cells today without the mid-level crud to obscure them!

Not sure if this has been touched on with regards to this subject, but supposedly more vivid and loud cig lightning bolts maybe +ve lightning strikes. It only makes up 5% of all strikes, but they are more dangerous than -ve CGs as they originate from the cirrus anvil rather than the base of the storm, and have to build up a much greater charge to bridge the greater distance to the ground. More on this here from the US NWS: http://www.srh.noaa.gov/srh/jetstream/lightning/positive.html interestingly the article mentions that +ve CGs are the dominant type of CG in winter storms and when storms are dissipating. Another point to note, though not from the article, is that CG lightning can be more prevalent or frequent in elevated or high based storms, as electrical charge tends to dissipate to the ground more easily through the cloud and rain without a lightning strike with surface based storms, whereas drier air beneath an elevated storm tends to allow the charge to build up more easily to result in a CG strike to from cloud to ground.

Storm & Convective Forecast Issued 2016-06-08 07:57:41 Valid: 08/06/2016 06z to 09/06/2016 06z DAY 1 CONVECTIVE FORECAST - WEDNESDAY 8TH-JUNE-2016 Synopsis Upper ridge will build in across the S/W UK between upper trough over the N Atlantic and upper trough over NE Europe and Wern Russia. A slack surface pressure pattern will cover the UK characterised by a warm and moist airmass which will be unstable to surface heating. Surface breeze convergence will trigger heavy showers and thunderstorms in places on Wednesday. ... W SCOTLAND, NW ENGLAND, EIRE/N. IRELAND, WALES, MIDLANDS, CENTRAL S and SE ENGLAND ... Stagnant warm and humid airmass across much of the UK and Ireland, characterised by PWAT (Precipitable Water) values of 1/ to 1.4 inches will become unstable to surface heating in sunny spells, ECMWF indicates 300-900 j/kg CAPE developing across the above areas early afternoon. Breeze convergence will develop inland from NE Wales/NW England SEward towad SE England, with a combination of orographic lift and breeze convergence across NW England, Scotland, EIRE/N. Ireland ... to create forced ascent to trigger localised heavy showers or storms ... which will generally move SEward. Thunderstorms will be less widespread than Tuesday, due to increased ridging aloft. However, where they occur they will again bring a risk of localised flooding, frequent cloud-to-ground lightning, hail and gusty winds. Given localised risk of flash flooding, have issued a marginal risk for parts of mainland UK in the above areas. Storms should fade after dark as diurnal heating stops. Issued by Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2016-06-08 07:57:41 Valid: 08/06/2016 06z to 09/06/2016 06z DAY 1 CONVECTIVE FORECAST - WEDNESDAY 8TH-JUNE-2016 Click here for the full forecastCheck the full storm forecast here

Moving SE across central and southern England as steering wind is NWly now upper trough is across E and NE UK. Occasional blue white sheet lightning to my west, but storms over west London, NW Surrey and Berks taking an eternity to move anywhere.