Convective/Storm Discussion Thread - 1st August onwards

[NO LONGER POSTING]

World class, first thunderstorms of 2018! Excluding any thunder snow 

[Flash bang flash bang etc]

Looks like a big squall pulling up over the CS. Is there a convergence zone in play cos some hefty showers pepping up near brighton

[Ben Sainsbury]

11 minutes ago, Flash bang flash bang etc said:

Looks like a big squall pulling up over the CS. Is there a convergence zone in play cos some hefty showers pepping up near brighton

That’s right!

[SMU]

2 bolts of Fork lightning here in the last 30 mins !

[sunnijim]

29 minutes ago, Nick F said:

2 rumbles of Thunder heard rumbling to the south of here in Croydon, sky going dark to the south, first thunder of the year I think

 

Wow! A real convective outbreak here in SE London.

Torrential convective raindrops,hail and distant thunder!

A real 'end of heatwave' look to the sky...hard to believe this time last week we were melting snow.

[Daniel*]

Just now, sunnijim said:

Wow! A real convective outbreak here in SE London.

Torrential convective raindrops,hail and distant thunder!

A real 'end of heatwave' look to the sky...hard to believe this time last week we were melting snow.

Quite impressive for this time of year. Annoyed! The cell split in two leaving me in no mans land. ?

[SMU]

8 minutes ago, Daniel* said:

Quite impressive for this time of year. Annoyed! The cell split in two leaving me in no mans land. ?

Karma for nicking all my snow

[Supacell]

A nice early storm for some and perhaps more opportunities through the coming week. I expect thundery activity will die down as the showers push north but still likely to bring some heavy showers around here through the evening hours.

[Dami]

40 minutes ago, Daniel* said:

Quite impressive for this time of year. Annoyed! The cell split in two leaving me in no mans land. ?

welcome to my world during the storm season. 

[NO LONGER POSTING]

World class, first thunderstorms of 2018! 

Watched the squall roll in over the Great Park 

Saw what looked like some rotation but can't confirm it unfortunately as we dashed to the cars 

[Daniel*]

50 minutes ago, Steve Murr said:

Karma for nicking all my snow

Ha generally you’ll do a lot better - it’s about bloody time I got it good!  

I wonder how Greenhithe did... there was a fantastic streamer one of several, one in particular was in early hours of Wednesday, Rotherhithe was sweet spot, we had brightest echoes.

Torrential snow... never seen snow build a depth like that in relative short time in a hour almost 10cm. Shame wind direction changed pushing it nw, as I would have been buried by sunrise. Bring on next beast..

 

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Mon 12 Mar 2018 - 05:59 UTC Tue 13 Mar 2018

ISSUED 21:49 UTC Sun 11 Mar 2018

ISSUED BY: Dan

Upper and surface low move slowly eastwards across southern Britain on Monday. Numerous bands of showery rain will rotate around the low centre across much of England and Wales, but any sufficient heating given cloud breaks will steepen lapse rates to allow a few slow-moving heavy showers to develop, some electrified.

Lightning risk looks greatest in a narrow curved corridor where low-level convergence is maximised from W Norfolk/The Fens through Cambs / W Essex / Herts / London / Kent / Surrey / Sussex etc, but confidence not high enough to upgrade to SLGT for now given marginal instability, saturated profiles and extensive cloud cover possible. Nonetheless, slow-moving nature of heavy showers could lead to some localised surface water issues. Such setups can produce a few funnel clouds or weak

 

http://www.convectiveweather.co.uk/forecast.php?date=2018-03-12

[Nick F]

Storm & Convective Forecast

Issued 2018-03-11 22:17:45
Valid: 12/03/2018 6am to 13/03/2018 6am

CONVECTIVE / STORM FORECAST - MONDAY 12TH MARCH 2018

Synopsis

Upper and collocated surface low will drift NE across S England and E Anglia during Monday, centred across London at noon circa 983mb, showers will circulate around the low across England and Wales, heavy and thundery across S England and E Anglia.

… S ENGLAND and E ANGLIA …

Occluded front wrapping around low moving NE will bring a lot of cloud and showery bands of rainfall to central and western areas of England along with Wales, best cloud breaks will be near centre of low track in the above areas, with insolation here yielding modest CAPE by early afternoon. So here most likely to see deepest convection and hence risk of lightning. Thundery showers here will be slow-moving, so heavier bursts of rain may lead to some localised surface flooding. Hail may also accompany heavier showers and funnel clouds can’t be ruled out with surface convergence zones developing along track of surface low.

Also on Netweather site here: https://www.netweather.tv/weather-forecasts/uk/convective

[Flash bang flash bang etc]

Anyone got any recommendations of where I could go next week (22nd > 25th) for some warmer weather and potential spring thunderstorms?

i have a small(ish) budget - so was thinking Italy / Malta / Portugal or maybe even Greece.

have some work to do while out there, so this is sort of a ‘laptop break’ but some thunderstorms here and there would be a perfect distraction :-D

[Windblade]

On ‎11‎/‎03‎/‎2018 at 17:42, Daniel* said:

Quite impressive for this time of year. Annoyed! The cell split in two leaving me in no mans land. ?

Thats my story as well. Heard my first faint rumble of the year yesterday early evening, looked outside and saw it dark to the south, jumped on the radar and saw a storm heading directly for me. Awesome I thought! 25 minutes later after hearing no more rumbles or seeing anything I checked the radar again, only to see the storm had split into two cells which passed either side of me.  You couldn't make it up. Of course, as usual the eastern most cell drifted off to Essex where it happily went balistic for hours afterwards. 

Edited March 12, 2018 by Windblade

[Flash bang flash bang etc]

4 hours ago, Windblade said:

Thats my story as well. Heard my first faint rumble of the year yesterday early evening, looked outside and saw it dark to the south, jumped on the radar and saw a storm heading directly for me. Awesome I thought! 25 minutes later after hearing no more rumbles or seeing anything I checked the radar again, only to see the storm had split into two cells which passed either side of me.  You couldn't make it up. Of course, as usual the eastern most cell drifted off to Essex where it happily went balistic for hours afterwards. 

Well I wouldn’t say ‘ballistic’ - ? but yeah they do seem to get the lions share of any activity and do seem to make the best of even the smallest instability ...

[Ben Sainsbury]

Advanced Outlook:

As it stands for many area in CS England and Midlands have a good chance for some decent thunderstorm activity over Thursday.

Current CAPE levels looks to be the highest we have seen all year, approaching 600J/kg of SB Cape. This combined with steep lapse rates looks to set off a few weakly electrified thunderstorms.

DLS, low dewpoints and relatively low SRH looks apparent for Thursday, reducing the risk of any real severity in any heavy showers or thunderstorms.

Still the potential is there!

 

 

Edited March 13, 2018 by Ben Sainsbury

[Windblade]

19 hours ago, Flash bang flash bang etc said:

Well I wouldn’t say ‘ballistic’ - ? but yeah they do seem to get the lions share of any activity and do seem to make the best of even the smallest instability ...

It looked pretty active on radar which is what I was basing that off. Exact same story the whole of last year - storm cells would pass parallel to me, dift over to Essex and then fire up for hours. Extremely frustrating.

Edited March 13, 2018 by Windblade

[Flash bang flash bang etc]

12 hours ago, Ben Sainsbury said:

Advanced Outlook:

As it stands for many area in CS England and Midlands have a good chance for some decent thunderstorm activity over Thursday.

Current CAPE levels looks to be the highest we have seen all year, approaching 600J/kg of SB Cape. This combined with steep lapse rates looks to set off a few weakly electrified thunderstorms.

DLS, low dewpoints and relatively low SRH looks apparent for Thursday, reducing the risk of any real severity in any heavy showers or thunderstorms.

Still the potential is there!

 

 

Have lightning symbols on google weather for godalming for friday ?

[Ben Sainsbury]

A quick review of what I had forecasted yesterday,

Amounts of CAPE look good for this time of year, up to 800J/kg

Continuation of theme for steep lapse rates tomorrow

Showers/Storms dependent on whether cloud clover can clear.

Overall severity risk and organisation of storms look on the low side.

Expect: Small Hail, Heavy Rainfall, Occasional Lightning & Strong Wind Gusts.

Have included a risk map below: (Favorable areas South Midlands into South Wales)

 

 

[Summer Sun]

Day 1 Convective Outlook

VALID 06:00 UTC Wed 14 Mar 2018 - 05:59 UTC Thu 15 Mar 2018

ISSUED 15:55 UTC Wed 14 Mar 2018

ISSUED BY: Dan

Upper trough over the Atlantic will slowly advance towards the British Isles, while a slow-moving front will continue to drift northeastwards across England, Wales and Northern Ireland. The post-frontal environment will be characterised by steepening lapse rates as the mid/upper levels continue to cool, with a few showers likely tonight - a low chance of a few isolated lightning strikes, this most likely over SW Ireland where showers will tend to be more widespread.

http://www.convectiveweather.co.uk/forecast.php?date=2018-03-14

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Thu 15 Mar 2018 - 05:59 UTC Fri 16 Mar 2018

ISSUED 21:39 UTC Wed 14 Mar 2018

ISSUED BY: Dan

Upper trough migrating slowly NE-wards across southern Britain and Ireland on Thursday. At the surface, an occluded front and associated frontal rain will shift northeastwards across northern and eastern areas, leaving somewhat of a clearance in central and southern parts.

Cold air aloft and steep mid-level lapse rates, associated with the upper trough, atop diurnal heating will generate 400-700 J/kg CAPE with a few scattered showers or thunderstorms developing from midday through to the early evening in association with a convergence zone (marked as an occlusion on the latest T+24 FSXX). Mean steering flow will result in showers/storms moving SSE to NNW, and while the main focus will be on surface-based convection over England and Wales, it is possible later in the afternoon and first part of the evening for some showers/thunderstorms over N France to approach S/SE England, though probably weakening by mid-evening.

 

Main threats are localised surface water issues from relatively slow-moving heavy downpours, and perhaps some hail 1.0-1.5cm in diameter. Some NWP guidance suggests showers/storms could be quite isolated, meaning many places even within the SLGT may not experience any lightning nearby - and there is some uncertainty as to the extent of the cloud cover left behind the main occluded front, which could serve to inhibit deep convection by reducing insolation. Such convergence zones can sometimes produce brief funnel clouds or a weak tornado.

 

http://www.convectiveweather.co.uk/forecast.php?date=2018-03-15

[Supacell]

It is a very messy picture today with an area of high pressure to the NE over Scandinavia and a couple of areas of low pressure to the west. An occluded front is currently sat through the middle of the country bringing outbreaks of light to moderate rain. Ahead of this resides some colder air as fairly strong winds blow in from the North Sea, behind it we have something milder and with slack winds. The chart below shows the situation by noon today with an obvious temperature gradient from north-east to south-west and rainfall most prevalent in the east along that front.

It is in the milder south-western half of the UK that there seems to be a risk of some well scattered thundery showers developing. The charts below show CAPE and LI at 3pm and then 6pm from the GFS model. I have zoomed in to show areas that are at risk. The final chart shows Convective Precipitation only and so for simplicity it does not show the area of dynamic precipitation across eastern parts.

The NMM shows a similar area with some CAPE build up this afternoon along with a similar area at risk of showers.

To me it looks like the best set up so far this year for showers to develop and contain hail and thunder. With very little shear they will likely be "spring type" pulse storms and both Euro4 and NMM high resolution models suggest they will be isolated in nature. Lines of wind convergence could provide the focus for showers and thunderstorms this afternoon. Showers and storms will be slow moving and this could lead to a risk of localised flooding in affected areas.

My guess is that anywhere south-west of a line from Liverpool to Essex is at risk, especially where wind convergence (below are the NMM predictions at 3pm and 6pm) combines with the higher CAPE. 

For anything to happen today there will need to be some surface heating and so this forecast relies on cloud breaking behind the occluded front as it moves away north-east. Tomorrow looks a similar set up and with similar areas being affected. By this stage there will also be snow showers moving into the north-east.

[Mokidugway]

1 hour ago, Supacell said:

...

Interesting convergence running through north west ,nice to be back talking bubbleupacus and not bloody snow .

Edited March 15, 2018 by Supacell
Remove need for scrolling through my post twice

[Nick F]

Storm forecast issued for today: