Convective/Storm Discussion Thread - 8th July onwards

[convector]

1 hour ago, Windblade said:

Absolutely 100 percent rotation there, as evidenced by your top two panoramic pics. Great shots.

Panorama's can be deceptive; there's no way to tell whether this is a supercell from those photos alone. It did, however, consistently produced lightning over a large linear distance between Leicester and Norwich, which implies the storm had a mesocyclone.

[Muffelchen]

5 hours ago, stainesbloke said:

Very heavy shower here about an hour ago, then a spell of warm sunshine. Now torrential again!

Yep got caught in that one working in a field in Egham Hythe. Colleagues in Datchet got it worse though!

[Another Kent clipper]

Well I had quite a mad one at work this afternoon but I took a couple of pictures of the April style showerage.  Very on-off rain

 

[Windblade]

8 hours ago, convector said:

Panorama's can be deceptive; there's no way to tell whether this is a supercell from those photos alone. It did, however, consistently produced lightning over a large linear distance between Leicester and Norwich, which implies the storm had a mesocyclone.

I've never found them to be deceptive personally. If you look at his pics you can clearly see the base is curved, hence rotation.

Edited July 28, 2017 by Windblade

[Stuart]

Day 1 Convective Outlook

VALID 06:00 UTC Fri 28 Jul 2017 - 05:59 UTC Sat 29 Jul 2017

ISSUED 09:02 UTC Fri 28 Jul 2017

ISSUED BY: Dan

Upper vortex to the NW of Scotland on Friday will maintain an unstable environment with numerous scattered showers across Scotland and Northern Ireland, some perhaps weakly-electrified given favourable mid-level lapse rates - lightning most likely over N + W Scotland and parts of Northern Ireland, but the risk in any given location generally not high enough for a SLGT.

 

Developing frontal system sliding NE across England and Wales in a strongly-sheared environment could have some elements of line convection, but with an overlap of some marginal instability then a few lightning strikes might be possible over north Wales and then northern England late afternoon into the evening - considered a fairly low risk at present

 

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-28

[Supacell]

Just a heads up for now as the models are still not in agreement over this but the GFS is throwing up an interesting scenario for late tomorrow into early hours of Sunday for southern parts of the UK in particular.

A warm front moves northwards during Saturday afternoon/evening across southern and eastern England and then a cold front moves SW to NE overnight as part of a developing low pressure system that seems to originate around the Bay of Biscay.

With this it appears that instability increases during the evening and night time hours in two pulses. One runs across the SE and into the far east of East Anglia during the evening and then another comes into the SW and moves NE across the Midlands during the early hours of the morning. The following are for midnight and then 3am on Sunday. I am no expert but whenever I see bright colours on here it tends to mean a bit of a thumbs up to thunderstorm activity.

      

In addition to a build up of some CAPE is an increase in deep layer shear. Again the charts below are for midnight then 3am on Sunday

   

Convective precipitation comes in two waves across the aforementioned areas.

   

A tornado risk being shown on the charts below

   

www.lightningwizard.com/maps

The NMM charts on Netweather seem to agree with the pulse across the SE (increasing CAPE during the night) but over the Midlands there is no CAPE build up, although there is heavy rain. It's a way off in forecasting terms, especially considering we are in a mobile pattern that can change from run to run, but it is something I will be watching.

 

Edited July 28, 2017 by Supacell

[LightningLover]

2 hours ago, Supacell said:

Just a heads up for now as the models are still not in agreement over this but the GFS is throwing up an interesting scenario for late tomorrow into early hours of Sunday for southern parts of the UK in particular.

A warm front moves northwards during Saturday afternoon/evening across southern and eastern England and then a cold front moves SW to NE overnight as part of a developing low pressure system that seems to originate around the Bay of Biscay.

With this it appears that instability increases during the evening and night time hours in two pulses. One runs across the SE and into the far east of East Anglia during the evening and then another comes into the SW and moves NE across the Midlands during the early hours of the morning. The following are for midnight and then 3am on Sunday. I am no expert but whenever I see bright colours on here it tends to mean a bit of a thumbs up to thunderstorm activity.

      

In addition to a build up of some CAPE is an increase in deep layer shear. Again the charts below are for midnight then 3am on Sunday

   

Convective precipitation comes in two waves across the aforementioned areas.

   

A tornado risk being shown on the charts below

   

www.lightningwizard.com/maps

The NMM charts on Netweather seem to agree with the pulse across the SE (increasing CAPE during the night) but over the Midlands there is no CAPE build up, although there is heavy rain. It's a way off in forecasting terms, especially considering we are in a mobile pattern that can change from run to run, but it is something I will be watching.

 

Its a risk! Would be nice to get some action!

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Sat 29 Jul 2017 - 05:59 UTC Sun 30 Jul 2017

ISSUED 19:06 UTC Fri 28 Jul 2017

ISSUED BY: Dan

Upper vortex to the NW of Scotland on Saturday will maintain a feed of cool mid-levels and hence marginally-steep mid-level lapse rates. Once more, numerous showers are expected across Scotland and Northern Ireland, some weakly-electrified - this more likely over N + NE mainland Scotland, and perhaps also E Northern Ireland into SW Scotland, though in general instability a little weaker than on Friday and complicated somewhat by some dynamic precipitation in western Scotland along an old occlusion. CAA overnight will steepen mid-level lapse rates from the west, with an increasing risk of some isolated/sporadic lightning spreading eastwards across Ireland and Scotland. Some small hail will be possible with the strongest cells.

Farther south, a developing wave along the quasi-stationary frontal boundary straddling the English Channel will begin to back the flow, allowing advection of a higher WBPT airmass into SE England as the warm front lifts back north. This will bring outbreaks of rain with some embedded convective elements across southern England during Saturday daytime, though little lightning at this stage given rather saturated profiles, limited convective depth and unimpressive mid-level lapse rates. Nonetheless, some heavy convective rain will be possible embedded within the returning warm front.

 

During the evening hours, falling heights and dry intrusion above the warm sector, and some instability advecting from France, may allow a few showers/thunderstorms (probably elevated, though perhaps not exclusively so) to develop over Kent/Surrey and/or Essex/Suffolk/Norfolk, before moving NE-wards out to the North Sea. Instability parameters are not particularly impressive in current NWP guidance, but given strong DLS any deep convection that does occur could become fairly well-organised, capable of gusty winds and perhaps some hail.

 

Stronger forcing arrives over the western Channel by midnight, which may then be responsible for some deep convection to develop during the early hours of Sunday, running NE-wards over CS/SE England, Home Counties and East Anglia, and largely clearing to the North Sea by the end of this forecast period. Lightning activity is uncertain but some will be possible, especially given steepening mid-level lapse rates within a strongly-sheared environment. Of more interest may be the scope for some linear elements, particularly near or along the cold front which could be capable of some very strong, gusty winds - if any convection can become rooted within the boundary layer, particularly as the cold front surges east, then there would be potential for a tornado also - especially east of the Isle of Wight.

 

Worth noting that the forecast evolution associated with the frontal wave in southern Britain currently carries a lot of uncertainty, and will need monitoring - further updates may be issued as confidence increases. It is possible that no lightning may occur at all with these developments.

 

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-29

[Summer Sun]

Storm Forecast
Valid: Sat 29 Jul 2017 06:00 to Sun 30 Jul 2017 06:00 UTC
Issued: Sat 29 Jul 2017 01:27
Forecaster: TASZAREK

A level 2 was issued for parts of W Russia mainly for large to very large hail, severe wind gusts, excessive precipitation and tornadoes.

A level 1 was issued for W Russia, E Belarus and N Ukraine mainly for large hail, severe wind gusts and excessive precipitation.

A level 1 was issued for N Italy and Alps mainly for large hail, excessive precipitation and severe wind gusts.

A level 1 was issued for N France, Benelux and NW Germany mainly for severe wind gusts.

A level 1 was issued for NE Spain and SW France mainly for large hail, severe wind gusts and excessive precipitation.

SYNOPSIS

Widespread thunderstorm activity with a potential of producing all kinds of severe weather is expected over E Europe. The highest threat for surface-based supercells capable of producing very large hail and tornadoes concerns late afternoon hours and area marked by level 2 over W Russia. Storms with a large hail, heavy rain and severe wind potential will be possible over Alpine area in the afternoon hours. Late and uncertain convective development with a possible supercell and multicell clusters is plausible over NE Spain/SW France. Low-topped storms with severe wind potential and under strong synoptic-scale lift are expected to develop in the late evening over N France and move to Benelux during nighttime.

DISCUSSION

...NW Europe...

Almost stationary large low covers British Isles. On its southern flank a jet streak stretches from Atlantic, through N France, S British Isles, Benelux and up to N Germany. A passage of the shortwave trough with high kinematics and marginal instability is expected by NWP models over N France and Benelux in the evening and nighttime hours. In the environment of high wind shear, small instability and decent QG-lift, a low-topped convection capable of producing severe wind gusts is predicted to develop in the late afternoon hours over N France and move NEwardly to Benelux and NW Germany in the evening and nighttime hours. Given very dynamic wind field and linear forcing, a development of a squall line with bowing segments and damaging wind gusts cannot be ruled out.

...NE Spain / SW France...

Under the influence of a shortwave, also storms over NE Spain and SW France should "fire-up" quite late, around 18 UTC. Given LL SE inflow of a moist air from Mediterranean and EML with 7 K/km lapse rates, ML CAPE over Spain may develop up to 1500-2000 J/kg but with evident cap. NWP models are not consistent in simulating CI, but if storms will overcome CIN and develop, an overlap of 15-20 m/s DLS may support evolution of multicells clusters and supercells capable of producing large hail, severe wind gusts and heavy rain.
...Alpine area...

A weak shortwave passes Alpine area in the afternoon hours. As a result a slowly moving cells are expected to develop in the environment featuring weak shear and small to moderate instability. Storms may be capable of producing locally marginally large hail and excessive rain. Downburst/microburst type severe wind gusts are also involved within these storms. Thanks to mountains interacting with a wind field, a 2-3 supercells with a large hail and severe wind potential cannot be ruled out.

...Eastern Europe...

Over Eastern Europe, a weakening broad low with a well-developed moist and highly unstable warm sector is moving Nwardly. This synoptic feature caused a widespread storm activity with an MCS on Friday evening and nighttime hours through Saturday. Within the support of a consistent broad moisture advection from Black Sea, it is expected that storm clusters will continue on Saturday morning, through afternoon and evening hours. Within the support of a strong diurnal heating, EML from Asia and well developed convergence zone, a new surface based storms are expected to "fire-up" in the afternoon hours and in the environment of > 2000 J/kg ML CAPE, mostly on the N and NE flank of the low. Roughly 15 m/s DLS and curved hodographs with SRH03 exceeding 200-300 (locally > 400) m2/s2 may organise convection into supercells with a potential of producing large to very large hail and tornadoes, especially over N flank of the low (around triple-point) where SRH01 and low-level jet along with LLS (> 10 m/s) are the highest. Multicell clusters will also pose a threat of excessive precipitation (PW > 40) and severe wind gusts. Low is predicted to occlude and cut-off its warm sector in the late afternoon hours. One or two large MCSs should form in the evening and move Nwardly. Severe thunderstorm activity should continue on Sunday in the similar area when diurnal heating and further moisture advection will regenerate environment.

http://www.estofex.org/

[A.J]

^^^ wrong thread Gavin.....ThIs should be in the European Convective thread 

[LightningLover]

Good morning everyone! Still eyeing up the thunderstorm potential this evening... Convective Weather's forecast (Dan) is filling me with hope. May have to stay up late tonight! And if any convection becomes rooted to the boundary layer, then there is the potential of a tornado...

[Summer Sun]

1 hour ago, ajpoolshark said:

^^^ wrong thread Gavin.....ThIs should be in the European Convective thread 

The map covers the south which I why I posted it here

[LightningLover]

Thunderstorms currently in the channel islands. Can anyone confirm?

[A.J]

32 minutes ago, Summer Sun said:

The map covers the south which I why I posted it here

why not just post the map then rather than the tons of text that isn't UK convective discussion?......lol

 

[NO LONGER POSTING]

Good to see some lightning in the channel! Looks good for later 

Edited July 29, 2017 by Surrey

[stainesbloke]

38 minutes ago, Surrey said:

Good to see some lightning in the channel! Looks good for later 

Nice little storm riding the boundary area there as that warm front builds north, not convinced we will see anything thundery here. Kent clipper maybe?

[LightningLover]

2 minutes ago, stainesbloke said:

Nice little storm riding the boundary area there as that warm front builds north, not convinced we will see anything thundery here. Kent clipper maybe?

Lets wait and see!

[LightningLover]

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-29

UPDATE 12:31 UTC Latest guidance has trended a little farther west, and hence a westwards extension of the SLGT. Broad theme remains the same though with (a) some mid-level instability release possible this afternoon over SE England with this initial pulse of precipitation, (b) then behind the warm front still some potential for deep convection to occur during the evening hours along the Theta-E ridge from Kent and north along the eastern fringe of East Anglia, and (c) finally the cold front surging eastwards during the early hours could produce some linear convective elements (perhaps void of lightning depending on true convective depth) capable of some very strong, gusty winds

 

[NO LONGER POSTING]

39 minutes ago, LightningLover said:

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-29

UPDATE 12:31 UTC Latest guidance has trended a little farther west, and hence a westwards extension of the SLGT. Broad theme remains the same though with (a) some mid-level instability release possible this afternoon over SE England with this initial pulse of precipitation, (b) then behind the warm front still some potential for deep convection to occur during the evening hours along the Theta-E ridge from Kent and north along the eastern fringe of East Anglia, and (c) finally the cold front surging eastwards during the early hours could produce some linear convective elements (perhaps void of lightning depending on true convective depth) capable of some very strong, gusty winds

 

The end part 

"

finally the cold front surging eastwards during the early hours could produce some linear convective elements (perhaps void of lightning depending on true convective depth) capable of some very strong, gusty winds"

 

Is now being picked up on the models, a tail like feature of the main area of rain

 

 

 

[LightningLover]

1 minute ago, Surrey said:

The end part 

"

finally the cold front surging eastwards during the early hours could produce some linear convective elements (perhaps void of lightning depending on true convective depth) capable of some very strong, gusty winds"

 

Is now being picked up on the models, a tail like feature of the main area of rain

 

 

Might stay up for a while tonight then...

 

[LightningLover]

I have to admit, it looks like it will be a fast-moving feature.

[Windblade]

Could be in with a shot of a nightime elevated storm then (with a risk of a tornado ). Let's see what happens. Good luck everyone and stay safe.

Edited July 29, 2017 by Windblade

[Chris K]

2 hours ago, Surrey said:

The end part 

"

finally the cold front surging eastwards during the early hours could produce some linear convective elements (perhaps void of lightning depending on true convective depth) capable of some very strong, gusty winds"

 

Is now being picked up on the models, a tail like feature of the main area of rain

 

 

 

Looks like the walk home from the pub later may be a tad damp

[Hurricane Andrew]

Tomorrow looks good  http://www.convectiveweather.co.uk/forecast.php?date=2017-07-30

[carinthian]

Currently have a nice lightning display out towards the Italian Border country in Bolzano direction. Sat outside on the veranda watching the show. Love it on a particular warm evening. My wife thinks I am mad sat there at this time of night !

c