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Convective/Storm Discussion Thread - 8th July onwards


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5 minutes ago, Quicksilver1989 said:

Things are looking good across the channel with the French storms seemingly heading in an NNE direction, question is will they maintain their intensity?

If they are surface based then absolutely not, if elevated then maybe ;) - experience. 

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Holy crap not bad eh ? Am well chuffed with this

That was amazing. The closest to lightning i've ever been....this was Warlingham area (Just oustide Croydon)...    

What a night it was, one of the best storms I have ever seen, maybe even better than July 3rd 2015! I some many great pictures on here today, so I thought I would share some of mine.  

Posted Images

12 minutes ago, Sun & Tanned said:

Hi there everyone, I just wondered if any of you kind people could help. I live near to Stokenchurch in Bucks and just wondered if we are likely to see any storms here tonight or tomorrow. 

It's just I have a new guide dog who is still in training and gets nervous at bangs etc and should I be in the firing line i will ask for someone to come and sit with him and me.

Your assistance and expertise is a lifeline for me. Thank you. 

I appreciate it's so hard to forecast but just wondered if I'm in a zone?

Thank you for your help and good luck everyone, stay safe 

Kindest regards.

Nothing is guaranteed when forecasting storms, and you may well see nothing, but it's as likely as it gets that you'll see some storms in the next 36 hours. 

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Just now, tomp456 said:

If they are surface based then absolutely not, if elevated then maybe ;) - experience. 

Quite often MCS, if surface based, will simply become elevated as they drift across the Channel.

What is quite rare, but not unheard of, is stronger MCS once becoming elevated, re-tapping in below the boundary layer thereby becoming surface based once more. Where GFS is interesting is that it is keen for SBCAPE to remain all through the night (albeit vastly weakening through night hours) so this scenario is not out of the question. 

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Can see on the winds at different levels, steering winds generally mid level say 700-500mb, more backed Sly in the west to SWly over to the east,

winds_15z.thumb.png.daecccf70287f3abd091464756b0ad1d.png

The 12z radiosonde ascent for Herstmonceux in E Sussex (SE England) shows steering flow SWly ... whereas Camborne in far SW England the steering flow is more Sly

2017071812_Herst.thumb.gif.a4ffda4485f5fe6ee65469f0a770cb2c.gif2017071812_Camb.thumb.gif.f475f15b6a44ac031ee28e52fd0ca015.gif

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1 minute ago, Harry said:

Quite often MCS, if surface based, will simply become elevated as they drift across the Channel.

What is quite rare, but not unheard of, is stronger MCS once becoming elevated, re-tapping in below the boundary layer thereby becoming surface based once more. Where GFS is interesting is that it is keen for SBCAPE to remain all through the night (albeit vastly weakening through night hours) so this scenario is not out of the question. 

Excellent! Lets hope we get an MCS hit head on! 

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Estofex

Mesoscale Discussion
Valid: Tue 18 Jul 2017 13:00 to Wed 19 Jul 2017 21:00 UTC
Issued: Tue 18 Jul 2017 13:48
Forecaster: TUSCHY

MESOSCALE DISCUSSION for

... N-France and S-UK ...

Latest remote sensing data indicates two ongoing thunderstorm clusters, one affecting SW-UK and a second one lifting from N-Brittany to the ENE. This activity developed ahead of a NE-ward drifting and deamplifying short-wave in the 300-500 hPa layer, which is also confirmed by latest WV data, showing a rather tight moisture gradient approaching the W-English Channel. This wave is forecast to move NE during the following hours towards CNTRL-UK.

Latest surface data places a warm front over far SW-UK, the E-English Channel towards Belgium. With a gradually consolidating and northward drifting surface low (in response to stronger hight falls to its west due to ongoing amplification of an upper-level trough), this front is forecast to lift north at a leisurely pace. Latest VIS loop indicates full sunshine ahead of both clusters with a deepening Cu field over NE-France in respone to moisture pooling along the warm front. Diabatic heating lowered surface dewpoints a bit, which are now around 15 °C and temperatures in the mid twenties over SW-UK and lower thirties over NW-France (ahead of both clusters).
12Z soundings show strong and even strengthening capping over SW-/S-UK, whereas full mixing and a deepening and dry subcloud layer are present over N-France.

Numeric continues to diverge substantially regarding the track of the thunderstorm clusters with one model suite taking the convection more to the north/northeast towards CNTRL-UK (probably in response to the passing short-wave), whereas another suite (with numerous limited area models) brings the activity more to the NE towards the E-English Channel.

As the MCS over NE-Brittany moves E/NE, it will take profit of uncontaminated inflow of warm/moist air and CAPE of 1-2 kJ/kg along the coast. A dry subcloud layer should support strengthening cold pool activity and a forward propagating MCS to the NE is expected. In addition, channeled NE-erly flow over the English Channel creates most intense LL outflow/inflow convergence along its NE/E-side, so a constant motion in this direction is expected. Onshore convection has a chance to root into the BL with a severe wind gust and large hail threat mainly over N/NE-France. A confined swath of severe to isolated damaging wind gusts is possible affecting the CNTRL-/E-English Channel and surrounding areas during the following hours! Towards SE-UK, a cooling BL offshore and a strengthening cap should force convection to become more elevated betimes with an excessive rainfall and large hail risk. However ongoing intense diabatic heating and expected strong NE-erly inflow over far SE-UK may keep this activity near surface based with an ongoing severe wind gust risk from onshore moving convection. During the night, this activity spreads towards Belgium and offshore towards the S-North Sea with a lowering severe risk.

The ongoing activity over SW-UK is forecast to lift north and northeast betimes in response to the passing short wave. Despite latest VIS data indicating surface based activity just offshore of SW-UK, the general mode should be an elevated one with an isolated excessive rainfall and large hail threat.

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Mesoscale Discussion
Valid: Tue 18 Jul 2017 13:00 to Wed 19 Jul 2017 21:00 UTC
Issued: Tue 18 Jul 2017 13:48
Forecaster: TUSCHY

MESOSCALE DISCUSSION for

... N-France and S-UK ...

Latest remote sensing data indicates two ongoing thunderstorm clusters, one affecting SW-UK and a second one lifting from N-Brittany to the ENE. This activity developed ahead of a NE-ward drifting and deamplifying short-wave in the 300-500 hPa layer, which is also confirmed by latest WV data, showing a rather tight moisture gradient approaching the W-English Channel. This wave is forecast to move NE during the following hours towards CNTRL-UK.

Latest surface data places a warm front over far SW-UK, the E-English Channel towards Belgium. With a gradually consolidating and northward drifting surface low (in response to stronger hight falls to its west due to ongoing amplification of an upper-level trough), this front is forecast to lift north at a leisurely pace. Latest VIS loop indicates full sunshine ahead of both clusters with a deepening Cu field over NE-France in respone to moisture pooling along the warm front. Diabatic heating lowered surface dewpoints a bit, which are now around 15 °C and temperatures in the mid twenties over SW-UK and lower thirties over NW-France (ahead of both clusters).
12Z soundings show strong and even strengthening capping over SW-/S-UK, whereas full mixing and a deepening and dry subcloud layer are present over N-France.

Numeric continues to diverge substantially regarding the track of the thunderstorm clusters with one model suite taking the convection more to the north/northeast towards CNTRL-UK (probably in response to the passing short-wave), whereas another suite (with numerous limited area models) brings the activity more to the NE towards the E-English Channel.

As the MCS over NE-Brittany moves E/NE, it will take profit of uncontaminated inflow of warm/moist air and CAPE of 1-2 kJ/kg along the coast. A dry subcloud layer should support strengthening cold pool activity and a forward propagating MCS to the NE is expected. In addition, channeled NE-erly flow over the English Channel creates most intense LL outflow/inflow convergence along its NE/E-side, so a constant motion in this direction is expected. Onshore convection has a chance to root into the BL with a severe wind gust and large hail threat mainly over N/NE-France. A confined swath of severe to isolated damaging wind gusts is possible affecting the CNTRL-/E-English Channel and surrounding areas during the following hours! Towards SE-UK, a cooling BL offshore and a strengthening cap should force convection to become more elevated betimes with an excessive rainfall and large hail risk. However ongoing intense diabatic heating and expected strong NE-erly inflow over far SE-UK may keep this activity near surface based with an ongoing severe wind gust risk from onshore moving convection. During the night, this activity spreads towards Belgium and offshore towards the S-North Sea with a lowering severe risk.

The ongoing activity over SW-UK is forecast to lift north and northeast betimes in response to the passing short wave. Despite latest VIS data indicating surface based activity just offshore of SW-UK, the general mode should be an elevated one with an isolated excessive rainfall and large hail threat.

http://www.estofex.org/

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Just now, Gordon Webb said:

Estofex

Mesoscale Discussion
Valid: Tue 18 Jul 2017 13:00 to Wed 19 Jul 2017 21:00 UTC
Issued: Tue 18 Jul 2017 13:48
Forecaster: TUSCHY

MESOSCALE DISCUSSION for

... N-France and S-UK ...

Latest remote sensing data indicates two ongoing thunderstorm clusters, one affecting SW-UK and a second one lifting from N-Brittany to the ENE. This activity developed ahead of a NE-ward drifting and deamplifying short-wave in the 300-500 hPa layer, which is also confirmed by latest WV data, showing a rather tight moisture gradient approaching the W-English Channel. This wave is forecast to move NE during the following hours towards CNTRL-UK.

Latest surface data places a warm front over far SW-UK, the E-English Channel towards Belgium. With a gradually consolidating and northward drifting surface low (in response to stronger hight falls to its west due to ongoing amplification of an upper-level trough), this front is forecast to lift north at a leisurely pace. Latest VIS loop indicates full sunshine ahead of both clusters with a deepening Cu field over NE-France in respone to moisture pooling along the warm front. Diabatic heating lowered surface dewpoints a bit, which are now around 15 °C and temperatures in the mid twenties over SW-UK and lower thirties over NW-France (ahead of both clusters).
12Z soundings show strong and even strengthening capping over SW-/S-UK, whereas full mixing and a deepening and dry subcloud layer are present over N-France.

Numeric continues to diverge substantially regarding the track of the thunderstorm clusters with one model suite taking the convection more to the north/northeast towards CNTRL-UK (probably in response to the passing short-wave), whereas another suite (with numerous limited area models) brings the activity more to the NE towards the E-English Channel.

As the MCS over NE-Brittany moves E/NE, it will take profit of uncontaminated inflow of warm/moist air and CAPE of 1-2 kJ/kg along the coast. A dry subcloud layer should support strengthening cold pool activity and a forward propagating MCS to the NE is expected. In addition, channeled NE-erly flow over the English Channel creates most intense LL outflow/inflow convergence along its NE/E-side, so a constant motion in this direction is expected. Onshore convection has a chance to root into the BL with a severe wind gust and large hail threat mainly over N/NE-France. A confined swath of severe to isolated damaging wind gusts is possible affecting the CNTRL-/E-English Channel and surrounding areas during the following hours! Towards SE-UK, a cooling BL offshore and a strengthening cap should force convection to become more elevated betimes with an excessive rainfall and large hail risk. However ongoing intense diabatic heating and expected strong NE-erly inflow over far SE-UK may keep this activity near surface based with an ongoing severe wind gust risk from onshore moving convection. During the night, this activity spreads towards Belgium and offshore towards the S-North Sea with a lowering severe risk.

The ongoing activity over SW-UK is forecast to lift north and northeast betimes in response to the passing short wave. Despite latest VIS data indicating surface based activity just offshore of SW-UK, the general mode should be an elevated one with an isolated excessive rainfall and large hail threat.

I am sure someone will correct me, but I don't think I've ever seen an MD from Estofex over the British Isles.

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1 minute ago, Gordon Webb said:

Estofex

Mesoscale Discussion
Valid: Tue 18 Jul 2017 13:00 to Wed 19 Jul 2017 21:00 UTC
Issued: Tue 18 Jul 2017 13:48
Forecaster: TUSCHY

MESOSCALE DISCUSSION for

... N-France and S-UK ...

Latest remote sensing data indicates two ongoing thunderstorm clusters, one affecting SW-UK and a second one lifting from N-Brittany to the ENE. This activity developed ahead of a NE-ward drifting and deamplifying short-wave in the 300-500 hPa layer, which is also confirmed by latest WV data, showing a rather tight moisture gradient approaching the W-English Channel. This wave is forecast to move NE during the following hours towards CNTRL-UK.

Latest surface data places a warm front over far SW-UK, the E-English Channel towards Belgium. With a gradually consolidating and northward drifting surface low (in response to stronger hight falls to its west due to ongoing amplification of an upper-level trough), this front is forecast to lift north at a leisurely pace. Latest VIS loop indicates full sunshine ahead of both clusters with a deepening Cu field over NE-France in respone to moisture pooling along the warm front. Diabatic heating lowered surface dewpoints a bit, which are now around 15 °C and temperatures in the mid twenties over SW-UK and lower thirties over NW-France (ahead of both clusters).
12Z soundings show strong and even strengthening capping over SW-/S-UK, whereas full mixing and a deepening and dry subcloud layer are present over N-France.

Numeric continues to diverge substantially regarding the track of the thunderstorm clusters with one model suite taking the convection more to the north/northeast towards CNTRL-UK (probably in response to the passing short-wave), whereas another suite (with numerous limited area models) brings the activity more to the NE towards the E-English Channel.

As the MCS over NE-Brittany moves E/NE, it will take profit of uncontaminated inflow of warm/moist air and CAPE of 1-2 kJ/kg along the coast. A dry subcloud layer should support strengthening cold pool activity and a forward propagating MCS to the NE is expected. In addition, channeled NE-erly flow over the English Channel creates most intense LL outflow/inflow convergence along its NE/E-side, so a constant motion in this direction is expected. Onshore convection has a chance to root into the BL with a severe wind gust and large hail threat mainly over N/NE-France. A confined swath of severe to isolated damaging wind gusts is possible affecting the CNTRL-/E-English Channel and surrounding areas during the following hours! Towards SE-UK, a cooling BL offshore and a strengthening cap should force convection to become more elevated betimes with an excessive rainfall and large hail risk. However ongoing intense diabatic heating and expected strong NE-erly inflow over far SE-UK may keep this activity near surface based with an ongoing severe wind gust risk from onshore moving convection. During the night, this activity spreads towards Belgium and offshore towards the S-North Sea with a lowering severe risk.

The ongoing activity over SW-UK is forecast to lift north and northeast betimes in response to the passing short wave. Despite latest VIS data indicating surface based activity just offshore of SW-UK, the general mode should be an elevated one with an isolated excessive rainfall and large hail threat.

FINALLY! Estofex!  This could become amazing now they are on board!

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I think tonight's storms in the south will be elevated, lots of spectacular lightning but little in the way of disruption.  Tomorrows storms in northern england look like being surfaced based and much more severe in nature (possibility of large hail,frequent lightning,flooding and maybe an isolated tornado.). 

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8 minutes ago, Gordon Webb said:

Estofex

Mesoscale Discussion
Valid: Tue 18 Jul 2017 13:00 to Wed 19 Jul 2017 21:00 UTC
Issued: Tue 18 Jul 2017 13:48
Forecaster: TUSCHY

MESOSCALE DISCUSSION for

... N-France and S-UK ...

Latest remote sensing data indicates two ongoing thunderstorm clusters, one affecting SW-UK and a second one lifting from N-Brittany to the ENE. This activity developed ahead of a NE-ward drifting and deamplifying short-wave in the 300-500 hPa layer, which is also confirmed by latest WV data, showing a rather tight moisture gradient approaching the W-English Channel. This wave is forecast to move NE during the following hours towards CNTRL-UK.

Latest surface data places a warm front over far SW-UK, the E-English Channel towards Belgium. With a gradually consolidating and northward drifting surface low (in response to stronger hight falls to its west due to ongoing amplification of an upper-level trough), this front is forecast to lift north at a leisurely pace. Latest VIS loop indicates full sunshine ahead of both clusters with a deepening Cu field over NE-France in respone to moisture pooling along the warm front. Diabatic heating lowered surface dewpoints a bit, which are now around 15 °C and temperatures in the mid twenties over SW-UK and lower thirties over NW-France (ahead of both clusters).
12Z soundings show strong and even strengthening capping over SW-/S-UK, whereas full mixing and a deepening and dry subcloud layer are present over N-France.

Numeric continues to diverge substantially regarding the track of the thunderstorm clusters with one model suite taking the convection more to the north/northeast towards CNTRL-UK (probably in response to the passing short-wave), whereas another suite (with numerous limited area models) brings the activity more to the NE towards the E-English Channel.

As the MCS over NE-Brittany moves E/NE, it will take profit of uncontaminated inflow of warm/moist air and CAPE of 1-2 kJ/kg along the coast. A dry subcloud layer should support strengthening cold pool activity and a forward propagating MCS to the NE is expected. In addition, channeled NE-erly flow over the English Channel creates most intense LL outflow/inflow convergence along its NE/E-side, so a constant motion in this direction is expected. Onshore convection has a chance to root into the BL with a severe wind gust and large hail threat mainly over N/NE-France. A confined swath of severe to isolated damaging wind gusts is possible affecting the CNTRL-/E-English Channel and surrounding areas during the following hours! Towards SE-UK, a cooling BL offshore and a strengthening cap should force convection to become more elevated betimes with an excessive rainfall and large hail risk. However ongoing intense diabatic heating and expected strong NE-erly inflow over far SE-UK may keep this activity near surface based with an ongoing severe wind gust risk from onshore moving convection. During the night, this activity spreads towards Belgium and offshore towards the S-North Sea with a lowering severe risk.

The ongoing activity over SW-UK is forecast to lift north and northeast betimes in response to the passing short wave. Despite latest VIS data indicating surface based activity just offshore of SW-UK, the general mode should be an elevated one with an isolated excessive rainfall and large hail threat.

Now all I have to do is work out what it means

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2 minutes ago, Harsh Climate said:

I think tonight's storms in the south will be elevated, lots of spectacular lightning but little in the way of disruption.  Tomorrows storms in northern england look like being surfaced based and much more severe in nature (possibility of large hail,frequent lightning,flooding and maybe an isolated tornado.). 

Given the changing parameters I am not too sure about this assumption.

MCS whether elevated or not can bring locally very severe conditions, not least a flooding risk as they can last several hours. Lightning in addition can cause widespread disruption. MCS experienced across my neck of the woods in late May kicked over hundreds of lightning strokes every minute, a decent proportion CG notwithstanding it's largely elevated nature.

The point made earlier (and emphased by Estofex) is that conditions could support the MCS remaining surface based, emphasising the severe risk.

Alas, I suspect more than likely it will remain largely elevated, but would stop well short of suggesting that means there wont be disruption!!

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3 minutes ago, tomp456 said:

When estofex put you under a mesoscale discussion 

 

giphy.gif

:rofl::rofl::rofl:

Or.....

 

shocked-smiley-33326281168.gif

Edited by Harry
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RE this

Estofex

Mesoscale Discussion
Valid: Tue 18 Jul 2017 13:00 to Wed 19 Jul 2017 21:00 UTC
Issued: Tue 18 Jul 2017 13:48
Forecaster: TUSCHY

MESOSCALE DISCUSSION for

... N-France and S-UK ...

What areas are at risk? It's hard to untangle in all the Technical discussion. Well for me anyway, granted I'm quite fick :crazy:

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Interesting for me is this part of the ESTOFEX discussion...A confined swath of severe to isolated damaging wind gusts is possible affecting the CNTRL-/E-English Channel and surrounding areas during the following hours! 

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Just now, Jasper Foxx said:

A friend has just linked me to this:

http://www.plymouthherald.co.uk/huge-thunderstorm-arrives-in-plymouth-live/story-30445770-detail/story.html

Tornado/funnel cloud? Or just a coincidental cloud formation?

Roll cloud, quite common in MCS setups. See from 00:30 onwards.

 

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