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Nick F

Storm & Convective Discussion - 7th August Onwards

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Posted (edited)
28 minutes ago, Supacell said:

My eyes are on tomorrow for the possibility of some early in the year convective potential. It is only March and so not a huge amount of CAPE but values in the region of 500 j/kg showing on the WRF and NMM models for northern England especially. This may be slightly overdone as GFS is a little more reserved with this but still quite impressive for so early in the year. Relatively cool air moving in from the north-west over the top of moist, warm air in situ over England is coupled with deep layer shear of up to 15-20 m/s in the areas where CAPE is highest.

CAPE.thumb.png.ac27991e3b63db17b79bac9b88faf957.png    DLS.thumb.png.0ad3a7cab47431d77f50937ecc19b65a.png

Although I am not expecting big summer thunderstorms there is certainly the potential for widespread heavy showers with some thunder and hail, more akin to April showers in March. Best areas on current guidance would likely be across NW England during the late morning and then transferring eastwards across N England through the early to mid afternoon. 

A chance of heavy showers with thunder across other parts too, and I would not be surprised to hear of the odd rumble almost anywhere. However, it is Northern England where my focus is for the chance of a stronger convective cell or two.

Always in the north 😩

This year’s been atrocious down south for thunderstorms, the north gets all the luck, etc etc.

😅

Edited by Flash bang flash bang etc

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Hold you forgot to put a hole where Sheffield is.That's a no storm area.

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1 hour ago, Supacell said:

My eyes are on tomorrow for the possibility of some early in the year convective potential. It is only March and so not a huge amount of CAPE but values in the region of 500 j/kg showing on the WRF and NMM models for northern England especially. This may be slightly overdone as GFS is a little more reserved with this but still quite impressive for so early in the year. Relatively cool air moving in from the north-west over the top of moist, warm air in situ over England is coupled with deep layer shear of up to 15-20 m/s in the areas where CAPE is highest.

CAPE.thumb.png.ac27991e3b63db17b79bac9b88faf957.png    DLS.thumb.png.0ad3a7cab47431d77f50937ecc19b65a.png

Although I am not expecting big summer thunderstorms there is certainly the potential for widespread heavy showers with some thunder and hail, more akin to April showers in March. Best areas on current guidance would likely be across NW England during the late morning and then transferring eastwards across N England through the early to mid afternoon. 

A chance of heavy showers with thunder across other parts too, and I would not be surprised to hear of the odd rumble almost anywhere. However, it is Northern England where my focus is for the chance of a stronger convective cell or two.

 Yes, I’m really looking forward to tomorrow. Looks good at my location around 11-12:00. 

 Also  I was wondering; how would you wrate the WRF at forecasting convective parameters? I use it all the time as my go-to high-res model and wondering how it performs. 

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37 minutes ago, Chris.R said:

 Yes, I’m really looking forward to tomorrow. Looks good at my location around 11-12:00. 

 Also  I was wondering; how would you wrate the WRF at forecasting convective parameters? I use it all the time as my go-to high-res model and wondering how it performs. 

Personally I rate the WRF quite highly. I tend to look at a combination of WRF and GFS for convective charts. I believe NMM is based on WRF, although I may be wrong there. For distribution of convective rainfall I found euro4 to be the most accurate.

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This is a blended EWN / WRF probability map for tomorrow:

47662169_F55D607A-B9A6-4C44-AD2A-6B846C5BFDE4.png.thumb.jpg.38cf71fa966ee3317b6785df195aaede.jpg

It transfers West to East throughout the day.

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38 minutes ago, Supacell said:

Personally I rate the WRF quite highly. I tend to look at a combination of WRF and GFS for convective charts. I believe NMM is based on WRF, although I may be wrong there. For distribution of convective rainfall I found euro4 to be the most accurate.

 Thanks 🙂 appreciate it. 

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Day 2 Convective Outlook

VALID 06:00 UTC Wed 06 Mar 2019 - 05:59 UTC Thu 07 Mar 2019

ISSUED 21:18 UTC Tue 05 Mar 2019

ISSUED BY: Dan

An upper trough will slowly migrate eastwards across Ireland on Wednesday, placing England and Wales on the forward side. A warm, moist low-level airmass will exist beneath cool mid-levels, creating reasonably steep mid-level lapse rates and a few hundred J/kg CAPE. 

Behind the main frontal precipitation, deep convection will likely already exist over the Irish Sea / west Wales / SW England on Wednesday morning, forced by a shortwave behind the surface cold front. This zone will be the primary focus for some sporadic lightning activity as it continues to track northeastwards across Wales / Midlands / N England through Wednesday daytime, aided by diurnal heating and low-level convergence.

Primary concern is rather saturated profiles / excessive cloud, which will tend to limit buoyancy somewhat. However, despite marginal instability the upper forcing coupled with strong shear should be enough to produce sporadic lightning strikes as scattered showers migrate NE-wards across the area. As such, have introduced a low-end SLGT to cover this risk. The strongest cells could produce hail up to 1.5cm in diameter.

Farther southeast, convective depth and instability will be somewhat limited, but even here a few isolated lightning strikes are possible, especially later in the afternoon - but coverage probably not widespread enough to warrant an upgrade to SLGT.

Shower coverage and intensity will gradually reduce during the evening hours as daytime heating subsides, with the focus for any isolated lightning activity overnight primarily confined to SW / W / NW Ireland.

http://www.convectiveweather.co.uk/forecast.php?date=2019-03-06

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Looking like the first storm chance of the year tomorrow then, Netweather SR Model looking good, always nice to see ConvectiveWeather on board as well 

 

image.png

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55 minutes ago, ChezWeather said:

Looking like the first storm chance of the year tomorrow then, Netweather SR Model looking good, always nice to see ConvectiveWeather on board as well 

 

image.png

Good start to the year for the north!  Pity I live at opposite end now!

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Big clap of thunder in Exeter at 4pm yesterday.

Just thought I'd mention it!

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Day 2 Convective Outlook

VALID 06:00 UTC Sat 09 Mar 2019 - 05:59 UTC Sun 10 Mar 2019

ISSUED 20:45 UTC Fri 08 Mar 2019

ISSUED BY: Dan

A broad westerly regime will dominate during Saturday across the British Isles, with subtle shortwaves helping to generate areas of enhanced convective activity. The pattern is quite complex, with NWP guidance offering slightly different forecast evolutions - and hence uncertainty is quite high in the specific detail.

Nonetheless, weak instability in a strongly-sheared environment suggests isolated lightning strikes may be possible as various convective / semi-convective features move quickly eastwards in the strong steering flow. Strong gusts of wind remain possible associated with areas of enhanced convective activity.

http://www.convectiveweather.co.uk/forecast.php?date=2019-03-09

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Posted (edited)

Day 2 Convective Outlook

VALID 06:00 UTC Sun 10 Mar 2019 - 05:59 UTC Mon 11 Mar 2019

ISSUED 21:45 UTC Sat 09 Mar 2019

ISSUED BY: Dan

Strong westerly upper flow persists across the British Isles, but gradually becoming more amplified with time allowing cold air aloft to spread farther south. This will result in very steep mid-level lapse rates and a few hundred J/kg CAPE. Once the main frontal precipitation clears to the North Sea by early afternoon on Sunday, numerous wintry showers will follow - most frequent in western parts, but moving well-inland on strong steering winds. Sporadic lightning, small hail and gusty winds will accompany some of these showers.

http://www.convectiveweather.co.uk/forecast.php?date=2019-03-10

Edited by Summer Sun

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Whoohooooo

First thunder of the year!

image.thumb.png.75d4ce99c10fb8925732d1f630fd1e3b.pngOur little friend is also enjoying the storm!

image.thumb.png.b577f78ea1113bcba821ca870f32f5d5.png

 

 

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Posted (edited)

Just had a smallest cell in Reading, about 5 flashes around the same time, over as quickly as it started. Hail too. Moving along the M4 towards London.

Edited by Robert Lewis

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Day 2 Convective Outlook

VALID 06:00 UTC Mon 11 Mar 2019 - 05:59 UTC Tue 12 Mar 2019

ISSUED 21:14 UTC Sun 10 Mar 2019

ISSUED BY: Dan

... SHOWERS MONDAY DAYTIME ...

On Monday morning an upper trough will depart the British Isles, moving across the North Sea, but there may be enough instability / shear overlap to produce a few isolated lightning strikes from scattered showers affecting western exposed areas (NW England, W Scotland, Northern Isles) before ridging from the west results in a marked decrease in convective depth - hence by midday any lightning potential (if any) will be confined to the Northern Isles.

... MONDAY NIGHT COLD FRONT ...

A quiet period will then evolve as the upper ridge traverses the British Isles, but soon followed by the next approaching upper trough from the Atlantic. A frontal system will push across Ireland and W Scotland during Monday afternoon, then eastwards across the remainder of Britain through Monday night.

A tongue of relatively warm, moist low-level air will be drawn northwards ahead of the surface cold front, creating a marked thermal boundary. This combined with a strongly-sheared environment, wind veer along the front and forced ascent will allow line segments to develop capable of producing brief periods of very heavy rain and gusty winds. A few lightning strikes are possible, but overall weak instability and saturated profiles suggests the likelihood of this is very low, and hence no threat levels have been introduced to cover this risk. Given low cloud bases, backed winds in the low-levels and strong low-level shear, a tornado is not ruled out. 

The risk of embedded line segments will continue beyond this forecast period into Tuesday as the cold front continues to migrate eastwards across England and Wales.

... MONDAY NIGHT SHOWERS ...

Behind the cold front, cooling aloft atop relatively warm seas will generate a few hundred J/kg CAPE in an environment with increasingly steep mid-level lapse rates. Numerous showers will begin to arrive into western Ireland and the Hebrides during the early hours of Tuesday, capable of producing a few sporadic lightning strikes, small hail and gusty winds - the risk in general increasing with each hour towards the end of the night.

http://www.convectiveweather.co.uk/forecast.php?date=2019-03-11

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Well, that was an interesting day yesterday! Gales, heavy showers, hail and in the evening heard a distant rumble - my first of the year.😊 Radar at the time confirmed a storm to my east and another to my south so the rumble could've come from either. A great start to the season so far. Hoping for a good stormy year this year.☔🌧🌩🌪⛈ 

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2020395972_StormMap.thumb.png.c2eeda1c982404f6b44cdd579a77d8ab.png

Quite an active 24 hours yesterday! 😊😁🌩

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Day 2 Convective Outlook

VALID 06:00 UTC Tue 12 Mar 2019 - 05:59 UTC Wed 13 Mar 2019

ISSUED 21:28 UTC Mon 11 Mar 2019

ISSUED BY: Dan

On the forward side of the larger-scale upper trough, an active cold front will move eastwards across England and Wales on Tuesday. Given a notable thermal gradient, marked wind veer, forced ascent and strongly sheared environment, line segments are expected with localised squalls. The potential for some damaging gusts of wind exists, and a tornado cannot be ruled out. However, weak instability and saturated profiles suggests the risk of lightning is considered very low.

The post-frontal environment is then characterised by notable cooling aloft, with steep mid-level lapse rates and a few hundred J/kg CAPE. Numerous showers are expected to develop over open seas, and move well-inland due to strong steering flow. Several troughs / occlusions will aid in organising more distinct bands of showers at times.

In terms of lightning potential, the best overlap of CAPE and shear will probably occur over western Scotland during Tuesday late afternoon / evening, but confidence is not high enough to upgrade to SLGT at this stage due to the rather messy mix of dynamic and convective precipitation (plus forecast profiles look rather saturated with strong winds throughout the vertical).

In any case, small hail is likely in many of the showers, with strong gusts of wind at times.

http://www.convectiveweather.co.uk/forecast.php?date=2019-03-12

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Lovely squall line now formed

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Day 2 Convective Outlook

VALID 06:00 UTC Wed 13 Mar 2019 - 05:59 UTC Thu 14 Mar 2019

ISSUED 21:03 UTC Tue 12 Mar 2019

ISSUED BY: Dan

The departing upper trough on Wednesday will be close enough to the British Isles to help generate a couple hundred J/kg CAPE. While instability will be weakening throughout the day, and convective depth reducing, strong shear on the rear side of the upper trough may be enough to compensate for a few isolated lightning strikes from the most intense showers.

Later in the day the next Atlantic frontal system will quickly slide southeastwards, followed by deeper convection / showers into western Scotland during the early hours of Thursday - and so there will be a (low) risk of lightning during the latter half of Wednesday night associated with this activity.

http://www.convectiveweather.co.uk/forecast.php?date=2019-03-13

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Day 2 Convective Outlook

VALID 06:00 UTC Fri 15 Mar 2019 - 05:59 UTC Sat 16 Mar 2019

ISSUED 19:26 UTC Thu 14 Mar 2019

ISSUED BY: Dan

A persistent, strong westerly flow covers the British Isles on Friday, with cold air aloft helping to generate a couple hundred J/kg CAPE over Scotland. Scattered showers will affect the area at times, in an environment with strong shear. A few isolated lightning strikes may be possible from the most intense cells.

http://www.convectiveweather.co.uk/forecast.php?date=2019-03-15

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Posted (edited)

Not UK storm related but just wanted to draw your attention to some storm footage filmed two days ago in Michigan whilst we wait for our storm season to hopefully start.

 

 

Edited by Supacell

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Day 2 Convective Outlook

VALID 06:00 UTC Sun 17 Mar 2019 - 05:59 UTC Mon 18 Mar 2019

ISSUED 20:37 UTC Sat 16 Mar 2019

ISSUED BY: Dan

Broad upper trough covers the British Isles on Sunday, gradually clearing to the east. Cold mid/upper levels will result in steep mid-level lapse rates and a few hundred J/kg CAPE in response to SSTs and diurnal heating inland. Scattered wintry showers are expected, especially in exposed northern and western areas, but steering flow and embedded troughs will help to push showers farther inland / southeastwards at times.

Under the upper trough shear will tend be a little weak (unidirectional and similar speeds at depth), however as the upper trough begins to clear eastwards strengthening flow and veering aloft will tend to increase the shear component across Ireland, and later Wales / SW England. This may help to organise a few of the showers here during the afternoon / early evening.

For the most part, any lightning activity will tend to be rather sporadic and not particularly long-lasting, given marginal instability and fairly weak shear - and in any case, the risk will diminish during Sunday evening as both daytime heating subsides and the upper trough clears away to the east. Nonetheless, the most intense cells could produce gusty winds and quite a bit of small hail.

http://www.convectiveweather.co.uk/forecast.php?date=2019-03-17

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