Convective/Storm Discussion Thread - 1st August onwards

[Mapantz]

Inversion at midday.

Eroded by late afternoon; showers developed.

[Flash bang flash bang etc]

15 minutes ago, jordan smith said:

You say that but I live in Aylesbury just north of the m4 and there's been unbroken sunshine since well before midday and there are a few isolated showers heading our way but bear in mind unbroken sunshine does not mean you'll get thunderstorms or showers because you need several other ingredients which we are absent of today tbh which explains why hardly anything has happened. Pressure is quite high which doesn't help.

Felt a little humid tho. And I thought it was only because of the the low SSTs over the channel which were taking the oomph out of the French storms?

It’s early in the season anyway - but would be nice to hit the ground running one year instead of this persistent teasing from the weather gods

 

[Jordan S]

Just now, Flash bang flash bang etc said:

Felt a little humid tho. And I thought it was only because of the the low SSTs over the channel which were taking the oomph out of the French storms?

It’s early in the season anyway - but would be nice to hit the ground running one year instead of this persistent teasing from the weather gods

 

The very cool sea surface temperatures in the channel is a contributing factor but humidity not particularly high which doesn't help also low wind shear the air is pretty stable but not stable enough to allow a few isolated thunderstorms to break out .

[Jordan S]

We have a very have shower approaching my location it is very close too.?

[Jordan S]

We have a very have shower approaching my location it is very close too.?

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Sun 15 Apr 2018 - 05:59 UTC Mon 16 Apr 2018

ISSUED 14:00 UTC Sat 14 Apr 2018

ISSUED BY: Dan

Upper trough will approach from the Atlantic on Sunday, cold pool aloft serving to steepen mid-level lapse rates - primarily over Ireland. A couple of occlusion/trough features will provide the focus for bands of showery rain moving NE-wards through the day,  turning increasingly convective in nature in response to some diurnal heating. Some sporadic / isolated lightning is possible from the strongest cells - particular focus is given to the north Midlands into Yorkshire / Lincolnshire (and perhaps Norfolk) where low-level convergence may enhance some forced ascent, but lightning coverage is not expected to be significant enough to upgrade to SLGT.

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-15

[Ben Sainsbury]

2 hours ago, jordan smith said:

The very cool sea surface temperatures in the channel is a contributing factor but humidity not particularly high which doesn't help also low wind shear the air is pretty stable but not stable enough to allow a few isolated thunderstorms to break out .

I’d kind of have to disagree with you, there definitely was some modest instability, steep (ish) lapse rates, wind shear not particularly important in regards the amount of showers that form, moreso the structure and longevity of showers.

The main reason for lack of activity was no proper trigger today...

The trough really just moved north too slowly, didn’t give enough opportunity for a larger mass of showers to develop, no convergence zone had formed until the evening over Reading etc, hence why the only showers formed across CS England.

Edited April 14, 2018 by Ben Sainsbury

[Jordan S]

3 hours ago, Ben Sainsbury said:

I’d kind of have to disagree with you, there definitely was some modest instability, steep (ish) lapse rates, wind shear not particularly important in regards the amount of showers that form, moreso the structure and longevity of showers.

The main reason for lack of activity was no proper trigger today...

The trough really just moved north too slowly, didn’t give enough opportunity for a larger mass of showers to develop, no convergence zone had formed until the evening over Reading etc, hence why the only showers formed across CS England.

You can disagree with me but what I'm saying is correct you say about steepish lapse rates but like I said not enough for any thunderstorms and you've also miss quoted me I said wind shear was one of many factors inhibiting any THUNDERY development didn't say it effected the amount of showers that would form but the rest of your text I agree with such as the trough moving too slowly. Anyway let's agree to disagree.

Edited April 15, 2018 by jordan smith

[Flash bang flash bang etc]

15 hours ago, Ben Sainsbury said:

I’d kind of have to disagree with you, there definitely was some modest instability, steep (ish) lapse rates, wind shear not particularly important in regards the amount of showers that form, moreso the structure and longevity of showers.

The main reason for lack of activity was no proper trigger today...

The trough really just moved north too slowly, didn’t give enough opportunity for a larger mass of showers to develop, no convergence zone had formed until the evening over Reading etc, hence why the only showers formed across CS England.

Yeah it was the frustratingly slow progress of that front from France which did it for me - literally touched land as the sun went down. Arg!

oh well - onto a new week - with hopefully better chances for all!

[convector]

The end of next week looks promising. High cape values thursday/friday on some models but will likely be anti-cyclonically capped until the weekend at least. GFS 6z was keeping warm air advection around into the week after, with low pressure closer to the UK, but the 12z is completely different of course. Too soon to tell right now, but at least 2018 storm season is finally within our sights 

[Flash bang flash bang etc]

Just now, convector said:

The end of next week looks promising. High cape values thursday/friday on some models but will likely be anti-cyclonically capped until the weekend at least. GFS 6z was keeping warm air advection around into the week after, with low pressure closer to the UK, but the 12z is completely different of course. Too soon to tell right now, but at least 2018 storm season is finally within our sights 

Hmmmm - capping is the enemy

:-/

[Jordan S]

1 minute ago, convector said:

The end of next week looks promising. High cape values thursday/friday on some models but will likely be anti-cyclonically capped until the weekend at least. GFS 6z was keeping warm air advection around into the week after, with low pressure closer to the UK, but the 12z is completely different of course. Too soon to tell right now, but at least 2018 storm season is finally within our sights 

Yeah perhaps Friday or Saturday the best chance ☺️

[Flash bang flash bang etc]

6 minutes ago, jordan smith said:

Yeah perhaps Friday or Saturday the best chance ☺️

Is it too early to have a vague guess at where might be best? I have 4 days off over the weekend and we were thinking of staying somewhere

[Jordan S]

8 minutes ago, Flash bang flash bang etc said:

Is it too early to have a vague guess at where might be best? I have 4 days off over the weekend and we were thinking of staying somewhere

Its too early for that the best advice is to just keep checking the charts and forecasts by Wednesday or Thursday I think we'll have a better idea.?

[Summer Sun]

Day 1 Convective Outlook

VALID 06:00 UTC Mon 16 Apr 2018 - 05:59 UTC Tue 17 Apr 2018

ISSUED 11:09 UTC Mon 16 Apr 2018

ISSUED BY: Dan

To the rear of the cold front/occlusion, some marginal instability may develop as mid-levels cool atop moist low-level airmass. Post-frontal trough may provide the focus for a few heavy showers during the early hours of Tuesday, organised in a rather linear fashion given the strongly sheared environment. Any lightning will likely be rather isolated (if any at all) given limited cloud depth, but some heavy showers with strong gusts of wind are possible.

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-16

[Windblade]

On ‎14‎/‎04‎/‎2018 at 18:52, Flash bang flash bang etc said:

Thing that frustrates me (again) is that the areas around the M4 that are now seeing some showers breaking out haven’t had the hours of solar heating we just had (sat24 showed general cloud cover this afternoon) and yet THEY get the convection.

We have a showery front moving in from the south where it’s been shown to have convective potential, but - yet again - some baffling science dictates that we get nothing, and as usual it all stalls and peters out (like it’s doing right now).

There is ALWAYS a reason we don’t get the goods - which in this case isn’t anything special - but it’s a good example of the trend that I imagine (like previous years) is gonna blight our storm chances time and time again during the coming summer. 

i just know it and it’s already bothering me. I don’t need excuses for the weather misbehaving - it’s not like we get hundreds of thousands of chances. It’s not like we live in Arkansas!

 

(On the plus side - it’s been a lovely afternoon)

 

 

...Anyway, no rain yet.

I know how you feel mate, I'm in a similar situation here and have been for several years but try and keep your chin up buddy. When you finally do see a spectacular storm the moment will be all the more special.  

[Windblade]

I'm thinking this warming airmass from France coupled with dirurnal heating could set off some pulse storms towards the end of the working week (cape and shear permitting of course). Would be awesome if that happened friday night as I have a good mate of mine coming over who's expressed an interest in storm chasing in the past when I've been discussing my hobby with him and wants to learn more about it. I'd happily take him out on a chase and see if we can find anything. Plus if I'm driving he can take pictures/shoot video. I'll be watching this closely to see how things develop.

[Windblade]

On ‎15‎/‎04‎/‎2018 at 17:38, Flash bang flash bang etc said:

Is it too early to have a vague guess at where might be best? I have 4 days off over the weekend and we were thinking of staying somewhere

Can't say for sure til nearer the time but at the moment I'd say the nearer the southeast coast the better but if you can't make it that far the southeast in general is where I'd suggest.

[Jordan S]

For now the southern half of the UK is the best place atm but it's too early to say what region is best ?

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Tue 17 Apr 2018 - 05:59 UTC Wed 18 Apr 2018

ISSUED 20:12 UTC Mon 16 Apr 2018

ISSUED BY: Dan

On the forward side of the large Atlantic upper trough, cool mid-levels will help generate some marginal instability in response to diurnal heating. Forecast profiles look capped at about 400mb by very dry air above, and this cap gradually lowers to nearer 600mb by evening (especially further south across Ireland).

Hence, while there is potential for some deep convection and a few heavy showers, in combination with diurnal heating and the passage of a shortwave trough, the potential depth of convection will be gradually reducing during the afternoon hours. Strong DLS may be enough to compensate for marginal CAPE to produce a few lightning strikes (but questionable). Some organisation of cells into linear features seems likely, with the potential to produce some strong gusts of wind - in fact the strongest cells may exhibit some supercell characteristics with perhaps some hail.

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-17

[poseidon]

Meteox lightning risk map for Sunday

Fingers crossed.

[Flash bang flash bang etc]

18 hours ago, poseidon said:

Meteox lightning risk map for Sunday

Fingers crossed.

This would be excellent

[Ben Sainsbury]

I'm going to give my overview of the thunderstorm potential for the next few days up until Sunday.

The main thing to note during this period is the dominance of high pressure which significantly reduces the risk of storms, along with lack of moisture and high CAPE values for majority of period. A few definitions for those who are learning I'll quickly go through them.

CAPE: Convective Available Potential Energy - Measure of amount of energy for convection, therefore higher CAPE = quicker storm formation and more frequent lightning.

DLS: Deep Layer Shear - A measure of wind shear between the mid levels of the atmosphere and surface. High DLS values means storms will become more organised and persistent bringing a greater chance of severe characteristics.

SRH: Storm Relative Helicity - Measure of potential for cyclonic updraft rotation. Therefore higher SRH, greater potential of supercelluar characteristics. 

PW: Precipitable Water - Indicates the amount of moisture within the air. Higher PW greater chance of storm formation but too high and atmosphere becomes saturated.

Tomorrow (Thursday):

As you see from the graphs below, we are seeing SB CAPE values of 1000J/kg, this is as a result of strong diurnal heating. As a result we see a few storms form across CS England into East Midlands. The Netweather NMM model shows the formation of a convergence zone which set off these storms. It must be noted that whilst the NMM model produces storms, the lack of available moisture (precipitable water) and under the influence of high pressure, I cannot see much potential tomorrow. However if a storm does form, the low PW values along with 30-40knts of DLS, means that any storm may last a long time from its sustained updraft. Lighting amounts will be fairly infrequent.

Friday: 

Friday warrants a similar risk to Thursday. CAPE values are fairly higher stretching towards 1500J/kg, but must be noted this isn't important if there isn't any available moisture. Again the NMM model are very generous with the breakout of storms, however precipitable water values are a little higher so I'd favour Friday over Tomorrow. We also see values of 30-40knts of DLS therefore any storm that does form will see more frequent lightning activity as the updraft will be long-lived. I must stress that even with these favourable parameters given high pressure is in control, we are more likely to see nothing rather than something. My best bet is just north of M4/Bristol Channel across SW Midlands.

Saturday: 

A much greater risk lies on Saturday, at this point high pressure tends to move back away to the east. As you see CAPE values are even higher approaching 1800J/kg, showing the potential for some very frequent lightning. The reason there is a much greater risk of Saturday is because of the much higher precipitable water values, lower pressure (whilst still high) and a well-defined convergence zone. DLS amounts are rather slim for Saturday however, storm relative helicity values which represent the potential for cyclonic motion within an updraft, are pushing towards 150-200m^2s^-2. Therefore any storms on Saturday I expect to form along a line from North Wales towards East Anglia and the London Area, a few storms just North of M4, but lower risk. These storms will exhibit the potential for supercelluar characteristics but these will be relatively short given lack of DLS and may only occur within a tight time frame. All storms will have a relatively short duration but will result in some very frequent lightning.

Sunday's potential remains to be seen as charts don't quite reach that time frame but interesting times nevertheless.

I hope this have given you an insight on what we could expect this upcoming week. I'm still learning myself all the time so apologies for any errors.

Edited April 18, 2018 by Ben Sainsbury

[Flash bang flash bang etc]

3 hours ago, Ben Sainsbury said:

I'm going to give my overview of the thunderstorm potential for the next few days up until Sunday.

The main thing to note during this period is the dominance of high pressure which significantly reduces the risk of storms, along with lack of moisture and high CAPE values for majority of period. A few definitions for those who are learning I'll quickly go through them.

CAPE: Convective Available Potential Energy - Measure of amount of energy for convection, therefore higher CAPE = quicker storm formation and more frequent lightning.

DLS: Deep Layer Shear - A measure of wind shear between the mid levels of the atmosphere and surface. High DLS values means storms will become more organised and persistent bringing a greater chance of severe characteristics.

SRH: Storm Relative Helicity - Measure of potential for cyclonic updraft rotation. Therefore higher SRH, greater potential of supercelluar characteristics. 

PW: Precipitable Water - Indicates the amount of moisture within the air. Higher PW greater chance of storm formation but too high and atmosphere becomes saturated.

Tomorrow (Thursday):

As you see from the graphs below, we are seeing SB CAPE values of 1000J/kg, this is as a result of strong diurnal heating. As a result we see a few storms form across CS England into East Midlands. The Netweather NMM model shows the formation of a convergence zone which set off these storms. It must be noted that whilst the NMM model produces storms, the lack of available moisture (precipitable water) and under the influence of high pressure, I cannot see much potential tomorrow. However if a storm does form, the low PW values along with 30-40knts of DLS, means that any storm may last a long time from its sustained updraft. Lighting amounts will be fairly infrequent.

Friday: 

Friday warrants a similar risk to Thursday. CAPE values are fairly higher stretching towards 1500J/kg, but must be noted this isn't important if there isn't any available moisture. Again the NMM model are very generous with the breakout of storms, however precipitable water values are a little higher so I'd favour Friday over Tomorrow. We also see values of 30-40knts of DLS therefore any storm that does form will see more frequent lightning activity as the updraft will be long-lived. I must stress that even with these favourable parameters given high pressure is in control, we are more likely to see nothing rather than something. My best bet is just north of M4/Bristol Channel across SW Midlands.

Saturday: 

A much greater risk lies on Saturday, at this point high pressure tends to move back away to the east. As you see CAPE values are even higher approaching 1800J/kg, showing the potential for some very frequent lightning. The reason there is a much greater risk of Saturday is because of the much higher precipitable water values, lower pressure (whilst still high) and a well-defined convergence zone. DLS amounts are rather slim for Saturday however, storm relative helicity values which represent the potential for cyclonic motion within an updraft, are pushing towards 150-200m^2s^-2. Therefore any storms on Saturday I expect to form along a line from North Wales towards East Anglia and the London Area, a few storms just North of M4, but lower risk. These storms will exhibit the potential for supercelluar characteristics but these will be relatively short given lack of DLS and may only occur within a tight time frame. All storms will have a relatively short duration but will result in some very frequent lightning.

Sunday's potential remains to be seen as charts don't quite reach that time frame but interesting times nevertheless.

I hope this have given you an insight on what we could expect this upcoming week. I'm still learning myself all the time so apologies for any errors.

Cheers ben! No offence to other forecasters who are also awesome - but if all storm predictions could be more like this it would be a perfect world ?

[Martin Auld]

Kinda wish they taught more storm related meteorology on my uni course, only had a couple of lectures on the topic and it was the most basic concepts. Hoping to fill some gaps in my knowledge here so keep these types of posts coming ?