Upcoming Convective / Storm Risk Discussion - w/c 12th May

[Coast]

And yes he does Adi, uses it all the time when Storms kick off 

 

I have come close to buying one several times, but we haven't had enough storm activity in the last few years to justify the cost!!!

[lewisosd]

I think this shift in thunderstorm activity came when the boxing day tsunami happened. Dot know how it could affect atmospheric patterns or could be pure coincidence

[AWD]

Well somewhere in the World had storms yesterday:

Is that a giant shark off the northern coast of Norway?

[Coast]

Is that a giant shark off the northern coast of Norway?

 

Maybe, perhaps it's eaten our sunshine?

[egret]

Hathers, I agree that there does appear to be a trend . Unscientific I know, but for me there does seem to be a link with cycles in solar activity.  It is quite possible that the actual link is very indirect. I know lots of academics have been investigating this area and I am always interested in latest findings.

 

Of course that is all covered in a different thread but I am not expecting a return to generally increased thunderstorm activity until around 2016.

[nitro_deluxe]

I'll give it till June 28th to see a half decent TS.

[Raidan]

Does anyone have or know how to access charts from the days back in the 80's and 90's when Bristol had proper thunderstorms? Would like to compare them with charts from 2000 to 2013 and somehow try and figure out what's changed and why we have such a poor record with storms.

[Coast]

Best I can think is:

 

http://www.wetterzentrale.de/topkarten/fsreaeur.html

[Raidan]

Thanks Coast its something to work with

[Supacell]

Maybe a long shot but in these times of low storm activity and straw clutching there may just be an opportunity tomorrow if things come together for NE England, particularly East Yorkshire. 

 

Admittedly SBCAPE is looking rather poor, although there is something there on the GFS charts:

 

 

However, CAPE through the levels looks more promising in the NE of England and add to this up to 60knts of deep layer shear this brings the chance that any storms that can form will become organised. Note also the CAPE in NE Scotland which could lead to some pulse storms here.

 

 

There is also some decent parcel layer depth into the evening hours over this area, which means although SBCAPE is rather poor there is the scope for CAPE to be released through a good depth of the atmosphere. It is therefore likely that the CAPE shown in the last chart could therefore be realised.

 

 

Then to the even more exciting part, and that is the addition of helicity which, combined with the other parameters, brings the risk of supercells and a tornado threat.

 

 

 

It is a possibility tomorrow could provide something special for a localised area, but an equal chance there will be nothing. 

 

I have just noticed Tony Gilbert on ukww is also seeing this potential and his forecast is a lot more in depth than mine, as he is a lot more knowledgeable than I. Tomorrow evening really needs watching across that NE portion of England.

Edited June 11, 2013 by Supacell

[NUT]

It may not come off but look at this for next thursday:

 

http://www.wetterzentrale.de/pics/Rtavn21611.png

[Supacell]

The chances I talked about two posts up have disappeared on the 12z charts. I will have another look tomorrow but it just goes to show how fragile the set up was.

 

Next Thursday has been showing off and on for a few runs. If it came off that would be a treat, but at such a timescale the likelihood is not very high (although not impossible either).

Edited June 11, 2013 by Supacell

[A.J]

the following from SKYWARN......

 

SKYWARN UK SEVERE THUNDERSTORM WATCH #019ISSUED: 1430UTC TUESDAY 11TH JUNE 2013

SKYWARN UK FORECASTS THE POTENTIAL FOR SEVERE THUNDERSTORM CONDITIONS AS FOLLOWS:STRONG, POTENTIALLY DAMAGING GUSTS - ENGLAND, WALES, NORTHERN IRELAND, SOUTHERN SCOTLANDLARGE, POTENTIALLY DAMAGING HAIL - ENGLAND, WALESTORNADOES - EASTERN, SOUTHERN AND NORTHERN ENGLAND

IN EFFECT FROM 0600UTC UNTIL 2100UTC WEDNESDAY 12TH JUNE 2013

A ROBUST WARM AIRMASS WILL BE ENCOURAGED NORTHWARD FROM THE BISCAY AREA IN CONJUNCTION WITH A SHARPLY OVERSPREADING UPPER JETSTREAM AND STRONG WINDS AT ALL LEVELS. DESTABILISATION ALONG THE WARM FRONT, TRIPLE POINT AND SOUTH OF THE JET NOSE IS EXPECTED TO YIELD STRONG CONVECTION IN A HIGHLY SATURATED PROFILE.

DISCUSSION: EARLY IN THE PERIOD, HEAVY SHOWERS AND POSSIBLE THUNDERSTORMS WILL BE ADVECTED INTO THE SOUTHWEST AND SOUTH OF ENGLAND, AS A WARMER THAN AVERAGE AIRMASS SURGES NORTHEAST. THE UPPER JET OVERSPREADS THIS PROVIDING AMPLE FORCING FOR STRONG CONVECTION DESPITE ONLY SLIGHT INSTABILITY. LATER IN THE PERIOD, THUNDERSTORMS ARE EXPECTED TO DEVELOP ALONG THE OCCLUDED FRONT OVER NORTHERN IRELAND, WALES AND SOUTHERN SCOTLAND, WITH FURTHER INITIATION FROM THE RESURGENT JETSTREAM AND STRONGER WARM AIR ADVECTION INTO WALES AND ENGLAND. THOUGH CONVECTION SHOULD BEGIN ELEVATED, DAYTIME HEATING AND A LONGER OVERLAND FETCH SHOULD ALLOW FOR SOME SURFACE-BASED INSTABILITY AND GREATER POTENTIAL FOR DEEPER CONVECTION FURTHER EAST ACROSS ALL PARTS OF ENGLAND AND PERHAPS SCOTLAND. THE SOUTHERN HALF OF THE UK WILL BE AT GREATER RISK OF STRONGER CONVECTION, WITH INTENSE RAINFALL AND POTENTIALLY LARGE HAIL. ALL AREAS HAVE SUFFICIENT LOW LEVEL HELICITY AND SHEAR FOR ENHANCED CHANCES OF TORNADOES, THOUGH AGAIN THIS RISK IS GREATER FURTHER EAST AND SOUTH. THIS WATCH MAY BE UPGRADED. PLEASE MONITOR WEATHER AND TRAVEL INFO AS NECESSARY.

SPOTTER ACTIVATION IS REQUESTED AND SPOTTERS ARE REQUESTED TO REPORT ALL FACTOR

[dave48]

Tomorrow looks interesting, certainly a well sheared environment and some favourable conditions for anything that does get going.

 

GFS and ECMWF still playing around with a thundery plume out in FI for next week. Different evolutions at the moment.

 

ECMWF below is earlier in its evolution with the low staying closer to the UK and pushing the plume through quickly.

 

 

The GFS is slower with a more southerly position for the low, bringing the plume later in the week.

 

[Convective]

Think chances are pretty low over here even tomorrow. The freezing sea around us doesn't help at all.

[Summer Sun]

Nothing from UKSAF or the Met office so far tonight so that warning may be a bit ott?

[Harry]

Was gong to remark it feels pleasantly (relatively) humid this evening with the sight of clouds pouring in from the south a fantastic change after weeks of cool dry northerlies/northeasterlies!!

MetO projecting mostly frontal activity, with some more intense spells amongst it.

I'm going to plump (for S Uk) for some embedded downpours with very sporadic occurrences of thunder and lightning (ie the majority will get no thunder at all). Further north, chances seem slightly better, but again largely frontal.

Will be interesting day/evening tomorrow of weeks of largely stagnant weather!

Edited June 11, 2013 by Harry

[East_England_Stormchaser91]

Best bit of news I've heard all year from SKYWARN , bring it on! I'm craving a good chase !

[Stuart]

Synopsis:

Two significant and deepening surface lows will cross western Britain during this forecast period, as they continue to dumbbell around a parent low situated south of Greenland. A strong jet will migrate northeastwards across southern Britain during the second half of the forecast period, while at the surface various bouts of moisture advection from the south will occur.

 

Discussion:

Difficult to pin-point any region over the U.K. with any significant convective potential, partly due to a very messy setup, but more largely due to changing multi-model frontal positions/features; indeed the 12z runs of several models have altered an otherwise relatively consistent story in comparison, so we continue to question whether this is a temporary phase which may revert back to the original forecast, or if the forecast is likely to continue to change overnight and through Wednesday. The most notable change is the delayed arrival of a secondary surface low/waving front over southern Britain by 2-3 hours compared to several previous multi-model runs.

For now, we will add areas/discussions based on current or 'earlier' thinking, with the proviso that modifications may be needed to both through Wednesday if the forecast evolution continues to change.

... SE SCOTLAND, FAR NE ENGLAND ...
Main focus for this area will be between 02z-08z, but stress a very low probability of lightning activity, hence no SLGT area. Forecast profiles are incredibly moist throughout the vertical, limiting instability somewhat, but it is possible in association with the northeastward-moving frontal system through the early morning for embedded elevated convection to develop/intensify. 30kts DLS would enable elevated convection to become reasonably well-organised as it continues to track from the Borders across the North Sea. Main threat, with PWAT values near 25mm, would be for locally large rainfall totals.

... E/NE SCOTLAND ...
Once the morning frontal rain clears the area, increased amounts of insolation should develop a couple hundred J/kg CAPE. Local wind convergence (particularly along Moray and north Aberdeenshire coasts) and/or upslope flow may allow a few scattered showers to form during the afternoon, with perhaps some isolated lightning from any stronger cell.

... C/N IRELAND, SW NORTHERN IRELAND ...
Along/ahead of the second occlusion, some instability may develop over some parts with a few hundred J/kg CAPE possible (even if elevated). The potential exists for perhaps some embedded convection to develop, especially (for surface based potential) if surface wind convergence occurs ahead of approaching occlusion. Up to 50kts DLS (including 25-30kts LLS) would enable any convection to become organised, with perhaps a funnel or brief tornado given low LCLs.

... PENNINES, YORKSHIRE, N LINCOLNSHIRE ...
Prior to the 12z model runs, there was some reasonable consistency at least for the potential for isolated convection over this area. Cloud breaks are/were expected from late morning through the afternoon hours, allowing some insolation to improve surface temperatures (into the low 20s degC), while a dry intrusion is forecast in the mid-levels.
A few hundred J/kg CAPE is possible, when coupled with orographic forcing and low-level convergence may allow a few convective showers to form during the mid-late afternoon and early evening hours. Given strong DLS (40-50kts), if surface winds can become backed sufficiently then there is the potential for an isolated low-topped supercell with attendent threat of hail and perhaps a tornado.

However, 12z forecast soundings suggest less vertical directional shear compared to previous runs, and due to the later arrival of the second frontal wave the overlap of the dry intrusion, surface heating and jet aloft is displaced. Hence if this current forecast evolution remains then this SLGT area may be omitted at some stage during Wednesday due to the decreasing probability of occurrence.

... ELSEWHERE ...

It is worth noting that elsewhere, particularly some southern parts of Britain, may experience isolated lightning activity with any embedded convection on the second frontal wave during the late afternoon and evening hours, but point probability remains to low (i.e. unlikely to occur) to issue any further SLGT areas. Again with PWAT values in excess of 30mm the main threat will be locally large rainfall totals if embedded convection can form.

 

http://ukasf.co.uk/storm-forecasts/247

[Methuselah]

Sod it! I'm 'elsewhere! 

[Staffordshire]

Basically lincoln as per.. haha

[Supacell]

I would say Lincolnshire, especially north Lincolnshire looks a decent bet - that is if anything does happen. I am hoping the GFS18z brings back the instability that has been removed on the GFS12z as with all the other parameters in place it could lead to something quite severe.

[Evening thunder]

That Skywarn forecast seems rather OTT to me considering this is the CAPE tomorrow:

 

Granted good shear but we often seem to get that around lows like this but like tomorrow not coinciding with much instability, in a relatively normal looking Tm flow? I guess it being summer means a slightly higher risk, who knows maybe this occasion is different.

 

Wouldn't be surprised to see a few sefrics amongst some rain/showers tomorrow somewhere but nothing too notable or severe is my guess, and surely not enough CAPE for large destructive hail? yes forcing from fronts but again this is common from such weather systems in the UK and I've never known large hail from them without decent CAPE?

 

I don't know if many people think theres a strong storm risk then maybe something isolated that's organised? or maybe I'll be wrong but not something I'd be happy chasing anyway.

 

It would be nice if some of the charts for next week come off, then we could be more in business in places.

Edited June 11, 2013 by Stormmad26

[Supacell]

That Skywarn forecast seems rather OTT to me considering this is the CAPE tomorrow

 

 

 

There was more SBCAPE showing on the earlier runs, which has been downgraded on the 12z. I don't have access to MLCAPE charts as the GFS ones on netweather are just showing surface CAPE. I think they could be interesting as the consensus is that these storms will be mostly elevated with a low risk of them becoming surface based.

[Evening thunder]

Ah ok fair enough

 

Not completely sure but I think Wetterzentrales CAPE charts may include ML CAPE as I've seen them show lots more than the Netweather GFS ones in plume events before

They perhaps show a little more but not too much

 

Edit: actually comparing them it seems similar to Netweather at that time, so perhaps they don't now. Maybe someone has NW Extra ML CAPE charts or something.

Edited June 11, 2013 by Stormmad26