Storm & Convective Discussion - 01/03/15 onwards

[Harry]

Aye, though think I'd take the structure of a supercell over the mess of a MCS any day lol. Large hail and high winds aside, supercells don't necessarily carry a tornado risk if certain factors don't favour that activity - such as relatively high LCLs (cloud base), or not much backing of the surface wind and veering within the lowest 1-3km, and therefore low SRH. 

 

June 28, 2012 is probably what we're all hoping to see again.  But looking back on that day, it's easy to see that a few tweaks to some of the factors could have produced something far more significant.

Of course, however the hail would be a pretty nailed on feature as well as potential straight line winds/down bursts...which wouldn't do my roof many favours lol.

I remember it well - 34C here in the SE with very high humidity (not so much as a pinhead of precipitation to show for it) - the ingredients were all there for a 'significant outbreak' bar perhaps (if memory serves well) a particularly strong jet (although there was some jet activity) - this is the thing we often lack when we have heat and humidity and modest capping.

The best thing was seeing on loop, the cells erupting over Wales (earlier than we'd all thought) and racing NE, followed by a succession of explosive developments over the Midlands throughout the afternoon.

[Mesoscale]

18th July and both the 19th and 20th September last year were pretty decent for the storms in my location (although we missed out on the 28th July last year where Brighton and parts north of me got hammered by some very decent lightning) The July 18th one had a well defined shelf cloud on the leading edge it almost looked like a plow, we got a little storm on the 19th and the one on the 20th went on for almost 4 hours, both at night, it reminded me of the storms I remember having as a kid in the early 90's.

Im not holding my breath for anything but I think we are due some intense storms, maybe even some large hail. I think we have been dodging the bullet for too long now.

Edited May 27, 2015 by Mesoscale

[NO LONGER POSTING]

er..

 

[Harry]

er..

 

 

Yes, I saw this...what on Earth is going on??

 

A depression like that this time of year is not great news...the anticyclonic pattern building in after though looks better, which should give way to the East based on current models which may allow a brief plume. Equally, there may be brief import of some relatively warm/humid air ahead of that depression, but timing as ever will be crucial.

[Harry]

Indeed, unfortunately (or fortunately depending on your persuasion to such things) synoptics seldom all overlay - when we have CAPE up in the thousands, its often due to a HP to our E, but with the jet way off to the north, or, with the jet running roughly the same direction as to low level winds (i.e strong southerly breeze at low/mid levels, with the jet also aligned roughly S-N)...its quite rare to have a SW-NE/W-E jet and a S/SE flow bring high temps/humidity...agreed it does happen, but I can't recall many occasions where this has materialised...when it does, like it did in 2012, we'll certainly know about it.

[Harry]

Agree there regarding the overlap of variables. Would seem that we can only have one and not both-- either it's large CAPE and weak shear, or very weak CAPE and strong shear lol. Indeed, generally we often talk of ridge and blocking highs to the east 'stalling' troughs to the west for our traditional storm setups, though such setups aren't usually supportive for something beyond multicell clusters with frequent lightning, gusty winds and perhaps moderate hail.

Rrea00120120628.gif

(28/06/12) 500mb height contours indicating W'erly mid-level jet aloft, with S'erly to SE'erly surface winds ahead of the cold front. The supercells having developed with the aid of a shortwave impulse ahead of the front around mid-afternoon. Can't remember what the CAPE values were that afternoon (Watnall sounding not available it would seem), though think they were generally mid-1000s, or a little higher. Shear wasn't particularly high either, though obviously the balance of instability and shear were sufficient given what arose as a result.

But yeah, if we can get another one of those this summer, it'll all be good.

I may be wrong but I thought 2012 supercell day saw CAPE in excess of 2000, perhaps even nearer 3000. I can't be sure, however I seem to recall that day being one of those "oh yeah we wish" scenarios 7 days out, but never dropping away significantly as the day drew closer and closer. Even on the day I seem to recall CAPE charts with deep oranges and reds slapped all over it with LIs in the order of -7/-8. I remember it as we had those conditions with very high temps and dew points, but equally obscene levels of CIN so didn't manage so much as a dinky Cu out of it.

Be good if there were some archived charts

Edited May 27, 2015 by Harry

[Supacell]

CAPE & LI chart from GFS on 28th June 2012

 

 

From NMM for same day

 

[NUT]

The famous 2012 June epic. We did not get one drop of rain here in the lowlands (we we're probably on the border line quite literaly)

[Harry]

CAPE & LI chart from GFS on 28th June 2012

 

ukcapeli2.png

 

From NMM for same day

 

NMM prediction 2pm.png

Nice to see my memory is in reasonable working order

[Lauren]

Why do I have no recollection of the 2012 storm? I remember the big one in June 2011.

[Supacell]

Why do I have no recollection of the 2012 storm? I remember the big one in June 2011.

They never really affected the SE. One supercell ran across the Midlands into Lincolnshire and then a second moved across NE England. Most other parts avoided anything of note.

Conversely I remember the 2011 one being a SE and EA only storm.

Edited May 28, 2015 by Supacell

[Supacell]

Tony G on ukww talking about a risk of low end supercells and tornadoes tomorrow. It may be worth keeping an eye out.

[Harry]

Tony G on ukww talking about a risk of low end supercells and tornadoes tomorrow. It may be worth keeping an eye out.

I did wonder - tomorrow afternoon looks especially interesting with a very active looking squall sweeping through most of southern and eastern England. Low level instability appears marginal however the forcing of the front could be sufficient to generate some electrical activity I feel, as well as some locally notable wind events.

I'm looking forward to it as squalls this time of year tend to bring dramatic skies and locally severe conditions...always a giggle

UKMO rainfall forecast picking out detailed wavey squall pattern, which is the first time I think I've seen that in a chart.

Edited May 28, 2015 by Harry

[Cloud 10]

Spanish plume alert on this evening's ECM.

 

[Harry]

Spanish plume alert on this evening's ECM.

ECM0-192.GIF

Deeply suspicious at the moment - ECM looking fairly good however GFS takes a different approach with a draw of fairly warm air however a fairly strong HP slap bang over us deflecting any real instability away to our South.

Far too early to call a week in advance however signs are pointing to a much warmer and continental pattern later next week which is always a step in the right direction

If however as you say the ECM synoptics prevail my money would be a on a fairly widespread and significant thundery outbreak - the evolution of that set up is for a low to spin up which, if the nicely aligned jet came into play we could be talking some severe stuff in the mix over possibly a few days...all to play for

Edited May 28, 2015 by Harry

[Weather-history]

[Cloud 10]

Deeply suspicious at the moment - ECM looking fairly good however GFS takes a different approach with a draw of fairly warm air however a fairly strong HP slap bang over us deflecting any real instability away to our South.

Far too early to call a week in advance however signs are pointing to a much warmer and continental pattern later next week which is always a step in the right direction

If however as you say the ECM synoptics prevail my money would be a on a fairly widespread and significant thundery outbreak - the evolution of that set up is for a low to spin up which, if the nicely aligned jet came into play we could be talking some severe stuff in the mix over possibly a few days...all to play for

 

 

Nice summary there Harry.

 

Good to see these sorts of charts appearing as we head for summer.

[Daniel*]

Nice summary there Harry.

Good to see these sorts of charts appearing as we head for summer.

To be fair these charts are more representative for what I expect for this time of year as the continent warms by the strengthening warming sun as does the possibilities.

It has been a slow start to the year I must say 1 or 2 cackles of Thunder not much else.

Edited May 28, 2015 by Daniel*

[East_England_Stormchaser91]

GFS is a cracker, but very marginal and will no doubt change!

Current handling of the potential plume sees a very interesting scenario. With a very humid SE flow coming in, we see a huge temperature contrast in excess of 15c! over a distance of 100 miles or less (say between Birmingham and Manchester eastwards) With a substantial jet aloft moving NE at the time of the CAPE build up in the Midlands and SW England, this would seem to me like supercells would be a considerable risk, forgive me if I'm wrong!

Interesting charts to observe at long last! Let the discussions begin

[Mesoscale]

28th June 2009 was a cracker If I remember correctly and 6th August 2006 sticks out in my mind as well but it was so long ago that Im not sure if I have the right date?
Best storms I have ever seen have been in the South East USA/Caribbean, one in Mexico when lightning struck a tree near us showering us with smouldering bark, one in Florida that turned International Drive into a river and one when I was sailing from Port Canaveral to Freeport in the Bahamas, it had constant anvil crawlers made even more epic because we were in the middle of the sea it was caused by Hurricane Irene, although coming back to Florida was the worst as the hurricane had made the sea very very angry, when you are on a 130k ton ship and you cannot walk down the corridors without being slammed against the walls you know its bad, dont even get me started on walking down the stairs.

I love this anticipation of getting storms, if it was guaranteed it wouldn't be as exciting.

Also why doesnt the UK have Pulse-Doppler radars?

Edited May 29, 2015 by Mesoscale

[Rain123]

If it is anything like the July 18th storms last year, then I'll be happy. 

[Harry]

Good shouts Meso and Rain123 - 17th/18th July last year, 28th June 2011(don't recall 2009) and 6th August 2006 definitely memorable for me

Last year being an exception (which was a fantastic year in my neck of the woods) the fact that only 3 or 4 dates stand out over the best part of a decade shows how shocking times have been. Let's hope this year is a continuation of last

[NO LONGER POSTING]

Some very intense rain about to hit Wales

[NL]

28th June 2009 was a cracker If I remember correctly and 6th August 2006 sticks out in my mind as well but it was so long ago that Im not sure if I have the right date?

Best storms I have ever seen have been in the South East USA/Caribbean, one in Mexico when lightning struck a tree near us showering us with smouldering bark, one in Florida that turned International Drive into a river and one when I was sailing from Port Canaveral to Freeport in the Bahamas, it had constant anvil crawlers made even more epic because we were in the middle of the sea it was caused by Hurricane Irene, although coming back to Florida was the worst as the hurricane had made the sea very very angry, when you are on a 130k ton ship and you cannot walk down the corridors without being slammed against the walls you know its bad, dont even get me started on walking down the stairs.

I love this anticipation of getting storms, if it was guaranteed it wouldn't be as exciting.

Also why doesnt the UK have Pulse-Doppler radars?

The UkMet O have 15 operational radars and all but one are doppler radar and have been since 2013.

http://www.rmets.org/sites/default/files/abstracts/Mar/20032013-sugier.pdf

[matty40s]

The squall line is starting to appear on the radar now.