Thunderstorms and Convective Potential

nacho libre

it seems that Galway city and bay get most of the lightning action in this part of the country:mad:

Snowbie

Nothing as exciting in the charts as was this time last night for today Thursday. Risk is mainly for the midlands later transferring east. Convection will only occur if sun gets to work on the ground heating it early on and which is forecast to happen. Cloud is also forecast to spill down from the NW later on in the day but might bump up the showers ahead of it aided by weak convergence.

No significant convergence from the 18Z, slight if any compared to 24hrs ago unfortunately.

Storm 10

Hi Snowbie

Would please explain to me how to read the Cape Chart, I read so much about it but I dont know how to read the chart and where the weather is likely to be bad.

I only came across the cape charts recently I have no problems with any other weather charts etc.

Snowbie

I'll try and simplify this as i can.
Cape is basically the potential energy of the atmosphere in a given area. Cape varies across an area but at it's greatest over flat regions where particles of air/droplets can rise undisturbed.

We measure cape as surface based (SB) or midlevel(ML) and in joules per kg (j/kg) The higher the value the better the potential.

SB cape will indicate an unstable atmosphere at surface level (energy) and this will give rise to cumuli formations but is only one parameter in the forecasting of Ts. High or very high SB cape does not mean Ts will occur.

ML cape will also indicate unstable conditions through mid level regions (850-700mb region) Most of the time but not always we can asscociate SB and ML cape together with a good indicator of heavy showers/storms. But if we ever find ML cape without SB, it is a good indicator of elevated storms or high based storms mainly from warm moist humid plumes from the south.

If there is high SB cape and no ML cape, there is a cap or inhibition in the atmosphere so the cloud will not build up to higher regions in the troposhere.No CB will form just cumulus congestus giving showers untill the cap/inversion level clears.

These are just 2 parameters in the forecasting of storms. Both values need other ingredients for Ts to occur but the main ones we look for first before moving onto the next.

Hope this helps, don't hesitate to ask if you need any more info.

Storm 10

Thanks Snowbie for that info certainly helps to understand the chart a bit better

darkman2

Some big thunderstorms likely to develope across the Midlands and North and they may extend East later. I expect to see some flash flooding especially in the North Midlands.

Deep Easterly

nacho libre wrote: »

it seems that Galway city and bay get most of the lightning action in this part of the country:mad:

Nacho, when are you ever going to realise that Galway is better in everything full stop?

The West Awakes!

Snowbie

darkman2 wrote: »

Some big thunderstorms likely to develope across the Midlands and North and they may extend East later. I expect to see some flash flooding especially in the North Midlands.

GFS does not agree, risk downgraded somewhat for the east and north midlands.
South midlands most a risk transferring to the SE later. Little more of a convergence than yesterdays output but still slight and most important no sun or very little.

Very little convection is occuring and now with the front starting to throw general cloud now down over the country. All from 06Z output but as always we shall see.

darkman2

We are seeing development increasing now so we will see how it goes but there is a convergence zone across the center of the country and lapse rates continue to steepen. With the wind SWrly in direction below the convergence zone (where Dublin is) then we are in the firing line. Like I say I think we will have storms this afternoon but we will see how it goes.

Most of the development so far seems to be in the same area as yesterday ie in the mid west.

Snowbie

Yes there seems to be convergence but still slight atm. That is the occluded/cold front re-developing across the centre of the country. With the air moist SW ahead of it been some what advected in, it's peeping up the front with cumulus visible on satellite. Some heavy bursts are likely along it with some cold air aloft with the chance of a rumble. Nowcasting as GFS did not get a grips with this.

Watch radar and sat during the afternoon to see the developing front and see if it becomes more active. I still think as it moves more south east where the convection will be greatest with the approaching front, this be the best chance for a storm.
Then as the front clears some beefy showers might develop to the north of the front.

maquiladora

Looks like some activity over Carlow.

darkman2

Disappointing so far in the midlands and East but Cork and North Leinster on radar look like having possible storms.

DOCARCH

Looks like something mushrooming over the Waterford/Dungarvan area?

http://www.sat24.com/frame.php?html=view&country=gb

Snowbie

South was always favoured best today ahead of the front from 06Z. Big downgrade from the 18Z and 00Z for the rest of the country but was right in the end. No prolonged sunny spell here and mostly cloudy which limited convection occuring.

Nice convection there over Waterford and east Cork, a few strikes from it too.

A bit of sun creates surface warming and moist warm air being forced to rise quicker ahead of the front will create some explosive convection but really if it where only that easy too, some other parameters involved in the setup.

Edit:Wind convergence in the attach over the south and the link above from the satelitte, more lift from Wicklow mtns.

Snowbie

Some increasing cape values over the east in the last hour upto 350j/kg. LI -0.5
Modeate downpour in the last hour from a shower. Max rain rate 47.8mm/hr.
Looking at sat, some embedded CB have recently grown in the N Dublin area.

Hal1

I would have driven through that rain shower at its peak, as discussed over in the 'current weather conditions' thread. It was one serious heavy shower.

nacho libre

Deep Easterly wrote: »

Nacho, when are you ever going to realise that Galway is better in everything full stop?

The West Awakes!

We'll see by Sunday evening:p

Snowbie

Still a bit away but GFS consistent on it's Ts potential this Wednesday.

For Ireland, the midlands and NW of the country are in good location for a Ts while over the Wales has the highest risk. The risk over Wales later moves into the Irish sea and across the east coast but by then it's around midnight before it gets here and Cape has decreased. Surface heating will be minimal at night but there is high humidity and warmth in a slack SE flow forecasted for Tuesday night and into Wednesday so the chance of an import to the east looks possible later Wednesday. Will update this as we get closer the time.

Storm 10

Hi Snowbie

Whats the chances of a TS in the West this coming weekend

Snowbie

Storm 10 wrote: »

Hi Snowbie

Whats the chances of a TS in the West this coming weekend

It is too far away to predict where storms will occur, it be as short as T+12 to be certain of a more exact favourable region. GFS will upgrade and downgrade over the coming days as it's hard to pinpoint airmass storms. The Azores HP will link with the Scandi HP during the week with a LP forming just NW off the Spanish Coast bringing a S to E wind direction atm.

My 2c on this would be, as long as the winds blow from a SE direction, the chances are good for the west. In fact anywhere west of Limerick to Antrim looks good for slow moving non severe storms now on Thursday and Friday if wind direction does as is forecasted to do and other vitals are in place.

So we look for the ingredients,
Heat ,
Humidity,
High Dewpoints,
and then later Wednesday
Moisture,
Instability.

Always the chance of a straw clutching import from Wales here for the east:D:rolleyes::(

nilhg

Speaking of straws, I've just spent the morning greasing up my old combine for a new harvest season (should be starting round about the weekend), so cheer as loud as you like for showers anywhere but Kildare.;)

Snowbie

2nd day in a row the fax charts have a trough lying over the East.
Risk has increased for the east from midnight tomorrow with the import potential from Wales still there also.

Midlands and NW still have the best chance of an isolated storm during daylight hours through surface convection while here left over energy from Wales seems to move over the sea at night.

Snowbie

The latest GFS(18Z) has opted out of an import from Wales in fact i think it there be little chance of any storms there.
We have the heat the humidity and the dewpoints favourable for development over Wales but the pressure is too high. This creates an inversion layer where in HP the air sinks drys and warms creating a lid so convection cannot punch through and tower the clouds which results in low instability.

But with forcing from a SE wind over the Pennines and Welsh Mtns, a convergence forms and might allow the odd isolated Cumulonimbus. At most heavy showers will form there and little or no chance of a storm even making it to the Welsh coast let alone the Irish coastline. Any moisture left in the atmosphere from Wales or UK pushes across the sea to our NE coast into Thursday morning.

Late in the day(wed evening) the West(Galway and Mayo) might have a chance of heavy showers as pressure falls slightly there from the SW and a bit of lift from the mtns again could aid in developing some towering cumulus with low and deep level wind shear being evident too.

Thursday, the risk is more widespread for Ireland and will post up tomorrow on that potential.

Snowbie

06Z has increased CAPE values in the North/NW today for the afternoon but as above pressure is still a wee bit high. The odd sharp shower later on in the afternoon/evening maybe. Also GFS is still progging a 50% risk of showers/storms towards the east overnight tonight.

Hal1

Man the conditions seem ideal for TS's, hot and sticky flying ants galore. :pac:

DOCARCH

Thunderstorm reported at Belmullet at 13.00.

Snowbie

Another area looking interesting is the trough forming near Biscay and just to the south of the Celtic sea. Already have picked up a couple of strikes from this and the whole area seems to be moving northwards. IR sat pic shows the mid to upper level cloud with CB's forming to the south of Ireland.

http://www.sat24.com/frame.php?html=view&country=gb&sat=ir

darkman2

I love these setups personally as I think they ultimately give us the best chance of our liveliest storms. Im watching developments today with increasing interest. Indeed the sky here has a charred look about it which can be a good sign sometimes. Thats definately what I would call a plume from Biscay which is the nursery for our summer storms traditionally. So lets see how it goes. I reckon we have decent chance tonight.

Hal1

Yes, I too would like to see the setup as described above.

Snowbie

Agreed lads but there is too much midlevel dry air in the mix (cap or a lid) atm but this could break as it is doing closer to the LP to our SW. If it remains constant however there might be a surprise for us later.

Regarding a plume, there is evidence just into Biscay according to the theata wet bulb temps from 06Z output. See if it is still there from 12Z but the presence from IR sat is that it is moving north. Now casting from now on. Watch the IR sat pic and look for the deep white clouds indicating CB's forming.

Hal1

These sferics aint showing on your detector Snowbie, would this be an accurate chart? It looks organised doesn't it.

Snowbie

They be out of range of my detector Hal but yeah the triangulated one is detecting them nicely but not a whole load of strikes though.

http://www.strikestareu.com/

Snowbie

Risk now moving up from the south interacting with energy moving across the sea from Wales from the 12Z output.
Maybe an interesting evening.

highdef

Well it is looking rather promising. If the storms do occur and if they dont arrive too late, I'll have my video camera ready and waiting to record the approaching storm. I'm on the 4th floor of my apt with nobody above me and I have some great views* from the south-south east right across to the west north-west.

* - great views for Dublin city!!!

maquiladora

What are the chances for Waterford tonight?

darkman2

First echos appearing far off the South Coast on radar moving north. I dont feel like staying up too late so hopefully it will arrive around midnight. Whether it will be in the form of storms or not remains to be seen but its a promising situation.

Storm 10

Some pretty intense rain moved up off the West and North coasts this afternoon but most of it stayed out at sea looked very heavy on the radar, no thunder though hopefully we may see some tonight or tomorrow

StratoQ

Belmullet reported a TS at 12Z today. Radar seemed to indicate some very heavy pockets of rain but the station registered under 2mm. So the pockets either stayed over the mountains or the radar was out.

Just as I type this - there's a few drops of rain here now. But nothing thundery.

Danno

Lovely and sunny here north of you StratoQ. Todays high was 20.4c which is lower than yesterdays. Where are all the 24s and 25s we were promised? We need more substantial heat to kick off a good storm!

Currently 19.3c with dew point of 16.2c (quite high DP). A light aircraft is flying circling around, so no thunderstorms are expected to develop in the next hour or so.

darkman2

The radar is acting up atm - hope they get it sorted.


There is probrably just the odd light shower around at the moment. Pressure is quite high but falling off from the South so heavier showers moving north later.

Deep Easterly

darkman2 wrote: »

Pressure is quite high but falling off from the South so heavier showers moving north later.

Pressure in this situation is relative to positioning of highs and lows rather than absolute I think. But nice that it is falling all the same. 1018.9 mb at the moment, quite a sharp drop from earlier.

Supercell

Must say I like the look of that 03z chart, am right in the 50% zone, not holding my breath though , Annamoe seems to be woeful for thunderstorms.

darkman2

Supercell wrote: »

Must say I like the look of that 03z chart, am right in the 50% zone, not holding my breath though , Annamoe seems to be woeful for thunderstorms.

Check out the latest radar. Looking juicy to the south;)

Danno

http://durrow.athost.net/lightning/ Some lightning being detected south of Waterford and Cork at the moment.

http://sat24.com/frame.php?html=zoom&xas=161&yas=188 Shows the clouds responsible.

Some dew points -

16.3 here - http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=ICOLAOIS2

15.9 Kilkenny - http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=IKILKENN2

15.6 Waterford - http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=MAS594

Interesting evening ahead. Probably that clump will hit East Cork/West Waterford round 8.30pm, move north through Tipp, East Galway and West Offaly before dying out after sunset.

Snowbie

Some convection just off SW Wales moving up towards the east. More CB's building in the clumps to our south.

Not tons of strikes but still appearing in the Celtic sea.

http://www.sat24.com/frame.php?html=view&country=gb&sat=vis

darkman2

Snowbie wrote: »

Some convection just off SW Wales moving up towards the east. More CB's building in the clumps to our south.

Not tons of strikes but still appearing in the Celtic sea.

http://www.sat24.com/frame.php?html=view&country=gb&sat=vis

No joy from the radar yet - seems all over the place atm.

Snowbie

The Lands End radar is suffering alot of anaprop and is on the blink today.
This is not a hopeful Biscay setup atm. There is only 1 storm and thats off the Spanish coast. The rest only are sporadic strikes and is completly disorganised on radar/sat. Still time to get going though but as ever will watch closely.

StratoQ

On latest Met É radar (10:30) the clump to the south has widened stretching below wex to Cork.

But its also showing precip over me and its still dry. I think a lot of it is evaporating before hitting the ground. So im taking it all with a pinch of salt atm

So all in all it may be some time before anything gets going. It would be nice though to be woken by a TS in the middle of the night.

Snowbie

All is quiet over Biscay and Celtic sea atm but cells are building.

From 03Z the risk increases in the east from midlevel cape(mid to high based) moving across the Irish sea but i think the GFS hss gone mad since 12Z. It is not handling the midlevel Cape that is over Biscay and moving north in a plume from Spain. But anyway the 18Z output with a attach shows the potential. Precip yes but storms is very hard to tell atm. Nowcasting or just a peaceful nights sleep.

Most areas at risk of heavy showers tomorrow but the midlands and NW be highest after the east and south in the morning.