Thursday / Friday Storm Discussion

[West Sussex Kate]

Bad weather is forcast for Thursday and Friday.

What's the storm situation?

Edited July 16, 2009 by Westsussex1

[Roger J Smith]

This is looking a lot stronger on the 00z model runs, in fact I would draw some comparisons to the June 2007 flooding rainfall event. The set-up is somewhat different, but the results may be similar (not to say that Hull will be ground zero this time, but ...)

The latest guidance shows a strengthening low hitting south central England by late today, and moving slowly northeast then north across England and then Scotland. It seems possible that this will set off some very heavy rainfall in an arc extending ahead of the low centre, Looks like Hampshire to about Lincs would be the path of heaviest rainfalls and there is potential here for as much as 2 or 3 inches locally.

As for the weekend, by then the heavy rain will be into Scotland and wrapping back around the low centre into Northern Ireland and perhaps northwest England for a time. The Open golf is going to be the Open Umbrella for sure. I wouldn't put the mortgage on Woods to win unless he's improved his wind and rain game from the last time he faced these conditions.

Meanwhile the weekend should be windy but on the partly cloudy side further south. Persons better informed than myself will be waking up soon and confronting this new guidance, so I would say, watch this space ...

[Nick F]

Bad weather is forcast for Thursday and Friday.

What's the storm situation?

Well - a look around and Netweather has a storm forecast: http://www.netweather.tv/index.cgi?action=convective;sess=

Estofex: http://www.estofex.org/

Plus latest thoughts in my blog here:

http://www.netweather.tv/forum/index.php?s...p;#entry1565094

[Coast]

So, what are the others predicting?

A big forecast for Europe from ESTOFEX:

Storm Forecast

Valid: Thu 16 Jul 2009 06:00 to Fri 17 Jul 2009 06:00 UTC

Issued: Wed 15 Jul 2009 19:57

Forecaster: GATZEN

A level 2 was issued for portions of northern France mainly for severe wind gusts.

A level 1 was issued for France mainly for severe wind gusts and large hail.

A level 1 was issued for south-eastern England mainly for excessive rain.

A level 1 was issued for north-eastern Spain mainly for severe wind gusts.

A level 1 was issued for western Russia mainly for large hail.

SYNOPSIS

An amplified long-wave trough over the eastern Atlantic yields a deep south-westerly flow from the Iberian Peninsula across western and central Europe into western Russia. Some short-wave troughs and mid-level jet streaks embedded in the main flow will travel north-eastward during the period, while the main trough still amplifies and cuts off over the British Isles. A strong mid-level jet is forecast to evolve at the edge of the trough that will point towards the Benelux countries at the end of the forecast period.

At lower levels, a well-defined frontal boundary stretches from Iberia to Germany. While the cold front will move eastwards in the southern portions, warm air advection is likely to the east of the approaching trough, where an elevated mixed layer currently over the Mediterranean will overspread quite moist low-level air masses in the range of the frontal boundary.

Further north-east, another large frontal wave will move across the Baltic Sea region. Warm and moist air masses will be advected into the western Russia region ahead of the associated mid-level trough. To the south, only weak mid-level winds are forecast in the range of a ridge from the Mediterranean to the Ukraine, but weak mid-level troughs will likely lead to some forcing.

DISCUSSION

England

As the mid-level jet streak approaches over The Channel, strong QG forcing is expected over England in the evening hours. At the surface, a convergence is expected to develop, and rather moist low-level air mass may become slightly unstable given moist-neutral profiles. Given favourable veering profiles to the east of this convergence, embedded mesocyclones may develop, and a tornado is not ruled out completely, but limiting factor will be weak instability. For the south-eastern portions, excessive rain may occur at the northern flank of the French MCS.

A SEVERE warning and forecast out from UKASF!!

Storm Forecast Issued: 2009-07-15 21:12:00

Valid: 2009-07-16 00:00:00 - 2009-07-16 23:59:00

Regions Affected

*SE & CS ENGLAND*, Midlands, Home Counties, Southwest England, south Wales, Scotland, Northern Ireland, Ireland ( all of the UK is included in the WATCH )

Synopsis

A complicated setup on Thursday, and one that will require close monitoring. An area of LOW pressure to the northwest of Scotland, and a second LOW pressure rapidly approaching from the southwest, will determine the weather conditions across the UK. Across Scotland, Ireland and Northern Ireland, daytime showers and thunderstorms will develop in response to daytime heating and local convergence zones. Light winds will ensure that the showers/storms will be slow-moving, and hence a risk of flash-flooding. Hail may accompany some of the showers/storms, though it must be highlighted that the risk of thunderstorms is somewhat less than recent days. Any showers/storms that do develop should decay during the evening hours. Elsewhere, cyclogenesis is forecast to occur over the Bay of Biscay as a sub-tropical area of LOW pressure deepens rapidly. At the same time, a plume of warm and moist air is advected across France towards the UK on the eastern flank of the LOW. The interaction of the two is expected to result with thunderstorm initiation across northern France during the late afternoon and evening hours. As the LOW rapidly approaches from Biscay, the thunderstorms are expected to rapidly merge into a large MCS, which is then forecast to move into the South/Southeast of England. The exact track of this MCS is far from certain – there is a lot of differences between the models, with some indicating that it may not even make it to UK shores, but may move across NE France and into Belgium instead. Nevertheless, the MCS will be developing in a very favourable environment for severe thunderstorms, and may take on supercellular characteristics, including the threat of moderate hail, locally extreme rainfall and perhaps tornadoes. Over Southwest England, an upper warm front will develop outbreaks of persistent rain during the afternoon hours, moving into the south Midlands/south Wales during the evening. Models are struggling with this scenario as to whether this rain will be electrical or not – current thinking is electrification will increase here in the evening hours, though it is not expected to be too widespread. Given the uncertainties present with regards to positioning, intensity of rainfall and eletricification, an update may be issued during Thursday as and when necessary.

I guess TORRO will update during the morning, here's a sprinkling of charts and models to cut out and paste on the bedroom wall:

Nothing suspicious there, I'm waiting for the 12z Herstmonceux Skew-T for a better idea of what we might get tonight in the SE, but if it gets across The Channel, we could get a humdinger!

[Gratts]

Looks like the south west and Wales are going to get a bit of a hammering. Current radar is like a childs colouring book! :lol:

[Radiating Dendrite]

I was just expecting rain and not a possible MCS!

Do we expect a good light show if this could make it across the channel and into the SE?

:lol:

[TEITS]

Nothing suspicious there, I'm waiting for the 12z Herstmonceux Skew-T for a better idea of what we might get tonight in the SE, but if it gets across The Channel, we could get a humdinger!

Certainly could and what an exciting situation to follow.

I have been following this on the models for the past few days now and the SE and E parts of E Anglia have generally been most at risk. Like you say the possible MCS may stay away from the UK shores but if it does hit then my word you're going to see some action. For me personally im just expecting heavy rain as the action may remain to my SE/E.

Still some uncertainity in the models which makes it more exciting. :lol:

Edited July 16, 2009 by THE EYE IN THE SKY

[Coast]

Do we expect a good light show if this could make it across the channel and into the SE?

Like all these knife-edge weather situations we won't know until its time for radar and detection watching. I suspect that this thread will be filled to the brim in the darker hours, I just can't say at this point if it will be with moaning and whinging posts or excited storm reports. In any event, the only way the forum will be quiet tonight is if a storm takes out the SE half of the National Grid!!!! :lol:

[Radiating Dendrite]

Like all these knife-edge weather situations we won't know until its time for radar and detection watching. I suspect that this thread will be filled to the brim in the darker hours, I just can't say at this point if it will be with moaning and whinging posts or excited storm reports. In any event, the only way the forum will be quiet tonight is if a storm takes out the SE half of the National Grid!!!! :lol:

That sounds good to moi!

[tornadomanuk]

Already a substantial and large area of RF touching the far tip of Cornwall, and expecting this to progress ENE and intensify in places during the day. Im certainly glad I have a day off today to radar watch. Certainly one of the most exciting weather 'events' to affect the UK for a little while now.

Edited July 16, 2009 by tornadomanuk

[Cloud 10]

:lol: :lol:

Looks like july's rainfall total will have topped the 100mm mark by the time this low pressure is done with us.

Some very colourful radar screens to come over the next couple of days!

[Harry]

Morning all - some exciting prospects then :lol: yay!!

A SLIGHT risk of severe from Nick F, Level 1 from Estofex, Severe risk from UKASF.

Will be interesting to see what TORRO issue - perhaps the most 'trigger happy' for the want of a better term - reading their forecasts is enough to make anyone collapse with excitement :lol:

EDIT - What is even more exciting, is the fact that GFS shows quite an increase in CAPE across EA/SE at 3am - that doesn't often happen! Which means should any precip run ashore into the SE, if it's not packing much of a punch (which if it does come ashore and is NOT packing a punch I'd be surprised anyway) we could well expect some rapid intensification in the early hours!

Edited July 16, 2009 by Harry

[Coast]

Looks like July's rainfall total will have topped the 100mm mark by the time this low pressure is done with us.

I'm certainly not expecting to have to water the garden tomorrow.....

[cjwardy]

Looks as though things down here in the SE could get interesting overnight and in the early hours. I'm hoping it gets so bad that I can't make the trip into work in West London from NW Kent :lol:

BBC this morning played down the event saying how they don't expect much to happen in the London area, just a few heavy showers..... :lol:

[Lynxus]

Looks as though things down here in the SE could get interesting overnight and in the early hours. I'm hoping it gets so bad that I can't make the trip into work in West London from NW Kent :lol:

BBC this morning played down the event saying how they don't expect much to happen in the London area, just a few heavy showers..... :lol:

BBC did the same round here. Saying the best weather will be in the SW and South uk... However looking at the radar, Unless those bright echos down the SW mean intense sunshine! i feel they are wayyyy off the mark today.

Everyone other site i can find mentions heavy rain and thunder!

[Tucco]

:lol: :lol:

Looks like july's rainfall total will have topped the 100mm mark by the time this low pressure is done with us.

Some very colourful radar screens to come over the next couple of days!

Could be nearer the 200mm mark for here if models prove correct.

Mark

Teesdale,Co Durham

Edited July 16, 2009 by Tucco

[cobbettp]

looks like we might get a shower this evening :lol:

[Neilsouth]

Where is the plume currently? , do we have a timescale for the warmer air for this possible MCS?

[cobbettp]

Where is the plume currently? , do we have a timescale for the warmer air for this possible MCS?

I think its over Northern france, Neilsouth

[Lewis]

Morning everyone, i just booked an holiday yesterday. Got a brilliant offer in a top of the range caravan, but guess what the catch was! I have to go tomorrow LOL! Miss's want happy with me booking it behind her back :lol: . So heres hoping we have no problems tomorrow with the weather, but i'm almost certain too miss out tonight, which is good because i dont want flooding again.

I did my little map thing below, the areas highlighted, get some sandbags ready is your proned to flooding. Like roger said it's looking nasty! Im still a little unsure of the track, but i think im safe and miss the lot. I have some sand bags on standby though.

Edited July 16, 2009 by Lewis

[Harry]

I think its over Northern france, Neilsouth

Yeah I think the same here - though having said this it already feels warmer today and the sky has that unmistakable hazy glow up at higher levels - this suggests to me that warmer and slightly more humid air is already making progress for us, if only at higher levels at the moment. Remember the warm and humid air is supposed to advect ahead of the Low pressure system, so should hopefully make its presence felt in advance of the arrival of any rain.

Though people more qualified will probably prove me wrong, lol!

BBC did the same round here. Saying the best weather will be in the SW and South uk... However looking at the radar, Unless those bright echos down the SW mean intense sunshine! i feel they are wayyyy off the mark today.

Everyone other site i can find mentions heavy rain and thunder!

The BBC has on COUNTLESS times got the the forecast very wrong when it comes to severe weather events, particularly thunderstorm activity. Two weeks ago, the mid afternoon and even early evening forecasts did NOT pick up on the threat of storms for the SE! Behold, nightfall - despite much discussion on here for the best part of 12-24 hours before the event, the BBC still failed to pick up and act on it! The result was an MCS producing intense rainfall, thunder and lightning to an extensive swathe of the SE, which ultimately COULD have cost lives (refer to neilsouth's account of the aforementioned events for greater detail, lol) - slightly emphatic you might think, but for those who have not witnessed an MCS before - they are certainly not your average thundery shower :lol:

This is not a personal attack on the BBC by any stretch - just the observation that when it comes to thundery forecasts, you are best advised to follow discussions on here, note forecasts issued by the experienced and educated members on here (certainly not me btw), and even watch the pretty colours and their directions yourself, before even considering switching over to a BBC channel for your storm information.

Edited July 16, 2009 by Harry

[Neilsouth]

Thanks for that reply

GOOD NEWS , altocumulus now coming up from the south/south west!. Going by time scale storms could be over the south/south east tonight

[Paul Sherman]

All seems to be going to plan atm.

Remember this is going to be a dual attack with the 1st attack showing its hand down in Devon and Cornwall at present. The 2nd wave will initiate over in Northern France later this afternoon and move NE Towards SW Germany and Benelux. (As shown on yesterdays models of a split in the Rainbands) It is the 2nd wave the BBC Will NOT Mention at the moment as it has not even initiated yet, but all the models have a handle on this and it is wether it can clip the South East as it trundles North East. Looks like the Rainbands merge further North around the Wash tomorrow before the Wrap around gives massive Totals in the NE & Scotland. As the Low deepens tomorrow expect more showers and storms across the whole of England and Wales.

Paul S

[A.J]

All seems to be going to plan atm.

Remember this is going to be a dual attack with the 1st attack showing its hand down in Devon and Cornwall at present. The 2nd wave will initiate over in Northern France later this afternoon and move NE Towards SW Germany and Benelux. (As shown on yesterdays models of a split in the Rainbands) It is the 2nd wave the BBC Will NOT Mention at the moment as it has not even initiated yet, but all the models have a handle on this and it is wether it can clip the South East as it trundles North East. Looks like the Rainbands merge further North around the Wash tomorrow before the Wrap around gives massive Totals in the NE & Scotland. As the Low deepens tomorrow expect more showers and storms across the whole of England and Wales.

Paul S

Bugger, and I have a day off tomorrow, was thinking of catching the cricket at Lords...That'll be a washout then

[dallas]

It's certainly not often Netweather issues a level 5 warning