Heavy Rain, Flooding, High Winds - 21st November onward

[jamesbhx]

A lot of it depends on where exactly the low tracks, even a shift of 50 miles would change the strength of wind that one particular area gets. Brest and Dinard are forecasting gusts of 45kts from 3pm tomorrow afternoon onwards. I'm still fairly confident that anywhere along the south coast round towards Essex could see peak gusts in the 60mph region on Saturday night in to early Sunday morning. The BBC and MetO are going with a similar sort of figure and based on the latest runs I see no reason to doubt it.

[Liam J]

Yes and the GFS 18z finally woke up and intensified the depression to be more in line with some of the other model outputs, took it's time though!

GFS progging gusts of 50-60mph through the Channel, 40mph+ over land, perhaps in excess of 60mph along the exposed SE coast and parts of EA.

NMM 18z also increasing the max gust speeds, in the 55mph region.

Pressure charts are plotted every 1mb above so they do look very intense and slightly exaggerated!

Edited November 23, 2012 by Liam J

[weirpig]

Just noticed how high these rain totals really are, just checked met office sight amber warnings for wales and south west, does anyone expect these to change considering current output.

[Terminal Moraine]

The NMM has significantly increased the rainfall totals for Saturday night/Sunday from the 12z to the 18z.

The 12z predicted around 17 mm for this part of the Peak District whereas the 18z has around 32mm. For parts of SW England the 12z was indicating around 20-25 mm, this is now up to 40-50mm.

[Liam J]

The NMM has significantly increased the rainfall totals for Saturday night/Sunday from the 12z to the 18z.

The 12z predicted around 17 mm for this part of the Peak District whereas the 18z has around 32mm. For parts of SW England the 12z was indicating around 20-25 mm, this is now up to 40-50mm.

Accumulated rainfall by 18z Sunday, for some areas the values have nearly doubled compared to the 12z.

Edited November 23, 2012 by Liam J

[Bobby]

Yes full agreement at last, another good soaking it seems for the worst hit areas. Then coming up to Monday's low, some of the ensembles have that rain stalling over the SW, if that 100+mm showing for the N. Midlands fell onto the already flooded SW again that could be disastrous. Something to watch. 100m in one go is enough to cause a lot of trouble in any situation.

e.g.

Edited November 23, 2012 by Barb-

[pyrotech]

Ship in position 45.30 -8.50 reporting a 5mb drop in pressure in 1 hour thats very impressive

[Storm Track]

Hello, everyone. I will be updated on this detail.

Storm Forecast

Valid: Sat 24 Nov 2012 06:00 to Sun 25 Nov 2012 06:00 UTC

Issued: Fri 23 Nov 2012 22:52

Forecaster: TUSCHY

SYNOPSIS and DISCUSSION

A low pressure area moves from the Bay of Biscay to the NE and crosses S-UK during the overnight hours. Placed beneath a coupled high-level jet configuration, constant strengthening of this feature is likely and even a transient warm-seclusion event may occur during the forecast period. This might insert some uncertainties regarding the final strengthening trend as this one will be a compact system with a chance of rapid pressure fluctuations. Also, with deep WAA forecast, only weak MUCAPE evolves which might induce convectively enhanced rainfall amounts beneath the deformation zone (interesting for those areas, already affected by flooding). However no DMC or electrified convection is expected right now. In addition, we monitor the eastward movement of dry high-tropospheric air towards the back-bent occlusion during the night, which could increase the overall severe wind gust risk (e.g. SE UK during the night). We will watch the area between the occlusion and the backside of the cold front/or triple point for enhanced DMC chances, which would mix severe wind gusts down to the surface.

For the rest of Europe, a quiet November day will be in store (in respect of thunderstorm development). Only W/SW Portugal may see an heavy rain risk with repeatedly onshore moving showers and isolated thunderstorms. The risk remains below our level 1 threshold. I also do not want to exclude an isolated spout event with gradually increasing LL CAPE.

Strong or severe thunderstorms may rotate, known as supercell storms or perhaps a tornado with hails, snow and heavy bands of rain with blustery winds. Even with or without a tornado, a severe thunderstorm can be damaging winds and life threatening event. Thunderstorms and lightning are among nature's most dazzling weather phenomena may occurs strong winds, flash flooding and hail can also accompany these killer storms can cause mayhem across Britain this weekend and into Monday night with more than 100mph winds are the risk remains below our level 1 threshold.

Edited November 24, 2012 by Storm Track

[ZONE 51]

The Storm is developing and heading towards our shores, through today the winds are going to start hitting the South and West coasts, these winds increasing through the day and becoming very strong with Gale force gusts, the first swath of severe winds first battering SW UK into the evening/night and eventually all of Southern UK being battered by Gales, the most severe of these winds affecting SE UK and up the Eastern side of UK through Saturday night and Sunday morning with the coastal areas being the hardest hit with 70-80mph damaging gusts, inland Southern UK widespread gusts of 50-60mph with a risk of 70mph gusts, these to damaging in some areas.

Northern regions could see Gales to, more particularly across from North Wales to the Wash area south seeing a risk of Gales.

The areas hardest hit from the winds from this storm are likely to be(at this stage)areas of SE England - Kent, Sussex, areas of East Anglia - Suffolk, Norfolk. Essex, The East coast up into Lincolnshire and the Humber, SW England - Devon and Cornwall. South/SW coastal areas.

Heavy and torrential rain is likely to affect many areas in the wind warning zones, this adding to the flooding problems, some areas seeing significant floods.

This rainfall could move into areas not in the wind warning zones on my map, it is a complex situation and did not cover flood risk on the same map as this could complicate things.

SE/ EA/ East coast, the strongests winds likely Saturday night into the early hours/morning Sunday.

Below is a map i have drawn up to indicate where i expect the winds to affect using model data.

ESS

Edited November 24, 2012 by ElectricSnowStorm

[Paul T]

My 4 main toughts:

-Big weather event set to happen in the next 24hrs, still time for the low to deepen slightly more than projected.

-Increasing jet over a developing Low always has some potential to spring a suprise.

-2 inches of rain will cripple many part of the south west on Saturday

-something is brewing!

Edited November 24, 2012 by Paul T

[Paul T]

somethings brewing;

[Terminal Moraine]

Yet another upgrade on the rainfall totals for the Peak District, and North Midlands generally, on the NMM 00z.

The amount for my area has increased from around 17mm on the 12z yesterday to around 40mm on the 00z. Is that it I wonder or will the 06z increase the amount still further?

[BARRY]

It's been raining here since 05:30 hours 1.7 mm has fallen already wind speed 28.3 mph barometer 1008.2 falling

[Coast]

More to come, lots more.....

[Supacell]

Met office rainfall prediction doesn't show that much rain here from this system, but a lot for already flooded SWern areas.

GFS shows some torrential rain for the SW, Wales and NW England for tonight but Monday is looking pretty bad around here with rain stalling over the North Midlands and dumping large totals. Exciting times for us weather enthusiasts but worrying times for anyone that has a home or business near to a river or areas that are flood prone.

Bear in mind too that 60-70mph winds across areas with thoroughly saturated ground has the potential to bring down numerous trees. Tonight not a good time to be travelling across southern areas.

[Coast]

SKYWARN UK SEVERE WEATHER WATCH #065

ISSUED: 1530UTC FRIDAY 23RD NOVEMBER 2012 (GJ)

SKYWARN UK HAS ISSUED A SEVERE WEATHER WATCH FOR THE FOLLOWING REGIONS:

SOUTHWEST ENGLAND WALES MIDLANDS NORTHEAST ENGLAND EAST ANGLIA SOUTHERN ENGLAND SOUTHEAST ENGLAND

IN EFFECT FROM 06Z SATURDAY 24TH UNTIL 12Z SUNDAY 25TH NOVEMBER 2012

DEEPENING LOW ORIGINATING IN THE BISCAY AREA

THERE IS A POSSIBILITY OF SEVERE WEATHER AFFECTING THE INDICATED REGIONS IN THE TIME PERIOD SPECIFIED. THREATS WITHIN THIS WATCH INCLUDE, BUT ARE NOT LIMITED TO:

HEAVY RAIN...FLASH FLOODING...RIVER FLOODING...STRONG GUSTS

DISCUSSION:

THERE IS MODERATE MODEL CONFIDENCE AND STRONG PARTNER AGENCY CONFIDENCE IN THE POSSIBILITY OF A SEVERE WEATHER RISK THROUGH THE WEEKEND. A LOW PRESSURE SYSTEM DEVELOPS AS IT APPROACHES SOUTHWEST ENGLAND, DEEPENING AS IT TRANSITS ENGLAND TO ~985MB OFF THE EAST COAST BY MIDDAY SUNDAY. THE SYSTEM IS CONFINED SPATIALLY, SO HEAVY AND OCCASIONALLY INTENSE RAINFALL WITH STRONG GUSTS CAN BE EXPECTED. GENERALLY ACCUMULATIONS MAY BE 30MM BUT EXPOSED COASTS AND HIGH GROUND OF THE SOUTHWEST MAY SEE IN EXCESS OF 50MM IN CONSECTUIVE PERIODS OF HEAVY RAIN. SOME PARTS OF THE MIDLANDS MAY SEE IN EXCESS OF 40MM DEPENDING UPON THE TRACK AND INTENSITY OF THE SYSTEM. OVERNIGHT INTO SUNDAY, AREAS NEIGHBOURING THE SOUTH COAST COULD SEE GUSTS IN EXCESS OF 60MPH, PERHAPS EXCEEDING 70MPH, WITH SIMILAR GUSTS AFFECTING THE COASTS OF NORTHEAST ENGLAND, EAST ANGLIA AND SOUTHEAST ENGLAND THROUGH SUNDAY MORNING.

DESPITE EXPECTED WEATHER CONDITIONS TRIGGERING WATCH CRITERIA, GROUND CONDITIONS AS A RESULT OF PRIOR RAINFALL AND RIVER FLOODING ACROSS SOUTHWEST ENGLAND AND THE WEST MIDLANDS WILL COMBINE TO GENERATE SERIOUSLY DISRUPTIVE FLOODING. IT IS NOT RECOMMENDED THAT SPOTTERS UNDERTAKE LENGTHY JOURNEYS FROM HOME. LOCAL REPORTS ACROSS THE WATCH AREAS FOR RAIN RATE/ACCUM, FLOODING OR WIND MAXIMUMS WOULD BE GREATLY APPRECIATED FOR POST-ANALYSIS. THIS WATCH MAY BE UPGRADED. PLEASE MONITOR WEATHER AND TRAVEL INFO AS NECESSARY.

http://www.skywarn.org.uk/current.html

[AWD]

So, what's the chance of this verifying?

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121124/06/300/h500slp.png

:p

[Bobby]

Rain has set in here and getting heavier and looks to be here until the early hours.

2 inches in places says 06z GFS, not very good.

[knightrider]

The Storm is developing and heading towards our shores, through today the winds are going to start hitting the South and West coasts, these winds increasing through the day and becoming very strong with Gale force gusts, the first swath of severe winds first battering SW UK into the evening/night and eventually all of Southern UK being battered by Gales, the most severe of these winds affecting SE UK and up the Eastern side of UK through Saturday night and Sunday morning with the coastal areas being the hardest hit with 70-80mph damaging gusts, inland Southern UK widespread gusts of 50-60mph with a risk of 70mph gusts, these to damaging in some areas.

Northern regions could see Gales to, more particularly across from North Wales to the Wash area south seeing a risk of Gales.

The areas hardest hit from the winds from this storm are likely to be(at this stage)areas of SE England - Kent, Sussex, areas of East Anglia - Suffolk, Norfolk. Essex, The East coast up into Lincolnshire and the Humber, SW England - Devon and Cornwall. South/SW coastal areas.

Heavy and torrential rain is likely to affect many areas in the wind warning zones, this adding to the flooding problems, some areas seeing significant floods.

This rainfall could move into areas not in the wind warning zones on my map, it is a complex situation and did not cover flood risk on the same map as this could complicate things.

SE/ EA/ East coast, the strongests winds likely Saturday night into the early hours/morning Sunday.

Below is a map i have drawn up to indicate where i expect the winds to affect using model data.

ESS

Ouch that storm warning is the most severe I've seen yet, it highlights 70 to 80mph across all of the South-East!

Started raining here about an hour ago, only light drizzle at the moment though.

[knightrider]

I've got a funny feeling looking at the pressure chart that the BBC / National weather forecasts have under estimated this 1 at least a little bit if not quite significantly!

[johnholmes]

So, what's the chance of this verifying?

http://cdn.nwstatic....300/h500slp.png

pretty slight over 2 weeks out I would have thought but keep that and see how each run for the same time each day shows for the same date/time?

[Snow and storms]

Looking forward to this one hitting us. Hope not to much damage!

Winds should be good here in Hastings. Does anyone remeber the focus on the rain before the 1987 storm hit? remind you of anything?

[Liam J]

Quite a strong easterly breeze picking up through the Channel as the depression begins making inroads with heavy pulses of rain into the SW & Wales making for some very worrying times for many people.

Love the map ESS, I do think the gust predictions are a little on the high side but we'll see. Generally exposed locations can expect 60mph+ gusts with the odd 65-70mph quite possible. Belgium & Holland look like taking quite a battering as the system continues to deepen as it moves into the North Sea.

Edited November 24, 2012 by Liam J

[Lynxus]

LOTS of rain between now and Monday. ( Next 42 hrs )

Obviously this isnt gospel and its going to vary slightly, but you get the idea.

[knightrider]

Looking forward to this one hitting us. Hope not to much damage!

Winds should be good here in Hastings. Does anyone remeber the focus on the rain before the 1987 storm hit? remind you of anything?

Yes indeed and also in the 1987 storm the depression suddenly deepened as it crossed the channel, so if the back edge of this low pressure tightens up before it hits land then we could all be in for an onslaught!