Storm Ciaran :Associated weather effects, primarily flooding risks, Advisory 29th -02 Nov 2023

The potential for this storm to swerve north is probably small given that its deepening is due to interaction with a polar vortex dropping southeast towards Ireland to capture the low around 48N 15W Wed night. The uncertainty lies in how much rain will be generated over land in south coast counties; we may have a more precise idea on that later today or early Wednesday, but potential is there for 30-60 mm rainfalls.

As to impacts on Britain and Channel regions, I posted this on net-weather recently:

This storm is going to slam the south coast and inland south with very strong wind gusts, the central pressure on 00z GFS run stays as before at a record low 949 mbs, and the gradient over the Channel would support 160-180 km/hr gusts. I realize the south coast is quite rugged and only has a few low lying coastal areas with developed land to receive a storm surge of 3-5 meters but where that is the case, total evacuation should be carried out on Wednesday if this monster is still on course. Expect widespread wind damage from southwest storm force winds 120-160 km/hr (and battering coastal waves, surge) in all areas south of the low's track, damage zone could include inland areas as far as Salisbury, Basingstoke, Croydon and all of Kent. I would expect results to show a gradient across greater London. When the low begins to fill around Berkshire later on Thursday, winds will spread out a bit more inland and drop below extreme gust levels into the 90-130 km/hr range for larger portions of the southeast and east. The more extreme gusts will move on into North Sea and Benelux, northern France when this slight moderation takes place, but once a band of very strong winds is created, it takes time for its momentum to dissipate.

South Wales to Severn valley could see the worst of rain-produced flooding, 40-60 mm could fall on already saturated watersheds. Closer to 20-40 mm likely further east. 

A contributing factor giving this extreme potential is the warm surrounding sea temperatures, 16-17 C in Channel. When a very deep upper low spirals down to capture this approaching storm, it will deepen explosively south of Ireland and be at full force approaching southern England around 0300h Thursday.

A lady called and asked if a hurricane was coming and I said yes, it defoe is. This of course is not a tropical storm but it will produce conditions similar to a cat-1 hurricane all along the south coast and could be close to a cat-2 hurricane over marine areas and I would be concerned about Channel Islands and exposed areas of n.w. to n.e. France also.

The low following along on Saturday is also quite deep, currently looks rather subdued for wind potential but there are ways this second low could intensify rapidly too; it will certainly be a fairly significant rain producer on top of all the recent and near future rainfalls expected. 

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(for Irish interests, second low is also of concern, another very deep low capable of intensifying and bringing further heavy rainfalls to south coast of Ireland.)

This probably won't be the last stormy interval of our approaching extended winter season, with various factors pointing to strong chances of jet stream being near Ireland a lot of the time. I was comparing Ciaran to the Defoe storm of 1703 which brought devastation to south of England (it occurred 26-27 Nov in O.S. or 7-8 Dec in Gregorian calendar, at a new moon. Track details are surmised from damage and a very few barometric readings, lowest of which was in east central England and around 950 mbs; current guidance brings Ciaran in at 949 mbs in southwest England Thursday around 0600h. It's one powerful looking gradient wind over the south coast of England by about noon. Will be interesting to see if these details verify or the actual Ciaran shows up a bit less intense (it probably can't be more intense, but I suppose anything is possible).

Yes unless we get a last minute nudge North this thing is a damp squib. Nothing on the horizon either other than showery conditions. A sneeze would cause flooding in Cork right now so it possibly will still cause that

Terribly sorry for your troubles. There are others probably better equipped than me to answer this on here but there's still some level of uncertainty in the outcome for the next few days.

The general outlook for the Cork area right now is wet and breezy this afternoon/evening, clearing into the morning. Then from tomorrow night into Thursday it's looking wet and blustery but nothing too severe with the rain clearing Thursday and staying dry Friday. High tides, river levels and saturated land may still result in some local flooding though, just to be aware. But this is all subject to change in the next 2 days, a slight shift in the storm's track could change that outlook considerably so I'd recommend you keep an eye on Met Eireann for updates.

Best to you and your family.

The downgrades continue on the 06z with ICON and GFS now bringing rainfall more in line with other models. Winds on Wednesday evening for parts of the west coast topping off at 90km/h looking like the strongest of the lot.

Advisory for Ireland update

On Tuesday and Wednesday, there will be heavy showers or longer spells of rain at times with flooding likely in places, as soils are saturated and river levels are high. Squally showers on Wednesday morning will be accompanied by very gusty conditions.

Later Wednesday and on Thursday, further rainfall associated with Storm Ciarán may lead to flooding. It is likely that the heaviest rain will be in southern and eastern coastal counties.

Additional Impacts:

Poor visibility

Difficult/dangerous driving conditions

This storm still very much in its infancy.

Nothing set in stone as to where will get a direct hit.

Could go about 100km N or S of latest guidance.

Be intesting to see impact and which model is most accurate.

Agree, and Southern England doesn't get the 120/130KM gusts we see in Southern Ireland probably once a year either. One of the reasons they got it so bad in 1987 is that they don't get these frequents storms that knock the weakest trees every so often. Also, the leaves being still on a lot of trees is a problem (if that forecast panned out).

Latest from ALAN at Carlowweather

As bearla:

Storm CIARAN will approach the north-western regions of France during the night from Wednesday to Thursday and will continue to rage during the morning of Thursday.

On the coast of Finistère, Côtes d'Armor and Cotentin, peaks of 150 to 170 km/h could be recorded. On the Morbihan coast and locally in Loire-Atlantique, gusts could reach 130 to 150 km/h.

Inland, gusts will reach 110 to 130 km/h in Brittany and Cotentin, and even higher in Finistère. They will reach 100 to 110 km/h, or locally a little more, from Vendée in Pays de Loire to Haute-Normandie and to the west of Hauts de France.

At the same time, a wave submergence phenomenon, associated with very strong waves, is expected.

The values ​​and location of the strongest wind gusts will be further refined by tomorrow evening.

I posted that yesterday crazy wind speeds expected

Indeed it could become a system that catches Met Eireann out!! Almost all the other models have very heavy rain just off the coast, very little room for error..

Ecm, red torrential spells just off South coast

The deep dive forecast is touting gusts of about 85mph(140kmh) over south Uk if they get a direct hit. The lowest November pressure on record is likely for South UK at around 950hPa , the previous record low being 959hPa. A Red Alert is likely for North France.Needless to say its a non event for Ireland, we dodged a bullet

I always look forward to the deep dive of a Tuesday too and the 10 day trend on a Wednesday!

Even The Wash Post is running something on this ...

https://archive.ph/fkh5S