Wednesday Storm (15/08):MOD WARNING #626 High Winds + Heavy Rain/Flooding Likely

ninebeanrows · 12-08-2012 07:23AM #1

We are set to move into a period of increasingly unsettled weather.

Focus turns to midweek as a low pressure system develops to our south in the Bay of Biscay and moves north over Ireland through Wednesday evening (as progged at current time).

The system has potential to dump serious rainfall amounts and is likely to be thundery. Rainfall amounts of up to 100mm in some areas look possible.

Winds will also gust to 50 or 60mph.

More to follow........

Deep Easterly · 12-08-2012 10:22AM

Slightly off topic but just discovered that Weatheronline now does 5 min radar sequence that covers this country as well which might come in very handy this week.

For some reason, the higher res Irish radar sequence still stuck on the 15 min

http://www.weatheronline.co.uk/cgi-app/radar?LANG=en&STRUCTUR=_&CONT=euro&CREG=nir

but if you copy the image URL, and simply change the actual time on it in increments of 5, you will get each of the 5 min images

EG:

http://www.weatheronline.co.uk/daten/radar/nir/2012/08/12/0900.gif

Change last number (time: 0900) to 0905

http://www.weatheronline.co.uk/daten/radar/nir/2012/08/12/0905.gif

Bit of a pain in the rump but still handy. I put together this short animation using the 5 min images that spans the period between midnight to 10am as an example.

Much smoother

but interesting to note a small jerky effect in the returns that are covered by the Shannon radar; this is even more noticeable when the animation is played at even higher speeds. Would love to know what the cause of this is.

On topic, some amount of energy in the skies here at the moment which is being transported up towards Mayo at a rapid rate.

Sierra Oscar · 12-08-2012 02:57PM

Is today's weather a warm up for what's to come? Flash flooding in Limerick at the moment, heaviest rain I have seen in a long time!

Seems that there is a lot of surface water around as it is so flooding is far more possible.

Iancar29 · 12-08-2012 04:53PM

https://www.youtube.com/watch?v=ZvCI-gNK_y4

bcmf · 12-08-2012 07:20PM

Due to sail to Cherbourg on Wed from Rosslare. Hate sailing at the calmest of times.I presume if this comes to pass the ferry will get hit by it (and the smell on the ferry will be atrociuos-most of it from me:()
So the good people of the weather forum will offer a massive downgrade on Tues eve.....WONT YIS!

leahyl · 12-08-2012 07:33PM

Snip<>

Is that for Wed Ian or for tonight?

Weylin · 12-08-2012 07:45PM

Snip<>

total balderdash..............
MT says 60mm rain ,you say 100mm,for fecks sake stop making up rubbish/scare mongering.

Sponge Bob · 12-08-2012 07:51PM

Whether 60mm or 100mm...it is still a lot of rain in a short period and worth a thread.

Redsunset · 12-08-2012 08:01PM

I have deleted a number of posts because they really added nothing to the thread.
Most were off topic and one word comments.
Please try to be more constructive in posting.

Sponge Bob · 13-08-2012 12:07AM

Looks like a stiff precipitation topup will arrive on Friday after a relatively blustery but drier thursday.

Redsunset · 13-08-2012 03:02AM

Ok lets look at this in more detail with current guidance. This is my own opinion and don't take it as gospel.

Let us first look at the coastal flooding risk

Current moon phase is a waning crescent = Good (Less high tide Height)

Strongest winds should hit south/south eastern parts come evening time and this happens to be High Tide.

Now Tidal surge is unknown but there could be a good push of water from the wind and the sea will be that bit higher anyway due to depression coming up from the south.

Conclusion
Keep an eye on any official coastal flood warnings.

Wind Strength

Now I was looking at 1987 storm development that hit southern England on October 15th and seeing if anything was similar.

It's the 975 just off the north west of Spain

And Wednesday 15th 2012

Now we see our 995 depression is much the same location however intensity at this stage is different by 20mb and that's alot. Colder polar air was making it's way into the rear of the 1987 storm and the temp difference and jet stream made it more intense.

1987 had a stronger jet stream. 220 km/h

Wednesdays 15th jet stream 170 km/h
She's still gonna pack a punch

Winds are usually strongest on south eastern quadrant of low pressure systems and this baby could hit south eastern Ireland for a short time with gusts of 45kts +

It should be a baby full of energy feeding off the warmer sea and the warm upper air before it dumps its contents on us. I think the rain part of storm could be very heavy at times and give some local flooding but push through fairly quickly for many and the winds lasting longer. Whatever happens its not going to be pleasant and I can just hear some of you already come Wednesday night, "Eh where's me Storm"

Remember this could very easy go in the bin as exact track of system will have a big say on who gets what. This is just an idea.Anyway that's my 2 pence worth.

maquiladora · 13-08-2012 08:05AM

Hi guys. I'm very busy lately and don't have much time to visit boards any more.

Just thought I'd drop into this thread to share some stuff from 0Z hi res HIRLAM model (that Met Eireann use).

At 60 hours the system looks more intense on HIRLAM than any of the global models. It has dropped 10mb in 10 hours on this model and looks to be still bombing at the 60 hour mark still well off the southwest coast.

Anyway this could all change again on the next run, just thought it was interesting.

dexter647 · 13-08-2012 08:23AM

Good to have you back maquiladora:)

Redsunset · 13-08-2012 10:30AM

A couple of posters BLATANTLY went out of their way this morning to try and troll the thread.
They were indeed very content to throw their nose up at the on thread warning.
They each received a three day ban and their posts removed.

PS
And we're only on page 1.

Redsunset · 13-08-2012 11:59AM

Ok latest model comparison time.
:eek::eek::eek::eek::eek::eek::eek::eek::eek:
Hirlam has this baby dropping 21mb from 995mb to 976mb which is almost BOMBING,:eek: (Bombogenesis = dropping 24mb or more in 24 hours)
Wed 6pm

ECM 12 NOON

GFS Wed 6pm

NOAA track

Anyway still a long way off but this baby could be short and sharp.:)

Nabber · 13-08-2012 12:11PM

The models aren't all agreeing on how deep it will be come Wednesday/Thursday.

Sponge Bob · 13-08-2012 12:16PM

Nabber wrote: »

The models aren't all agreeing on how deep it will be come Wednesday/Thursday.

Very true, and Met É are holding off issuing a specific storm warning for now. They are in a 'wet and windy' holding pattern.

I would expect a more strongly worded alert from Met É later on today.

UKMO have just issued a Yellow Alert.

http://www.metoffice.gov.uk/public/weather/warnings/?regionName=ni

Issued at: 1151 on Mon 13 Aug 2012
Valid from: 0600 on Wed 15 Aug 2012
Valid to: 2359 on Wed 15 Aug 2012
Heavy rain, accompanied by strong winds, is expected to spread north during Wednesday morning and afternoon, to affect parts of western England, much of Wales and Northern Ireland. The heaviest rain is likely to clear from the south by evening, but the strong winds may peak a little later. The public should be aware of the possibility of surface water flooding and the likelihood of difficult conditions for travel and some summer holiday pursuits.

Redsunset · 13-08-2012 12:20PM

Nabber wrote: »

The models aren't all agreeing on how deep it will be come Wednesday/Thursday.

Correct and perhaps ECM is over doing it but it's nearly always the form horse.

Deep Easterly · 13-08-2012 02:57PM

Interestingly, today is the 33rd anniversary of the infamous 'Fastnet Race' tragedy off our south coast. This storm started off as a benign wave depression in the mid-Atlantic but really exploded as it approached the SW coast during the evening of the 13th August 1979.

This depression deepened further as it moved over Ireland on the 14th giving some heavy rain in places but the strongest of the winds remained along its southern flank out to sea resulting in even more loss of life.

Sponge Bob · 13-08-2012 03:31PM

Ah sure that Fastnet storm was nothing, it had a pressure around 980hpa at its lowest .....Oh! ummmmm Ooops! :eek:

maquiladora · 13-08-2012 03:57PM

I don't have time to post pics, but just comparing the 12Z GFS with the 12Z NAE (hi res UK Met model) there is almost 20mb difference at 48 hours. GFS has it at 986 and NAE has 968, roughly the same location.

Sponge Bob · 13-08-2012 04:10PM

NAE 12z run shows the core pressure dropping from around 992 to 968 in 9 hours starting Tuesday 21z and ending Wednesday 06z.

eskimocat · 13-08-2012 04:17PM

Redsunset wrote: »

Hirlam has this baby dropping 21mb from 995mb to 976mb which is almost BOMBING,:eek: (Bombogenesis = dropping 24mb or more in 24 hours)
QUOTE]

Well! Its funny what you learn as you go along, I always thought that when ye would refer to the pressure 'bombing' that it was merely a turn of phrase, like it 'dropped like a stone', not an actual recognised term! Interesting Thanks for sharing that Redsunset.

So are we looking at 'bombing' now????

Redsunset · 13-08-2012 04:41PM

I'm saying nothing.

Sponge Bob · 13-08-2012 04:42PM

eskimocat wrote: »

Well! Its funny what you learn as you go along, I always thought that when ye would refer to the pressure 'bombing' that it was merely a turn of phrase

A Bomb Cyclone is a meteorological term dating back even to US Airforce observations around WW2 Eskimocat.

The 24mb in 24 hour rule applies to a Bomb at 60n ..ie in the Shetlands or in nearby Bergen where one of the first academic observations was written on the subject by a chap named Tor Bergeron .

Each 1mb fall in pressure in a Bomb Cyclone is a 'Bergeron' unit.

Up in Donegal the core pressure needs to fall around 23mb in 24hours while in Cork it would be de Bomb if the pressure fell around 21 or 22mb in 24 hours.

Subsequent papers revised this Bomb definition when ADJUSTED for Latitude (especially the paper below) and a Bomb at Irish Latitudes is not quite a 24mb drop in 24 hours while down at 25n the pressure need but fall 12mb in 24 hours.

http://journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281980%29108%3C1589%3ASDCOT%3E2.0.CO%3B2

As the cyclone is developing most rapidly at around 48n we could reasonably surmise that it will become a bomb if the core pressure falls by a mere 20mb in 12 hours..as is forecast by some models ....after which it will wander north to our shores.

Nabber · 13-08-2012 05:20PM

Looking at Redsunsets chart. We are heading into Hurricane force winds. Tomorrow will paint a better picture. One thing is for sure. Its going to be windy, how windy is the question.

Will Met.ie make a call on this tonight do you think?

Redsunset · 13-08-2012 05:23PM

Can't see them making a call for a good while yet.Too much uncertainty. Tomorrow should firm it up more.

Su Campu · 13-08-2012 05:24PM

It's an interesting system alright but going on the models it will have occluded and peaked before reaching us, but there is always the possibility with a bomb like this that it will take a path slightly left of the models' tracks. This might mean it is in a stronger state windwise when it reaches us, but in any case is it drawing on some rich moisture from the south and it will dump a fair bit of rain on many areas, especially windward slopes.

leahyl · 13-08-2012 05:55PM

I refuse to get too "excited" about this because most likely it will just be the usual heavy rain and a bit of wind but thanks for all the info on here - will be watching this with interest.

Apologies that my post earlier wasn't suitable for this thread - I was genuinely shocked by the charts as it looked fairly fierce - hence the :-O.

M.T. Cranium · 13-08-2012 06:04PM

Will upgrade Boards forecast wording to storm force winds 75% likely at this stage, hurricane gusts 50% likely. Concerned about potential from GEM upper air guidance more than that model's rather pedestrian looking surface low.

00z model runs may provide different solutions but have time to shape this either more intense again at 0630, or backing off, as we have stressed the word potential.

maquiladora · 13-08-2012 06:14PM

12Z HIRLAM @ 54 hours. Center of 976 on the south coast. Possible storm force winds for southeast coast and gales inland.

Quite a difference between the global models and HIRLAM, NAE. Hard to call but interesting to see how it develops.

Wednesday Storm (15/08):MOD WARNING #626 High Winds + Heavy Rain/Flooding Likely

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