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Storm Francis - 24th/25th August 2020

  • 22-08-2020 1:34pm
    #1
    Moderators, Science, Health & Environment Moderators Posts: 10,468 Mod ✭✭✭✭ Meteorite58


    Thought it might be timely to begin a thread about the next system approaching later Monday 24th into Tues 25th. Not sure if it will be giving a storm name , it is up to UK Met to call this one and it might just fall under the criteria for naming it.
    Anyway we can keep an eye on it and see how it progresses.

    ECM, UKMO, ARPEGE and GFS all quite well grouped in track and strength at this early stage but there is obviously variances in where the strongest winds will be. Models in the last couple of runs show the track of the system more crossing central Ireland keeping the strongest winds in the SW and along Southern coasts. The further S the system the more it will take the strongest winds offshore and like wise the further N it tracks the stronger the winds inland. It may be that a large area of Ireland does not get any notable winds from this.

    Rain wise looks heavy especially in the W and along S and SE coasts.

    Los of instability could lead to some vigorous thunderstorms from early morning moving up through the country from the SW I reckon.

    Just to Note that ICON has given the system a very flabby look on its latest run and not showing any significant winds, big departure from the last run and this might be an outlier.

    The GFS is probably a fair representation of the models in general for the moment anyway if perhaps a bit stronger.



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Comments

  • Registered Users Posts: 8,202 ✭✭✭ Gaoth Laidir


    The 12Z analysis just now shows where Tuesday's system is originating. An area of high theta-e, under an increasing jetstream, which will reach around 270 kph at 200 hPa tomorrow. A lot of scope for changes in how the deepening surface low phases with this jet later tomorrow and during Monday, so no point looking at specifics for now, but at least it's more of a typical baroclinic storm, rather than of post-tropical origin.

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  • Registered Users Posts: 9,183 ✭✭✭ sdanseo


    Looks awesome in terms of its symmetry and proportions in size to Ireland, giving it a tropical-like appearance and structure. Parts of the country would experience a few different types of weather in quick succession and some would see the eye pass over with almost no weather to speak of in the lull, more similar to a tropical storm than a European windstorm with their ill defined centres.

    Impressive on a map and dramatic looking for the likes of IWC but in terms of windspeed a low-grade tropical storm for now.

    Tropical systems of a lower apparent strength can still pack a punch compared to what we're used to, (others will be surely able to expand on that and the reasons why I hope?) so will be a very interesting one to follow nonetheless.


  • Registered Users Posts: 6,034 ✭✭✭ Oneiric 3


    Fairly reasonable agreement on the 06z En suite that the south would be at the higher risk of seeing the strongest of any winds from this system, but early days yet.

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    New Moon



  • Registered Users Posts: 9,183 ✭✭✭ sdanseo


    I keep being stuck by the more compact / cyclonic appearance of this and also Ellen. Just more visually impressive.

    12Z ECM not convinced of anything more than perhaps 100km/h gusts.
    UKMO has the core of the wind well out to sea, albeit slightly stronger.
    6Z GFS showing a stronger system.

    All looks benign in comparison to early Ellen charts but also slower moving with larger areas of the strongest winds perhaps lasting 6 to 8 hrs in places.

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  • Moderators, Science, Health & Environment Moderators Posts: 10,468 Mod ✭✭✭✭ Meteorite58


    Again the GFS ECM and ARPEGE sre fairly well grouped. UKMO and ICON taking a lower track through the SW to the SE and hence keeping the stronger winds off shore.



    I think the main factor showing up atm is the rainfall amounts, can see the models showing large amounts falling in 24 hrs, between 20 and 35m widespread and up to 50 mm in places possible. I wouldn't take the areas being shown as definite's, just an indication of possible heavy rain leading to spot flooding or more localised flooding.

    Still early days and has been discussed, modelling currently proving a bit more tricky as less data available due to less marine and air traffic.



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  • Registered Users Posts: 30,554 ✭✭✭✭ Graces7


    Thank you. Just read re next Tuesday and already covered!


  • Registered Users Posts: 8,202 ✭✭✭ Gaoth Laidir


    The UKMO have it as a fast-moving system, with its centre passing right over the centre of Ireland. It won't just affect Ireland, however, so it will be a race to see which country names it first. Could be us, the UK or Netherlands, but in any case it would be Francis.

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  • Registered Users Posts: 8,202 ✭✭✭ Gaoth Laidir


    Analysis at 7 am. The low is not developing as quickly as forecast this time yesterday. Still just a frontal wave at around 42N 45W.

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    Forecast yesterday

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  • Registered Users Posts: 2,384 ✭✭✭ JanuarySnowstor


    Precipitation looks very heavy especially for Western and Northwestern areas.
    Not so sure about the wind, looks like yellow levels for much of the country with orange levels in Southern coastal parts.
    Certainly one to keep an eye on


  • Registered Users Posts: 8,202 ✭✭✭ Gaoth Laidir




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  • Registered Users Posts: 1,258 ✭✭✭ JackieChang


    Wind's picking up now.


  • Registered Users Posts: 2,384 ✭✭✭ JanuarySnowstor


    JMA looking quite potent this morning
    Only a matter of time before this one is named.
    Yellow rainfall warning most probable!
    An orange wind warning is also possible though orange seems to be the max for this one


  • Registered Users Posts: 2,384 ✭✭✭ JanuarySnowstor


    http://www.meteociel.fr/modeles/jma/runs/2020082306/J48-21.GIF?23-6

    Latest 06z Jma nudging it further North
    Severe enough so soon after Ellen with a storm force gradient in the southwest


  • Moderators, Science, Health & Environment Moderators Posts: 10,468 Mod ✭✭✭✭ Meteorite58


    Looking quite windy now for early Tuesday across the southern half of the country and more so in the SW and S coasts. All areas look to be a bit windy at some stage, parts of the Northern half of the country will experience calm conditions as the center of the Low passes over and turn windy after. Very heavy rainfall and possibly thundery as the initial fronts go through. ECM, ARPEGE, EURO 4 on a slightly more Northerly track than GFS, ICON but only just.

    Would tend to side with ARPEGE for the moment as looking like the probable winds that we could get and an idea of rainfall accumulations. A bit further S will reduce the winds a bit.

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  • Registered Users Posts: 8,715 ✭✭✭ igCorcaigh


    Yellow wind and rain warnings issued.


  • Registered Users Posts: 905 ✭✭✭ Silver-Tiger


    Earlier than usual for these? Would they just be too get people's attention with the possibility that upgrades may come?


  • Registered Users Posts: 8,715 ✭✭✭ igCorcaigh


    Earlier than usual for these? Would they just be too get people's attention with the possibility that upgrades may come?

    Sufficient level of confidence in yellow conditions? Might upgrade to orange.


  • Registered Users Posts: 3,442 ✭✭✭ endainoz


    Earlier than usual for these? Would they just be too get people's attention with the possibility that upgrades may come?

    Possibly, bit I'd be more afraid this won't be needed at all as it will be seen as not as powerful as the last one. Considering the atrocious amount of rain forecast combined with what's fallen already, many trees could be under pressure.


  • Registered Users Posts: 7,985 ✭✭✭ brevity


    My two days “holidays” in Killarney should be fun...


  • Registered Users Posts: 611 ✭✭✭ TTLF


    going to Galway during this, I'm actually pretty excited to see what happens. Fun times ahead.


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  • Registered Users Posts: 8,202 ✭✭✭ Gaoth Laidir


    12Z analysis, showing the 1011-hPa low around half way between New Foundland and the Azores. It's currently underneath the cloud head of a 270-kph jet.

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  • Registered Users Posts: 9,393 ✭✭✭ Oscar Bravo


    Latest Met Eireann warnings

    Status Yellow - Wind warning for Munster and Wexford

    It will become very windy on Tuesday as strong southwest winds veer westerly with widespread mean speeds between 50 and 65km/h and gusts between 90 and 110km/h, higher in coastal areas.

    Valid: 06:00 Tuesday 25/08/2020 to 19:00 Tuesday

    Status Yellow - Rainfall warning for Connacht, Donegal, Cork, Kerry and Waterford

    Intense rainfall is expected at times Monday night and on Tuesday. Falls of 30 to 50mm are expected with surface flooding.

    This rainfall will further elevate river levels and may result in river flooding also.

    Valid: 00:00 Tuesday 25/08/2020 to 23:59 Tuesday 25/08/2020


  • Registered Users Posts: 2,384 ✭✭✭ JanuarySnowstor


    https://modeles.meteociel.fr/modeles/icon/gruns/2020082312/icon-0-45.png?23-12

    Icon is first out the blocks this evening and it keeps the low pressure quite flabby. No wind event here but of course it got Ellen wrong also!


  • Registered Users Posts: 2,384 ✭✭✭ JanuarySnowstor


    https://modeles.meteociel.fr/modeles/gfs/runs/2020082312/gfs-0-48.png?12
    12z Gfs, slightly tighter gradient across the South!
    Orange territory for wind!


  • Registered Users Posts: 155 ✭✭ watlantic


    Certainly an interesting Monday night/Tuesday morning ahead. The rain and T-storm potential looks quite dramatic on the ECMWF model run, particularly for the west. GFS has the central pressure a bit lower and the storm's arrival a bit earlier, but overall there's good model consensus. Bft 8 to 9 (possibly stronger gusts locally)winds seem less of a threat this time, but significant amounts of precipitation could be dumped in places in a relatively short time frame.


  • Registered Users Posts: 8,202 ✭✭✭ Gaoth Laidir


    The latest UKMO fax for 12Z tomorrow has the low 4 hPa higher than the 00Z forecast run had it, 998 vs 994 hPa. Positionwise a hair further east.

    Latest forecast cycle

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    00Z forecast cycle

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  • Registered Users Posts: 2,384 ✭✭✭ JanuarySnowstor


    http://modeles.meteociel.fr/modeles/gem/runs/2020082312/gem-0-48.png?12
    Gem similar to gfs, tight gradient across the South!


  • Registered Users Posts: 9,183 ✭✭✭ sdanseo


    GFS much of the same really. Wind field a bit larger and further south. No orange level wind over land.

    Fine margins though, 25km/h higher is red territory which of course is more a failing of the absolutely ridiculous warning criteria than anything meaningful.

    Bear in mind at this range in advance of Ellen one model (ECM) was calling for 202km/h in around the same location.

    Rainfall though is a different story. Much of Galway and Mayo well into orange warning territory >50mm/24h.


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  • Registered Users Posts: 2,384 ✭✭✭ JanuarySnowstor


    http://www.meteociel.fr/modeles/jma/runs/2020082312/J42-21.GIF?23-12
    This evenings Jma not for off a full blown storm.
    Nudges the system further North than the others bringing more of the country into orange category.
    Met Eireann will likely name this system later this evening


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  • Registered Users Posts: 664 ✭✭✭ Tazio


    http://modeles.meteociel.fr/modeles/gem/runs/2020082312/gem-0-48.png?12
    Gem similar to gfs, tight gradient across the South!

    Yea saw that too..it's been hinting on and off for a while at another Kerry / Cork storm again . Great


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