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Wave Depression Watch 16th/17th November - Low Risk of Intense Storm

  • 13-11-2010 7:37pm
    #1
    Closed Accounts Posts: 5,150 ✭✭✭


    Couldn't find an appropriate thread post on regarding this but latest 12z model runs are continuing to show a possible potant wave depression developing and affecting Ireland during the coming mid-week period.

    Maquiladora and M.T have already mentioned this possible development in other threads. The ECMWF/UKMO & GFS runs tonight continue to show the potential for a developing wave to the SW of Ireland on monday which may have an impact on Ireland later on.


    GFS 12z forecast for next Tues 12:00 UTC:


    134689.gif



    UKMO 12z forecast for Wed 12:00 UTC
    :

    134690.gif



    ECMWF 12z forecast for Wed 12:00 UTC:

    134691.gif



    All 3 models in agreement regarding this possiblity but postioning of the feature is not. It may well come to nothing closer the time and may bring nothing more than an average wet day over Ireland. Might be worth discussing though for better or worse as there is little else of interest on the weather front at the moment!!




    All images c/o Meteocentre


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Comments

  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    Something to keep an eye on alright DE. Models are showing better agreement on this now but I still feel there is a lot of uncertainty with the track and intensity.

    Hi-res look at the 12Z ECM :

    15oba7s.gif

    Centre of the depression at 978 right over Cork. Small core and fairly nice looking isobars. I'm sure that would bring gales to the south/southeast coasts and perhaps further inland depending on how it tracked?


    12Z GFS develops it further west, limiting the threat of strong winds to more western/northwestern coasts:

    2q8bxur.gif

    12Z NOGAPS and CMC develop it too but as a slightly weaker system and take it up through the middle of the country.



    I agree DE, worth keeping an eye on cause there isnt much else happening! Will probably turn out to be nothing special but that won't stop me dreaming of a re-run of Xmas Eve 97. :D


  • Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    The NOGAPS develops up to 60kt mean winds with this system off the south on Tuesday, which I'm sure won't happen. The EMCWF, GFS and UKMO are pretty similar in having a closed low near or over us Tuesday, but it's notable that the FAX charts (UK MET and German) don't, so the human thinking is siding against it. We'll see if they change their minds over the next day or two.


    10111700_1312.gif

    DWD (German) for Tuesday midday.
    134716.png


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    18Z GFS deepens it more but takes the track further west than the last run. I thought the track might come more in line with the ECM/UKMO but seems to be going in the other direction. :rolleyes:


  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    Indeed Su & Maq, Gerry Murphy didn't alude this either on the RTE weather tonight. :o


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora




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  • Registered Users Posts: 5,564 ✭✭✭Pangea


    Whats a wave depression and what effect has it?


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    18Z NOGAPS is further west too. Still looks windy though.


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    Pangea wrote: »
    Whats a wave depression and what effect has it?

    Its just a secondary low. Same effects : wind/rain.

    The example on this page actually looks very similar to what some of the models are showing.

    http://science.jrank.org/pages/65031/secondary-depression-%28wave-depression%29.html


  • Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    Su that chart seems to be the same the 0Z GME at 84 hours, doesn't look like 12Z models were taken into account there?

    Correct, the 12Zz run only goes to 72hrs - the 00Z run goes to 108. We'll see what they say in the morning after tonight's...

    There's still some uncertainty resulting from the complexity of the upper flow forecast around Monday. Like Carmen, this low will spawn from another larger low off the US east coast, and gets caught by a strengthening jetstreak formed late tomorrow by a blast of arctic airmass down Baffin Bay. But unlike Carmen, this jetstreak doesn't become that strong or longlasting, and splits up Monday night, with the upper trough digging slowly eastwards. I think the exact dynamics of this split are not fully resolved, and this is causing the uncertainty.

    In any case, I can't see there being enough upper forcing to cause too much of a wind event, but it remains to be seen what we get in the way of rain from it.


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    Here is the latest UKMO 72 hour FAX which does show the secondary low developing to our southwest. (The 84 hour chat hasn't been updated yet)

    2wml5as.gif

    Looks like there wasn't much adjusted there from the 12Z UKMO model run.


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  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    0Z ECM


    72 Hours
    2h3dc9w.jpg

    96 Hours
    ivwd8x.jpg


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    Looking at the other 06Z and 0Z models, there has been a very clear shift to the west on the track of this thing. Models will probably shift even further west later and right now I'd say the chances are this will end up being well out at sea. Chances of strong winds impacting us from this are falling. :(


  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    Looking at the other 06Z and 0Z models, there has been a very clear shift to the west on the track of this thing. Models will probably shift even further west later and right now I'd say the chances are this will end up being well out at sea. Chances of strong winds impacting us from this are falling. :(

    GFS 12z run keeping up this theme also, potentially some very strong winds just off the west coast but the best worst of them missing us.


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    GFS 12z run keeping up this theme also, potentially some very strong winds just off the west coast but the best worst of them missing us.

    Yep, gales just touching the very edge of the west coast but its too far away from us really. Same old story...

    12Z NAE, UKMO and GME take the same track too. :rolleyes:


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    Couple of the other models still showing something a bit more interesting though :

    12Z COMAPS

    2dt80gg.gif

    12Z CMC/GEM

    15f2csn.gif


  • Registered Users Posts: 12,778 ✭✭✭✭ninebeanrows


    These waves are notoriously difficult to forecast as exactly when the intensification takes place can alter the end position.

    Even right up until 24 hours before the event the path of these vicious wave lows can change.

    Important to continue to keep and eye on it because if it did hit land could hit with some extreme winds.


  • Registered Users Posts: 12,778 ✭✭✭✭ninebeanrows


    Runs this evening really ramping up the intensity of this low, as i said before the exact positioning will be subject to big changes.

    ECM throws it quite close to the western Seaboard.

    A really Vicious system.

    Just an unrelated warning, looking well into the ECM run may create unparalleled cold weather ramping, i advise to avoid just at the moment!:D

    ECM1-48.GIF

    ECM1-72.GIF


  • Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    This one's a tricky little fecker, you'd think there's not much there to cause this to intensify, but some of the models want to spin it up all the same. It forms in the right rear quadrant of a small little jetstreak that doesn't last through tomorrow, so for Tuesday there's not much dynamic forcing remaing from above. I think maybe the exact details of this jet may be slightly different between the models and that's what has the GFS so far west and the ECMWF more to the east..... Tomorrow will tell a lot, especially sat pics later in the day and tomorrow night.


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    12Z NOGAPS :

    21kc76f.gif

    And a closer look at the 12Z ECM :

    a0f8j.gif

    Just needs to be a bit further east...

    16ga5ab.gif

    But since there is still a good bit of uncertainty with this one, who knows eh?


  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    This evening's ECM run is also fairly close to its ensemble mean at 72hrs;

    134815.gif

    General intermodel consensus is for this feature to slip up along the west coast Tuesday night/Wednesday morning. Certainly a tight looking feature as others have said!


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  • Registered Users Posts: 5,849 ✭✭✭Storm 10


    Watched BBC weather for the week ahead and the Girl said winds would reach 60mph on Wednesday as a low pressure moves in, she also showed the chart for the weekend and it was totally at odds with Met Eireann who said the weekend would be calm and cold and BBC showed a low pressure moving up from the South. The BBC one is close to what MT is saying

    Who do we trust??


  • Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    There's some slight variation in how the ECMWF is handling the upper features in the vicinity of where this low will originate. Comparing its 1800Z forecast wv image to the actual, there is a slight difference in the location of moisture, aswell as the form and intensity of the dark strip just to the south. Will this difference be insignificant when it comes to the crunch? We'll have to wait and see.

    For a larger view of the north atlantic, click here and toggle between WV6.2 and Psuedo WV to see the actual and forecast wv images, respectively. Note how well these match in most other areas, showing that the model's on top of things there. The only discrepancy exists in the area highlighted (and in Baffin Bay, but that could be to do with imagery issues with high latitude areas and not with the model)

    134823.png

    134824.png


  • Registered Users Posts: 12,778 ✭✭✭✭ninebeanrows


    Both NAE and GFS 18z take this low further south.

    Enough to impact the west coast.

    Further deviation would bring a direct hit.

    Thanks alot for that very informative post Su.


  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly



    Thanks alot for that very informative post Su.

    +1

    Latest Hirlam has a very narrow line of 24m/s + windspeeds occurring in a tight gradient south of the low as it moves up along the coast:

    134839.png


    with some strong winds for s and e coasts as well. Will be interesting to see how later runs manage this.


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    Yeah 18Z is a slight upgrade. Charts below show highest gusts from the 18Z and 12Z over a period of 5 days.

    18Z:
    11c8h9f.gif

    12Z:
    2z54oeg.gif


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    48 hour OPC chart issued at 9pm...

    2z732i9.jpg


  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    Just a quick sum up of this morning's runs (00z). Main models this morning have this tight little low just far enough to the west for us to escape the worst effects of it. However, it may still need watching just in case as this fairly deep wave depression is forecast to be forced up against rapidly rising pressure over Scandinavia by a destabilising airmass rushing beneath it from the Atlantic, which is just one of the factors I think as to why the models are are keen to keep the isobaric gradient tight around its center as it passes close to Ireland:

    134851.png





    Whether or nay, still looks like it could be blustery/windy enough tomorrow evening as the frontal zone makes it way up over the country.


  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    Yeah I don't see any upgrade on the 0z models, there seems to be pretty good agreement now on the track. Looks like it will be wet and windy, but not stormy...(if it turns out like the models now show)

    Met Eireann is going for "strong to gale fore and gusty south to southeast winds".

    Meanwhile, the latest OPC 48 hour chart has :

    r0cvh4.jpg


  • Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    Tomorrow's system could be given the name Felice or Gundula. I'd prefer Gundula because cos it's so.....Irish sounding! :rolleyes:

    http://www.met.fu-berlin.de/adopt-a-vortex/tief/


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  • Registered Users Posts: 11,134 ✭✭✭✭maquiladora


    06Z NAE has the low a bit further south and east from 33 hours on.

    06Z GFS seems to have very little change from the 0Z over the next 48 hours.


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