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OCTOBER PATTERN INDEX (OPI) MONITORING WINTER SEASON 2014-2015


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Posted
  • Location: Hadleigh, Suffolk
  • Weather Preferences: An Alpine climate - snowy winters and sunny summers
  • Location: Hadleigh, Suffolk

    A very interesting final OPI Report, made more so because we find ourselves in the position of having the mainstream forecasters using their LRF models to predict "no real cold" for the winter and we have the OPI and SAI clearly disagreeing. A fascinating winter ahead. Good luck to the OPI Team!!

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    As ever, a great summary of how things stand from Ed and I think for the last 19, or pretty much 20 days now we have all been waiting for this point in the month and beyond. It's been rather 'fun' wat

    The discussion of the OPI index trend is understandably causing a lot of interest and (cautious) excitement amongst members after Riccardo's very interesting opening post that started this thread. The

    The monitoring page of the “October pattern index†(OPI) is presented. The OPI index  represents a analytic synthesis of the October hemispheric pattern at 500 hPa, and shows from  previous studi

    Posted Images

    Posted
  • Location: Rotherhithe, 5.8M ASL
  • Location: Rotherhithe, 5.8M ASL

    Well a great reading.... It does fill with me excitement but I remain reserved.

    Winter 14/15 looks to be Interspersed with very wet and snowy bouts, neither 2 dominating a very changeable pattern looks to be on the cards, proper winter stuff :good:

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    Posted
  • Location: Near King's Lynn 13.68m ASL
  • Weather Preferences: Hoar Frost, Snow, Misty Autumn mornings
  • Location: Near King's Lynn 13.68m ASL

    1962/63, 2009/10, 1985/86 in their analog years.... I've already put them through the composite maker...

    The other years in those composite anomalies are pretty mouth-watering too. I wonder how they selected them given the index only hindcasts to 76?

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    Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.

    The other years in those composite anomalies are pretty mouth-watering too. I wonder how they selected them given the index only hindcasts to 76?

    It does make you wonder. I suspect that any data they use in the index is available pre 76, so why not calculate the OPI for these years?

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    Posted
  • Location: Sunderland
  • Weather Preferences: cold
  • Location: Sunderland

    Certainly looking cold...

    When using uniform scales, to try and see how each compares, this is what comes out:

    (using 500mb GPH from -160mb to 160mb anomaly, 850mb temp from -4c to 4c anomaly)

     

    December

    post-12276-0-72613600-1415658979_thumb.ppost-12276-0-28607800-1415658984_thumb.p

    Slightly cooler with rather insignificant anomalies, very much in line with the reduced OPI-Dec CET correlation, though stratospheric changes in November as pointed out by Chiono and many more could be integral to seeing which way it tips (seems like either average or thereabouts, to pretty cold).

     

    January

    post-12276-0-41526700-1415658990_thumb.ppost-12276-0-19401900-1415658995_thumb.p

    Much more marked, again various other factors will probably temper or accentuate this, but the +ve GPH much stronger to the north-west, with Scandinavia in particular much colder. Showing a -NAO pattern more conductive to longer lasting cold.

     

    February

    post-12276-0-70522800-1415659000_thumb.ppost-12276-0-87577000-1415659006_thumb.p

    Far away, we can dream though...

     

     

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    Posted
  • Location: Portrush. (NI) UK
  • Location: Portrush. (NI) UK

    It does make you wonder. I suspect that any data they use in the index is available pre 76, so why not calculate the OPI for these years?

    Would it mean going through the traditional hand written charts to hind cast previous years, which would in itself be quite a lot of work.

    So the OPI team only work from Satellite era data.

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    Posted
  • Location: Weymouth, Dorset
  • Location: Weymouth, Dorset

    A very interesting final OPI Report, made more so because we find ourselves in the position of having the mainstream forecasters using their LRF models to predict "no real cold" for the winter and we have the OPI and SAI clearly disagreeing. A fascinating winter ahead. Good luck to the OPI Team!!

    No surprises in the forecast, we already knew the analogue years from the OPI and SAI figures but fair play to them, they have stuck to their guns when they could have tempered their expectations to cover themselves, in light of virtually all the long rangers signalling a mild zonal winter period.

    This makes the forthcoming winter easily the most interesting in prospect I can ever remember.

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    Posted
  • Location: Banbury
  • Location: Banbury

    No surprises in the forecast, we already knew the analogue years from the OPI and SAI figures but fair play to them, they have stuck to their guns when they could have tempered their expectations to cover themselves, in light of virtually all the long rangers signalling a mild zonal winter period.

    This makes the forthcoming winter easily the most interesting in prospect I can ever remember.

     

    Remember the Met do say " a little further out colder periods are likely" or something like that

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    Posted
  • Location: Now moved to tropical Bradford on Avon
  • Weather Preferences: Cold, snow and summer heatwaves.
  • Location: Now moved to tropical Bradford on Avon

    That forecast looks to good to be true I just get a gut feeling its going to fall flat this year though.. :sorry:

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    Posted
  • Location: New Ash green 150M / 500 FT
  • Location: New Ash green 150M / 500 FT

    Nice forecast- ties up mine together.

     

    Only frustration is no wave 1 forecast....

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    Posted
  • Location: Sunderland
  • Weather Preferences: cold
  • Location: Sunderland

    When comparing the years used on the analogue for October AO, with November AO in brackets (trivial, perhaps, but I've done it nonetheless):
    1959: -0.249 (-1.411)

    1962: -0.016 (-1.112)

    1965: 0.394 (-1.341)

    1968: -1.013 (-2.183)

    1969: 0.098 (0.326)

    1976: -0.804 (-0.087)

    1985: 1.035 (-1.218)

    2009: -1.540 (0.459)

    2014: -1.134

     

    With the AO set to trend quite low in the next few days, 68/69?

     

    Further on from this, each of the winters used by the OPI analogue have featured a sub -2 AO month:

    (DJF CET 4.6) 1959/1960: -0.042, -2.484, -2.212

    ( -0.3) 1962/1963: -0.711, -3.311, -1.721

    ( 4.4) 1965/1966: 0.163, -3.232, -1.438

    ( 3.2) 1968/1969: -0.783, -2.967, -3.114

    ( 3.3) 1969/1970: -1.856, -2.412, -1.325

    ( 3.3) 1976/1977: -2.074, -3.767, -2.010

    ( 2.9) 1985/1986: -1.948, -0.568, -2.904

    ( 2.4) 2009/2010: -3.413, -2.587, -4.266

    Dec average AO: -1.33

    Jan average AO: -2.67

    Feb average AO: -2.38

     

    With these composite years, there's no wonder the OPI f'cast is full on, each January is sub -2, with the exception of 1985/1986, which featured one of the coldest Februaries in the last 200 years. 

    Edited by Isolated Frost
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    Posted
  • Location: @scotlandwx
  • Weather Preferences: Crystal Clear High Pressure & Blue Skies
  • Location: @scotlandwx

    That's a helluva forecast - some big hitting, historical winters in those analogs, no messing around there and a very strong temp anomaly.  As S4 writes fair play to them for sticking to the forecast. I agree would be good to see the info. from the wave part of the forecast.

     

     

     

     

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    Posted
  • Location: Surrey and SW France.
  • Location: Surrey and SW France.

    Would it mean going through the traditional hand written charts to hind cast previous years, which would in itself be quite a lot of work.

    So the OPI team only work from Satellite era data.

     

    According to their paper, all work is carried out using The NCEP archives which are available on Meteociel and Wetterzentrale - that goes back a long way but only 1976-2012 is used for the study.

     

    5 In fact, the European Wetterzentrale cards were used only for the calculation of winter geopotential anomalies over Europe during the validation / analysis of the results (see Section 4).

    6 As explained in the previous section, the angular parameter φ describing the inclination of the average monthly ottobrino, is obtained as the simple average of the 31 daily axes relative to just 31 days comprising the month of October. Therefore, the calculation method implemented in the software Telemappa NG, has as its main aim is to get the daily axis of the VP, from the single-day hemispheric Meteociel discharged from the historical archives NCEP.

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    Posted
  • Location: Ireland
  • Location: Ireland

    The other years in those composite anomalies are pretty mouth-watering too. I wonder how they selected them given the index only hindcasts to 76?

    The composite anomalies are for winters with an AO of -1.5 or lower. Since the OPI figure is -2.1 they therefore expect a strongly negative -AO winter (below -1.5) since this is what they say the OPI correlates closely to.

    Edited by radiohead
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    An intriguing forecast. Such a large negative height anomaly.... how many winters/winter months in the past have had such a large negative height anomaly and also been notably colder than average? The height anomaly would also suggest wetter than average, also how many wetter than average winters/winter months have had also been cold?


    Forecast looks colder than average and wet/unsettled, especially for the S.

     

    Anyway, we'll see what reality serves up!

    Edited by Bobby
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    Posted
  • Location: Inbhir Nis / Inverness - 636 ft asl
  • Weather Preferences: Freezing fog, frost, snow, sunshine.
  • Location: Inbhir Nis / Inverness - 636 ft asl

    An intriguing forecast. Such a large negative height anomaly.... how many winters/winter months in the past have had such a large negative height anomaly and also been notably colder than average? The forecast would also suggest wetter than average, also how many wetter than average winters/winter months have had also been cold?

    Forecast looks colder than average and wet/unsettled, especially for the S.

     

    Anyway, we'll see what reality serves up!

    1947 must've been reasonably 'wet' to produce so much snow?

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    Posted
  • Location: Ireland
  • Location: Ireland

    An intriguing forecast. Such a large negative height anomaly.... how many winters/winter months in the past have had such a large negative height anomaly and also been notably colder than average? The forecast would also suggest wetter than average, also how many wetter than average winters/winter months have had also been cold?

    Forecast looks colder than average and wet/unsettled, especially for the S.

     

    Anyway, we'll see what reality serves up!

    It could also mean snowfests.

    A southerly tracking jet battling with cold air...

    Mouthwatering potential.

    Lets hope they are right!

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    Posted
  • Location: Exile from Argyll
  • Location: Exile from Argyll

    Think of the past winter 500mb anomaly where we saw all the very cold air out west over the Atlantic....

     

    r4f3gKd.gif

     

    ....push that pattern south and eastwards, with a wind from the east rather than sea track modified returning polar maritime air.

     

    We can actually see signs of this beginning in some of the recent model runs,

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    No disrespect to anyone but this type of post makes me chuckle. Personally I'm inclined to side with the OPI teams hard work, experience and scientific methodology over anyone's 'gut feeling'.

    Won't be until March/April before we really know who is right or wrong but until then its shaping up to be a fascinating winter either way.

     

    More importantly, if someone's gut feeling proves to be correct over someone else's scientific work, it is still the scientific work that has won and deserves the credit. :-)

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    Posted
  • Location: Coatbridge, North Lanarkshire (this lockdown) Freuchie, Fife (normally)
  • Weather Preferences: cold and snowy in winter, a good mix of weather the rest of the time
  • Location: Coatbridge, North Lanarkshire (this lockdown) Freuchie, Fife (normally)

    RE the low height anomaly, that's perfectly normal - usually it's perhaps a few degrees further south in the coldest winters but given the increased likelihood that less cold incursions are likely to be in the form of uber zonality rather than blocking around or to the south (and that also explains the precipitation being above average)

    While many of the coldest winters have generally been drier than average too it certainly isn't difficult to find recent cold winters with rainfall around or above average - 09/10 for example saw above average rainfall for eastern areas and for the south and southeast of England in particular, 2012/13 was wetter than average almost everywhere and all the cold winters at the back end of the 70s (77,78 and 79) along with 68/69 and 69/70 saw rainfall around or above average for England and Wales. However, I would expect below average rainfall for the NW of Scotland in particular if the OPI setup comes off - none of the years I've listed and none of the anomaly years have anything other than drier than average conditions for the far northwest, with the jet generally tracking over or to the south of England.

    Edited by LomondSnowstorm
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    Posted
  • Location: Penkridge
  • Weather Preferences: Virgins
  • Location: Penkridge

    1947 was wet, with many snow events on just the right side of the sweet spot to deliver snow instead of rain.

    There were plenty of thaws too.

    I'll take 47 over 63 all day long, one produced wonder, the other was just plain dangerous.

    Edited by Skyraker
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    Posted
  • Location: Hindolveston North Norfolk 68m asl
  • Weather Preferences: Sunny Warm summers Cold Frosty winters
  • Location: Hindolveston North Norfolk 68m asl

    Agreed this really is shaping up to be a very interesting winter season with the OPI and SAI strongly pointing to a very -AO winter and totally at odds with the main LRF models and Meto forecast, I really hope this forecast works out for the team.

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    Posted
  • Location: Bedford, 30m asl
  • Location: Bedford, 30m asl

    The only caveat I would add is that I can't make out whether the analogue provided is their actual forecast, or whether it is just highlighting what happens in deeply negative AO years - I suspect the latter

    Of course either way with their expectation of a negative AO it bodes well, but I wouldn't be necessarily taking the composite charts at absolute face value.

    From their text it looks as though they certainly expect it to be below average overall in NW Europe, but not necessarily severely so.

    Still great to see a forecast from them and certainly what many of us were hoping for :)

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