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len

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Posts posted by len

    Model Output Discussion - 15th March onwards

    in Forecast Model Discussion

    Posted · Edited by len

    38 minutes ago, Scorcher said:

    That's an amazing map thinking back to only a few years ago when we had the cold blob in the North Atlantic- it's the opposite situation now.

    I recall back then that the SSTs off the Eastern Seaboard of the US were anomalously warm rather than cold as they are now.

    Incredible to see some of the biggest warm anomalies globally being around the UK.

    I visualise the Gulfstream off the Eastern US Seaborad like a wandering, thrashing tail of warm water.
    The average temperature of the Ocean there blurs out these omnipresent wanderings.
    So,....... where the tail of warm water currently is- must always be anomalously warm relative to the surrounding water ....
    And the surrounding water must always be anomalously cool because its average includes times when it is the warm tail.
    The warm/cool streaks are always there when I look. It just shows you where the warm tail (& Labrador cool tail) is positioned relative to an average of positions. But that part of the Ocean never has a broad, flat average signal


     

    • Like 2

    Model Output Discussion - New Year and Beyond

    in Forecast Model Discussion

    Posted

    2 hours ago, KTtom said:

    As its quiet, any chance someone could give a laymans explanation of this chart, it baffles me! Obviously nothing to do with pressure ?

    I believe this is the "spread", or variation, in the perturbations ..... of sea-level pressure.
    So in this instance the yellow area NE of UK  is highly uncertain. ie. the solutions here are highly variable. It could be High or Low pressure perhaps. A straw to clutch.
     

    • Like 3
    • Thanks 1
    • Insightful 1

    Model Output Discussion - Happy New Year!

    in Forecast Model Discussion

    Posted

    48 minutes ago, Mattwolves said:

    Pretty amazing, any models showing cold should not be taken seriously!! But if they are showing mild.. Then it's bound to be right! Had to have a little laugh regarding those EC 46 weeklies as well, 5 weeks of mild.... This time last year, they were showing 5 weeks of cold!! Then you read the Exeter update who just about mention every weather type going for the next few weeks, and you kind of draw to the conclusion off.... Does anybody actually know! Some deep FI cold building out East on some of those 12z ensembles... Let the cold build and the snow will follow..

    gens-11-0-384.png

    gens-12-0-348.png

    gens-14-0-384.png

    gens-19-0-384.png

    I understand why you might like to regularly post cherry-picked perturbations, but inexperienced lurkers here may not qute understand that you can ALWAYS find whatever you want somewhere amongst the perturbations.

    Instead of cherry-picking only what you wish for, why not try random-selection, or offset your choice-morsels with the "worst perturbations"?

    • Like 8

    Model output discussion - summer rolls on

    in Forecast Model Discussion

    Posted

    23 minutes ago, Mike Poole said:

    To add to MWB response ^, I've put most of this through Google translate a while back and have come to the following conclusions, anyone please correct me if I've got details wrong. 

    A cluster is a group of runs that meteorologists think are similar for forecasts several days out.

    Example chart:

    image.thumb.jpg.a76ff470cb5c292f4bcd18d992fa7874.jpg

    The colours show geopotential height anomaly at 500mbar (Z500) against 1981-2010 data, a question remains in my mind whether this changes with seasons?, contours show actual Z500 values for one run for each cluster (of runs that are deemed by the guys at ECMWF to be similar).

    Top left is the time of the run, and the time of the forecast.

    Top right, the flokkunigluggy thing is the time frames that this particular cluster is valid, before or after there may be more or fewer clusters, depending on what the models are saying.

    Then the 6 cluster diagrams, in order of decreasing likelihood, these break the 51 ECM ensembles into groups that behave the same way as uncertainty increases as forecast time increases. The numbers above each chart state the number of runs in each cluster, and the percentage, and then the Fulltr. This means 'delegate' so this is the number of the ensemble run which best reflects the cluster as a whole, so it's not an average, it's one run that best fits the defined cluster in the interpretation of ECMWF. 

    Finally, the bottom bit depicts four synoptic patterns relevant to Iceland, and fortunately for us also!,  and gives their likelihood from climatology, colour coded as follows:

    Blue - Positive North Atlantic Oscillation (NAO)

    Green - Negative NAO

    Red - (Scandi) Blocking

    Purple - (Atlantic) Ridge

    These colours also border the cluster plots above, basically saying (because the plots themselves cover such a small area of the globe) what the wider picture for each cluster is. 

    Hope that helps!

     

    Thanks to both you & MWB.

    Much clearer. I get it about 80% now! Hope it helps others.

    • Like 1

    Model output discussion - summer rolls on

    in Forecast Model Discussion

    Posted

    7 hours ago, Man With Beard said:

    But look at how this Mid-Atlantic ridge is expected to develop. Compare D9, D11 and D13. Watch how the oranges /reds work their way, on the majority of clusters, from left to right. This suggests to me a good chance of a ridge passing through the UK at a higher latitude than in the past 10 days, eventually turning the flow more southerly. 

    ec-ens_nat_z500scenarios_2018081512_216.

    ec-ens_nat_z500scenarios_2018081512_264.

    ec-ens_nat_z500scenarios_2018081512_300.

    Thanks for posting these regularly MWB.

    They look really interesting. Trouble is, (my Icelandic being shakey n'all) I haven't a clue what they mean MWB?

    I've been hoping someone else would ask.....but obviously they all read Icelandic.

    Any chance of a rundown please?

    Len

    • Like 1

    Model Output Discussion - 1st July Onwards 18z--->

    in Forecast Model Discussion

    Posted · Edited by len

    I'm not sure how accurate the JMA composites are but taken at face value, they would indicate a very warm region 1+2 in August should translate to the exact opposite of what we see being modelled for the UK.

     

    GXTOCFS.png

     

    http://ds.data.jma.go.jp/gmd/tcc/tcc/products/clisys/newoceanindex/index.html

     

    Hi Nouska

     

    That red (as I understand it, having visited the page) might mean a high "positive circulation anomaly"

    Which might mean "unusually vigorous altantic flow"???

    Therefore depressingly confirming more of what we've got

    This is a layman's reading of it.....and I don't know what  "element z500latlon" means?

    Can someone clarify please?

     

    Len

    • Like 1

    Model Output Discussion - 3rd May Onwards 00z--->

    in Forecast Model Discussion

    Posted

    The Azores ridge is unable to encourage a euro height rise

    we seem to be stuck in this pattern and hope that the less settled spells are the ones which are short lived.

    No likelihood of late spring/early summer temps.

    Of course, the old adage that stuff equals itself out could promise some very plumey summer conditions

    .

    Seems to be the exact opposite of the idea of the North Pacific warm "blob" causing a High.

    We have a stubborn Mid-Atlantic cold SST anomaly. And the Mid-Atlantic High seems unable to leave it?

    • Like 1

    'Warm blob' in Pacific Ocean linked to weird weather across the US

    in Weather Around The World

    Posted

    Posted 19 April 2015 - 20:56

    nicknacknoo, on 19 Apr 2015 - 14:14, said:snapback.png

     

    From John Holmes

     

    your answer is in the link K provided with an interview with a BBC weatherman-good stuff

     

    Perhaps someone could explain how a warm blob gives rise to hp....... I would have thought the reverse to be true, with the air being heated more than normal and rising?

     

    your answer is in the link K provided with an interview with a BBC weatherman-good stuff"

     

    --------------------------------

    Sorry John, but I've listened to it 3 times and it doesn't explain at all.

    He says "the area of warm water warms the air above it" . He doesn't say why this encourages High Pressure.... rather than, (as I & nicknacknoo expect) LOW Pressure!

    I can see why the JetStream ridge that is there could cause the warm water; but, to my understanding, the warm water should be a negative feedback for High Pressure not a reinforcing/causative factor.

    Can somebody explain please?

    Personally I think we have a JS ridge for other, stonger factors and the warm blob is a side-effect?

    Model Output Discussion 31/05/14 onwards.

    in Forecast Model Discussion

    Posted

    I'm not either of your required helpers but here's what phase one looks like for July. The link is here.

     

    http://www.americanwx.com/raleighwx/MJO/MJO.html

     

    Posted Image

    Whether the phase of MJO has any bearing on the weeks ahead is IMO moot while there is such disagreement between

    the main model suite.

     

    Posted Image

     

    Hi Gael

    Could you please tell me how to find the last image above. (With the different forecast plots on one image)

    Have been searching been searching NOAA MJO products in vain!

    Thanks

    New Met Website; Where are the longer-term text forecasts?

    in Spring Weather Discussion

    Posted

    Hi len,

     

    On the home page click on "weather" in the top left, Then click "UK outlook". on this page..http://www.metoffice.gov.uk/public/weather

     

    Thanks.....but this does not work for me

     

    (1)Clicking on the word "Weather" does nothing!

    (2)Clicking on the words "UK forecast" underneath (Did you mean this?) produces a "UK page" that is supervened (within a fraction of a second) by my location 5-day forecast

     

    Any more ideas?

     

    Anyone else find it on the new site???

     

    Len

    HELP! RainToday stopped working?

    in Spring Weather Discussion

    Posted

    Hello,

     

    About 2 weeks ago my Raintoday link ceased to show the echoes. I just have a blank map!

     

    If I do a fresh search for RainToday it still comes up with a blank map???

     

    On my wifes laptop it still works! We Both use Firefox.

     

    I see someone else on the web had this problem....but no solution.

     

    Any Help please?

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