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frosty ground

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Posts posted by frosty ground

    North West England Regional Discussion Thread 15/1/2018 onwards

    in Regional

    Posted

    3 minutes ago, karyo said:

    Like I said the warmer seas are fueling the shortwaves so they gain more strength. The shortwave that the models picked up a few days ago is tonight's full blown low. It interrupts our cold air. Also, it has made the Atlantic pattern flatter where a few days ago a ridge looked like was going to develop. 

    How can a warmer world and hence warmer oceans not affect our winters? Do you think our little island is an exception to the trend? 

    Finally, nobody said there won't be any cold winters again so I don't know where you got that from? They are becoming a rarity but they will still happen.

    The ridge failing has nothing to do with tonight low, in fact there where a few runs with the low and a ridge still followed.

     

    Model output discussion - mid-winter

    in Forecast Model Discussion

    Posted

    37 minutes ago, Johnp said:

    Can we put to bed now the notion of the stratosphere forecasts being much more accurate? 

    At the ens of the day (GFS for example) forecasts are all intrinsically related to the same nwp model runs and therefore prone to the same swings and flaws.

    I think its more down to people not understanding them, they probably should be banned from this thread and left to the technical thread.

    North West England Regional Discussion Thread 15/1/2018 onwards

    in Regional

    Posted

    Just now, karyo said:

    Whether they are the symptom or the cause the result is the same. Sea temperatures are rising, air temperatures are rising, sea ice is reducing and the days of snow cover are plummeting! 

    You said increased sea temperatures are creating shortwave..... (they are not) Short wave are created by two different air masses meeting usually one advocating over the other.
    Short waves are not stopping blocks from forming, they are not redirecting the Jet.
    The world is getting warmer that much is true, is this affecting our winters? who knows, but the UK has had spells of warmer and colder winters in the past and even with the background warming the same will still be true.
     

    North West England Regional Discussion Thread 15/1/2018 onwards

    in Regional

    Posted

    13 minutes ago, karyo said:

    Warmer seas give more fuel to shortwaves in the expense of northern blocking. The difference is even more pronounced on areas that used to be covered by ice but the ice has gone. Why do you think the blocking that models often show gets watered down or disappears completely as we approach T0?

    Why do people that that short wave, feature low down in the atmosphere are capable of derailing upper atmosphere blocks?

    The shortwave spoilers (as Nick in the MO thread calls them) are symptoms not the cause.


     

    North West England Regional Discussion Thread 15/1/2018 onwards

    in Regional

    Posted

    7 minutes ago, karyo said:

    Well yes, things always change so that the cold uppers get interrupted. This usually happens because the models pick up a shortwave which blocks the cold air. Just like the one that will affect us tonight. The plethora of shortwaves is another symptom of warmer seas.

    Shortwave have always existed and are created by two different air masses advances either CAA over Warm are or WAA over Cold

    North West England Regional Discussion Thread 15/1/2018 onwards

    in Regional

    Posted

    3 minutes ago, karyo said:

    The ice/snow cover melted overnight when the uppers were below -5. If that's the case then the whole polar maritime was a mild sector apart from a few hours when we hit -7/-8.

    That's what was forecast and the temps you talk about didn't really have time to embed in, its not like we where under those conditions for a day or two was it?

    had the flow been as originally forecast (the temps would have got colder and colder but things change, that's life.

    Model output discussion - mid-winter

    in Forecast Model Discussion

    Posted

    19 minutes ago, nick sussex said:

    In terms of the MJO the weakening is in relation to interference from a Rossby wave.

    That's mentioned here in yesterdays Tropics update:

    During the next two weeks, the current MJO signal is forecast to continue its eastward propagation. La Nina, the low frequency state, is expected to remain entrenched in the central and eastern Pacific. For Week-1, the RMM-index shows movement into Phase 4 for the MJO, moving the enhanced convective region over the Maritime Continent. The forecast shows deterioration in the amplitude of the signal over the next week and into the beginning of Week-2. This is most likely due to expected Rossby wave activity in the Pacific. Model guidance reflects this solution, though the GFS model forecasts a larger decay to the signal than the European model. Despite the weakening, eastward propagation into Phase 5 is expected for the MJO signal. The convective envelope of the MJO is likely to destructively interfere with the base state as it moves into the western Pacific. This is reflected in the shift of forecasted precipitation patterns for the Pacific from Week-1 to Week2.
     

    So the Models got it wrong originally hence why forecasts based upon MJO was also wrong.

    North West England Regional Discussion Thread 15/1/2018 onwards

    in Regional

    Posted

    11 minutes ago, karyo said:

    My interest for cold and snow never ceases but realistically as February progresses the sun becomes a major enemy for any lasting snow.

    Mind you, we can't even get snow to last a day in January now. I had a nice covering (of hail mostly) when I went to bed and it still managed to melt completely by the time I woke up at 7am. That's diabolical for mid January on a night with cold uppers.

    But expected when you get a mild sector........

    Do people really believe that there where no marginal events or non events in the 60/70/80's

    Model output discussion - mid-winter

    in Forecast Model Discussion

    Posted

    1 minute ago, Ed Stone said:

    Interesting, Swebby, and you've just reminded me of a question I have: do the models ever have the faintest idea where the MJO is, at any given time? Or do the models do their workings totally independently of teleconnection forecasts?:cc_confused:

    I thought all those MJO forecasts where generated from the models.

    To me it looks like people are using MJO forecast generated by models as a signal for future development except they call it teleconnetics.

    When the models looked good for next week and beyond the MJO got trotted out that supported the current  output, which to me is basically reading the models but in a different way, then when the models changed we where told that maybe the models are not reading the MJO signal right, except the MJO signal was derived from previous output therefore the statement should have been the Models misread the MJO originally.

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