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bluearmy

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Posts posted by bluearmy

    Model Output Discussion - Spring Has Sprung

    in Forecast Model Discussion

    Posted

     Singularity there have been a couple of gfs ops recently that downwelled within a couple days on the cross sectionals - tended to be those that developed a large split vortex later on with the Arctic ridge dropping into the Atlantic ridge pushing north.  I suppose that the weak strat vortex this season makes it prone to that. Of course that’s not a standard NH strat winter profile 

    for developments next week, still uncertainty around how the ssw will manifest itself. Currently backing off a split solution (of any note).   The eps clusters look better in the extended. 

    • Like 2

    Model Output Discussion - Spring Has Sprung

    in Forecast Model Discussion

    Posted

     Singularity. It is open to interpretation.  This winter is quite strange high up and perhaps difficult to make judgments upon.  If you look at the 00z gfs op, you will see a neg AO in the trop which is nothing to do with the reversal high up that occurs at the same time. The positive flow sitting between in the mid to lower strat  

    image.thumb.png.3ad9c02b0d258fce451b37844ad21e96.png
     

    in the past, we have seen reversals take place with a positive AO in place and within a few days a big ridge is thrown up on the pacific side which punches across the Arctic and affects our side of the NH.  That would be visible as the blue negative flow in the cross sectional chart working down top to bottom. That’s what a QTR is.  This winter with the trop and strat generally in tandem it’s probably not so relevant. It’s been tough to see whether the impetus for neg flow has come from a downwelling wave or is instigated from the trop and then quickly upwelled. Mike has posted on this a fair bit. 

    fwiw, next weeks reversal is currently uncertain in how it plays out. I think that until we get a handle on that we can’t set much store in the modelling for week 2. 

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    Model discussion highlights

    in Forecast Model Discussion

    Posted

     This won’t be exactly how it plays out 

    The 12z runs have begun to sniff out the way forward but they can’t have stumbled across the correct route first time.  At least it makes the next few runs worth watching …..

    note that the mid/upper strat was more split on the 00z run at day 10 than the 12z. Another run which doesn’t stack up as you might have expected 


    Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5034508
    • Like 1

    Model Output Discussion - Spring Has Sprung

    in Forecast Model Discussion

    Posted

     This won’t be exactly how it plays out 

    The 12z runs have begun to sniff out the way forward but they can’t have stumbled across the correct route first time.  At least it makes the next few runs worth watching …..

    note that the mid/upper strat was more split on the 00z run at day 10 than the 12z. Another run which doesn’t stack up as you might have expected 

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    • Insightful 3

    Model Output Discussion - Spring Has Sprung

    in Forecast Model Discussion

    Posted

    Weatherbell is down this morning. Looks like the geps are late on meteociel too

    the gefs were a curates egg 

    mean not far from something exceptional but at two weeks range 

    the eps clusters don’t look too good 

    I guess pre ssw modelling unreliability should be our hope here. there are some more than interesting gefs members so hopefully we can roll the ssw dice and get a qtr like those show 

     

     Dennis I appreciate this is your area dennis but if we have a strongly coupled atmosphere then we would likely see a trop response within days (as 18z showed yesterday) 

    but also more affects in March as you post

    • Like 3

    Model Output Discussion - Spring Has Sprung

    in Forecast Model Discussion

    Posted

     IDO the gfs has a poor vortex split with an atlantic segment left to our west. This is the risk of the split ssw solution. We’ve had three decent results from the last five and the gefs mean is better than the op. 
     

    I think the displacement solution won’t bring the scandi trough far enough south (for the majority of the populated U.K.) .  So we are probably at the mercy of the ssw dice roll for winter's last hurrah ……

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    Model Output Discussion - Spring Has Sprung

    in Forecast Model Discussion

    Posted

     sebastiaan1973 yes Sebastian- finally a gfs op which splits through the strat and trop. Recent runs that have split high up but not low down and in the trop didn’t make much sense.  We take our chances with a split and hope it’s a big reversal or we play safe with an Asian displacement and hope that an Atlantic ridge can fill the space left rather than an atlantic trough (extended from the Canadian tpv)  which has been shown on recent gfs ops 

     Penguin16 if you are actually a penguin then I understand 

    • Like 12
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    Model Output Discussion - Spring Has Sprung

    in Forecast Model Discussion

    Posted · Edited by bluearmy

    I did say last week jan that I had concerns that feb could be a v frustrating month with patterns that bit too far north for the U.K. to benefit 

    it is panning out that way atm but with a notable reversal of upper flow likely just beyond  mid month we can expect the modelling to struggle and flap around a bit now as it looks beyond day 10 

    as @feb1991blizzard has noted, the gfs op modelling of the strat looks somewhat strange over the past few runs. 

    • Like 3
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