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Pattern Failbruary Thread

NickyBGuarantee said:
Yes this is fantasy and wont happen but this is why I say Ill take a naked +PNA over a naked -NAO although both would be nice but the GFS gives the entire SE a significant winter storm with about as positive as an NAO could be View attachment 112183
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This isn't really telling the whole story. There is actually an insanely strong TPV that is basically acting as a temporary, pseudo -NAO that sets the whole thing up and then gets out of the way. There's plenty of research to suggest that most of the big dog storms come as the NAO is receding - the NAO sets the table and aligns the wave pattern in a favorable way, the NAO does not in and of itself produce any winter storms.
 
NickyBGuarantee said:
Yes this is fantasy and wont happen but this is why I say Ill take a naked +PNA over a naked -NAO although both would be nice but the GFS gives the entire SE a significant winter storm with about as positive as an NAO could be View attachment 112183
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Yes the western ridge is great here but you are leaving out the fact that the cold vortex in SE Canada is acting as a pseudo -nao here and suppressing the height field. You lose the cold vortex and you can still cut not to mention it's accelerating the flow and there's not much room for amplification so the likely end solution may not be as juicy as the gfs suggests
 
SD said:
Yes the western ridge is great here but you are leaving out the fact that the cold vortex in SE Canada is acting as a pseudo -nao here and suppressing the height field. You lose the cold vortex and you can still cut not to mention it's accelerating the flow and there's not much room for amplification so the likely end solution may not be as juicy as the gfs suggests
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Yes, these scenarios can create a "block" of sorts. I am simply saying the NAO is positive the entire run and we get a great winter set up regardless. The PNA is positive most of the run and if we did not have the +PNA here it wouldn't matter if there's a "pseudo" set up or not we would be flooded with pacific air and get warm air or maybe a cold rain. +PNA is more key for us than a -NAO is my only point
 
SD said:
Yes the western ridge is great here but you are leaving out the fact that the cold vortex in SE Canada is acting as a pseudo -nao here and suppressing the height field. You lose the cold vortex and you can still cut not to mention it's accelerating the flow and there's not much room for amplification so the likely end solution may not be as juicy as the gfs suggests
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And therein beats the heart of the issue. The GFS is excellent, and I mean excellent at showing these unreal solutions at the outer edges of its range. I can hardly name a time when we get up to the event and the height field looks anything like this. I don't know why it does this, and if it were showing this at 24 hours, I'd totally agree that a +NAO is just fine. But I can almost guarantee you that the PV will be well north when we get to Day 15. It's just not reality, usually. Maybe 1 out of 50 times it works out that way, but it usually does not.
 
NickyBGuarantee said:
Yes, these scenarios can create a "block" of sorts. I am simply saying the NAO is positive the entire run and we get a great winter set up regardless. The PNA is positive most of the run and if we did not have the +PNA here it wouldn't matter if there's a "pseudo" set up or not we would be flooded with pacific air and get warm air or maybe a cold rain. +PNA is more key for us than a -NAO is my only point
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If you want a true pna driven winter storm in central nc this is what you wantgfs_z500_vort_us_41 (5).png

The ridge/trough couplet suppress the pattern naturally but allows for amplification along the coast

Here:gfs_z500_vort_us_65 (3).png
It opens up amplification concerns and warm noses if there's phasing or it shears the flow leading to SE/E trends and relies on extra factors. What the gfs has late in its run is probably a once in a decade plus perfect setup
 
Rain Cold said:
And therein beats the heart of the issue. The GFS is excellent, and I mean excellent at showing these unreal solutions at the outer edges of its range. I can hardly name a time when we get up to the event and the height field looks anything like this. I don't know why it does this, and if it were showing this at 24 hours, I'd totally agree that a +NAO is just fine. But I can almost guarantee you that the PV will be well north when we get to Day 15. It's just not reality, usually. Maybe 1 out of 50 times it works out that way, but it usually does not.
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This is a fantastic post. It has to be down to the GFS post-truncation resolution because if reality rountinely matched the end-of-the-run GFS, I'm pretty sure RDU would mirror Boston for average annual snowfall. There are clearly some kind of cascading errors that result in late run (+300 hr) evolutions that always favor these physics-defying PV intrusions that never happen, and usually trend further and further north almost until verification. Come to think of it, it is probably some minor bias in the GFS (strong vortexes too far south) that gets exponentially magnified beyond truncation...
 
Chazwin said:
Way to early to call that. Things are gonna be mild the first few days of the month.
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But the month is shorter, so when the hammer drops, there will be less day to formulate! I’m going -2 below avg for the month at GSP
 
The GFS dangles the carrot yet again. Why even run the model past hour 200?


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Hypsometric said:
This is a fantastic post. It has to be down to the GFS post-truncation resolution because if reality rountinely matched the end-of-the-run GFS, I'm pretty sure RDU would mirror Boston for average annual snowfall. There are clearly some kind of cascading errors that result in late run (+300 hr) evolutions that always favor these physics-defying PV intrusions that never happen, and usually trend further and further north almost until verification. Come to think of it, it is probably some minor bias in the GFS (strong vortexes too far south) that gets exponentially magnified beyond truncation...
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Yep, you're probably right. The thing I take away is that the model still thinks that through the next couple of weeks we will still have the potential for wintry weather. Disregarding the magnitude of any threat or cold outbreak seems wise. But suffice it to say, according to the GFS, winter is not done, not by a long shot. That's what I take away just from the Ops run. If other ensemble suites concur, that obviously increases confidence.

I'm just thrilled that we're not being sent to unending SER purgatory for the rest of the winter like we were promised way back in December ?
 
Rain Cold said:
Yep, you're probably right. The thing I take away is that the model still thinks that through the next couple of weeks we will still have the potential for wintry weather. Disregarding the magnitude of any threat or cold outbreak seems wise. But suffice it to say, according to the GFS, winter is not done, not by a long shot. That's what I take away just from the Ops run. If other ensemble suites concur, that obviously increases confidence.

I'm just thrilled that we're not being sent to unending SER purgatory for the rest of the winter like we were promised way back in December ?
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Agreed, and I think this (below) is why the GFS is delaying a return trip to SER purgatory. If we can avoid 4/5 through most of the month, we still are alive. If we don't, you can pack away your winter coats (at least until spring, when the inevitable perfect +PNA/-west based NAO sets up).

diagram_40days_forecast_GEFSBC_member.gif
 
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