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POWERSTROKE

February Pattern and Storm Discussion

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Well February starts tomorrow.  Will we finish the winter strong or seasonable?  Will the models give us anything to follow?

 

Based on all of the evidence and observations from December to now, I would wager that it depends on which part of the SE you happen to inhabit.

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Looks like it is up to the Great Pacific to decide what February will deal us.

 

It sure would be nice to see CPC have to back peddle on their 6 - 10 and 8-14 day prognonstic outlook that they issued on January 30.     They are right the vast majority of the time, maybe this one will be different.

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CPC's predictions were really struggling In the month of January IMHO. Though to be fair I think they rated the January 30 prediction five out of five confidence level!

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Let me be clear, I don't think February will be a complete dud, but I do think we will end up either normal or slightly above normal throughout much of the southeast US.  There may be one or two VERY minor wintry precip chances in SOME areas but all in all, I don't see any major events this month unless we see some more severe weather which is a strong possibility.  I think by and large the ohio valley and maybe the upper midwest will be the place to be to see any respectable snows this month as I see a neutral to positive NAO, a mainly neutral to - PNA and a neutral to positive EPO taking shape for the month. 

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Let me be clear, I don't think February will be a complete dud, but I do think we will end up either normal or slightly above normal throughout much of the southeast US.  There may be one or two VERY minor wintry precip chances in SOME areas but all in all, I don't see any major events this month unless we see some more severe weather which is a strong possibility.  I think by and large the ohio valley and maybe the upper midwest will be the place to be to see any respectable snows this month as I see a neutral to positive NAO, a mainly neutral to - PNA and a neutral to positive EPO taking shape for the month. 

 

You may be correct, but the extended esembles for the CMC, GFS, and EURO are all showing a strong +PNA setting up by mid month. 

 

I'm not sure how all of this will play out, but I'm pretty confident the SE will have a few more periods of winter wx during the month (mid to late). 

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I wouldn't count on it.  The models have notoriously done this all winter in this time frame only to change their tune as the time drew closer.  What physical mechanism do they appear to be keying on to drive this positive PNA and do you tend to agree with them?  If so, why?  Thanks!  I am just curious as to what I may be missing...I have been watching this stuff for years but am not claiming to be an expert by any stretch :)

 

For reference, here are the 11-15 day 12Z GFS ensembles, showing some ridging over the pacific northwest as you described but a positive NAO...just took a look at the 12Z Canadian ensembles and they look similar with some ridging on the west coast but with a positive NAO...definitely not a SE snowstorm pattern...and the EURO ensembles are showing the same thing...the cold looks to me to stay bottled up in Russia and Siberia to be honest...

 

12zENS11-15day500mbHeightAnomalyNH.gif

You may be correct, but the extended esembles for the CMC, GFS, and EURO are all showing a strong +PNA setting up by mid month. 

 

I'm not sure how all of this will play out, but I'm pretty confident the SE will have a few more periods of winter wx during the month (mid to late). 

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I wouldn't count on it.  The models have notoriously done this all winter in this time frame only to change their tune as the time drew closer.  What physical mechanism do they appear to be keying on to drive this positive PNA and do you tend to agree with them?  If so, why?  Thanks!  I am just curious as to what I may be missing...I have been watching this stuff for years but am not claiming to be an expert by any stretch :)

 

For reference, here are the 11-15 day 12Z GFS ensembles, showing some ridging over the pacific northwest as you described but a positive NAO...just took a look at the 12Z Canadian ensembles and they look similar with some ridging on the west coast but with a positive NAO...definitely not a SE snowstorm pattern...and the EURO ensembles are showing the same thing...the cold looks to me to stay bottled up in Russia and Siberia to be honest...

 

12zENS11-15day500mbHeightAnomalyNH.gif

 

You will also notice a nice split flow on the chart above. All is takes is one energetic system to cruise along and tap in to the cool air mass to the north to get a good storm in the SE. Yes, the NAO is not exactly cooperating but you don't necessarily need this. There are soooo many different parameters out there (PNA, EPO, MJO, NAO, PDO, etc) and it's difficult to pinpoint the ramifications of one let alone all of them combined for the US or even the SE. That's what makes long term forecasting such a challenge. IMO, I think the bigger scale features (Nino, Nina, MJO, etc) have much more influence. We all know this is not an exact science. I'm far from a good long term forecaster, as I'm always still learning. 

 

Actually, the period above is probably just the start to what I think will be a rather blocky pattern heading into the remainder of the month. Once their are good kinks in the flow, things can and will happen. I'm sure we'll have warm periods but there will also be cold periods as well. 

 

Good discussion......

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We haven't seen a lot of true split flow this winter. What we have seen is a lot of northern stream energy (which will probably continue). As a result, we've seen low pressure move across the northern tier, move through the lakes region, and often intensify once moving off the coast. This helps to create a psuedo 50/50, that due to the lack of blocking, has been rather transient. So instead of HP building in and locking in for long periods across the Lakes and NE, it has generally moved out. Unfortunately, given the lack of a STJ, we have had very little opportunity for precipitation when these periods of transitory HP have existed.

The point is, if, IF we get a split flow like the GFS is showing, and if we continue to have an active northern stream, the odds of winter weather will increase substantially, even without blocking. Energy in the STJ will have a good chance of undercutting a cold air mass at some point. Of course, this is all predicated on there being cold air available to tap. If the PV and all the cold retreat to the north pole or Asia, we can probably forget it.

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Excellent post!  I think my argument is that I am worried about the cold air availability...but if we can get the STJ AND some cold air as mentioned (I saw this but didn't see any real cold air to work with and thus my skepticism), then all bets are off.  However, I still remain skeptical.  We shall see.  Good discussion and thanks to Greensboro for his above post!  Maybe, just maybe, the MJO can finally begin to impact the pattern a bit in our favor.

We haven't seen a lot of true split flow this winter. What we have seen is a lot of northern stream energy (which will probably continue). As a result, we've seen low pressure move across the northern tier, move through the lakes region, and often intensify once moving off the coast. This helps to create a psuedo 50/50, that due to the lack of blocking, has been rather transient. So instead of HP building in and locking in for long periods across the Lakes and NE, it has generally moved out. Unfortunately, given the lack of a STJ, we have had very little opportunity for precipitation when these periods of transitory HP have existed.

The point is, if, IF we get a split flow like the GFS is showing, and if we continue to have an active northern stream, the odds of winter weather will increase substantially, even without blocking. Energy in the STJ will have a good chance of undercutting a cold air mass at some point. Of course, this is all predicated on there being cold air available to tap. If the PV and all the cold retreat to the north pole or Asia, we can probably forget it.

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We haven't seen a lot of true split flow this winter. What we have seen is a lot of northern stream energy (which will probably continue). As a result, we've seen low pressure move across the northern tier, move through the lakes region, and often intensify once moving off the coast. This helps to create a psuedo 50/50, that due to the lack of blocking, has been rather transient. So instead of HP building in and locking in for long periods across the Lakes and NE, it has generally moved out. Unfortunately, given the lack of a STJ, we have had very little opportunity for precipitation when these periods of transitory HP have existed.

The point is, if, IF we get a split flow like the GFS is showing, and if we continue to have an active northern stream, the odds of winter weather will increase substantially, even without blocking. Energy in the STJ will have a good chance of undercutting a cold air mass at some point. Of course, this is all predicated on there being cold air available to tap. If the PV and all the cold retreat to the north pole or Asia, we can probably forget it.

 

Agreed.  That's my biggest concern for the rest of February; where's the cold air?  Even the ensembles all the way out really do not show any cold air getting in to the south.  The split flow, the increased activity under the ridge produces lows coming up to our south, great, but without the cold air tap it's just more cool rain. 

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Excellent post!  I think my argument is that I am worried about the cold air availability...but if we can get the STJ AND some cold air as mentioned (I saw this but didn't see any real cold air to work with and thus my skepticism), then all bets are off.  However, I still remain skeptical.  We shall see.  Good discussion and thanks to Greensboro for his above post!  Maybe, just maybe, the MJO can finally begin to impact the pattern a bit in our favor.

 

 

Agreed.  That's my biggest concern for the rest of February; where's the cold air?  Even the ensembles all the way out really do not show any cold air getting in to the south.  The split flow, the increased activity under the ridge produces lows coming up to our south, great, but without the cold air tap it's just more cool rain. 

The 12Z Euro certainly doesn't give any confidence of any really cold air around the 10 day period, and the 12Z GFS Ens is in fairly good agreement. I haven't seen the 12Z Euro Ens yet, but it'll probably be in line with that. Beyond that, the 12Z GFS Ens, start to look a bit better at moving the cold SE out of the North Pole. Hopefully, if they're rushing the pattern, it won't be by too much. But, yeah, the cold coming back is a concern. If it can just get into the NE, then a good HP in the right spot can funnel low level cold down here, even though 850s might not look all that great. We'll see....

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The 12Z Euro certainly doesn't give any confidence of any really cold air around the 10 day period, and the 12Z GFS Ens is in fairly good agreement. I haven't seen the 12Z Euro Ens yet, but it'll probably be in line with that. Beyond that, the 12Z GFS Ens, start to look a bit better at moving the cold SE out of the North Pole. Hopefully, if they're rushing the pattern, it won't be by too much. But, yeah, the cold coming back is a concern. If it can just get into the NE, then a good HP in the right spot can funnel low level cold down here, even though 850s might not look all that great. We'll see....

And of course, the Euro ENS at day 10 look nice and toasty. Nice trough out west, SE ridge, and all the cold air locked up at the North Pole.

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I wouldn't count on it.  The models have notoriously done this all winter in this time frame only to change their tune as the time drew closer.  What physical mechanism do they appear to be keying on to drive this positive PNA and do you tend to agree with them?  If so, why?  Thanks!  I am just curious as to what I may be missing...I have been watching this stuff for years but am not claiming to be an expert by any stretch :)

 

For reference, here are the 11-15 day 12Z GFS ensembles, showing some ridging over the pacific northwest as you described but a positive NAO...just took a look at the 12Z Canadian ensembles and they look similar with some ridging on the west coast but with a positive NAO...definitely not a SE snowstorm pattern...and the EURO ensembles are showing the same thing...the cold looks to me to stay bottled up in Russia and Siberia to be honest...

 

12zENS11-15day500mbHeightAnomalyNH.gif

This was mainly my point in the other thread that we were discussing. The nao is crap and has been since that brief 2 week time around Christmas. I don't know what is driving the split flow +pna being shown on the models. MJO? Or the Aleutian low? What has caused the pna to go positive from the very long - state in was in during the fall? I really don't know very much about long range forecasting, and I find I learn more every winter.

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And of course, the Euro ENS at day 10 look nice and toasty. Nice trough out west, SE ridge, and all the cold air locked up at the North Pole.

There is really not any cold air anywhere on the euro ensembles. But I would take my chances with a split flow any day. The one problem we could have is even in a split flow everything could cut without any blocking. You are correct with us having mostly northern stream energy all year. It always helps when the vort is south of you.12zecmwfenshourly850mbTempAnomalyNH240.g

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There is really not any cold air anywhere on the euro ensembles. But I would take my chances with a split flow any day. The one problem we could have is even in a split flow everything could cut without any blocking. You are correct with us having mostly northern stream energy all year. It always helps when the vort is south of you.

Yup, we could definitely see some cutters if we can't get some sort of blocking or vortex pressing south from SE Canada.

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Well February starts tomorrow.  Will we finish the winter strong or seasonable?  Will the models give us anything to follow?

 

 A good and probably favored possibility is neither of the above..i.e., mild for Feb.. Based on the warm Dec/Jan analogs I've been following, Feb. as a whole is leaning mild with some chance for cooling late.

 

  Fwiw, the just released Euro weeklies have wall to wall above normal temperatures  in the SE US (for all four Feb. weeks). This is the warmest Euro weeklies release since late Dec. No telling if this will verify as the weeklies have been very inconsistent lately. However, based on the analogs, it is quite believable.

 

  Hopefully, those same analogs' favoring of a below normal March, with March quite possibly being the coldest winter month for much of the SE US, will end up prevailing. I don't think winter will end early regardless of what Feb. brings. If anything, a warm Feb. gives me more confidence that the analogs will continue to have predictive value and, therefore, hopefully means that a chilly March will be in store.

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 A good and probably favored possibility is neither of the above..i.e., mild for Feb.. Based on the warm Dec/Jan analogs I've been following, Feb. as a whole is leaning mild for the month as a whole with some chance for cooling late.

 

  Fwiw, the just released Euro weeklies have wall to wall above normal temperatures  in the SE US (for all four Feb. weeks). This is the warmest Euro weeklies release since late Dec. No telling if this will verify as the weeklies have been very inconsistent lately. However, based on the analogs, it is quite believable.

 

  Hopefully, those same analogs' favoring of a below normal March, with March quite possibly being the coldest winter month for much of the SE US, will end up prevailing. I don't think winter will end early regardless of what Feb. brings. If anything, a warm Feb. gives me more confidence that the analogs will continue to have predictive value and, therefore, hopefully means that a chilly March will be in store.

Put my money on those weeklies busting here week one in Greensboro if they are wall to wall warm as you say. We will have neg departure temp wise feb 1-7 when it's all averaged out. I don't have access but how can one have faith in them if they bust the first week in a 4 week output.

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BINGO!  Excellent point that needed to be brought up...and again...with no cold air around...good luck getting any wintry wx...

There is really not any cold air anywhere on the euro ensembles. But I would take my chances with a split flow any day. The one problem we could have is even in a split flow everything could cut without any blocking. You are correct with us having mostly northern stream energy all year. It always helps when the vort is south of you.12zecmwfenshourly850mbTempAnomalyNH240.g

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Due to the fact that the ENSO has been basically neutral, does it create more havoc with medium to long range forecasting?

La Nada's I believe are the most volatile of all global weather patterns because of all the major factors and players are all fighting for dominance.    The 2011 Super Tornado Outbreak occurred in a La Nada as well as many other major severe weather outbreaks.   There have been extreme variabilities this winter as again all the players are trying to fight again for dominance.   

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Put my money on those weeklies busting here week one in Greensboro if they are wall to wall warm as you say. We will have neg departure temp wise feb 1-7 when it's all averaged out. I don't have access but how can one have faith in them if they bust the first week in a 4 week output.

 

 Actually, the first week of today's Euro weeklies is for 2/4-10, not 2/1-7. My wording (four Feb. weeks) was confusing. My bad.

 

  If you consider 2/4-10, I'm confident that much of the E US will average near or above normal. Atlanta certainly looks warm as of now for the period as a whole. I'd be surprised if Greensboro weren't above normal for 2/4-10. We'll see.

 

 Aside: Other than perhaps some flurries, I'm not seeing any possiblities for sig. wintry precip. in the Atlanta-Athens corridor in the forseeable future. It wouldn't surprise me if I'm thinking very differently about a month from now.

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 Actually, the first week of today's Euro weeklies is for 2/4-10, not 2/1-7. My wording (four Feb. weeks) was confusing. My bad.

 

  If you consider 2/4-10, I'm confident that much of the E US will average near or above normal. Atlanta certainly looks warm as of now for the period as a whole. I'd be surprised if Greensboro weren't above normal for 2/4-10. We'll see.

 

 Aside: Other than perhaps some flurries, I'm not seeing any possiblities for sig. wintry precip. in the Atlanta-Athens corridor in the forseeable future. It wouldn't surprise me if I'm thinking very differently about a month from now.

Our normals have now begun to climb.  From this point on, each week will require a further negative departure from normal to produce winter precip. The clock is ticking

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