Re: Long Range Thread 29.0

[sroc4]

HOLY SCHNIKEES…….I have to take a deeper look, but I still like the period from about December 5th-7th for another wintry event, but I think a big dog is brewing for about the 9th-12th. I’ll have more to say on this in due course, but I’d suggest that we get our sleep, because the opening of December could be pretty awesome.

Coincidence?




GEM wasn’t far off either.

Get your rest, folks. This signal is legit.

Looking at some of the tea leaves this morning Id say I have to agree.  A legit serious storm seems to be brewing for sure.  A few things that I really like.  

First and foremost cold air should be readily available.  The pattern following todays system moving through looks to be one reinforcing cold shot after another for awhile compliments of a -EPO/WPO, but more importantly the establishment to what seems to be a fairly robust and potentially entrenched +PNA.  Heehaw and I discussed this a little last weekend, but what this means is the development of a "split flow" at 200mb which will translate to 500mb.  Here is Heehaws comments from Sunday:

We'll have to see but damn this early December jet on the EPS is so dramatically different than what we had December 2023. Nice split flow with western ridge helping ooze cold air to ES. If this keeps up have to like December for a snow event right to coast.

 I've said this in prev yeas, but IMHO a +PNA is probably more important that any other teleconnection; esp for the coastal plain.  At least in recent years we have had one transient +PNA after another such that we have needed to rely on the perfect timing and ability of of N/S energy to dig into the S/S energy just right because Pac energy crashes the coast at the most inopportune times which ultimately flattened our PNA ridge.  This consequently moderates cold air sources, prevents/limits interactions between N/S and S/S energy and leads to storms that never materializing into anything noteworthy.  This has been exceptionally true for the coast in the recent past.

Anyway back to this year.  Here is a look at what Im talking about with what we want to see at 500mb.  



This look begins to take shape between hr 72-90 as of last nights 00z runs.  Looking across all three ensemble packages, GEFS, EPS, and GEFS,  this look appears to be firmly set up pretty much throughout the runs which takes us out to mid December.  Now there are some differences at various times between models etc, but there is a shit ton to like about the pattern for the next two weeks.  Now I am one to hesitate and say things like "we have been burned so many times in the past..." but I am going to go out on a limb and say that if we dont see at least some form of accumulating snow out of the next two weeks all the way down to the coast I truly will be shocked.  

Now more specifically about Ray Ray's window of approx. Dec7-9th, I think was his time frame, I also really like how the -NAO is actually forecast to relax towards a more neutral state.  IMHO when you have "favorable" teleconnections in both the western and eastern domains, relative to our little NE region, that are too robust at the same time, you tend to get the cold, but no major storms.  Its when one or the other tend to ease up that it allows the ingredients, ie: n/s an s/s energy, to come together just right along the coast to give us a bigger ticket outcome.  This has been esp true for when the Pac domain cooperates and the -NAO domain is the tele that relaxes.  So while Im certainly not ready to sound any alarms I too think a fairly robust storm signal exists in Rays window for a Godzilla type set up for at least some of us on this board, with the coastal plain certainly in the game given that the cold air seems to be in place for this window.  On top of that I also think there will be more than one opportunity to accumulate down to the coast ove the next 2 weeks should the pattern truly stay set up like it appears is the case.  One threat at a time though.  

I do want to make one comment about the longer term.  I have heard many amateur and professional weather enthusiast claim that a La Nina is no longer a threat.  I personally would say not so fast.  I still think we could potentially reach La Nina status before we are said and done.  The last two weeks the SOI has been in a fairly robust La Nina state.  https://www.longpaddock.qld.gov.au/soi/  The result has seen the Easterlies kicking up across the trop pac and the ENSO regions have begun to cool again over the past 2 weeks as well.  You can see by the image below that even though thre has been some moderation of the developing La Nina since Sept, there is still cold subsurface temps, so if the easterlies cont to blow for awhile it will cause upwelling in the eastern Pac and cooling at the surface from east to west as well.  Now whether or not by the strictest of definitions a mild La Nina actually gets established I still think this exciting pattern I just outlined for the next 2 weeks will unfort collapse at some point, and the dreaded SE Ridge will shifts our storm track back west into the spine of the Apps and GL sometime towards the middle to end of Dec.  How long it lasts I'm not sure, but I think its coming.  I def could be wrong on this point, but we'll see.  



For the next two weeks; however,.....

WE TRACK!!  

[rb924119]

HOLY SCHNIKEES…….I have to take a deeper look, but I still like the period from about December 5th-7th for another wintry event, but I think a big dog is brewing for about the 9th-12th. I’ll have more to say on this in due course, but I’d suggest that we get our sleep, because the opening of December could be pretty awesome.

Coincidence?




GEM wasn’t far off either.

Get your rest, folks. This signal is legit.

Looking at some of the tea leaves this morning Id say I have to agree.  A legit serious storm seems to be brewing for sure.  A few things that I really like.  

First and foremost cold air should be readily available.  The pattern following todays system moving through looks to be one reinforcing cold shot after another for awhile compliments of a -EPO/WPO, but more importantly the establishment to what seems to be a fairly robust and potentially entrenched +PNA.  Heehaw and I discussed this a little last weekend, but what this means is the development of a "split flow" at 200mb which will translate to 500mb.  Here is Heehaws comments from Sunday:

We'll have to see but damn this early December jet on the EPS is so dramatically different than what we had December 2023. Nice split flow with western ridge helping ooze cold air to ES. If this keeps up have to like December for a snow event right to coast.

 I've said this in prev yeas, but IMHO a +PNA is probably more important that any other teleconnection; esp for the coastal plain.  At least in recent years we have had one transient +PNA after another such that we have needed to rely on the perfect timing and ability of of N/S energy to dig into the S/S energy just right because Pac energy crashes the coast at the most inopportune times which ultimately flattened our PNA ridge.  This consequently moderates cold air sources, prevents/limits interactions between N/S and S/S energy and leads to storms that never materializing into anything noteworthy.  This has been exceptionally true for the coast in the recent past.

Anyway back to this year.  Here is a look at what Im talking about with what we want to see at 500mb.  



This look begins to take shape between hr 72-90 as of last nights 00z runs.  Looking across all three ensemble packages, GEFS, EPS, and GEFS,  this look appears to be firmly set up pretty much throughout the runs which takes us out to mid December.  Now there are some differences at various times between models etc, but there is a shit ton to like about the pattern for the next two weeks.  Now I am one to hesitate and say things like "we have been burned so many times in the past..." but I am going to go out on a limb and say that if we dont see at least some form of accumulating snow out of the next two weeks all the way down to the coast I truly will be shocked.  

Now more specifically about Ray Ray's window of approx. Dec7-9th, I think was his time frame, I also really like how the -NAO is actually forecast to relax towards a more neutral state.  IMHO when you have "favorable" teleconnections in both the western and eastern domains, relative to our little NE region, that are too robust at the same time, you tend to get the cold, but no major storms.  Its when one or the other tend to ease up that it allows the ingredients, ie: n/s an s/s energy, to come together just right along the coast to give us a bigger ticket outcome.  This has been esp true for when the Pac domain cooperates and the -NAO domain is the tele that relaxes.  So while Im certainly not ready to sound any alarms I too think a fairly robust storm signal exists in Rays window for a Godzilla type set up for at least some of us on this board, with the coastal plain certainly in the game given that the cold air seems to be in place for this window.  On top of that I also think there will be more than one opportunity to accumulate down to the coast ove the next 2 weeks should the pattern truly stay set up like it appears is the case.  One threat at a time though.  

I do want to make one comment about the longer term.  I have heard many amateur and professional weather enthusiast claim that a La Nina is no longer a threat.  I personally would say not so fast.  I still think we could potentially reach La Nina status before we are said and done.  The last two weeks the SOI has been in a fairly robust La Nina state.  https://www.longpaddock.qld.gov.au/soi/  The result has seen the Easterlies kicking up across the trop pac and the ENSO regions have begun to cool again over the past 2 weeks as well.  You can see by the image below that even though thre has been some moderation of the developing La Nina since Sept, there is still cold subsurface temps, so if the easterlies cont to blow for awhile it will cause upwelling in the eastern Pac and cooling at the surface from east to west as well.  Now whether or not by the strictest of definitions a mild La Nina actually gets established I still think this exciting pattern I just outlined for the next 2 weeks will unfort collapse at some point, and the dreaded SE Ridge will shifts our storm track back west into the spine of the Apps and GL sometime towards the middle to end of Dec.  How long it lasts I'm not sure, but I think its coming.  I def could be wrong on this point, but we'll see.  



For the next two weeks; however,.....

WE TRACK!!  

Chef’s kiss to this, brother. Great write-up!

The only thing I will say is that even if the ENSO state changes, there will definitely be a lag in the effect, typically two to three months, which would set it up roughly for mid- to late-January or into February. However, we will have to see how well it couples, if at all. Remember, we have had two winter seasons in a row now where the ENSO state never coupled to the atmosphere. Last year, it was the change in the Pacific SST anomaly configuration in the Maritime Continent that royally flushed our winter down the proverbial toilet; not the ENSO state. Now, I think it was mugsy who posted that research by Eric Webb that indicates the Pacific pattern in the Northern Hemisphere could be persistent. If* that’s the case, and if* a typical La Niña response is observed, having that little bit of resistance from the Southeast Ridge could set us up to be in the classic battleground, which goes back to heehaw’s earlier points, especially if* we keep seeing these “homegrown” western NAO domain blocking initiations (which of the three “if’s”, I am inclined to believe these will continue). There’s a lot to consider this season, so it should be fun, even if only from a meteorological perspective. I echo your sentiments though; WE TRACK!!!

[heehaw453]

I think we wait until 12/5 for something minor. Note this gif showing the PNA spike on 12/5 and the vortex over the Hudson Bay which may have a wave break to slide down the PNA ridge. It's n/s so it's lacking moisture and nothing in the Atlantic will slow it down to allow for it to blow up. As time moves along towards 12/10 east Atlantic blocking kicks in coupled with the split flow progressing to more consolidation between n/s and s/s (southern stream) jets. The end of the gif sequence and the pic below you can really see it.



now something noteworthy can pop as s/s interacts with n/s and east based Atlantic blocking takes hold     
It should be cold enough but a H parked over eastern Quebec would be nice

[rb924119]

I’m not writing December 5th off just yet, as that looks like it might have some room to trend further south/stronger, but I am absolutely sounding the alarm for the 9th-12th. Game on!

[jmanley32]

Happy belated Thanksgiving all! Will the coast have a shot with the latter Ray? If it is unlikely I would just as well personally not put to much time or effort into following it. I saw the 00z run but it looks like a initial dump followed by a soaking rain for many that would probably wash it all away. I am in southern CT right now with the parents and it really is not all that cold for Nov./early Dec. On another note Mt. Holly VT where their second home is got 17 inches yesterday (4-10 was forecasted)! Actually unusual for any snow as of recent years. Maybe this is a good sign for all of us as we get closer to Jan/Feb which is when the coast is more likely to cash in. I wouldn't mind a Dec. storm though.

[rb924119]

Happy belated Thanksgiving all! Will the coast have a shot with the latter Ray? If it is unlikely I would just as well personally not put to much time or effort into following it. I saw the 00z run but it looks like an initial dump followed by a soaking rain for many that would probably wash it all away. I am in southern CT right now with the parents and it really is not all that cold for Nov./early Dec. On another note Mt. Holly VT where their second home is got 17 inches yesterday (4-10 was forecasted)! Actually unusual for any snow as of recent years. Maybe this is a good sign for all of us as we get closer to Jan/Feb which is when the coast is more likely to cash in. I wouldn't mind a Dec. storm though.

On a quick glance, everybody would be in the ballgame for at least some snow with this one, at least from this vantage point. Now, specifics of who sees wet versus white and how much of each or neither need to be ironed out, but I think this is the best look that we’ve seen in a while on the whole, and the maximum potential, if realized, is pretty high.

[jmanley32]

Happy belated Thanksgiving all! Will the coast have a shot with the latter Ray? If it is unlikely I would just as well personally not put to much time or effort into following it. I saw the 00z run but it looks like an initial dump followed by a soaking rain for many that would probably wash it all away. I am in southern CT right now with the parents and it really is not all that cold for Nov./early Dec. On another note Mt. Holly VT where their second home is got 17 inches yesterday (4-10 was forecasted)! Actually unusual for any snow as of recent years. Maybe this is a good sign for all of us as we get closer to Jan/Feb which is when the coast is more likely to cash in. I wouldn't mind a Dec. storm though.

On a quick glance, everybody would be in the ballgame for at least some snow with this one, at least from this vantage point. Now, specifics of who sees wet versus white and how much of each or neither need to be ironed out, but I think this is the best look that we’ve seen in a while on the whole, and the maximum potential, if realized, is pretty high.

Cool, I'll check in every so often over the next week.

[dkodgis]

Ray, the viscerals are almost ready: the entrails are soon quite right to predict the storm in a week. Could you post a few images of what you are relying on?

[Frank_Wx]

We’re entering our first stretch of colder than normal weather for this season. And it will be here to stay for the next 7-9 days in part from an active MJO wave that is currently in phase 4 and heading into phase 5. This is shown to amplify the west coast ridge (+PNA) and keep the cold locked into the eastern US. Check out the Euro Ensembles 500mb Day 6-9 averages map.



The downsides I see are our trough axis and lack of NAO blocking. One trend I’m seeing in the medium to long range is that while the cold is here, the threat for storms is not as obvious because of the +NAO and progressive northern jet. The multiple waves of northern energy are not diving deep enough into the central/eastern CONUS despite the west coast ridging. One potential system catching my attention is shown between December 8th and 10th on current guidance. We could see some pseudo NAO blocking develop which is enough to slow the jet down and promote a more favorably positioned trough. So, let’s see if we’re able to get something come together because I do think come the middle of December we are likely going to get milder again (the MJO wave likely gets into the warm phases unless it dies off before it does).

[rb924119]

Ray, the viscerals are almost ready: the entrails are soon quite right to predict the storm in a week. Could you post a few images of what you are relying on?

Interestingly, there's really no model, operational runs included, that is yet showing what I think will happen, or even the potential. I guess the closest is last night's 00z Spire run, but even that isn't a great representation - it's displaced too far northwest in my opinion. However, I'm pretty sure that I will have a chance to record a video discussion between tonight and tomorrow, so that will really help to demonstrate where my head is at with it, unless we get operational runs today that exemplify the ideas.

[rb924119]

We’re entering our first stretch of colder than normal weather for this season. And it will be here to stay for the next 7-9 days in part from an active MJO wave that is currently in phase 4 and heading into phase 5. This is shown to amplify the west coast ridge (+PNA) and keep the cold locked into the eastern US. Check out the Euro Ensembles 500mb Day 6-9 averages map.



The downsides I see are our trough axis and lack of NAO blocking. One trend I’m seeing in the medium to long range is that while the cold is here, the threat for storms is not as obvious because of the +NAO and progressive northern jet. The multiple waves of northern energy are not diving deep enough into the central/eastern CONUS despite the west coast ridging. One potential system catching my attention is shown between December 8th and 10th on current guidance. We could see some pseudo NAO blocking develop which is enough to slow the jet down and promote a more favorably positioned trough. So, let’s see if we’re able to get something come together because I do think come the middle of December we are likely going to get milder again (the MJO wave likely gets into the warm phases unless it dies off before it does).

Good post, Frank, although I'm going to respectfully disagree with the following:

"The downsides I see are our trough axis and lack of NAO blocking. One trend I’m seeing in the medium to long range is that while the cold is here, the threat for storms is not as obvious because of the +NAO and progressive northern jet. The multiple waves of northern energy are not diving deep enough into the central/eastern CONUS despite the west coast ridging."

I think verbatim you're right, but reading the tea leaves a bit I think reveals that your second thought regarding the potential for the pseudo NAO blocking is more accurate. What I think the models are currently having issues resolving is the response of southern tier of the western Atlantic domain. There's going to be a 50/50 low initially that looks to drift southeastward, which should result in height rises to its north. Simultaneously, we should see our storm of interest taking shape across the central U.S. as one piece of energy dives down the eastern flank of the ridge while another piece is ejecting out from the Southwest. As those phase, the long-wave trough is going to be forced to elongate and amplify, but in response to this AND the southeastward drift of the 50/50 low, height rises should* effectively pinch that southern lobe off from the main long-wave trough, resulting in a classic bowling ball closed mid-level low swinging through the interior Southeast with positive height anomalies arching over the top. Will it be classified as a technical -NAO? maybe, maybe not - statistics are a funny thing. But effectively, I think it should still function as one.

[rb924119]

12z GFS and GEM took steps, but a long way to go.

[rb924119]

We’re entering our first stretch of colder than normal weather for this season. And it will be here to stay for the next 7-9 days in part from an active MJO wave that is currently in phase 4 and heading into phase 5. This is shown to amplify the west coast ridge (+PNA) and keep the cold locked into the eastern US. Check out the Euro Ensembles 500mb Day 6-9 averages map.



The downsides I see are our trough axis and lack of NAO blocking. One trend I’m seeing in the medium to long range is that while the cold is here, the threat for storms is not as obvious because of the +NAO and progressive northern jet. The multiple waves of northern energy are not diving deep enough into the central/eastern CONUS despite the west coast ridging. One potential system catching my attention is shown between December 8th and 10th on current guidance. We could see some pseudo NAO blocking develop which is enough to slow the jet down and promote a more favorably positioned trough. So, let’s see if we’re able to get something come together because I do think come the middle of December we are likely going to get milder again (the MJO wave likely gets into the warm phases unless it dies off before it does).

Good post, Frank, although I'm going to respectfully disagree with the following:

"The downsides I see are our trough axis and lack of NAO blocking. One trend I’m seeing in the medium to long range is that while the cold is here, the threat for storms is not as obvious because of the +NAO and progressive northern jet. The multiple waves of northern energy are not diving deep enough into the central/eastern CONUS despite the west coast ridging."

I think verbatim you're right, but reading the tea leaves a bit I think reveals that your second thought regarding the potential for the pseudo NAO blocking is more accurate. What I think the models are currently having issues resolving is the response of southern tier of the western Atlantic domain. There's going to be a 50/50 low initially that looks to drift southeastward, which should result in height rises to its north. Simultaneously, we should see our storm of interest taking shape across the central U.S. as one piece of energy dives down the eastern flank of the ridge while another piece is ejecting out from the Southwest. As those phase, the long-wave trough is going to be forced to elongate and amplify, but in response to this AND the southeastward drift of the 50/50 low, height rises should* effectively pinch that southern lobe off from the main long-wave trough, resulting in a classic bowling ball closed mid-level low swinging through the interior Southeast with positive height anomalies arching over the top. Will it be classified as a technical -NAO? maybe, maybe not - statistics are a funny thing. But effectively, I think it should still function as one.

Paging Damian…..

Ok, now THIS is better certainly fits the above discussion pretty well, though there’s still room for improvement here - a lot of room.

[rb924119]

18z GFS Op is also much better, but I don’t put much stock in it. Still, it’s nice to see some operational support, or at least hints at support, even at a 10-11 day lead haha

[dkodgis]

Ray: the stuff dreams are made of

[heehaw453]

Models not picking up on discrete threats just yet. However nothing IMO has changed for next 10 days. Very minor clipper on 12/5 maybe a coating to an inch for jackpots? Then after 12/7 S/S interaction coupled with Atlantic blocking to increase threat level as we head towards 12/10. Let me also state early-mid December snowfalls exceeding 4" are rare for the I95 and coastal plain. The s/w energies after 12/7 must merge properly otherwise you'd run the risk of warm solutions or solutions that miss east. Personally I am keeping expectations set to a minor event to show for the cold air. The Big Dog would be for the alignment of the stars and climo warrants caution.

This IMO starts the increased threat window on 12/7

[Frank_Wx]

We’re entering our first stretch of colder than normal weather for this season. And it will be here to stay for the next 7-9 days in part from an active MJO wave that is currently in phase 4 and heading into phase 5. This is shown to amplify the west coast ridge (+PNA) and keep the cold locked into the eastern US. Check out the Euro Ensembles 500mb Day 6-9 averages map.



The downsides I see are our trough axis and lack of NAO blocking. One trend I’m seeing in the medium to long range is that while the cold is here, the threat for storms is not as obvious because of the +NAO and progressive northern jet. The multiple waves of northern energy are not diving deep enough into the central/eastern CONUS despite the west coast ridging. One potential system catching my attention is shown between December 8th and 10th on current guidance. We could see some pseudo NAO blocking develop which is enough to slow the jet down and promote a more favorably positioned trough. So, let’s see if we’re able to get something come together because I do think come the middle of December we are likely going to get milder again (the MJO wave likely gets into the warm phases unless it dies off before it does).

Good post, Frank, although I'm going to respectfully disagree with the following:

"The downsides I see are our trough axis and lack of NAO blocking. One trend I’m seeing in the medium to long range is that while the cold is here, the threat for storms is not as obvious because of the +NAO and progressive northern jet. The multiple waves of northern energy are not diving deep enough into the central/eastern CONUS despite the west coast ridging."

I think verbatim you're right, but reading the tea leaves a bit I think reveals that your second thought regarding the potential for the pseudo NAO blocking is more accurate. What I think the models are currently having issues resolving is the response of southern tier of the western Atlantic domain. There's going to be a 50/50 low initially that looks to drift southeastward, which should result in height rises to its north. Simultaneously, we should see our storm of interest taking shape across the central U.S. as one piece of energy dives down the eastern flank of the ridge while another piece is ejecting out from the Southwest. As those phase, the long-wave trough is going to be forced to elongate and amplify, but in response to this AND the southeastward drift of the 50/50 low, height rises should* effectively pinch that southern lobe off from the main long-wave trough, resulting in a classic bowling ball closed mid-level low swinging through the interior Southeast with positive height anomalies arching over the top. Will it be classified as a technical -NAO? maybe, maybe not - statistics are a funny thing. But effectively, I think it should still function as one.

What is your observation as to why we're seeing so much pacific energy being held back in the SW CONUS? Is it just a function of the continuous retrograding and amplification of the PNA ridge to the north? Something about the pattern aloft does not feel quite right. Whether it's the split-flow look over the western U.S. or the positively tilted trough over the eastern U.S. I'm not so sure.
DEC 5th



DEC 8th



DEC 9th

[MattyICE]

I feel like the SW/Baja LP not ejecting has been quite a thorn/theme over the past several winters.

[sroc4]

Well once again LR evolving into nothingness.  Looking less and less likely for anything of any real significance in our window before the progressive zonal pattern returns mid month. Not done yet but getting closer.

[heehaw453]

Well once again LR evolving into nothingness.  Looking less and less likely for anything of any real significance in our window before the progressive zonal pattern returns mid month. Not done yet but getting closer.

Agreed. I believe minor event possible on 12/8 as per 06Z GEFS. There is a lot of spread on the ensembles now at D6 (GEPS,EPS,GEFS).

This would supply cold air and depending on low pressure strength some moisture to work with. If this setup is false, then the 10 days of cold air will probably will be wasted and we get nothing to show for it. Still think we get something minor but sig is tough in early December...

[docstox12]

Well once again LR evolving into nothingness.  Looking less and less likely for anything of any real significance in our window before the progressive zonal pattern returns mid month. Not done yet but getting closer.

Agreed. I believe minor event possible on 12/8 as per 06Z GEFS. There is a lot of spread on the ensembles now at D6 (GEPS,EPS,GEFS).

This would supply cold air and depending on low pressure strength some moisture to work with. If this setup is false, then the 10 days of cold air will probably will be wasted and we get nothing to show for it. Still think we get something minor but sig is tough in early December...

Nothing worse than a period of ,cold air with nothing to show for it, followed by a soaking rainstorm.Been there done that over many winters in the Tri State area.Hoping something pops up regardless of the LR.

[HectorO]

I love the cold weather and getting us into the holiday spirit. My only fear with what is considered a long cold period for us, is the fear that mid-month will warm back up too much. I hope it at least stays cold.

[rb924119]

We’re entering our first stretch of colder than normal weather for this season. And it will be here to stay for the next 7-9 days in part from an active MJO wave that is currently in phase 4 and heading into phase 5. This is shown to amplify the west coast ridge (+PNA) and keep the cold locked into the eastern US. Check out the Euro Ensembles 500mb Day 6-9 averages map.



The downsides I see are our trough axis and lack of NAO blocking. One trend I’m seeing in the medium to long range is that while the cold is here, the threat for storms is not as obvious because of the +NAO and progressive northern jet. The multiple waves of northern energy are not diving deep enough into the central/eastern CONUS despite the west coast ridging. One potential system catching my attention is shown between December 8th and 10th on current guidance. We could see some pseudo NAO blocking develop which is enough to slow the jet down and promote a more favorably positioned trough. So, let’s see if we’re able to get something come together because I do think come the middle of December we are likely going to get milder again (the MJO wave likely gets into the warm phases unless it dies off before it does).

Good post, Frank, although I'm going to respectfully disagree with the following:

"The downsides I see are our trough axis and lack of NAO blocking. One trend I’m seeing in the medium to long range is that while the cold is here, the threat for storms is not as obvious because of the +NAO and progressive northern jet. The multiple waves of northern energy are not diving deep enough into the central/eastern CONUS despite the west coast ridging."

I think verbatim you're right, but reading the tea leaves a bit I think reveals that your second thought regarding the potential for the pseudo NAO blocking is more accurate. What I think the models are currently having issues resolving is the response of southern tier of the western Atlantic domain. There's going to be a 50/50 low initially that looks to drift southeastward, which should result in height rises to its north. Simultaneously, we should see our storm of interest taking shape across the central U.S. as one piece of energy dives down the eastern flank of the ridge while another piece is ejecting out from the Southwest. As those phase, the long-wave trough is going to be forced to elongate and amplify, but in response to this AND the southeastward drift of the 50/50 low, height rises should* effectively pinch that southern lobe off from the main long-wave trough, resulting in a classic bowling ball closed mid-level low swinging through the interior Southeast with positive height anomalies arching over the top. Will it be classified as a technical -NAO? maybe, maybe not - statistics are a funny thing. But effectively, I think it should still function as one.

What is your observation as to why we're seeing so much pacific energy being held back in the SW CONUS? Is it just a function of the continuous retrograding and amplification of the PNA ridge to the north? Something about the pattern aloft does not feel quite right. Whether it's the split-flow look over the western U.S. or the positively tilted trough over the eastern U.S. I'm not so sure.
DEC 5th



DEC 8th



DEC 9th

This is a good question, and to be honest, I’m not sure that I know the answer. This type of situation is something that I have definitely gotten burned by in the past - several busts of mine have been seeded in the thought that energy that buries into the Southwest should fully eject, and then reality proves that it only dribbles out over the span of several days, or doesn’t make it out at all and just sits there and festers, screwing everything up in otherwise good or great pattern. And, this is to heehaw’s point about it being a feature that we have seen fairly frequently in the last decade. In years past, my default was that it was just the Euro bias on display, but after being proven wrong enough times, it’s not so easy to dismiss as a viable outcome.

Now, I haven’t had a chance to look much at todays guidance, but the threat for the 9th-12th is far from dead, though yesterday’s guidance trended unfavorably with respect to the western ridge axis placement (off the West Coast, which is too far back for us unless we had extreme west-based NAO blocking, which we won’t here). The way to offset that, though, is to get a properly timed ejection of that southwestern energy. As long as it arrives EITHER with, OR slightly behind a true northern stream impulse (fresh injection of truly arctic air, and in the latter case, quickly followed by an amplifying wave along the frontal boundary), we can snow pretty bigly. With SO MANY other individual pieces of energy on the map, models are going to have a very hard time dialing the timing of that southwestern energy’s ejection and any potential downstream interactions. Because with each piece of northern stream energy, the ridge reshuffles. So until we can know exactly which piece we need to focus on, it’s a crapshoot. Ensembles are the way to go to try to figure out the individual wave and timing, in my opinion. But yeah, I don’t think this threat is dead yet, and I’m holding course for now.

[rb924119]

If I’m being honest, and as bias-free as possible, if I was to bet on adjustments, I would bet that we eventually see northern stream energy trend toward more favorable timing with respect to its position relative to the southwestern energy (either simultaneous with or ahead of it). The wildcard is how the southwestern behaves. Because the western ridge will be reshuffling in response to the diving northern stream. My guess? We see at least a partial ejection, and this time, because the pattern is retracting, we should see a full ejection. Why? Because essentially, as that ridge reshuffles, the “cap” created by the positively oriented ridge axis comes off, thereby freeing the southwestern energy instead of keeping it trapped. How compressed the downstream flow is will be determined by where the northern stream is (if ahead, more compressed, if behind, not compressed) and how the height field responds to the sinking 50/50 remnant low. As I said, I think the pattern overall supports a better northern stream position relative to the southern stream, but I’ll see how modeling evolves over the coming days. If I have to adjust, I will, but again, holding course for now. I will say, though, if we come away with nothing to show for this pattern, I’d chalk it up to pretty poor luck and be pretty surprised and disappointed.

[rb924119]

One other thing I want lol add is this: If there’s a storm signal, models will usually “lose”it from about Day 8 down to about Day 5/6, only to “bring it back” once inside five or six days lead time. Anecdotal, sure, but I feel that’s been almost always the case, except a very few. It’s not that the storm threat actually disappeared, but the models probably over-corrected in some form, which “disappeared” the storm. As they get a better sense of the expected conditions, they re-correct again usually toward what they originally had to at least some degree.

[rb924119]

We’re entering our first stretch of colder than normal weather for this season. And it will be here to stay for the next 7-9 days in part from an active MJO wave that is currently in phase 4 and heading into phase 5. This is shown to amplify the west coast ridge (+PNA) and keep the cold locked into the eastern US. Check out the Euro Ensembles 500mb Day 6-9 averages map.



The downsides I see are our trough axis and lack of NAO blocking. One trend I’m seeing in the medium to long range is that while the cold is here, the threat for storms is not as obvious because of the +NAO and progressive northern jet. The multiple waves of northern energy are not diving deep enough into the central/eastern CONUS despite the west coast ridging. One potential system catching my attention is shown between December 8th and 10th on current guidance. We could see some pseudo NAO blocking develop which is enough to slow the jet down and promote a more favorably positioned trough. So, let’s see if we’re able to get something come together because I do think come the middle of December we are likely going to get milder again (the MJO wave likely gets into the warm phases unless it dies off before it does).

Good post, Frank, although I'm going to respectfully disagree with the following:

"The downsides I see are our trough axis and lack of NAO blocking. One trend I’m seeing in the medium to long range is that while the cold is here, the threat for storms is not as obvious because of the +NAO and progressive northern jet. The multiple waves of northern energy are not diving deep enough into the central/eastern CONUS despite the west coast ridging."

I think verbatim you're right, but reading the tea leaves a bit I think reveals that your second thought regarding the potential for the pseudo NAO blocking is more accurate. What I think the models are currently having issues resolving is the response of southern tier of the western Atlantic domain. There's going to be a 50/50 low initially that looks to drift southeastward, which should result in height rises to its north. Simultaneously, we should see our storm of interest taking shape across the central U.S. as one piece of energy dives down the eastern flank of the ridge while another piece is ejecting out from the Southwest. As those phase, the long-wave trough is going to be forced to elongate and amplify, but in response to this AND the southeastward drift of the 50/50 low, height rises should* effectively pinch that southern lobe off from the main long-wave trough, resulting in a classic bowling ball closed mid-level low swinging through the interior Southeast with positive height anomalies arching over the top. Will it be classified as a technical -NAO? maybe, maybe not - statistics are a funny thing. But effectively, I think it should still function as one.

What is your observation as to why we're seeing so much pacific energy being held back in the SW CONUS? Is it just a function of the continuous retrograding and amplification of the PNA ridge to the north? Something about the pattern aloft does not feel quite right. Whether it's the split-flow look over the western U.S. or the positively tilted trough over the eastern U.S. I'm not so sure.
DEC 5th



DEC 8th



DEC 9th

Thinking more about your lead question, Frank, as I was drifting off to sleep while pondering my place and purpose in this universe, the true meaning of life, and a myriad of other questions that have baffled many a theologian (LOL), I came up with a hypothesis:

I wonder if the “drag” on the southwestern energy is manifested by upstream easterly or northeasterly flow coming across the Rockies behind the trough axis? In theory, that air is being driven to ascend, but because it’s ascending upstream of the trough axis, it acts “re-center” the base of the trough (thinking in terms of height anomalies). So instead of having a nice uniform trough that propagates smoothly over the Rockies and makes the bend, that trough base starts to distend and get distorted upstream. Given enough time, cold air keeps getting forced to rise over the Rockies upstream from the original trough axis on the easterly or northeasterly flow, which further cools it and continues to deepen the trough. The feedback continues, and as it does, that distorted trough re-centers further west with the new height field minimum, establishes a new trough axis, which then reorients the downstream height field enough to start redirecting some height falls BACK toward the Rockies. Continue this process, and consider that it’s occurring on the eastern flank of an anti-cyclonically breaking ridge (ridge folds over clockwise), which adds further easterly momentum flux beneath it, and that’s how you effectively trap the southwestern energy. This continues until the pattern retracts far enough to alter the flow so that there is no more ascent over the Rockies being forced on an easterly or northeasterly flow, rather a typical westerly flow, and things can proceed. To give credit, this might have been something that Bastardi mentioned a while back, but I can’t recall, so if he did, then due credit to him, but this is the most logical thing I can come up with. Now, why it only seems to be a theme more recently? I don’t know lol

Although, I feel like I remember reading either ‘93-‘94 and/or ‘95-‘96 had a persistent southwestern trough like that which just kept sending impulses out along what was an essentially stalled frontal boundary throughout most of the winter. I’d have to check, though. Or, maybe one of our more seasoned veterans can add further insight into those winters, because I was too young for the meteorological component of memory at that point haha

[billg315]

I don't remember anything about the patterns that caused those winters, but I remember both of those winters well. 1994 was cold with numerous storms producing lots of snow N&W and a couple prodigious snow and ice storms along the I-95. 1996 was also cold and snowy with a historic snowstorm in early January. So, whatever we had those winters, bring it back. lol

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