brooklynwx99

GEFS looks great broad 500mb trough over the TN Valley and some confluent flow downstream thanks to the SE Canada ULL NS energy getting picked up consistently as well

very difficult to draw it up much better than this broad 500mb trough over the TN valley, confluence over the NE and phasing imminent pretty classic look

It looks like we are finally entering an extremely favorable pattern starting around the 14-16th. The Pacific jet retraction will take place during that time, and the +PNA/-EPO will be able to strengthen and remain stable thanks to a semi-permanent Aleutian ULL: This pattern is pretty much a complete 180 from what we saw for most of December, as there is cross-polar flow established that continues throughout much, if not all of the month. This pattern is highly reminiscent of the 2013-15 winters, where there were extreme arctic outbreaks as well as increased storminess to go along with it. Now, this pattern is certainly not one that you'd normally see in a Nina, and here's why: Note the negative height anomalies in the S US along with the split flow W of S CA. This signals that the STJ will be open for business, which is rare in -ENSO winters where the northern stream is dominant and the STJ is often nowhere to be found. The main reason, at least to me, as to why this pattern is so potent is because of the split flow. There will be highly amplified shortwaves rolling S off of the western ridging that will be able to phase with cutoff lows and other pieces of energy from the southern stream. This is accomplished by the W ridging being a bit more poleward than usual: it allows for significant cross-polar flow, but it also keeps the STJ open. This is often how we get our largest storms. There is also an immense cold supply here, as our air will be sourced from Siberia. Hints of transient -NAO blocking have also been showing up on the OP runs, and there's some on the ENS means as well. Transient blocks are really all you need when it comes to large storms, as we've seen in the past. Overall, this is just a loaded pattern and I would honestly be quite surprised if there isn't a MECS (or two!) between the 15th and the end of the month. Our next threat is around the 15th, and there's already a lot of phasing potential there. We will likely have to wait until after the 20th for the pattern to mature a bit, but a KU is certainly on the table.

It looks like we are finally entering an extremely favorable pattern starting around the 14-16th. The Pacific jet retraction will take place during that time, and the +PNA/-EPO will be able to strengthen and remain stable thanks to a semi-permanent Aleutian ULL: This pattern is pretty much a complete 180 from what we saw for most of December, as there is cross-polar flow established that continues throughout much, if not all of the month. This pattern is highly reminiscent of the 2013-15 winters, where there were extreme arctic outbreaks as well as increased storminess to go along with it. Now, this pattern is certainly not one that you'd normally see in a Nina, and here's why: Note the negative height anomalies in the S US along with the split flow W of S CA. This signals that the STJ will be open for business, which is rare in -ENSO winters where the northern stream is dominant and the STJ is often nowhere to be found. The main reason, at least to me, as to why this pattern is so potent is because of the split flow. There will be highly amplified shortwaves rolling S off of the western ridging that will be able to phase with cutoff lows and other pieces of energy from the southern stream. This is accomplished by the W ridging being a bit more poleward than usual: it allows for significant cross-polar flow, but it also keeps the STJ open. This is often how we get our largest storms. There is also an immense cold supply here, as our air will be sourced from Siberia. Hints of transient -NAO blocking have also been showing up on the OP runs, and there's some on the ENS means as well. Transient blocks are really all you need when it comes to large storms, as we've seen in the past. Overall, this is just a loaded pattern and I would honestly be quite surprised if there isn't a MECS (or two!) between the 15th and the end of the month. Our next threat is around the 15th, and there's already a lot of phasing potential there. We will likely have to wait until after the 20th for the pattern to mature a bit, but a KU is certainly on the table.

It looks like we are finally entering an extremely favorable pattern starting around the 14-16th. The Pacific jet retraction will take place during that time, and the +PNA/-EPO will be able to strengthen and remain stable thanks to a semi-permanent Aleutian ULL: This pattern is pretty much a complete 180 from what we saw for most of December, as there is cross-polar flow established that continues throughout much, if not all of the month. This pattern is highly reminiscent of the 2013-15 winters, where there were extreme arctic outbreaks as well as increased storminess to go along with it. Now, this pattern is certainly not one that you'd normally see in a Nina, and here's why: Note the negative height anomalies in the S US along with the split flow W of S CA. This signals that the STJ will be open for business, which is rare in -ENSO winters where the northern stream is dominant and the STJ is often nowhere to be found. The main reason, at least to me, as to why this pattern is so potent is because of the split flow. There will be highly amplified shortwaves rolling S off of the western ridging that will be able to phase with cutoff lows and other pieces of energy from the southern stream. This is accomplished by the W ridging being a bit more poleward than usual: it allows for significant cross-polar flow, but it also keeps the STJ open. This is often how we get our largest storms. There is also an immense cold supply here, as our air will be sourced from Siberia. Hints of transient -NAO blocking have also been showing up on the OP runs, and there's some on the ENS means as well. Transient blocks are really all you need when it comes to large storms, as we've seen in the past. Overall, this is just a loaded pattern and I would honestly be quite surprised if there isn't a MECS (or two!) between the 15th and the end of the month. Our next threat is around the 15th, and there's already a lot of phasing potential there. We will likely have to wait until after the 20th for the pattern to mature a bit, but a KU is certainly on the table.

holy crap

the 12z GFS looks a bit better at 500mb! more buckling of the trough with appreciably higher heights over NJ. much more PVA into the region overall I was not expecting a positive shift at 12z here, so this is great to see. the GFS really isn't backing down here as it improved in all facets

the NAM made a huge shift at 500mb, namely in the positive interaction of the NS rather than a negative confluent push, as we had seen a couple of days ago the initial vort is more amped, which is great, but the NS is now helping to turn heights in a more southerly direction. look at the wind bards S of LI: almost due S from WSW last run. this drastically changes the angle of the PVA

the NAM made a huge shift at 500mb, namely in the positive interaction of the NS rather than a negative confluent push, as we had seen a couple of days ago the initial vort is more amped, which is great, but the NS is now helping to turn heights in a more southerly direction. look at the wind bards S of LI: almost due S from WSW last run. this drastically changes the angle of the PVA

wow, this is much more robust. closed contour at 500mb as well as higher heights over NJ

NAM is way more amped through 25

Monday's system just got more interesting with the significant amplified shift from the GEFS a couple more ticks like this and we're in business

wow, this is an amazing look. strong vort diving S of the region with great jet support

overall, this event is certainly a "thread the needle" type storm, but things still look interesting given today's trend of a stronger, slower SS vort with less NS interaction. a GFS-like solution can't be discarded at this juncture it looks like the American models are doing a decent job with this, as the ECMWF and RGEM took some steps towards the GFS/NAM. the 18z ECMWF made a nice shift towards a more favorable solution: of course, this remains rather unlikely, but I think it's worth looking to see if the 00z runs continue this trend

overall, this event is certainly a "thread the needle" type storm, but things still look interesting given today's trend of a stronger, slower SS vort with less NS interaction. a GFS-like solution cannot be discarded at this juncture it looks like the American models are doing a decent job with this, as the ECMWF and RGEM took some steps towards the GFS/NAM. the 18z ECMWF made a nice shift towards a more favorable solution: of course, this remains rather unlikely, but I think it's worth looking to see if the 00z runs continue this trend

yeah... this system is pretty intriguing if that southern stream energy can separate enough. if so, it would be able to amplify and become something like the 00z GFS, which is a gorgeous solution at 500mb. cold air would not be a problem given a good source region in Canada and a rapidly developing SLP the ECMWF made a step towards holding the SS energy back, which is the main thing to look for here imo the GEFS is also more in favor of greater stream separation as well as a more amplified southern stream... these both bode well for this event more amplified ridging out west as well, this likely helps the SS gain amplitude

My original disagreement with those posts was that, at the time of my post, the -PNA was not nearly at the strength that it was. Therefore, I was claiming that the 3 SD ridge over Greenland would overpower the -PNA, which happens an overwhelming majority of the time. However, we ended up getting 510dam heights over Seattle, which is something that nobody could predict more than a few days in advance, let alone more than 10 days. I did anticipate the -PNA, but there was no way that anybody could see its record breaking nature at that lead time, which is what fully overwhelmed the pattern. Look, LR forecasting is hard, and I did not want to derail my intuition based on the slight possibility that an unprecedented event would occur. It would be just as bad if I said there would be a blizzard over the metro if there was a mean trough over the E US at 180 hours. Everyone makes mistakes though, the weather humbles everyone.

Unfortunately, although the anomalous -NAO/-EPO couplet did develop, it is impossible to overcome a record breaking -PNA. If the PNA was negative but not completely unprecedented (which is what I wrongly predicted), then this month would’ve turned out much differently. Nobody could’ve have seen the PNA being that overpowering, as it was literally a historical event, and there was no indication that an event of such magnitude would unfold. A “normal” -PNA would have been easily overcome by the -NAO, not a -3 sigma trough. So yes, there was a complete pattern change, but we got very unlucky and I’d be lying if I said I wasn’t a bit frustrated about it.

The GEFS and EPS have a gorgeous pattern evolution towards the end of their runs... this is thanks to the extension of the Pacific jet in the medium-long range: This jet extension is thanks in part to the +EAMT that is forecasted to develop in the short range: So, overall, it looks like there is some forcing that may be able to shake up this pattern. The jet extension will allow for the anomalous Aleutian ridge to build poleward and kick the mean trough out of the Pac NW and into the N Plains. This, in turn will allow for cold air to bleed into the E US: It's nice to see the changes to the Pacific jet, as those kinds of shifts on modeling are usually representative of a large shift in the pattern and not a temporary blip. It's great to see the blocking signal still holding strong as well, as the 50/50 ULL and -NAO remain prominent features throughout the runs. As long as the mean position of the trough changes to anywhere east of where it is now, that would be a massive improvement. The patterns on the end of the runs would be quite cold and stormy with the Pacific becoming much more favorable with the cold dumping into the midsection of the country. Now, of course, this could be a head fake, but I really don't believe so. The MJO is taking its time propagating through the Pacific, and Phase 7 forcing is more favorable in January anyway, so I don't see it as an issue. The +EAMT is also forecast to begin very soon, and the changes to the jet over the Pacific aren't very far out either. The forcing mechanisms that might help shake things up are in a tangible range. Overall, I would like to see these changes continue into the weekend. The Jan 2 period is intriguing, as there could be some TPV influence in Canada and some SS wave trying to cut underneath. That's really all you can say at this range. However, it's nice that we're getting some chances, and we have that possible threat as well as the small WAA push in a couple days that's worth keeping an eye on for some light snow.

The GEFS and EPS have a gorgeous pattern evolution towards the end of their runs... this is thanks to the extension of the Pacific jet in the medium-long range: This jet extension is thanks in part to the +EAMT that is forecasted to develop in the short range: So, overall, it looks like there is some forcing that may be able to shake up this pattern. The jet extension will allow for the anomalous Aleutian ridge to build poleward and kick the mean trough out of the Pac NW and into the N Plains. This, in turn will allow for cold air to bleed into the E US. It's nice to see the changes to the Pacific jet, as those kinds of shifts on modeling are usually representative of a large shift in the pattern and not a temporary blip. It's great to see the blocking signal still holding strong as well, as the 50/50 ULL and -NAO remain prominent features throughout the runs. As long as the mean position of the trough changes to anywhere east of where it is now, that would be a massive improvement. The patterns on the end of the runs would be quite cold and stormy with the Pacific becoming much more favorable with the cold dumping into the midsection of the country. Now, of course, this could be a head fake, but I really don't believe so. The MJO is taking its time propagating through the Pacific, and Phase 7 forcing is more favorable in January anyway, so I don't see it as an issue. The +EAMT is also forecast to begin very soon, and the changes to the jet over the Pacific aren't very far out either. The forcing mechanisms that might help shake things up are in a tangible range. Overall, I would like to see these changes continue into the weekend. The Jan 2 period is intriguing, as there could be some TPV influence in Canada and some SS wave trying to cut underneath. That's really all you can say at this range. However, it's nice that we're getting some chances.

The GEFS and EPS have a gorgeous pattern evolution towards the end of their runs... this is thanks to the extension of the Pacific jet in the medium-long range: This jet extension is thanks in part to the +EAMT that is forecasted to develop in the short range: So, overall, it looks like there is some forcing that may be able to shake up this pattern. The jet extension will allow for the anomalous Aleutian ridge to build poleward and kick the mean trough out of the Pac NW and into the N Plains. This, in turn will allow for cold air to bleed into the E US: It's nice to see the changes to the Pacific jet, as those kinds of shifts on modeling are usually representative of a large shift in the pattern and not a temporary blip. It's great to see the blocking signal still holding strong as well, as the 50/50 ULL and -NAO remain prominent features throughout the runs. As long as the mean position of the trough changes to anywhere east of where it is now, that would be a massive improvement. The patterns on the end of the runs would be quite cold and stormy with the Pacific becoming much more favorable with the cold dumping into the midsection of the country. Now, of course, this could be a head fake, but I really don't believe so. The MJO is taking its time propagating through the Pacific, and Phase 7 forcing is more favorable in January anyway, so I don't see it as an issue. The +EAMT is also forecast to begin very soon, and the changes to the jet over the Pacific aren't very far out either. The forcing mechanisms that might help shake things up are in a tangible range. Overall, I would like to see these changes continue into the weekend. The Jan 2 period is intriguing, as there could be some TPV influence in Canada and some SS wave trying to cut underneath. That's really all you can say at this range. However, it's nice that we're getting some chances, and we have that possible threat as well as the small WAA push in a couple days that's worth keeping an eye on for some light snow.

thanks! I usually post in the NYC subregion but I figured that most of the time my thoughts are just as applicable down here I really am quite optimistic about this pattern to close out the month. it's not perfect by any means, but it will provide chances and that's really all you can ask for in late December. early January could be nuts though if the WC only gets a touch better with that -NAO. it wouldn't have to be a big shift at all

That much of an anomalous west-based -NAO on a 10-15 day mean is just insane. We should start to see some chances around Christmas into the New Year with shortwaves rolling underneath the block (like the 12z GFS). It might warm up for a bit as the SE ridge pumps for a day or two in that timeframe, but that will be transient if it happens. Models often take a while to see the full effect of the block on the longwave pattern, and the EPS has generally done a horrible job from the start determining the strength of the block to begin with, so I'm not so sure I trust its depiction of the pattern over the CONUS as much as the other ensembles. The progression of tropical forcing will allow for the PNA region to become much more favorable for larger snowfall chances heading into early January. The GEFS and GEPS show this well as the trough focuses more towards the Rockies and cold air begins to spill into the E/C US as ridging begins to move towards the WC: That would be all this pattern needs to go from a bit better than average to something with huge potential, and it looks to be progressing that way as of now. Also, I've been hearing a lot of complaints about temperatures not being cold enough yet (not here, just generally), and I don't think that's as big of an issue as many make it out to be. Usually, when we see these big -NAO patterns, we're late in the season and climo is much more unfavorable temps-wise. However, we're in peak climo, and above normal 850mb temperatures are still cold enough to snow. We don't need big negative departures: Most of the NE/MA is either at normal or very slightly below average at 850mb, but temperatures are more than cold enough for any system going south of the region. With a pattern that'll allow for that, this is all that's needed to see snowfall events.

That much of an anomalous west-based -NAO on a 10-15 day mean is just insane. We should start to see some chances around Christmas into the New Year with shortwaves rolling underneath the block (like the 12z GFS). It might warm up for a bit as the SE ridge pumps for a day or two in that timeframe, but that will be transient if it happens. Models often take a while to see the full effect of the block on the longwave pattern, and the EPS has generally done a horrible job from the start determining the strength of the block to begin with, so I'm not so sure I trust its depiction of the pattern over the CONUS as much as the other ensembles. The progression of tropical forcing will allow for the PNA region to become much more favorable for larger snowfall chances heading into early January. The GEFS and GEPS show this well as the trough focuses more towards the Rockies and cold air begins to spill into the E/C US as ridging begins to move towards the WC: That would be all this pattern needs to go from a bit better than average to something with huge potential, and it looks to be progressing that way as of now. Also, I've been hearing a lot of complaints about temperatures not being cold enough yet (not here, just generally), and I don't think that's as big of an issue as many make it out to be. Usually, when we see these big -NAO patterns, we're late in the season and climo is much more unfavorable temps-wise. However, we're in peak climo, and above normal 850mb temperatures are still cold enough to snow. We don't need big negative departures: Most of the NE is either at normal or very slightly below average at 850mb, but temperatures are more than cold enough for any system going south of the region. With a pattern that'll allow for that, this is all that's needed to see snowfall events.

I can also take OP runs from 192 hours at face value