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Pattern The Great December Dump

The differences between the Euro & GFS really are stark even at day 5. Euro digs our shortwave of interest into the southwestern US while the GFS progresses the wave out into the southern Rockies & phases w/ the longwave trough over the plains & south-central Canada.

Timing is everything in this pattern

ecmwf_z500a_us_6.png

gfs_z500a_us_20.png
 
Webberweather53 said:
The differences between the Euro & GFS really are stark even at day 5. Euro digs our shortwave of interest into the southwestern US while the GFS progresses the wave out into the southern Rockies & phases w/ the longwave trough over the plains & south-central Canada.

Timing is everything in this pattern

View attachment 26999

View attachment 27000
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Webb, is timing ever not everything?
 
The GFS seems to be heading for a dud. I'm noticing one big error with the low that can be traced back even before 48hr. Notice that big low off the coast of CA and OR. The GFS has it subtlely further east so the energy phases and goes North well out of our way. The Euro luckily is much further west, so it becomes a cutoff low and digs.

Luckily we have the euro on our side and the usual problem of a sustainable high has high confidence according to Webb. I think models should cave to each other within a day or 2. Subtle changes are extremely important!
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Sleet City USA said:
Webb, is timing ever not everything?
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It's even more important here imo in this kind of pattern because the northern stream waves are moving very quickly in the mean stream flow. In a more classic -NAO pattern which decelerates the northern stream & the southern stream is often more prominent, our windows to fit a storm are typically larger although the air masses that come with them are marginal.
 
I’m ready to see what the GEFS has to say about this wether it will say the GFS is wrong or back the GFS
 
So the big takeaways that I got here is that the right pattern for a storm is coming and all we need is good timing. Honestly despite the fact that it's currently a day 6-8 affair and that the GFS is poop, I honestly think this should be watched and not dismissed, unless ofc everything goes poof on the next runs.

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Webberweather53 said:
It's even more important here imo in this kind of pattern because the northern stream waves are moving very quickly in the mean stream flow. In a more classic -NAO pattern which decelerates the northern stream & the southern stream is often more prominent, our windows to fit a storm are typically larger although the air masses that come with them are marginal.
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If you think about it in this manner: during -EPO/+TNH we have a stronger height and temperature gradient between us and central Canada, this height gradient means the jet stream is stronger and so are the corresponding winds >>> faster moving shortwaves. On the other hand, with -NAO and Baffin Bay blocks theres typically a “traffic jam” immediately upstream over North America that slows northern stream waves down a lot and the height gradient is also weaker. The subtropical jet (STJ) on the other hand is much stronger as -NAOs are often a symptom of El Niño or a sub seasonal convective boost from the Pacific & W hem which “juice” the STJ.
All of this really means the phase speeds of the waves in the two streams are often more comparable in -NAOs vs +TNH/-EPOs, thus there’s inherently a larger window of time for phasing &/or interaction between the polar and subtropical jet as long as their initial placement is roughly the same.
 
Jessy89 said:
Euro is all by itself. Question is does it hold on to it tonight’s runs.


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Including a good chunk of EPS members, until we can get the majority to see wintery precip, I'm still skeptical.
 
And I have seen this movie before. One model, this time the GFS, shows a storm in the long range, at least 14 days out, only for it to go poof, and then another model, this time the Euro, shows it out of nowhere inside 10 days. And then the one that showed it in the long range eventually shows the storm again when we get closer.
 
Brick Tamland said:
And I have seen this movie before. One model, this time the GFS, shows a storm in the long range, at least 14 days out, only for it to go poof, and then another model, this time the Euro, shows it out of nowhere inside 10 days. And then the one that showed it in the long range eventually shows the storm again when we get closer.
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Sounds familiar ??
 
Next euro runs when 9pm or so? I wouldn’t be surprised if it backs off.


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Webberweather53 said:
It's Brad P I know but I don't think this is a horrible take on tracking winter storms.

He says we're not even to step 1 yet, obviously that's bull ?.

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In all fairness to Brad, he’s had some pretty big busted forecasts the last few years especially for those of us in the southeastern part of CLT metro
 
Jessy89 said:
Next euro runs when 9pm or so? I wouldn’t be surprised if it backs off.


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The 18z Euro has already run, it goes out to 90hrs only, from the looks of it, even better than 12z having the low further west which should help it cutoff. The 18z EPS that goes out to 144hrs just started and should have data in by 9.

The main 00z Euro runs around 12:45 to about 2am.


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After spending time looking over data and coming up with thoughts I have came up with a prediction. This is not a forecast, it is a prediction which this prediction has a good chance at verifying. I have not backed down for days now. Keep in mind, I use a blend of models (not just one, or two, or three) to generate my predictions.

Using a blend of the Euro, GFS, CMC and the GEFS/EPS this is what I have came up with (map below) I think the Euro is 24 hours too slow with the storm system. So, instead of the low developing Wednesday into Thursday, I think the storm system will begin to develop Tuesday and track along the Gulf coast and out along the southeastern coast by dawn Wednesday. Why? because the polar and STJ is going to converge Tuesday afternoon/evening, at that point, the low pressure will develop quickly and start tracking along the fast moving jet streak over night Tuesday into Wednesday. At the time of the convergence, overrunning is possible Tuesday evening before the low kicks out and rides along the fast moving jet.

The low pressure system will likely be a fast mover, due to the convergence of the polar and sub-tropical jet, thus will increase jet streak winds high as 140kts. Even though, the low pressure system will likely be a fast mover, I do think it will bring tremendous amounts of snow totals because there will be strong convection in the upper-levels. The strong convection would be caused by, of course strong vertical motion due to the convergence of the polar and STJ. Which of course, strong convection would mean high QPF amounts. Not only that, the cold air mass will be immensely deep, colder it is, the higher the snow ratios will be.

More about the map, a mesoscale high pressure may build over the northeastern US overnight Tuesday into Wednesday morning. For area's east of the mountains, p-type will greatly depend on how much WAA will take place. But, overall, I think this system will bring mostly snow, and heavy snow at that.

SnowStormMap.jpg

Euro showing high QPF levels, this would be a tremendous amount of snow. Again, the reason of high QPF levels is due to the strong vertical motion in the upper level that will induce strong convection cause by the convergence of the polar and STJ.

Euroqpf_024h.conus.png



JetStreamWinds.png


Anyone that has access to the upper-levels from the Euro, such as the jet stream winds, vort, please add. We need to see what's going on with the jet streams/vort on the Euro. Also, due the polar and STJ convergence, I think the storm system would be stronger than modeled on the Euro.
 
WxWatch said:
After spending time looking over data and coming up with thoughts I have came up with a prediction. This is not a forecast, it is a prediction which this prediction has a good chance at verifying. I have not backed down for days now. Keep in mind, I use a blend of models (not just one, or two, or three) to generate my predictions.

Using a blend of the Euro, GFS, CMC and the GEFS/EPS this is what I have came up with (map below) I think the Euro is 24 hours too slow with the storm system. So, instead of the low developing Wednesday into Thursday, I think the storm system will begin to develop Tuesday and track along the Gulf coast and out along the southeastern coast by dawn Wednesday. Why? because the polar and STJ is going to converge Tuesday afternoon/evening, at that point, the low pressure will develop quickly and start tracking along the fast moving jet streak over night Tuesday into Wednesday. At the time of the convergence, overrunning is possible Tuesday evening before the low kicks out and rides along the fast moving jet.

The low pressure system will likely be a fast mover, due to the convergence of the polar and sub-tropical jet, thus will increase jet streak winds high as 140kts. Even though, the low pressure system will likely be a fast mover, I do think it will bring tremendous amounts of snow totals because there will be strong convection in the upper-levels. The strong convection would be caused by, of course strong vertical motion due to the convergence of the polar and STJ. Which of course, strong convection would mean high QPF amounts. Not only that, the cold air mass will be immensely deep, colder it is, the higher the snow ratios will be.

More about the map, a mesoscale high pressure may build over the northeastern US overnight Tuesday into Wednesday morning. For area's east of the mountains, p-type will greatly depend on how much WAA will take place. But, overall, I think this system will bring mostly snow, and heavy snow at that.

View attachment 27002

Euro showing high QPF levels, this would be a tremendous amount of snow. Again, the reason of high QPF levels is due to the strong vertical motion in the upper level that will induce strong convection cause by the convergence of the polar and STJ.

View attachment 27003



View attachment 27004


Anyone that has access to the upper-levels from the Euro, such as the jet stream winds, vort, please add. We need to see what's going on with the jet streams/vort on the Euro. Also, due the polar and STJ convergence, I think the storm system would be stronger than modeled on the Euro.
Click to expand...
Usually, high QPF and deep cold, don’t occur together. That’s a reason the South hasn’t seen many 12” + snowstorms.
 
WxWatch said:
After spending time looking over data and coming up with thoughts I have came up with a prediction. This is not a forecast, it is a prediction which this prediction has a good chance at verifying. I have not backed down for days now. Keep in mind, I use a blend of models (not just one, or two, or three) to generate my predictions.

Using a blend of the Euro, GFS, CMC and the GEFS/EPS this is what I have came up with (map below) I think the Euro is 24 hours too slow with the storm system. So, instead of the low developing Wednesday into Thursday, I think the storm system will begin to develop Tuesday and track along the Gulf coast and out along the southeastern coast by dawn Wednesday. Why? because the polar and STJ is going to converge Tuesday afternoon/evening, at that point, the low pressure will develop quickly and start tracking along the fast moving jet streak over night Tuesday into Wednesday. At the time of the convergence, overrunning is possible Tuesday evening before the low kicks out and rides along the fast moving jet.

The low pressure system will likely be a fast mover, due to the convergence of the polar and sub-tropical jet, thus will increase jet streak winds high as 140kts. Even though, the low pressure system will likely be a fast mover, I do think it will bring tremendous amounts of snow totals because there will be strong convection in the upper-levels. The strong convection would be caused by, of course strong vertical motion due to the convergence of the polar and STJ. Which of course, strong convection would mean high QPF amounts. Not only that, the cold air mass will be immensely deep, colder it is, the higher the snow ratios will be.

More about the map, a mesoscale high pressure may build over the northeastern US overnight Tuesday into Wednesday morning. For area's east of the mountains, p-type will greatly depend on how much WAA will take place. But, overall, I think this system will bring mostly snow, and heavy snow at that.

View attachment 27002

Euro showing high QPF levels, this would be a tremendous amount of snow. Again, the reason of high QPF levels is due to the strong vertical motion in the upper level that will induce strong convection cause by the convergence of the polar and STJ.

View attachment 27003



View attachment 27004


Anyone that has access to the upper-levels from the Euro, such as the jet stream winds, vort, please add. We need to see what's going on with the jet streams/vort on the Euro. Also, due the polar and STJ convergence, I think the storm system would be stronger than modeled on the Euro.
Click to expand...

Very detailed prediction but when will models jump on board and show quite a snow storm. I mean your basically saying this thing is gonna dump a swath of a foot of snow on people the middle of next week. If models don’t show this soon people will be caught off guard and unprepared for such a storm.


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WxWatch said:
In this case they would occur together, because of the polar and STJ convergence. That is one of the biggest factors that would trigger the snow storm.
Click to expand...
Video?

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WxWatch said:
After spending time looking over data and coming up with thoughts I have came up with a prediction. This is not a forecast, it is a prediction which this prediction has a good chance at verifying. I have not backed down for days now. Keep in mind, I use a blend of models (not just one, or two, or three) to generate my predictions.

Using a blend of the Euro, GFS, CMC and the GEFS/EPS this is what I have came up with (map below) I think the Euro is 24 hours too slow with the storm system. So, instead of the low developing Wednesday into Thursday, I think the storm system will begin to develop Tuesday and track along the Gulf coast and out along the southeastern coast by dawn Wednesday. Why? because the polar and STJ is going to converge Tuesday afternoon/evening, at that point, the low pressure will develop quickly and start tracking along the fast moving jet streak over night Tuesday into Wednesday. At the time of the convergence, overrunning is possible Tuesday evening before the low kicks out and rides along the fast moving jet.

The low pressure system will likely be a fast mover, due to the convergence of the polar and sub-tropical jet, thus will increase jet streak winds high as 140kts. Even though, the low pressure system will likely be a fast mover, I do think it will bring tremendous amounts of snow totals because there will be strong convection in the upper-levels. The strong convection would be caused by, of course strong vertical motion due to the convergence of the polar and STJ. Which of course, strong convection would mean high QPF amounts. Not only that, the cold air mass will be immensely deep, colder it is, the higher the snow ratios will be.

More about the map, a mesoscale high pressure may build over the northeastern US overnight Tuesday into Wednesday morning. For area's east of the mountains, p-type will greatly depend on how much WAA will take place. But, overall, I think this system will bring mostly snow, and heavy snow at that.

View attachment 27002

Euro showing high QPF levels, this would be a tremendous amount of snow. Again, the reason of high QPF levels is due to the strong vertical motion in the upper level that will induce strong convection cause by the convergence of the polar and STJ.

View attachment 27003



View attachment 27004


Anyone that has access to the upper-levels from the Euro, such as the jet stream winds, vort, please add. We need to see what's going on with the jet streams/vort on the Euro. Also, due the polar and STJ convergence, I think the storm system would be stronger than modeled on the Euro.
Click to expand...
I can't tell if you know the future, if you actually just have supreme confidence that this is going to happen, or what it is. But you really seem to really be all in on this. I tell you one thing, if this thing drops a massive snowstorm like you are saying, you become a legend. Lol but it's really hard to believe something like this is going to happen. Just very interested to see if the Euro does anything similar tonight that it did this afternoon.
 
WxWatch said:
In this case they would occur together, because of the polar and STJ convergence. That is one of the biggest factors that would trigger the snow storm.
Click to expand...
Thanks for the big post! One thing I would point out is that if you're expecting heavy wet snow, you won't get high ratios. If you're expecting high ratios due to deep cold, the snow will be more powdery in nature. Might be good to incorporate that variable into your model. Might help with predicting or forecasting or estimating (not sure how we're using these terms now??) snow depth.
 
It seems like it has been a very long time since we've seen a true Arctic blast in the early to middle part of December for the Southeastern US.
 
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