JAN 20th-22nd potential..

[Stephen Turner]

18z GFS had 0.57" for KPNE. That sounds like a respectable snow storm to me.

I really would love to see the ECM come on board tonight though.

when does the ECM come out?

[earthlight]

when does the ECM come out?

Euro runs twice a day, 12z and 00z..which is equivalent to roughly 12:45 pm and 12:45 am.

[Snowtrain]

Maybe I'm misunderstanding you. To me this doesn't look like a signal for an epic storm. But if you mean it's a strong - you might even say epic - signal for some kind of storm, then I would agree. I think this looks like a legitimate threat for a somewhat run of the mill moderate snowstorm for a large swatch of the northeast. The synoptic pattern during this period looks relatively progressive and none of the modeling has a longwave trof with sufficient amplitude to thrust this threat into the major category except possibly the GGEM. But even the Canadian, which produces a higher amplitude trof and much more rapidly deepending surface low, moves the SLP along pretty quickly. At second glance the NAM is almost as impressive as the GEM as well.

It's true that the GFS has trended away from the dampening flat wave, lagging southern stream scenario, but I feel we're headed towards a moderate snowstorm if the pieces come together. To me this setup does not look epic, ultra dynamic, historical, or however you want to call it. 0.8-1.2 liq. eq. upper limit with something like .4-.8 more likely.

\

Agree here, only b/c the system shows no sign of lasting more than 12hr's. How many "epic" events weren't 24+hr long storms with long reaching effects felt throughout the entire east coast.

[eduggs]

Fair opinion, but I disagree. The dynamics with this system are actually pretty impressive. If it were just a northern stream feature, I guess you might say it's "typical", but even then..the height falls would be impressive and the shortwave dynamic. In this system specifically, as modeled right now, we're seeing a "southern stream" feature getting involved. The reason I quote it is because it's not the definition of a southern stream, but it definitely heads that direction as it breaks off from the Pacific Jet and then dives towards the Southern US.

You aren't going to get a 2" liquid QPF bomb with a 970mb low off the coast, but you can't say this system isn't "dynamic". The surface low is already being modeled in the 980's by some models. The UVV's and omega values are already being forecast to be extremely impressive with deep cyclogenesis. This can create a Dec 9, 2005 type snow bomb..where you get very intense snow moving through the area with whiteout conditions for a few hours, owing to the very strong dynamic forcing aloft..and then when the system deepens so rapidly you can often get rapid surface cyclone maturing..and a CCB development.

Well it's got me checking every 6 hours so it's not like I'm completely dismissing it. I just mean that I don't think it will be particularly special meteorologically. No we don't get strong coastal cyclogenesis every week, but across the North American mid-latitudes this sort of development is not particularly noteworthy. Isolated snow bombs are cool but so are persistent lake effect bands.

Of course these things are inherently unpredictable but at this stage if I were to broadly categorize the threat, I would place it cleanly below the Dec 26th and Jan 11 events.

[baroclinic_instability]

CIMSS had a really good blog entry after the storm last week.

http://cimss.ssec.wi...g/archives/7395

I love CIMSS Scott Bachmeier is a very smart man and has a great synoptic/forecasting background. He has done some great research.

[Mikehobbyst]

Just what we need with all the snow on top of snow, the darn snowpiles will still be around till Easter which falls on 4/24/2011. Enough is enough ...

[baroclinic_instability]

Yes this is precisely what happend with the boxing day storm, correct? The northern stream latched on the backside of the southern S/W. Is there any significance to this evolution in regards to increasing the dynamics of the phased system. For instance does it cause the trought to tilt negatively quicker or slow down the forward motion of the system? Thanks in advance.

Th early phase is key. Read the back-forth between amPSU and I. But yeah, the secondary wave acts like a "trigger" to incite the development of the upper level cold front downward and to induce deep cyclogenesis as a response.

[tornadojay]

Fair opinion, but I disagree. The dynamics with this system are actually pretty impressive. If it were just a northern stream feature, I guess you might say it's "typical", but even then..the height falls would be impressive and the shortwave dynamic. In this system specifically, as modeled right now, we're seeing a "southern stream" feature getting involved. The reason I quote it is because it's not the definition of a southern stream, but it definitely heads that direction as it breaks off from the Pacific Jet and then dives towards the Southern US.

You aren't going to get a 2" liquid QPF bomb with a 970mb low off the coast, but you can't say this system isn't "dynamic". The surface low is already being modeled in the 980's by some models. The UVV's and omega values are already being forecast to be extremely impressive with deep cyclogenesis. This can create a Dec 9, 2005 type snow bomb..where you get very intense snow moving through the area with whiteout conditions for a few hours, owing to the very strong dynamic forcing aloft..and then when the system deepens so rapidly you can often get rapid surface cyclone maturing..and a CCB development.

Yes, I definitely agree with John on this. This system actually has a lot of forcing mechanisms working behind it and all at about the same time. There is definitely large scale synoptic forcing both from a thermal perspective, but also from 500 mb and above perspective. If you look at the thermal advection at 850 mb, even just looking at the map, you can see there is strong thermal forcing with height lines and isotherms pretty much crossing perpindicularly. Another way to back this up is to look at the wind profile with respect to height. Remember, that with strong WAA, winds will rapidly veer with height. Although it happens for a short duration, you can see by the map below between Jan 21st and the 22nd that there is fairly strong veering with height at the lower levels, indicative of WAA forcing. Also, there is a pretty serious vortmax pushing through producing vorticity advection. That adds to the forcing. Finally, there is a large jet streak to our south and we are in a favorable quadrant for upward forcing as well. The only thing working against a very heavy snowfall is the speed of the system. Of course, if it becomes a more amplified solution in time and has a chance to close off a bit, that could help out.

EDIT: By the way.. you can see the first system for tomorrow really has a lot of warm air advection forcing. Note the 30-40 knot southeast wind. The forcing parameter is not only based on the amount of turn with height, but also on the wind speed itself.

[baroclinic_instability]

Well it's got me checking every 6 hours so it's not like I'm completely dismissing it. I just mean that I don't think it will be particularly special meteorologically. No we don't get strong coastal cyclogenesis every week, but across the North American mid-latitudes this sort of development is not particularly noteworthy. Isolated snow bombs are cool but so are persistent lake effect bands.

Of course these things are inherently unpredictable but at this stage if I were to broadly categorize the threat, I would place it cleanly below the Dec 26th and Jan 11 events.

Agree to disagree then. This is quite special were it to happen--even if it is not an HECS. It is all relative I guess--DC would die for an event like this the way this winter has gone. Reverse the roles--and in a bad year--you would beg for an event such as this as well.

[Snowtrain]

Th early phase is key. Read the back-forth between amPSU and I. But yeah, the secondary wave acts like a "trigger" to incite the development of the upper level cold front downward and to induce deep cyclogenesis as a response.

Thank you much! I greatly appreciate your input on this thead. I was reading your's and ampsu's dialogue, but my untrained vocabulary leaves me in a ball of confusion;)

[am19psu]

Thank you much! I greatly appreciate your input on this thead. I was reading your's and ampsu's dialogue, but my untrained vocabulary leaves me in a ball of confusion;)

In all seriousness, if you have some questions, start a thread on it. There are lots of mets in this forum that will be willing to help.

[eduggs]

\

Agree here, only b/c the system shows no sign of lasting more than 12hr's. How many "epic" events weren't 24+hr long storms with long reaching effects felt throughout the entire east coast.

Yeah, it does look relatively short duration. But I think there's some room to slow this down/drag it out.

I think my downplaying this potential event is a reaction to other posters' playing it up so strongly. When every event is described with such rarified adjectives, it becomes difficult to distinguish to truly rare and spectacular threats. I actually believe some places in the region could see a foot of snow on Friday if things broke right.

[baroclinic_instability]

Yeah, it does look relatively short duration. But I think there's some room to slow this down/drag it out.

I think my downplaying this potential event is a reaction to other posters' playing it up so strongly. When every event is described with such rarified adjectives, it becomes difficult to distinguish to truly rare and spectacular threats. I actually believe some places in the region could see a foot of snow on Friday if things broke right.

It probably won't slow down without any blocking and the overall configuration of the trough. The cyclone will be embedded in some very fast westerlies "de-amplifying" as it ejects NE--in other words speeding up.

[eduggs]

Agree to disagree then. This is quite special were it to happen--even if it is not an HECS. It is all relative I guess--DC would die for an event like this the way this winter has gone. Reverse the roles--and in a bad year--you would beg for an event such as this as well.

Yup, disagree but probably more of principle than on any technical aspects.

Yes, in a bad year I would hope for snow from this threat or any that would produce snow. Matter of fact I'm looking forward to it as is. But I firmly believe this is not a special or unique synoptic setup. When the trof axis is further east or especially west, these events go by largely unnoticed. But they happen with regularity. What catches the eye is that the wave timing and very distinct baroclinicity are coinciding with the natural coastal baroclinic zone at just the right lat and lon to threaten our region with snowfall.

[Snowtrain]

Yeah, it does look relatively short duration. But I think there's some room to slow this down/drag it out.

I think my downplaying this potential event is a reaction to other posters' playing it up so strongly. When every event is described with such rarified adjectives, it becomes difficult to distinguish to truly rare and spectacular threats. I actually believe some places in the region could see a foot of snow on Friday if things broke right.

I didn't think you were downplaying the event at all, rather making and assumption as did I, that when someone mentions an "epic" signal that that it would relate to a HECS being shown on the models. I think that the use of the acronym HECS is so overused on many of the weather forums/sites by users when a coastal low is depicted on the models. When I think of "epic" or HECS I immediatley think Jan 96, Mar 93, Feb 83 to name a few. These stoms that we have expereinced over the last one and half winter seasons have been extremely dynamic in their own rights and had HECS like effects associated with them, but these effects were farily localized. I believe a true HECS has to have far stretching effects felt throughout the region and the duration of said events are typically 24hr+. just an opinion.

[eduggs]

It probably won't slow down without any blocking and the overall configuration of the trough. The cyclone will be embedded in some very fast westerlies "de-amplifying" as it ejects NE--in other words speeding up.

Right. I don't mean that the largescale flow could slow down. Just that our coastal low pressure center could slow as it moves along the SNE coastal waters a la the Canadian depiction. With it's deeper, negatively tilted trof and eventual mid-level cutoff. SLP matures quicker and further south and begins to occlude and stack (and hence slow) further SW than, for example, the 18z GFS.

[earthlight]

\

Agree here, only b/c the system shows no sign of lasting more than 12hr's. How many "epic" events weren't 24+hr long storms with long reaching effects felt throughout the entire east coast.

I think the duration argument is kinda weak. We've had plenty of hard hitting events that last 12 hours or less. Again, I'm not trying to argue that this is going to be an epic HECS. But I think there's some argument (or maybe I am misunderstanding a bit, could be) going on that this event is mundane. I don't think you can call it mundane given the dynamics being portrayed by most guidance at this point. The shortwave is very strong, the dynamics and forcing are also very strong. Getting a 980's mb low to form from a northern stream shortwave diving southeast..and having it develop so far south as some models indicate is not your run of the mill mid-latitude cyclone.

So I guess that's where both sides of the argument can come from. I'm not saying this is an epic event aka a HECS..but I also don't think it's a mundane run of the mill cyclone. It has the potential to falll into the "MECS" category if all the pieces come together.

By the way, some great discussion ongoing in this thread. Good stuff dudes.

[eduggs]

I didn't think you were downplaying the event at all, rather making and assumption as did I, that when someone mentions an "epic" signal that that it would relate to a HECS being shown on the models. I think that the use of the acronym HECS is so overused on many of the weather forums/sites by users when a coastal low is depicted on the models. When I think of "epic" or HECS I immediatley think Jan 96, Mar 93, Feb 83 to name a few. These stoms that we have expereinced over the last one and half winter seasons have been extremely dynamic in their own rights and had HECS like effects associated with them, but these effects were farily localized. I believe a true HECS has to have far stretching effects felt throughout the region and the duration of said events are typically 24hr+. just an opinion.

I think this is well stated. And I feel the same.

[earthlight]

Agree to disagree then. This is quite special were it to happen--even if it is not an HECS. It is all relative I guess--DC would die for an event like this the way this winter has gone. Reverse the roles--and in a bad year--you would beg for an event such as this as well.

Yeah this is where I'm coming from as well. It's just not too often you see this type of northern stream amplification (and interaction with another shortwave while that's happening) at this latitude. There's a reason why we all remember these events and can list the dates off the top of our heads.

[tombo82685]

Th early phase is key. Read the back-forth between amPSU and I. But yeah, the secondary wave acts like a "trigger" to incite the development of the upper level cold front downward and to induce deep cyclogenesis as a response.

so, we want an earlier phase? Wouldn't and earlier phase be bad for the cities and coast? What i see if we get an earlier phase the hgts will increase moreso out ahead of the front thus pumping the se ridge and pushing the 850/925 mb temps to the cities or even past. I would think less of a phase would eep a colder solution but less precip.

[jm1220]

I think the duration argument is kinda weak. We've had plenty of hard hitting events that last 12 hours or less. Again, I'm not trying to argue that this is going to be an epic HECS. But I think there's some argument (or maybe I am misunderstanding a bit, could be) going on that this event is mundane. I don't think you can call it mundane given the dynamics being portrayed by most guidance at this point. The shortwave is very strong, the dynamics and forcing are also very strong. Getting a 980's mb low to form from a northern stream shortwave diving southeast..and having it develop so far south as some models indicate is not your run of the mill mid-latitude cyclone.

So I guess that's where both sides of the argument can come from. I'm not saying this is an epic event aka a HECS..but I also don't think it's a mundane run of the mill cyclone. It has the potential to falll into the "MECS" category if all the pieces come together.

By the way, some great discussion ongoing in this thread. Good stuff dudes.

This could be a memorable storm for some if the pieces come together properly, but I'm still concerned about an outcome that phases the streams too soon and causes some along the coast to mix over or go to rain. I'm not as worried about an OTS solution, since the tendency this winter has been to amplify/phase whenever possible. Without much blocking though, I could see it happening unfavorably and the low tracking too far west. Hopefully I'm wrong though!!

[TheTrials]

one thing I always like to look for is the gom being open for business, and as you can see by the 850 charts, its wide open.

[am19psu]

Not sure if you guys saw or not, but the planes were out in the Atlantic for the 0z data ingest. Should be interesting to see if it changes anything.

[baroclinic_instability]

Yeah this is where I'm coming from as well. It's just not too often you see this type of northern stream amplification (and interaction with another shortwave while that's happening) at this latitude. There's a reason why we all remember these events and can list the dates off the top of our heads.

Exactly. It is still special. Semantics are coming into play here as well since the whole discussion started with "epic". Maybe not epic, but as you said, by no means mundane. Hopefully Dr. No changes its attitude on the western S/W tonite and that its current solution does not verify

There is still a dud threat--plenty high enough where this isn't set in stone by any stretch.

[baroclinic_instability]

Not sure if you guys saw or not, but the planes were out in the Pacific for the 0z data ingest. Should be interesting to see if it changes anything.

Do you have a link for tonights flights? I remember hearing of it on the main nws.noaa.gov page.

[eduggs]

I think the duration argument is kinda weak. We've had plenty of hard hitting events that last 12 hours or less. Again, I'm not trying to argue that this is going to be an epic HECS. But I think there's some argument (or maybe I am misunderstanding a bit, could be) going on that this event is mundane. I don't think you can call it mundane given the dynamics being portrayed by most guidance at this point. The shortwave is very strong, the dynamics and forcing are also very strong. Getting a 980's mb low to form from a northern stream shortwave diving southeast..and having it develop so far south as some models indicate is not your run of the mill mid-latitude cyclone.

So I guess that's where both sides of the argument can come from. I'm not saying this is an epic event aka a HECS..but I also don't think it's a mundane run of the mill cyclone. It has the potential to falll into the "MECS" category if all the pieces come together.

By the way, some great discussion ongoing in this thread. Good stuff dudes.

The height field orientation and evolution just look more well suited to a Canadian Maritimes gale than a major mid-atlantic snowstorm. Strong shortwaves traverse the country all the time and almost always blow up between the Gulf of Maine and Newfoundland. I'm as big a snow hound as anyone, but I've seen modeled setups like this 100 times in 15 years of tracking. Blizzards can come out of nowhere, I admit that, but this is not the sort that gives me goosebumps.

If we move toward and even past the GGEM then all bets are off.

[am19psu]

Do you have a link for tonights flights? I remember hearing of it on the main nws.noaa.gov page.

It was the Atlantic, not Pacific. My bad. Anyway, here are the two places I look:

http://www.nhc.noaa.gov/reconlist.shtml

http://weather.noaa.gov/tgstatus/

[jrodd321]

Maybe I'm misunderstanding you. To me this doesn't look like a signal for an epic storm. But if you mean it's a strong - you might even say epic - signal for some kind of storm, then I would agree. I think this looks like a legitimate threat for a somewhat run of the mill moderate snowstorm for a large swatch of the northeast. The synoptic pattern during this period looks relatively progressive and none of the modeling has a longwave trof with sufficient amplitude to thrust this threat into the major category except possibly the GGEM. But even the Canadian, which produces a higher amplitude trof and much more rapidly deepending surface low, moves the SLP along pretty quickly. At second glance the NAM is almost as impressive as the GEM as well.

It's true that the GFS has trended away from the dampening flat wave, lagging southern stream scenario, but I feel we're headed towards a moderate snowstorm if the pieces come together. To me this setup does not look epic, ultra dynamic, historical, or however you want to call it. 0.8-1.2 liq. eq. upper limit with something like .4-.8 more likely.

Haha yea sorry about that. I just meant epic how this thing went from a strung out low coming across the states to now bombing off the coast. Epic "turn of events" is what I was aiming for haha.

[earthlight]

Exactly. It is still special. Semantics are coming into play here as well since the whole discussion started with "epic". Maybe not epic, but as you said, by no means mundane. Hopefully Dr. No changes its attitude on the western S/W tonite and that its current solution does not verify

There is still a dud threat--plenty high enough where this isn't set in stone by any stretch.

Always is there..which is why I have a pet peeve for people calling setups "thread the needle" events. A month or so ago, we had the entire board calling the event a "thread the needle" setup. It was far from it, everything was in place including historic blocking, a very strong shortwave, well placed baroclinic zone, etc. The truth is that every snowstorm, nor'easter, etc that gives us big snow is a "thread the needle" event. Every one of them can go wrong with one slight adjustment.

[baroclinic_instability]

Always is there..which is why I have a pet peeve for people calling setups "thread the needle" events. A month or so ago, we had the entire board calling the event a "thread the needle" setup. It was far from it, everything was in place including historic blocking, a very strong shortwave, well placed baroclinic zone, etc. The truth is that every snowstorm, nor'easter, etc that gives us big snow is a "thread the needle" event. Every one of them can go wrong with one slight adjustment.

Well yes and no. All the teleconnectors in the world don't produce epic storms alone--but the right synoptic/meso "ingredients" as well. Some events require much more things to go "right" for them to happen at all--and some simply have a larger window of opportunity to develop than others. But yeah I agree, the dud threat is always there. At least with this one we will know somewhat soon and not have to wait 24-48 hours before the event.