December 18-20 Potential Talking Points

[earthlight]

Though I see what you and John are saying and generally side with your take on the PNA situation, perhaps thread the needle isn't the best term, but I think you have to admit that this is at least more of a "thread the needle" than if we had the +PNA. I think timing is more crucial with this setup than if we had the +PNA, but I agree it may be getting a little too much attention given the amazing retrograding block.

I just think there's too much being made about the "lower probability" of the event (people are referencing exact percentages and all that). I think every winter weather event at 140 hours has a pretty low percentage of occurring on the eastern coastal plain. That being said, if you're going to use odds, you therefore can't ignore the fact that we do in fact have a big -NAO/Greenland block, as well as a favorably positioned vortex in Southeast Canada, and a nice psuedo-split flow with a shortwave progged to develop into the southwest US from the Pacific Jet.

I do understand the "thread the needle" idea because of the timing, the lack of the PNA, etc. But every, every single event is a thread the needle event then. Feb 10, 2010 was a thread the needle event, Feb 26, 2010 was a thread the needle event, Dec 19, 2009 was a thread the needle event, you get what I am saying I'm sure. Here's a day or so before Dec 19, 2009. Is the phase going to happen? The PV is causing a northwest flow at H5 over the Northeast. Any type of phase here bringing the sfc low back towards the coast would be the result of a thread the needle type setup.

http://www.meteo.psu.edu/~gadomski/NARR/2009/121721.png

By the way I wasn't calling you out specifically in this post, just trying to have some constructive discussion with some constructive criticism (and not criticizing you either, I haven't seen you post on the matter).

[am19psu]

Let me be clear, a significant snow storm is definitely possible, but it's not like every single factor you look for is there right now. That's why all of the mets are downplaying this at the moment (well except DT). Wes' probabilities are spot on, imo. Even though it's been shown off and on in the models the last few days, this has more working against it (everything else) than for it (retrograding NAO). There's not much of a 50/50 low, there's not a strong cP or cA high building down out of Canada, the ridge axis is over Casper, not Boise, etc.

[NJwinter23]

I just think there's too much being made about the "lower probability" of the event (people are referencing exact percentages and all that). I think every winter weather event at 140 hours has a pretty low percentage of occurring on the eastern coastal plain. That being said, if you're going to use odds, you therefore can't ignore the fact that we do in fact have a big -NAO/Greenland block, as well as a favorably positioned vortex in Southeast Canada, and a nice psuedo-split flow with a shortwave progged to develop into the southwest US from the Pacific Jet.

I do understand the "thread the needle" idea because of the timing, the lack of the PNA, etc. But every, every single event is a thread the needle event then. Feb 10, 2010 was a thread the needle event, Feb 26, 2010 was a thread the needle event, Dec 19, 2009 was a thread the needle event, you get what I am saying I'm sure. Here's a day or so before Dec 19, 2009. Is the phase going to happen? The PV is causing a northwest flow at H5 over the Northeast. Any type of phase here bringing the sfc low back towards the coast would be the result of a thread the needle type setup.

http://www.meteo.psu...2009/121721.png

By the way I wasn't calling you out specifically in this post, just trying to have some constructive discussion with some constructive criticism (and not criticizing you either, I haven't seen you post on the matter).

Well I just feel that with events such as last Feb. or Dec..you had the ridge set in the right spot out west and the nao block obviously, the energy slows down substantially and everything just has much more time to come together for an east coast storm. Of course how far north that storm gets was the big issue last year...In this case it seems to me the pieces are moving faster across the country, and its possible that the phasing and gathering can definitely wait to happen offshore, perhaps because of the PNA situation and the ridge axis being further east then we'd like.

I'm very encouraged by this potential though like you at this stage. I hope the euro jumps back on board in the next 2 days. Let's not forget it was the first to pick up on this storm in the day8+ range (I believe).

I'm always up for discussions like this and constructive criticism John. I'm a young Met with a lot to learn still, whether it be from Mets or knowledgeable non-Mets.

[Radders]

Fair enough. I just feel that with events such as last Feb. or Dec..you had the ridge in the right spot out west and the nao block obviously, the energy slows down substantially and everything just comes together for an east coast storm. Of course how far north that storm gets was the big issue last year...In this case it seems to me the pieces are moving faster across the country, and its possible that the phasing and gathering can definitely wait to happen offshore, perhaps because of the PNA situation...

Good points here about the PNA and how this slows down the flow, versus a faster, more zonal flow, albeit a quasi split flow. I may be over simplifying this, but in my basic way of thinking, if the flow is slower, then there is certainly more opportunity for a phase to occur over a time period, than a faster flow where everything needs to be more perfectly aligned.

By the way, great discussion - This is a real learning experience for me, and watching the evolution of these potential storms is fascinating regardless of whether they materialize or not.

[Kaner587]

Well I just feel that with events such as last Feb. or Dec..you had the ridge set in the right spot out west and the nao block obviously, the energy slows down substantially and everything just comes together for an east coast storm. Of course how far north that storm gets was the big issue last year...In this case it seems to me the pieces are moving faster across the country, and its possible that the phasing and gathering can definitely wait to happen offshore, perhaps because of the PNA situation...

I'm very encouraged by this potential though like you at this stage. I hope the euro jumps back on board in the next 2 days. Let's not forget it was the first to pick up on this storm in the day8+ range (I believe).

sure was...oringally had it like a Feb 25th-26th type storm getting pulled nw and then w into NYS

[phlwx]

Let me be clear, a significant snow storm is definitely possible, but it's not like every single factor you look for is there right now. That's why all of the mets are downplaying this at the moment (well except DT). Wes' probabilities are spot on, imo. Even though it's been shown off and on in the models the last few days, this has more working against it (everything else) than for it (retrograding NAO). There's not much of a 50/50 low, there's not a strong cP or cA high building down out of Canada, the ridge axis is over Casper, not Boise, etc.

I agree with Wes and you at this point. Something will probably pop but whether it phases and pulls along the coast or simply scoots away and doesn't phase in time is the wildcard. It is a "thread the needle" event since this isn't an optimal setup as you pointed out but I think some are trying to make this out into a "likely" scenario when it's clear that it's simply "possible."

[earthlight]

Well I just feel that with events such as last Feb. or Dec..you had the ridge set in the right spot out west and the nao block obviously, the energy slows down substantially and everything just has much more time to come together for an east coast storm. Of course how far north that storm gets was the big issue last year...In this case it seems to me the pieces are moving faster across the country, and its possible that the phasing and gathering can definitely wait to happen offshore, perhaps because of the PNA situation and the ridge axis being further east then we'd like.

I'm very encouraged by this potential though like you at this stage. I hope the euro jumps back on board in the next 2 days. Let's not forget it was the first to pick up on this storm in the day8+ range (I believe).

I'm always up for discussions like this and constructive criticism John. I'm a young Met with a lot to learn still, whether it be from Mets or knowledgeable non-Mets.

You also have fair points--I think there are sides to both arguments. Part of my argument could be stemming from the typical Nina pattern which usually doesn't feature any potential like this. The psuedo-split flow which develops out west is fairly uncharacteristic and to see a shortwave dig that far south into the Southern states is not expected either. Also, although we don't have a big +PNA ridge, we have some semblance of a ridge there being driven up by the vortex off the coast of the NPAC..and the Polar Vortex and Greenland block teaming up to slow down the pattern. Regarding the discussion, I think this is awesome, im still a student so obviously I still have a ton to learn as well.

Back to the ridge real quick, here's a good example of the importance of it and the shortwave diving southeast from Montana into the Plains. The first link is the 12z GFS (flat) and the second is the 18z GFS. The ridge is much more defined at 18z, which sends the shortwave over the top of it and into the broad trough over the Southeast, further amplifying the shortwave energy. Not a typical +PNA ridge, but it's definitely something that will help us.

http://www.meteo.psu.edu/~gadomski/AVN_12z/f126.gif

http://www.meteo.psu.edu/~gadomski/AVN_18z/f120.gif

[eduggs]

The surface low came out of Northern Florida this run and still heavily impacted our area--that is very rare and I would be shocked if we saw something like that come to fruition.

I had it in the back of my mind that most cases of "all snow" in NYC had the low originate in northern FL. I could be wrong and will double check later. Regardless, a low tracking from Georgia/N. FL does not bother me as long as we get the height field to parallel the coastline before the surface low is east of Newport, RI.

[earthlight]

I had it in the back of my mind that most cases of "all snow" in NYC had the low originate in northern FL. I could be wrong and will double check later. Regardless, a low tracking from Georgia/N. FL does not bother me as long as we get the height field to parallel the coastline before the surface low is east of Newport, RI.

You know, admittedly that post was more of a snap-reaction than anything. I just couldn't remember off the top of my head any surface lows that came out of Florida, off the coast, and then impacted us with the CCB. But I am sure it has happened before, just not in my recent memory. Edit...all I had to do was look back to Dec 19 of last year (not a totally awful analog) to see the occurrence, poor memory on my part.

[NJwinter23]

You also have fair points--I think there are sides to both arguments. Part of my argument could be stemming from the typical Nina pattern which usually doesn't feature any potential like this. The psuedo-split flow which develops out west is fairly uncharacteristic and to see a shortwave dig that far south into the Southern states is not expected either. Also, although we don't have a big +PNA ridge, we have some semblance of a ridge there being driven up by the vortex off the coast of the NPAC..and the Polar Vortex and Greenland block teaming up to slow down the pattern. Regarding the discussion, I think this is awesome, im still a student so obviously I still have a ton to learn as well.

Back to the ridge real quick, here's a good example of the importance of it and the shortwave diving southeast from Montana into the Plains. The first link is the 12z GFS (flat) and the second is the 18z GFS. The ridge is much more defined at 18z, which sends the shortwave over the top of it and into the broad trough over the Southeast, further amplifying the shortwave energy. Not a typical +PNA ridge, but it's definitely something that will help us.

http://www.meteo.psu...VN_12z/f126.gif

http://www.meteo.psu...VN_18z/f120.gif

Definitely see what you're saying. That ridge axis is about 100-200 miles too far east then we'd typically want, which I think opens the concerns from am19psu and Wes of further east development, an open door if yopu will, but it's just a potential wrench in the setup thats all. This storm definitely has a higher chance then normal of working out then the average storm thats for sure. You know your stuff John. The only difference between me and you is a couple of years and a red color as far as I see it. Where do you attend? (apologies if I dont answer back tnight...i need to go to sleep and wake up for work at 2am lol...we'll continue this discussion over the next few days I'm sure)

[Feb]

Let me be clear, a significant snow storm is definitely possible, but it's not like every single factor you look for is there right now. That's why all of the mets are downplaying this at the moment (well except DT). Wes' probabilities are spot on, imo. Even though it's been shown off and on in the models the last few days, this has more working against it (everything else) than for it (retrograding NAO). There's not much of a 50/50 low, there's not a strong cP or cA high building down out of Canada, the ridge axis is over Casper, not Boise, etc.

In the 18z GFS thread Wes said his 25% chance for the storm is probably to low. He said he might bump it up to 30% but said that is probably also to low.

[am19psu]

In the 18z GFS thread Wes said his 25% chance for the storm is probably to low. He said he might bump it up to 30% but said that is probably also to low.

I think he is probably just second guessing himself given everyone else's enthusiasm. Look at the 18z ensemble vs. the DC snow composite with a critical eye and you'll see many key differences.

[Dsnowx53]

Wes made a good post about how the 18z GFS 500mb ensemble mean is kind of similar to the composite for big DC snows.

Yeah, we don't have a 50/50 low or an arctic high, but with the huge block in place, the cold is there...no, it's not arctic, but obviously cold air at this point is not a big concern. And we certainly do have confluence although it's not from a 50/50 low...the huge retrograding block is helping to fill many "voids" so to speak, since it helps to create a pattern that looks almost as if we do have a 50/50 low in place, or a PNA ridge. Obviously, you'd probably like there to be more of a PNA ridge, but as we've said before, the GOA low is just far enough west to where it at least helps the heights out there a tad...we don't necessarily need the true PNA ridge.

The fact that the pattern is pretty similar to the big DC snow composite certainly means something, IMO.

[earthlight]

Definitely see what you're saying. That ridge axis is about 100-200 miles too far east then we'd typically want, which I think opens the concerns from am19psu and Wes of further east development, an open door if yopu will, but it's just a potential wrench in the setup thats all. This storm definitely has a higher chance then normal of working out then the average storm thats for sure. You know your stuff John. The only difference between me and you is a couple of years and a red color as far as I see it. Where do you attend? (apologies if I dont answer back tnight...i need to go to sleep and wake up for work at 2am lol...we'll continue this discussion over the next few days I'm sure)

I'm studying at Kean in my Junior year, don't worry about the reply, we all have lives (except for some select few on here, lol!). Yeah, you typically want that ridge axis a bit further west (although it is further west prior to that), but that may not apply quite as much given the fact that it's not your typical sturdy west coast ridge axis. I also believe that as modeled, the Greenland/North Canada ridging and PV orientation could offset the lack of the PNA ridge..and allow things to slow down a bit within the active flow. That being said, everything is still a long ways off so a lot of this is still speculation at this point.

[am19psu]

I'm studying at Kean in my Junior year, don't worry about the reply, we all have lives (except for some select few on here, lol!). Yeah, you typically want that ridge axis a bit further west (although it is further west prior to that), but that may not apply quite as much given the fact that it's not your typical sturdy west coast ridge axis. I also believe that as modeled, the Greenland/North Canada ridging and PV orientation could offset the lack of the PNA ridge..and allow things to slow down a bit within the active flow. That being said, everything is still a long ways off so a lot of this is still speculation at this point.

More than anything, you need the trough to split and amplify (which you've stated). If that happens, then we could be in business. Ideally, we'll need some cyclonic wave breaking in the southern stream to have a good shot at snow without the 50/50 low. Incidentally, this is also where the +PNA ridge helps, by promoting the cyclonic wave breaking. Like I said, I'm not ruling it out (I'm out with 15% to a big box retail client), but I'd like to see a lot more support before I buy off whole hog.

[Chris L]

If we had the PNA ridge, and EPO Ridge in place, then getting a bonafide KU storm would be nearly a lock with a block this

massive

But it can still be an excellent storm regardless... But IF the PV can get in faster a la 0z GFS....then all bets are off.

[NaoPos]

More than anything, you need the trough to split and amplify (which you've stated). If that happens, then we could be in business. Ideally, we'll need some cyclonic wave breaking in the southern stream to have a good shot at snow without the 50/50 low. Incidentally, this is also where the +PNA ridge helps, by promoting the cyclonic wave breaking. Like I said, I'm not ruling it out (I'm out with 15% to a big box retail client), but I'd like to see a lot more support before I buy off whole hog.

WOUldn't the presence of the PV in combination with the Nao block, supplement a "true" 50/50 low?

[am19psu]

WOUldn't the presence of the PV in combination with the Nao block, supplement a "true" 50/50 low?

Well, it really depends on how amplified the trough is meridionally. That's the point I've been trying to make. Look at the 12z Euro for a counterexample to the PV/-NAO combo.

[Absolute Humidity]

WOUldn't the presence of the PV in combination with the Nao block, supplement a "true" 50/50 low?

Correct me if I'm wrong but wasen't this the setup that enabled Feb 5 th storm last year? Although the extream confluence from the PV sheared out the northern mid Atlantic/southern New England, forcing the low out to sea.

[earthlight]

I'm not too opposed to the 00z NAM at 84 hours, although it definitely could be better in regards to the Polar Vortex orientation. It has the shortwave coming through Idaho into Montana which we wanted to see--and the broad trough looks good over the Central US.

[eduggs]

I'm not too opposed to the 00z NAM at 84 hours, although it definitely could be better in regards to the Polar Vortex orientation. It has the shortwave coming through Idaho into Montana which we wanted to see--and the broad trough looks good over the Central US.

Yeah, agree with this assessment. It looks close enough to the 18z GFS to maintain the status quo.

[earthlight]

Yeah, agree with this assessment. It looks close enough to the 18z GFS to maintain the status quo.

One thing is for sure, it's completely lost compared to it's 18z run at 84 hours. To be expected, I guess, from the later hours of a short term higher resolution model.

[earthlight]

GFS still jumping around with the main features. Blocking is moving in much faster over Greenland this run--but it seems to be splitting the PV slower as well. A whole array of solutions still remain possible, we're still only at +36 hours.

[earthlight]

Through 48 hours the ridging building southwest from Greenland into Northern Canada is hundreds of miles south compared to the 18z run and trying it's best to split the Polar Vortex. That being said, the Polar Vortex feature is much stronger this go around than 18z, even stronger than 12z, which may not be a good sign.

[earthlight]

Certainly further south with the PV thus far--and my gut feeling based on positioning of the Pac Jet, Greenland Ridging, and PV says this run may end up slightly right of the last 18z run. That being said, who knows, we saw the 18z run pull off a late-game comeback with the energy over Montana diving southeast and amplifying the trough.

[earthlight]

Meanwhile, the shortwave trough in the south is about to enter Mexico at hour 66.

[earthlight]

H5 winds are blowing hard out of the west over the Mid-Atlantic thanks to the PV and confluence being much further south--they were southwest at this time at 18z

[earthlight]

Weird look at 96 hours, definitely some big changes compared to 18z. The flow over the east has recovered, but the trough axis is further east in general. It's going to take a quick recovery or this will be a close but not quite there type run.

[Radders]

At 96, the energy from the s/w in Montana and the s/w in New Mexico is starting to align and enhance the broad trough..

[blazess556]

its coming west