December Medium/Long Range Discussion

[frd]

28 minutes ago, showmethesnow said:

Not sure this is much of a thread the needle type setup unless you are talking north of DC. I look at the setup now, -NAO, 50/50, semblance of a banana high, trough in the midwest, strong gulf low and advancing +PNA and it pretty much screams east coast storm somewhere in the mid-Atlantic of which at this time would be centered on VA. That bullseye will move a little, I am thinking north at this time, but all in all I think this is starting to become a high confidence call as long as we see strong enough SS energy. As far as his concerns of the 500's closing off and going for the capture to our west screwing the midlevels? Would probably be very short in duration with the strong blocking overtop with a quick transfer to the east with the 500s once again trying to catch the surface so very little damage done to the midlevels especially east of the Apps.  

I enjoy your posts showme.

Thought I share this from the NY City thread as Don S . always has great insights too. 

this is from DonS @donsutherland1

keep in mind his post was from about 10 hours ago. and he is focusing on NYC. but interesting in that his comments below revealed an interesting best match . 

the data is prior to December 20 th in all cases  

This is what he said:

The best match for the forecast 500 mb height anomalies is the December 2-3, 1896 snowstorm.

The following snowstorms dumped 6" or more snow at Raleigh prior to December 20:

December 2-3, 1896: 7.5"
December 12-13, 1917: 7.1"
December 17, 1930: 7.0"
December 11, 1958: 9.1"

Snowfall for select cities from those storms was as follows:

December 2-3, 1896:
Greenville-Spartanburg, SC: 10.5"
New York City: None
Philadelphia: None
Washington, DC: None

 

 

 

[frd]

I believe this is connected to strat wave activity mid month 

 

[psuhoffman]

Additionally that vort is slowing the stj down. Even the runs that hit us now stall and wait a bit. Get that northern stream lobe out of the way and the whole stj system might come in faster, get the convective cooling processes going inland which would tighten the coastal baroclinocity and encourage a favorable surface track...then the ball is rolling downhill. These big cut off storms are more variable and often variable isn't good for us. 

[Ralph Wiggum]

Btw my last post was irt how we will probably see 2 camps for a few days with the coming threat and a roller coaster type run of models where subtle 500mb changes will make for big surface changes basically supporting what a few of the knowledgable posters have been saying here . We will probably not see such a short range change as we did 18 years ago but at the current lead time with the next threat I expect sudden shifts from suite to suite until we get within 84 hours or so.

[frd]

Someone mentioned Weds. yesterday as did DT as well. About potential for snow shows and even squalls

I see HM mentioning it today as well.  

When DT mentioned it yesterday is was more so for VA and areas close,  by but HM talking about a Norlun-ish set up ...... 

So, keep an eye out for Weds. 

>>>

 

 

[Scud]

17 minutes ago, frd said:

Someone mentioned Weds. yesterday as did DT as well. About potential for snow shows and even squalls

I see HM mentioning it today as well.  

When DT mentioned it yesterday is was more so for VA and areas close,  by but HM talking about a Norlun-ish set up ...... 

So, keep an eye out for Weds. 

>>>

 

 

The ghost of the old "5d tease."

[mattie g]

30 minutes ago, frd said:

I enjoy your posts showme.

Thought I share this from the NY City thread as Don S . always has great insights too. 

this is from DonS @donsutherland1

keep in mind his post was from about 10 hours ago. and he is focusing on NYC. but interesting in that his comments below revealed an interesting best match . 

the data is prior to December 20 th in all cases  

This is what he said:

The best match for the forecast 500 mb height anomalies is the December 2-3, 1896 snowstorm.

The following snowstorms dumped 6" or more snow at Raleigh prior to December 20:

December 2-3, 1896: 7.5"
December 12-13, 1917: 7.1"
December 17, 1930: 7.0"
December 11, 1958: 9.1"

Snowfall for select cities from those storms was as follows:

December 2-3, 1896:
Greenville-Spartanburg, SC: 10.5"
New York City: None
Philadelphia: None
Washington, DC: None

 

 

 

I always wonder how in the world we would know what the 500mb anomalies were back in 1896. Anyone want to explain? It can only be a guess, right?

[aldie 22]

The way this story has gone in the past there will be a run midweek that destroys us...excitement will ramp and then....

[CAPE]

11 minutes ago, psuhoffman said:

Right now the problem is both the slowing of the stj system and the timing and trajectory of that northern stream vort diving in on top of us.  The true broad cold injected this week is waning by the time the stj system arrives. The vort coming in on the backside of the northern stream trough is of little use for injecting more cold because its rotating down to our northeast. What it is doing is flattening the flow along the east coast to suppress the storm. So that vort is useless to us. Might as well get it out of the way. The cold issue is one of timing. The stj took too long. Now it will have to take the perfect track (create its own cold) all that jazz we are familiar with. It's more marginal temp wise then it would have been a day earlier. Doesn't mean it can't work. But that vort diving into the northeast won't help in any way. Just get rid of it. 

Not sure I agree completely. If the NS vort gets out of the way and we lose the confluence as the storm approaches, ridging will build out in front, and yes the low will gain latitude- but will likely track inland somewhat, and instead of high pressure to our N/NE, there will likely be a high sliding off the coast to our E/SE. That is a recipe for a mixed event with a stale cold air mass, and while places inland and higher elevations might stay all frozen, that is likely a mostly rain scenario for the coastal plain. You worry about being fringed, but I have to be concerned about 850 and surface temps soaring above 0C.  

[pasnownut]

2 hours ago, Ralph Wiggum said:

Climatology for early Dec says your beliefs are justified. Not to say HECS dont happen still but I'm right there with you.

said that yesterday, so add a +1 to your camp.

[psuhoffman]

18 minutes ago, C.A.P.E. said:

Not sure I agree completely. If the NS vort gets out of the way and we lose the confluence as the storm approaches, ridging will build out in front, and yes the low will gain latitude- but will likely track inland somewhat, and instead of high pressure to our N/NE, there will likely be a high sliding off the coast to our E/SE. That is a recipe for a mixed event with a stale cold air mass, and while places inland and higher elevations might stay all frozen, that is likely a mostly rain scenario for the coastal plain. You worry about being fringed, but I have to be concerned about 850 and surface temps soaring above 0C.  

I'm not disagreeing that rain could become a problem but the issue is that vort diving down into New England is unlikely to help. Because of the trajectory it takes (coming in on top or to our northeast) for it to be close enough to provide any assistance with cold it would have to squash the storm. With a lobe rotating down into New England the only way that is providing us with cold is if it's still right there and then it's going to flatten the heights and squash. What we needed was the cold to be injected from the north or northwest then to have general confluence to our north to help hold it in but not a strong northern stream vort diving in on top of us. That's what killed the mid march threat last year btw. The one that got squashed before we finally scored a hit.  

[CAPE]

1 hour ago, showmethesnow said:

Not sure this is much of a thread the needle type setup unless you are talking north of DC. I look at the setup now, -NAO, 50/50, semblance of a banana high, trough in the midwest, strong gulf low and advancing +PNA and it pretty much screams east coast storm somewhere in the mid-Atlantic of which at this time would be centered on VA. That bullseye will move a little, I am thinking north at this time, but all in all I think this is starting to become a high confidence call as long as we see strong enough SS energy. As far as his concerns of the 500's closing off and going for the capture to our west screwing the midlevels? Would probably be very short in duration with the strong blocking overtop with a quick transfer to the east with the 500s once again trying to catch the surface so very little damage done to the midlevels especially east of the Apps.  

Not sure I would characterize it as" thread the needle". We need the confluence, but we don't need a lobe rotating down that digs too far and completely squashes the storm. Its more of timing deal, and also the strength/amplitude of the features in the NS.

[poolz1]

It will take a bit to get some real cold back into the pattern after this relax coming up.  Not that there wont be enough to work with under the right conditions but no true cold building in Canada.  The end of the EPS run looks primed to get the process started in week 3...possibly the end of week 2.  Weeklies have been tough to gain anything from recently but I'm still interested in their take on wk 3/4 tonight.  They have a good 00z run to base it off of....00z lost the closed blue ball over the pole, more trough S of the Aleutians and heights trying to poke into AK and further N.

[nj2va]

Simply for S&G analysis...6z ICON only goes to 120 but comparing it to 0z last night (which was not suppressed), the confluence is further north at the end of the run.  I'd extrapolate and assume its not a suppressed slider.

[showmethesnow]

21 minutes ago, C.A.P.E. said:

Not sure I would characterize it as" thread the needle". We need the confluence, but we don't need a lobe rotating down that digs too far and completely squashes the storm. Its more of timing deal, and also the strength/amplitude of the features in the NS.

Sorry for the confusion, I was more so referencing vice-regents post that you had quoted then you. And as far as not threading the needle that was in reference to seeing a SEC somewhere in the mid-Atlantic in general with a swath of heavy snow vs. a squashed, weak POS running OTS. As to where the snow sets up and how far into the coastal plains it can get is still to be determined. Think though that temps will be more forgiving then people now think.

[CAPE]

23 minutes ago, psuhoffman said:

I'm not disagreeing that rain could become a problem but the issue is that vort diving down into New England is unlikely to help. Because of the trajectory it takes (coming in on top or to our northeast) for it to be close enough to provide any assistance with cold it would have to squash the storm. With a lobe rotating down into New England the only way that is providing us with cold is if it's still right there and then it's going to flatten the heights and squash. What we needed was the cold to be injected from the north or northwest then to have general confluence to our north to help hold it in but not a strong northern stream vort diving in on top of us. That's what killed the mid march threat last year btw. The one that got squashed before we finally scored a hit.  

The setup is not going to allow for cold air to advect in, so we have to work with the marginal cold that will be in place. I agree that the trailing vort rotating down on recent runs, if it digs too much, is not going to help. And of course the timing of the ss energy has changed, and may continue to shift in future runs. But we did have some runs as recently as Sat where the NS vortices were further NE/flatter, resulting in less confluence, and the storm tracked inland. Its a balancing act as usual, but this one has a lot of moving parts.

[Maestrobjwa]

10 minutes ago, psuhoffman said:

I'm not disagreeing that rain could become a problem but the issue is that vort diving down into New England is unlikely to help. Because of the trajectory it takes (coming in on top or to our northeast) for it to be close enough to provide any assistance with cold it would have to squash the storm. With a lobe rotating down into New England the only way that is providing us with cold is if it's still right there and then it's going to flatten the heights and squash. What we needed was the cold to be injected from the north or northwest then to have general confluence to our north to help hold it in but not a strong northern stream vort diving in on top of us. That's what killed the mid march threat last year btw. The one that got squashed before we finally scored a hit.  

That one has been burned into my mind...it's basically turning into that crap all over again! Once again a ns vort coming at the wrong time in the wrong position, smh Bad fortune

[MN Transplant]

41 minutes ago, mattie g said:

I always wonder how in the world we would know what the 500mb anomalies were back in 1896. Anyone want to explain? It can only be a guess, right?

Given enough surface data (especially pressure), the structure of the atmosphere can be backed out using numerical techniques.  Basically, if you have a surface chart from 1885, you can use models to determine what the atmosphere should have looked like to produce those obs.  It is obviously subject to some error, but placements of ridges/troughs shouldn't be that far off. 

[donsutherland1]

1 hour ago, frd said:

I enjoy your posts showme.

Thought I share this from the NY City thread as Don S . always has great insights too. 

this is from DonS @donsutherland1

keep in mind his post was from about 10 hours ago. and he is focusing on NYC. but interesting in that his comments below revealed an interesting best match . 

the data is prior to December 20 th in all cases  

This is what he said:

The best match for the forecast 500 mb height anomalies is the December 2-3, 1896 snowstorm.

The following snowstorms dumped 6" or more snow at Raleigh prior to December 20:

December 2-3, 1896: 7.5"
December 12-13, 1917: 7.1"
December 17, 1930: 7.0"
December 11, 1958: 9.1"

Snowfall for select cities from those storms was as follows:

December 2-3, 1896:
Greenville-Spartanburg, SC: 10.5"
New York City: None
Philadelphia: None
Washington, DC: None

 

 

 

Thanks for the kind words. The changes on the 0z EPS were immaterial. I could see some snow reaching the Washington-Baltimore area, but we'll have to see how the 500 mb pattern evolves from what is currently forecast.

[psuhoffman]

24 minutes ago, poolz1 said:

It will take a bit to get some real cold back into the pattern after this relax coming up.  Not that there wont be enough to work with under the right conditions but no true cold building in Canada.  The end of the EPS run looks primed to get the process started in week 3...possibly the end of week 2.  Weeklies have been tough to gain anything from recently but I'm still interested in their take on wk 3/4 tonight.  They have a good 00z run to base it off of....00z lost the closed blue ball over the pole, more trough S of the Aleutians and heights trying to poke into AK and further N.

I agree about "real cold" but the pattern setting up towards the holidays is one that could produce a frozen event if the stj undercuts the ridging in canada.  After that...if the trough in the Pac NW retrogrades and the EPO ridge pops we could go back into a cold pattern.  One of the signs of a good year is when the bad periods arent that bad and quickly reload into a good pattern.  

[psuhoffman]

29 minutes ago, Maestrobjwa said:

That one has been burned into my mind...it's basically turning into that crap all over again! Once again a ns vort coming at the wrong time in the wrong position, smh Bad fortune

My only advice would be to calm down and just assume most "threats" will fail.  It's only the first week of December and some seem already way too invested in this one threat.  Overall...I like that we seem to be creating chances as a pretty good clip.  Its still way too early to judge failure as a bad sign for the rest of the winter.  Just getting "threats" this early is a good sign imo.  There are no signs of the kind of winter killing pattern drivers like a raging positive AO or NAO and the blue ball over Alaska is becoming very transient looking.  I am very optimistic on the whole for winter but any given storm threat from range should be taken as low probability.  Our climo is what it is!

As for this specific threat... As Don pointed out the current H5 configuration looks more like a southern mid atlantic hit and the guidance definitely has converged on that.  But....the system is very healthy and it would only take a slight error in the current h5 forecast for everything to shift north...and north is more likely then south with the northern stream features imo.  We just have to wait and see... I feel pretty confident the typical north adjustment will happen the last 72 hours.  But that adjustment isnt 500 miles like it once was.  We haven't really had any instances of a "late save" here lately because we have either been in the target zone or pretty far out of it going into the final stretch the last few years.  We have seen some "not even close" misses become "close but no cigar" or fringe type events.  If this is targeting VA I think we are in good shape.  If this starts to look like a SC/NC event...it might be too much to ask.  I was good with where the majority of guidance was last night.  The euro suite improved and kept us in the game.  

[midatlanticweather]

25 minutes ago, psuhoffman said:

My only advice would be to calm down and just assume most "threats" will fail.  It's only the first week of December and some seem already way too invested in this one threat.  Overall...I like that we seem to be creating chances as a pretty good clip.  Its still way too early to judge failure as a bad sign for the rest of the winter.  Just getting "threats" this early is a good sign imo.  There are no signs of the kind of winter killing pattern drivers like a raging positive AO or NAO and the blue ball over Alaska is becoming very transient looking.  I am very optimistic on the whole for winter but any given storm threat from range should be taken as low probability.  Our climo is what it is!

As for this specific threat... As Don pointed out the current H5 configuration looks more like a southern mid atlantic hit and the guidance definitely has converged on that.  But....the system is very healthy and it would only take a slight error in the current h5 forecast for everything to shift north...and north is more likely then south with the northern stream features imo.  We just have to wait and see... I feel pretty confident the typical north adjustment will happen the last 72 hours.  But that adjustment isnt 500 miles like it once was.  We haven't really had any instances of a "late save" here lately because we have either been in the target zone or pretty far out of it going into the final stretch the last few years.  We have seen some "not even close" misses become "close but no cigar" or fringe type events.  If this is targeting VA I think we are in good shape.  If this starts to look like a SC/NC event...it might be too much to ask.  I was good with where the majority of guidance was last night.  The euro suite improved and kept us in the game.  

Great summary! How I feel! If we continue to see general improvements at the major runs, we may be able to reel this one in! I think VA is probably bullseye, and I would be less confident if NC except NW NC! SW VA seems the gold spot no matter what to me!

[psuhoffman]

Icon went south, targets central VA but I kind of like how it looks overall. 

[nj2va]

12z ICON is a hit for central VA, especially back west towards Roanoke where the highest snow totals would be concentrated verbatim.  Just need a slight tug north of the low and it'd be good for NVA/DC.  

[psuhoffman]

1 minute ago, nj2va said:

12z ICON is a hit for central VA, especially back west towards Roanoke where the highest snow totals would be concentrated verbatim.  Just need a slight tug north of the low and it'd be good for NVA/DC.  

Just need the northern stream vort that's diving through New England to adjust north a little bit. 

[Hyphnx]

ICON showing the rain/snow line right in RVA. 

[midatlanticweather]

Snow Shower activity increased (from what I can see) for Wednesday. I do not like where the Shortwave is coming ashore out west.. we will see.

 

[nj2va]

1 minute ago, psuhoffman said:

Just need the northern stream vort that's diving through New England to adjust north a little bit. 

Yeah, this is a key feature to hone in on if I'm interpreting things right...even a tiny adjustment would work...

[clskinsfan]

The one thing I am noticing about the most recent runs is the temps. This isnt really a very cold air mass. We are going to need a cranked up vort to get the cold to mix down. Double edged sword. Too much push with the cold air and it gets squashed. Not enough and we most likely have temp issues. 

[pasnownut]

3 minutes ago, midatlanticweather said:

Snow Shower activity increased (from what I can see) for Wednesday. I do not like where the Shortwave is coming ashore out west.. we will see.

 

FWIW @ 84 its about 150 miles NE of 6z location.