December 2019 Med/Long Range Disco

[Maestrobjwa]

29 minutes ago, Ralph Wiggum said:

We have heart breaks of our own with these up here. You say Philly can do ok....up here we say the same that we usually fail but NYC usually does good. And in NYC they say BOS. So, yeah funny how that works. NAO block ftw! C'mon lets do this even if it goes to sh!t afterwards. Need a DC-BOS special to break the ice early.

Man it feels like it's been forever...(been almost 4 years since just a DC-Philly one!) And one advantage Philly has: you guys can score in Nina's...giving you more chances for snow over a given period of years! (In ninas primaries come, fart on top of us, then transfer and explode in you guy's region, lol)

[psuhoffman]

Truth is with a late developing coastal the further northeast the better.  These often develop slower than guidance and screw over whoever thought they were in the southern area of snowfall. 

I also get annoyed with the “it jumped over us” thing. It didn’t jump over us.  If the primary tracks to our south we do fine with a miller b. When that happens it’s usually a miller a/b hybrid since a pure northern stream miller b has a hard time digging far enough south and not get squashed doing it to work. But when a system comes at us from the west at our latitude it doesn’t jump. The best lift from the WAA associated with the low simply goes north of us and the mirage of good precip from the upslope to our west dries up when it downslopes. Same as with a clipper.  We will always get less precip from a southwesterly flow due to downslope in any system. Then the coastal is going to develop a ccb way too late if it’s developing at our latitude. The only reason it looks like a jump is the mountains to our west create the illusion the system created snow all around us. Really the snow just went to our northwest as the primary tracked to our northwest or too close to us to keep us in the best WAA precip to the north of the track and downsloping killed the rest. The coastal is irrelevant since it develops after the system passes us. If the primary tracks to our south we do fine as we keep enough of an easterly wind component. That just doesn’t happen often because we are too far south.  

ETA:  Once every long while there is a true system that transfers over a long distance and “jumps” completely over an area but it’s way more rare than we use that term for any system reaching west to east that develops into a coastal late. 

[yoda]

Is the look on the h5 level on the 00z Euro good or bad at the end of its run?  Kind of looks like a meh to serviceable look to me in early December... do i have that wrong?

[CAPE]

2 hours ago, yoda said:

Is the look on the h5 level on the 00z Euro good or bad at the end of its run?  Kind of looks like a meh to serviceable look to me in early December... do i have that wrong?

If you are referring to the end of the op run, that is a pretty interesting look, and the same period that is being discussed in the posts above. It has a primary low running well to our NW and manages to develop a coastal south of our latitude, but too little too late for our region. Verbatim it would be cold chasing rain. It appears to be a period to watch.

If you are referring to the end of the Euro ensemble run- it looks "ok" but the reason it has that ambiguous look is there is a large spread on the individual members, in particular the location and magnitude of any cold air. There are quite a few that would have us torching with a SE ridge for example.

[showmethesnow]

Looking over the 00Z runs for the system centered around the 2nd we see a degradation in all (GFS, GEFS, EPS) except the Euro. Our chances begin and end (at least as the setup is currently projected) on having strong blocking forming over top of this system in southern Canada. What we have seen though is a weakening of the higher heights in that region as energy dropping down from the arctic regions is having an impact. 

Below we have the 18Z that was oh so close to legit snow for the DC/Balt corridor. Notice the energy in northern Canada as well as the higher heights underneath it extending from central Canada to the western coast. This is a solid wall that will eventually force the central US storm which is trying to gain latitude to transfer to the southeast 

 

 

Now compare that same energy on the 00Z. We are seeing this pressing farther south and lagging somewhat from the previous run. This is probably about the worst spot we would want to see this feature as it is just slightly east of the closed low's longitude to its south. A storms natural inclination is to move NEward (barring other forcing mechanisms) as it tries to gain latitude. So we really don't need a solid wall (blocking) coast to coast, we just need to see it above and slightly to the east of a system to counter this NE inclination. And if you look below the shortwave is breaking down this blocking exactly where we do not want to see. Naturally we see a more northern solution with our storm farther down the road.

 

The GEFS and the EPS have also degraded as well. Though with their smoothing it is not as obvious and clear cut as the above example the tendencies I am seeing indicate it is more then likely this same shortwave is the culprit with most of their members as well. The lone exception is that the Euro actually improved as it is seeing less interaction from its prior run with this shortwave in regards to the blocking.

Now we are dealing with energy that there is no way the models are going to have a decent handle on at 6+ days. Energy that with just slight adjustments to the east/west/north can mean a big difference to the final outcome (If in fact the models have a decent handle on the blocking). So chances are good we will see swings run to run from a full blown cutter to a transferring low off the VA tidewater or anything in between. For the record, though I can see the possibilities here I put our chances at seeing anything somewhat noteworthy at low odds especially outside the mountains and possibly some of the favored areas. I will consider it a win if we just see some mood flakes in the air at some point. It is only early December after all and there is a good reason we don't typically see much until around Christmas or afterwards. I am just looking at this as a training exercise for all the CONUS transversing bowling balls that we will be tracking this winter. In fact I think I might even pull out my Kocin books and study the many KUs spawned by these bowling balls. Need to know how our KUs this winter compare to prior ones after all. 

 

 

 

[CAPE]

@showmethesnow

Nice write up. I have always thought the Dec 2-3 period had limited potential, but I have warmed up to it a bit. It still looks like it ultimately ends up cold chasing rain with any secondary development occurring too late for the MA. Worth watching for sure. I have been a bit more intrigued with a possible clipper beyond that period, with the cold air in place and NS energy dropping in. Not that clippers are high probability events for this area in early Dec either lol. 

But hey, we  anyway.

[Ralph Wiggum]

Thought this was worth noting on the GEFS. Past few runs show less of a trof near the NAO region towards the end of the range (240) I pay attention to and more of a ridging look. Isnt a stout -NAO look by any means but delays the flip to a +NAO with each run. 

Eta: the growing blue ball in the midwest isnt horrible. Maybe we can score some sort of quick hitting NS system if that look holds.

[WxUSAF]

Yeah, the pattern in the 3rd-5th time frame that I was interested in, now seems entirely northern stream dominated. The ensembles now see a +PNA in that time frame which wasn’t there a few days ago. So a clipper type storm is probably the only option in that window unless the look changes. Which is possible because we’re still 10 days out. I liked the broader, more E-W oriented trough with energy coming out of the southwest. Now it’s more N-S oriented, so colder, but also drier. 6z gfs actually has a clipper in that timeframe. 

[MDstorm]

2 hours ago, showmethesnow said:

Looking over the 00Z runs for the system centered around the 2nd we see a degradation in all (GFS, GEFS, EPS) except the Euro. 

 

 

 

 

 

Nice write-up.  However, you really need to avoid the word “degradation” so early in your analysis.  It’s like revealing the name of the killer in a murder mystery within the first paragraph of a novel.  I almost lost interest and almost stopped reading your write-up after just a few seconds.

 

[showmethesnow]

I know some on here are panicking about what we are seeing in regards to the PV, NAO and the AO in the extended. Maybe hold off on that for awhile. With all the turmoil and abuse we are seeing in regards to the strat PV there really is no way to know with certainty what to expect in the upper latitudes. Now below we are seeing some indications of a possibility I can see occurring (Something I have mentioned off hand several times in the last couple of days). Not particularly favoring this solution at this time but it is one I think has some merit.

Below we have the EPS that is now starting to pick up on stronger/higher heights developing in the northeastern Atlantic. We are also seeing some ridging into Greenland as well. Also note that we see the PV extending a little farther south onto our side of the globe from previous runs as well as the stronger neg pressure anomalies on the southern edge of this extension. I will tie this all together a little later.

 

Here we have the GEFS. Now the GEFS is lagging behind the EPS somewhat but we are seeing some signs here as well. We are seeing stronger heights/ridging in the NE Atlantic over prior runs. But there are no indications as of yet of ridging into Greenland. BUT... what we are seeing run over run recently is that the strong Neg anomalies over Greenland/NAO domain continue to weaken. We are also seeing the extension of the PV on our side of the globe extending farther south as well. We are also seeing the stronger negative anomalies migrating southward in the southern extension of the pv.

 

Now to tie all this together. We have seen a tendency for the ensembles to under play or even not see the ridging/higher heights within the NAO domain in the extended only to start picking up on them more so as the period nears in time. We have also seen several times already where the verified height builds over Greenland are initiated/reinforced from the NE Atlantic. Putting these two things together and seeing the tendencies on the above ensembles it probably isn't too far a reach to think that in fact we may see, if not a -NAO, at least a weak positive or neutral when it comes to verification vs. the strong +NAO that they have been forecasting.

Now as far as seeing the pv extension extending farther south vs previous runs that is pretty much a no brainer. Shows that the piece of pv that more then likely gets planted on our side of the globe will probably be located somewhere south of Greenland as opposed to sitting squarely on it or just to its west (+++NAO). The farther away from Greenland/NAO domain the better (weaker +NAO if not a neutral or even -NAO depending how far south it drops). One last thing. I like to see where the greatest neg anomalies are occurring. Often they will give you a clue as to where future runs may take a trough. The closer they are occurring to the base of a trough can be indicative that we will see a deeper drop of that trough in future runs. As you can see on the EPS we are seeing the stronger neg anomalies showing up in the base of the upper latitude trough/pv extension. Now remember that the piece of pv will be embedded within this trough. The farther south the trough drops then more then likely the pv follows (farther away from the NAO domain). Now what we are seeing on the GEFS is a little different. What we are seeing is the greatest anomalies are sitting squarely within the middle of this extension. The way this is shown these greatest departures are probably giving us a clue as to where the piece of pv will be located (quite often in the northern sector of the greatest anomalies). Needless to say if the above is true this would place the pv somewhere in the vicinity of just east of the northern Hudson Bay region and not over or just to the west of Greenland. This is the difference between a +++NAO vs. a Weak + or neutral. One last thing is that we have been seeing these greatest neg anomalies migrating southward over the last few runs from being squarely over Greenland to where we are now seeing them just to the east of the Hudson Bay. Again, an indication that the GEFS is seeing a farther south movement of the PV.

 

Now what could all this possibly mean? It means that those of us freaking out over this are freaking out over a possible model induced illusion. Now I am not predicting this at this time but below is one possibility I think has some decent odds of occurring. Just a rough idea and nothing more. We possibly see stronger ridging into Greenland. The ridging is more important here as opposed to seeing a -NAO value. Considering all of this will be occurring on the periphery of the NAO domain there is a very real chance we see a neutral or even weak +NAO and yet that won't be truly indicative of what we have. With this ridging we should see a pinching and elongation of the broad based PV to where we have one distinct piece of pv on the other side of the globe and one on this side. The placement of ridging in Greenland should force our piece of the pv farther southward then currently projected into central or even possibly southern Canada. Now what occurs in the Pacific could come into play as well. Currently we are seeing weaker heights/ridging in the EPO region. I tend to believe that feature is probably being under played at this time. Think that will come in stronger and that will force an extension of the pv southward towards the Aleutians in a favorable position. We have been seeing a tendency for lower pressures occurring in this region so this idea isn't far fetched at all . I will mention one other possibility in regards to the PAC as well. If we in fact see the EPO ridge axis more west/east vs. north/south I can see the scenario of a distinct split of the 500 mb pv as we see a ridge bridge between the EPO and the Greenland ridging (If in fact there is greenland ridging).

 

Now the above could very well be nothing more then the models doing their thing dancing back and forth. Then again maybe not. One other thing that leads me to believe the above scenario has some merit is what we are seeing in the stratosphere. We are seeing some extreme warming coming up shortly in the upper levels of the atmosphere that will be sitting squarely over the pole. Now the question here is do we see these propagate downwards somewhat into lower levels (100 mb, 200 mbs) where they can become an influence at 500 mbs. These warmer temps tend to induce higher heights/pressures. If we start seeing this migration downwards of this warmth in future runs I think that will probably be a good indication that we are going to see a much deeper drop of the pv (or even a split) on our side of the globe as we see stronger height builds in the upper levels over the polar regions. Again, not a prediction just noting something we can keep an eye on.

One last comment because this is long winded enough. With how all this looks to play out  you probably need to eyeball what we are physically seeing occurring in the upper latitudes and not just the indice values and declare we are screwed. There is a very real chance that these values won't look favorable and yet they won't tell the whole story.

[showmethesnow]

6 minutes ago, MDstorm said:

Nice write-up.  However, you really need to avoid the word “degradation” so early in your analysis.  It’s like revealing the name of the killer in a murder mystery within the first paragraph of a novel.  I almost lost interest and almost stopped reading your write-up after just a few seconds.

 

How about a small, teeny, tiny step backwards? 

eta: after all these years you would think I would know better.

[psuhoffman]

2 hours ago, WxUSAF said:

Yeah, the pattern in the 3rd-5th time frame that I was interested in, now seems entirely northern stream dominated. The ensembles now see a +PNA in that time frame which wasn’t there a few days ago. So a clipper type storm is probably the only option in that window unless the look changes. Which is possible because we’re still 10 days out. I liked the broader, more E-W oriented trough with energy coming out of the southwest. Now it’s more N-S oriented, so colder, but also drier. 6z gfs actually has a clipper in that timeframe. 

Yea without blocking to slow down the flow a -epo/-pna is actually a better chance for a decent snow. It also increases the chances of a cutter but you have to roll the dice to win.  With an epo/pna ridge we really actually want some southeast ridge or else it’s a dry look. 

[nj2va]

The first week of December’s pattern as currently advertised is great for the mountains in Garrett County & WV.  Cold/dry NS dominant patterns is a boon for upslope conditions out there.  

[frd]

2 hours ago, showmethesnow said:

know some on here are panicking about what we are seeing in regards to the PV, NAO and the AO in the extended. Maybe hold off on that for awhile. With all the turmoil and abuse we are seeing in regards to the strat PV there really is no way to know with certainty what to expect in the upper latitudes.

Great update,  I hope we eventually see  some positive signs in the HL.  Seeing some +4 to +5 AO ensemble members is a bit worrisome, and the recent 4 day trends continues more so positive. 

Noticing these huge bowling bowls moving across the country with that fast Pac jet is reminiscent of last winter to a degree. Alaska is set to record a fast Pac jet up there this early week.  

Another thing to watch, and I believe there is a statistical correlation here to our area from DC North is that having a + PNA in December is key to accumulating snowfall. Maybe more so than a -AO.  That relationship probably changes in January. So difficult lately getting the PNA to go + and remaining so.    

I love to see the Pac and the HL align down the road.  If you go HM's route there is hope in December.   

[CAPE]

10 minutes ago, nj2va said:

The first week of December’s pattern as currently advertised is great for the mountains in Garrett County & WV.  Cold/dry NS dominant patterns is a boon for upslope conditions out there.  

[Bob Chill]

Not a fan of the gefs/geps trend. Both agree on a legit +ao/nao and midlatitude flow looking like a pac air flood. Current long lead look is very similar to the crappy seasonal/weekly guidance for Dec now. Could be totally wrong or just a temporary flip before a cold pattern returns. Or it could be the beginning of an extended mild period in the conus. 

[jaydreb]

2 minutes ago, Bob Chill said:

Not a fan of the gefs/geps trend. Both agree on a legit +ao/nao and midlatitude flow looking like a pac air flood. Current long lead look is very similar to the crappy seasonal/weekly guidance for Dec now. Could be totally wrong or just a temporary flip before a cold pattern returns. Or it could be the beginning of an extended mild period in the conus. 

That strong -NAO disappates so quickly.  Like within 3 days it is gone and replaced by a seriously +NAO.  Figures that this year the seasonals/weeklies will nail it.  

[WxUSAF]

I agree that’s how it’s looking now past the 7th or so, but things have been very changeable D10+ as we know. Look at the 12z GEFS depiction of the NAO. Even vs a day or two ago, it’s holding onto the Greenland ridging much more. Just a wag since I haven’t looked at individual members, but I get the sense from the mean that there’s probably very wide divergence in solutions in the long range. Still think we got a decent chance of freezing/frozen precip the first week of the month. Beyond that...dunno.

[Bob Chill]

1 minute ago, jaydreb said:

That strong -NAO disappates so quickly.  Like within 3 days it is gone and replaced by a seriously +NAO.  Figures that this year the seasonals/weeklies will nail it.  

NAO domain is really small and volatile so that doesn't bug me. It's the damn AO turning into a cold vacuum and polar jet magnet that has me concerned. What's being advertised now isn't just a positive AO... it's an extremely positive AO and will no doubt make it really hard for winter wx in these parts if that's where we're going...

[nj2va]

4 minutes ago, WxUSAF said:

I agree that’s how it’s looking now past the 7th or so, but things have been very changeable D10+ as we know. Look at the 12z GEFS depiction of the NAO. Even vs a day or two ago, it’s holding onto the Greenland ridging much more. Just a wag since I haven’t looked at individual members, but I get the sense from the mean that there’s probably very wide divergence in solutions in the long range. Still think we got a decent chance of freezing/frozen precip the first week of the month. Beyond that...dunno.

IMO its only worth focusing on the next 10 days...beyond that, the models have been changing as you note.  I’m just excited we open December with cold weather...hopefully can time a clipper that drops some frozen in the area.  

[Bob Chill]

5 minutes ago, WxUSAF said:

I agree that’s how it’s looking now past the 7th or so, but things have been very changeable D10+ as we know. Look at the 12z GEFS depiction of the NAO. Even vs a day or two ago, it’s holding onto the Greenland ridging much more. Just a wag since I haven’t looked at individual members, but I get the sense from the mean that there’s probably very wide divergence in solutions in the long range. Still think we got a decent chance of freezing/frozen precip the first week of the month. Beyond that...dunno.

There's def a window first week of Dec. Might have a couple shots mixed in there. Just pray the +4 AO down the line is a phantom. We'll spend half of met winter trying to get out from under it. 

[wxdude64]

7 minutes ago, Bob Chill said:

There's def a window first week of Dec. Might have a couple shots mixed in there. Just pray the +4 AO down the line is a phantom. We'll spend half of met winter trying to get out from under it. 

truth!!

[frd]

9 minutes ago, Bob Chill said:

NAO domain is really small and volatile so that doesn't bug me. It's the damn AO turning into a cold vacuum and polar jet magnet that has me concerned. What's being advertised now isn't just a positive AO... it's an extremely positive AO and will no doubt make it really hard for winter wx in these parts if that's where we're going...

All hail @Isotherm, that is his call and progression to a T .

The tropics impact the higher latitudes and blocking.  He and a couple others called this a month ago.

Hey, but no winners yet, as it is Nov. 24 th not Dec. 24th.  However, as Bob stated, the trends with the AO are very concerning. 

If we reverse and empty all the cold air in Canada and lose snow cover up North, it will take weeks to recover.   

I myself speculate,  once we get to mid January, we diverge from last year and go very cold and very stormy.  I might buy Tom's progression  for December, but I feel there is a decent opportunity this winter for some cold powder storms and high ticket snow events.   

[Maestrobjwa]

11 minutes ago, Bob Chill said:

There's def a window first week of Dec. Might have a couple shots mixed in there. Just pray the +4 AO down the line is a phantom. We'll spend half of met winter trying to get out from under it. 

I'm guessing that's why very +AO Decembers led to below average snow for the season...(I guess being shutout the first half of winter decreases the amount of chances...thus lower snowfall totals...ack)

Sounds like whatever chance we have the first week of Dec may be the last we see for a little while if the +AO verfies...

[frd]

6 minutes ago, Maestrobjwa said:

I'm guessing that's why very +AO Decembers led to below average snow for the season...(I guess being shutout the first half of winter decreases the amount of chances...thus lower snowfall totals...ack)

Sounds like whatever chance we have the first week of Dec may be the last we see for a little while if the +AO verfies...

Many times the state of the AO in December provides clues to the AO state for Jan and Feb. 

Having measurable snow in our area, such as DC and Baltimore during December , normally correlates to a decent snow season. Works many times, of course there are exceptions.  

Also, you will hear how things just are not syncing up like they use to. Some signals you look at would have you assume winter will be normal, but then the pattern head fakes and we go very warm.  

 

[CAPE]

GEFS has the upper strat on fire heading towards the end of the first week of Dec, and if that verifies there should be some impacts down the road on the troposphere. So I guess what I am saying is...SWE will save us from a prolonged ++AO.

[CAPE]

Anyone have any QBO updates? The new u30 data should be out in a week.

[WxUSAF]

51 minutes ago, Bob Chill said:

There's def a window first week of Dec. Might have a couple shots mixed in there. Just pray the +4 AO down the line is a phantom. We'll spend half of met winter trying to get out from under it. 

HM seems confident it’s temporary, if it happens. Plus the strat shenanigans.

[Bob Chill]

22 minutes ago, frd said:

Many times the state of the AO in December provides clues to the AO state for Jan and Feb. 

Having measurable snow in our area, such as DC and Baltimore during December , normally correlates to a decent snow season. Works many times, of course there are exceptions.  

Also, you will hear how things just are not syncing up like they use to. Some signals you look at would have you assume winter will be normal, but then the pattern head fakes and we go very warm.  

 

Exactly. It's not that a +3 or +4 AO over a couple days means we're in trouble. It's when we get a monthly mean AO of +1.25 or higher that spells trouble. 

The thing I don't like seeing is the size/expanse of BN heights in the AO region. If ens are right, the entire AO domain space has below normal heights. Upper level features like that are hard to break down. Typical strong AO periods take 45-60 to release their grip. 

I'm not implying that I think ens are a lock and have it all nailed down. Lots can change over 1-2 weeks. However, it is one of the Dec features that's kinda scary and something to not ignore. Similar to a big vortex over AK. Things you never want to see in December...

[Ralph Wiggum]

Euro really grabbing onto what the GEFS was hinting at ie keeping the ridging near Greenland a little longer. Not only does it hold onto it, the Euro strengthens it. Not the greatest position but a testament to how changes can be sudden and this is only 8 days out. Also note some of the EPO ridge feeding the AO region. Could still go either way lots of uncertainty. I do like the persistent ridging in the N Atlantic feeding part of the NAO region.