December Medium/Long Range Discussion

[Wonderdog]

21 minutes ago, BristowWx said:

6 days still.  Looks solid to me.  You know what’s happens if all guidance shows a hit. I feel pretty good about this and I never feel good..ever.

This one is and will continue to be nerve racking. I like the trends from overnight. Just hope everyone is right about the old GFS. 

[BristowWx]

21 minutes ago, Scud said:

Thought you went to sleep.....

Decided to just go to work and wait for 6z runs...I have a problem.

[Scud]

1 minute ago, BristowWx said:

Decided to just go to work and wait for 6z runs...I have a problem.

We all do....

[luckyamaha]

1 minute ago, Scud said:

We all do....

I work nights so i miss the mid day runs but get the happy hour and late night ones. FV3, FV3, FV3...

[showmethesnow]

After looking over the latest EPS run I thought I would show what just some small changes could mean with the outcome of our possibly storm. Some of the changes are very subtle and hard to pick up on.

Below we have the 12Z run from yesterday. Excuse that the file is corrupted but it still shows the features I want to point out.

First notice the region circled through the mid-Atlantic. We are starting to see a relax in the confluence through the region but at this point it is a little to late as the gulf low has already progressed to Florida and it would take a tremendous effort to pull that north in time for our region (DC/Balt). One other point about that is look at the flow. We are seeing a W/NW trajectory on it through our region. Now we have the trough dropping down through the mid-west behind the low and the tiniest hints of ridging in front of it. We also see lower pressures around the 50/50 region which signify the passage of a surface 50/50 through that region. Above that we see ridging into Greenland (east based -NAO). Now look at the flow around the 50/50 region and the -NAO. We see some kinking thus some backing of the flow but nothing to write home about. 

 

Now compare the above to the latest run. First notice the circled area through our region. Now it may not look much different then the previous example, confluence is still there, yada, yada, yada, but there is a difference. Look at the flow through our region. It has a westerly trajectory as opposed to the previous which had a northerly component to it. Now what is not shown is that the lead into this snapshot also shows a more westerly component above the storm and through our region as well. This may not seem like a big deal but it is. The more northerly component to the flow in the previous example is pushing against any attempts for the storm to the south to gain latitude as it strengthens whereas the more westerly flow is not. Now why we are seeing differences in the flow can be attributed to what I consider positive changes to the trough dropping down through the mid-west. We are seeing a deeper drop by the trough as well as seeing the upper portions of it respond as well with more NS energy dropping in. To see what I mean look at the 558 mb line compared to the previous example. Now because of this change with the trough we are seeing a better response from our gulf low as it begins to pick up on its influence. We are seeing a slightly slower progression of the low with an adjusted track inside of our previous example (north and west). Now lets look upstream of the storm. In front of the storm, though subtle, we are seeing slightly stronger hints of ridging and this is probably in response to what we are seeing in the 50/50 region and the -NAO. We are seeing a slightly stronger -NAO then the previous example with it extending a little farther to the west. This in affect is creating more kinking of the flow around the 50/50 thus more backing of the flow. Thus stronger hints of ridging on the east coast are showing up. Now all this still will probably not get it done for us DC and north but it is much closer then some probably realize.

 

Now lets look at the surface for the corresponding maps. This is yesterdays 12z. Notice the low below Greenland that has just rotated through the 50/50 region. The High pressures over-top the storm and the low pressure itself. Now compare to the latest run below.

 

The changes we saw at 500 mbs are being reflected on the surface. First look at the gulf low where we have seen a slower progression and an adjustment north and west of the previous run. We are seeing a weaker more northerly blocking high over-top (Just thought I would mention this is the typical Banana high we see in many of our big storms). We are also seeing a stronger surface low running through the 50/50 region. Now one other thing I will point out is that we are now seeing kinking on the northwest portion of the gulf low running up the western side of the Apps. This leads me to believe that the EPS is once again considering a hybrid Miller (A/B). Honestly the map below strongly suggests east coast storm somewhere through the mid-Atlantic down into the SE.

 

 

Now I have liked this period for roughly a week now and that never changed even through some horrible runs the last couple of days. At this point, as I see some of the changes we are seeing on the models, my confidence is growing that we see at least a SEC somewhere on the east coast. So unless we see weak SS energy (as many have mentioned) I highly doubt we see some of the more suppressed, weak and OTS solutions we were seeing on the models. About the only question I have at this point is how far north we see the impacts. At this point the models would suggest DC and south for any major impact. Could most definitely be right. But I tend to believe we see this farther north then currently progged to where at the very least PSU is getting fringed. 

 

Now despite some of the solutions thrown out there I really like the setup at this point. If I were to call this, and the solution I have favored for a couple days now, I would say we see a Miller A/B impacting through our region at least to the PA line. Primary low driving towards or into Tennessee before blocking over-top forces a secondary to from in the SE and quickly take over. We see this low run up the coast to off of the VA/MD coast where it will stall for a period of time, if not retrograde, as it waits for the upper levels to catch up to it. I also would not be surprised to see this impacting into the coastal NE as well. So I guess I am on the record now. Feel free to mock me if I am wrong.  

[BristowWx]

Confluence looks a touch stronger on FV3 just looking at h5 at hr 138.  only out that far but it might be a close call getting it up far enough north.  We shall see.

[showmethesnow]

1 hour ago, stormtracker said:

6z trended better, especially at H5 level with that NE screw job s/w moving out faster.  So that's good I guess

Still not ideal but we definitely did see a strong improvement.

[BristowWx]

5 minutes ago, losetoa6 said:

6z gefs just coming in and the  mean bumped north .

If nothing else at least at this point there is one factor we need to watch...h5 confluence...not waiting for cold air..not moisture starved or waiting for a phase...its either a 1 or 0...either it comes north or it doesn't...makes it simple at least right now.

[showmethesnow]

4 minutes ago, losetoa6 said:

Gefs

 

You can clearly  see a positive step at h5 with less confluence on the 6z

6z

 

0z

 

Seeing some of the positive changes at 500s that the EPS was showing.

[BristowWx]

Site crashed at hr 138 on TT for me.  Of course it did. 

[H2O]

To me the GFS and Euro are just world different wrt how they handle the vorts @ 500 levels leading up to and what happens as the LP wants to start climbing the coast.  

[H2O]

FV and euro are much closer in showing the same thing at the 500 lvl

[Scud]

06z FV3 stll hopping. Still don't believe 12-18 inches of snow in Darlington SC will verify...

[Scraff]

Good morning!  Liking the overnight runs. Fingers crossed the north trend is underway...

[Ralph Wiggum]

6 minutes ago, Scud said:

06z FV3 stll hopping. Still don't believe 12-18 inches of snow in Darlington SC will verify...

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

[aldie 22]

6 minutes ago, Scud said:

06z FV3 stll hopping. Still don't believe 12-18 inches of snow in Darlington SC will verify...

Maybe not that amount but it is certainly possible that is where the event and qpf is centered. 

[showmethesnow]

Just had a chance to look at the EPS snowfall maps. The slight differences I mentioned previously had a vast difference on snowfall means. DC/Balt are squarely in play at this time as far as the EPS is concerned. Quite a few SECs with a couple HECs thrown into the mix. Fully expect to see future runs up the ante especially if we see the overnight trends continue.

[aldie 22]

Just now, 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.

Doesn't have to be snow for that area to be the bullseye 

[Scud]

Some good news. 00z UKMET is identical to CMC.

[BristowWx]

6 minutes ago, Scraff said:

Good morning!  Liking the overnight runs. Fingers crossed the north trend is underway...

Would have felt better if 6z FV3 was not as suppressed.  It was easy to see why just looking at h5.  just another data point I suppose 

[Vice-Regent]

You don't want to lose "all" of your confluence. The LP is already in danger of cutting off at H5 and becoming a high elevation snow event. Typical thread the needle early December event.

[CAPE]

20 minutes ago, Vice-Regent said:

You don't want to lose "all" of your confluence. The LP is already in danger of cutting off at H5 and becoming a high elevation snow event. Typical thread the needle early December event.

Walking a bit of a tightrope with the timing of the NS vorts and the confluence. Gotta have it with this set up, but don't want too much of a good thing. OTOH if the confluence ends up weaker or further NE, this event could be more wet than white for the coastal plain.

[RobertRath]

I know everyone is focused on this storm but I’m interested in December in the long term after the storm. Have we dodged the extended, big warmup people were seeing days ago?

[psuhoffman]

7 hours ago, Bob Chill said:

0z gefs is pretty bad for our area. Strong support for southern slider. 

Gefs under dispersal was never fixed. Disappointed they aren't switching the gefs with the op next month. I'm looking forward to that more. Gefs has been doing ok with the high latitude at range but they still jump run to run too much and with mid latitude cyclones in the medium to long range they are a bunch of Minnie Mes saying yes that to whatever the op does. 

[dallen7908]

Rollercoaster ride continues: Percent of EPS ensembles that give Baltimore (BWI?) at least 1, 3, 6, and 12" of snow/sleet through early next week

[showmethesnow]

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

Walking a bit of a tightrope with the timing of the NS vorts and the confluence. Gotta have it with this set up, but don't want too much of a good thing. OTOH if the confluence ends up weaker or further NE, this event could be more wet than white for the coastal plain.

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.  

[BristowWx]

7 minutes ago, RobertRath said:

I know everyone is focused on this storm but I’m interested in December in the long term after the storm. Have we dodged the extended, big warmup people were seeing days ago?

considering we cant resolve h5 details for next weekend with any degree of consistency I'm gonna say no to that question.   

[dallen7908]

10 minutes ago, RobertRath said:

I know everyone is focused on this storm but I’m interested in December in the long term after the storm. Have we dodged the extended, big warmup people were seeing days ago?

CPC outlook for December 15 to 28 issued this past Friday (Dan Collins lead forecaster) 

"Temperature forecasts from the ECMWF, CFS and JMA model consensus, as well as the SubX MME, predict likely above normal temperatures along the Pacific coast of the CONUS, and from the Pacific Northwest across the Great Plains into the eastern U.S., more consistent with statistical forecasts that consider El Nino conditions. "

This does not scream "extended big warmup" but we should have our fair share of days in the upper 40s and low 50s. 

 

[Ralph Wiggum]

Y'all should take a look at some of the similarities between the coming threat and Jan 2000 irt slp sliding off the SE Coast barely missing a phase and the actual verification where a phase just barely happened and allowed for quite a change in storm track. Sort of what we r seeing between say the Euro camp vs the GFS camp. Some minor timing diffs aloft are creating 2 specific camps....non-phased and southern slider vs phased and farther N and closer to the coast. Not uncommon and the only reason I mention "that" storm is because of similar surface progs and location and how we are now talking possible phase vs non-phase with thus one. I also spent a fair amount of time studying that one and how many of us missed it until about 36 hours or so lead time. 

[psuhoffman]

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

Walking a bit of a tightrope with the timing of the NS vorts and the confluence. Gotta have it with this set up, but don't want too much of a good thing. OTOH if the confluence ends up weaker or further NE, this event could be more wet than white for the coastal plain.

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.