NYC/PHL 12/21-12/27 Forecast Threats

[Zir0b]

Also, you are referencing the ridge axis way too late on your images. So it's actually further west when it matters.

fair enough...still i don't think it is ideall for the MECS/HECS depticted by the GFS...the pattern is definitely favorable for a snowfall of 4-8" though and i guess the blocking over the Hudson's Bay region would help to force more energy downstream to aide in the GFS solution, so yeah it is a possibility

[tombo82685]

wow does it cold after the inland storm -16 to -20 925mb temps

[RowanBrandon]

Cold Conveyor Belt

Okay, but what exactly is it though?

[LVblizzard]

anyways, anyone have the 18z nogaps, curious to see what that shows

12 hours later it's sub-960 mb, giving eastern SNE a moderate snowstorm.

[ace0927]

This one will be painful if it fails given how consistent overall the GFS/Euro have been....the Mt. Holly discussion sort of seems to pump up the GEM, maybe my memory is bad but I swear that thing waffles more than any model I've ever seen from run to run yet they mention its consistent, the only storm I can clearly recall the GEM nailing big time was the 2/25 event this past winter.

well the GGEM had a monster bomb at 0Z last night with the h5 fields resembling Jan 8 1996....

[ag3]

NAM and GFS both went back to the northern, faster SW placement.

It's clear for this storm and for our area, this is what we want.

For the mid-Atlantic, the slower, more south, more diggier solution is better but too many things can go wrong with that.

I'm hoping 18z models got newer satellite data and now the storm will be a northern track like this.

0z tonight is very big.

[Bluescat1]

This one will be painful if it fails given how consistent overall the GFS/Euro have been....the Mt. Holly discussion sort of seems to pump up the GEM, maybe my memory is bad but I swear that thing waffles more than any model I've ever seen from run to run yet they mention its consistent, the only storm I can clearly recall the GEM nailing big time was the 2/25 event this past winter.

If I read it correctly they said it did well with the "swing and a miss" over this past weekend.

[ace0927]

wow at the -NAO that is developing towards the end of the 18Z GFS run....

[LVblizzard]

Okay, but what exactly is it though?

I'm not exactly sure, some other experienced people on here probably know though. All I know is that the CCB is where the bands of heavy snow are during an east coast storm.

[Alpha5]

fair enough...still i don't think it is ideall for the MECS/HECS depticted by the GFS...the pattern is definitely favorable for a snowfall of 4-8" though and i guess the blocking over the Hudson's Bay region would help to force more energy downstream to aide in the GFS solution, so yeah it is a possibility

The PNA Ridge is definitely helping, although the ridge axis is too far east for some in the MA, its still relatively rare to have something like that in such a strong nina.

We have not had one so far this month and as a result little snow for 195. What the PNA ridge does is it eseentially shelters the energy for the storm from the fast Pac flow that would otherwise tear it apart. This ridge instead drives the pacific flow up into a strong meridial flow into canada, then down the backside of the ridge. This will, again, shelter the storm and allow it to dig without disruption.

That is why were talking about a big storm threat. If we did not have this feature, we would not have this storm

[Zir0b]

0z tonight is very big.

So is 0z tomorrow night...and they day after....and the day after....and the day after....

[SnowGoose69]

If I read it correctly they said it did well with the "swing and a miss" over this past weekend.

Overall it did, thats correct, it may have had one run that was almost a hit if I recall but that was all, it was never really close, but in the long run I've always found its worse than the Euro/GFS on coastal systems, especially Miller Bs, it tends to be better with Miller As from what I've noticed.

[Edge Weather]

HPC said that they believe the northern stream will be stronger and therefore have more influence on this storm, which makes more sense.

NAM and GFS both went back to the northern, faster SW placement.

It's clear for this storm and for our area, this is what we want.

For the mid-Atlantic, the slower, more south, more diggier solution is better but too many things can go wrong with that.

I'm hoping 18z models got newer satellite data and now the storm will be a northern track like this.

0z tonight is very big.

[SnoSki14]

The long range looks insane, highly indicative of a major transition from blocking to non-blocking back to a blocking patter for early January.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/18/images/gfs_ten_384l.gif

LOL Road trip to Florida

[Stormlover74]

Here is a definition I found in pretty technical terms

Cold Conveyor Belt (CCB)

The cold conveyor belt (marked CCB in the figure above) originates poleward and east of the low pressure center, typically in the westerly flow on the backside of a high pressure system to the east. This air flows westward, on the cold side of the warm front, below the WCB, toward the center of the low pressure circulation. The air becomes saturated through a combination of precipitation falling into the CCB from the WCB above and slow ascent from the boundary layer to the mid-troposphere north of the low center (see figure above). The flow eventually rises and turn anticyclonically into the upper tropospheric ridge ahead of the developing cyclone.

I'm not exactly sure, some other experienced people on here probably know though. All I know is that the CCB is where the bands of heavy snow are during an east coast storm.

[Stormlover74]

GFS says all the snow gets washed away in a flooding new years day rainstorm before frigid air returns

The long range looks insane, highly indicative of a major transition from blocking to non-blocking back to a blocking patter for early January.

http://www.nco.ncep....fs_ten_384l.gif

LOL Road trip to Florida

[psv88]

Here is a definition I found in pretty technical terms

Cold Conveyor Belt (CCB)

The cold conveyor belt (marked CCB in the figure above) originates poleward and east of the low pressure center, typically in the westerly flow on the backside of a high pressure system to the east. This air flows westward, on the cold side of the warm front, below the WCB, toward the center of the low pressure circulation. The air becomes saturated through a combination of precipitation falling into the CCB from the WCB above and slow ascent from the boundary layer to the mid-troposphere north of the low center (see figure above). The flow eventually rises and turn anticyclonically into the upper tropospheric ridge ahead of the developing cyclone.

ok and now in english.

[winterwx21]

So is 0z tomorrow night...and they day after....and the day after....and the day after....

Yeah it's pretty funny. There is no "big" model run 5 days before a storm. Have to get quite a bit closer before we call any runs big. Remember for this storm that just missed us, a Euro run buried us just a couple days before the storm. We know how that worked out, so it's downright silly to think model runs now are that important.

[Bluescat1]

Overall it did, thats correct, it may have had one run that was almost a hit if I recall but that was all, it was never really close, but in the long run I've always found its worse than the Euro/GFS on coastal systems, especially Miller Bs, it tends to be better with Miller As from what I've noticed.

I agree, but that was their reasoning since the models are all over the place.

[SnowGoose69]

Yeah it's pretty funny. There is no "big" model run 5 days before a storm. Have to get quite a bit closer before we call any runs big. Remember for this storm that just missed us, a Euro run buried us just a couple days before the storm. We know how that worked out, so it's downright silly to think model runs now are that important.

As the wave gets closer to the CA coast and eventually onshore the overall depictions are more accurate, once that thing is onshore I doubt we'll see any major changes, even the last event was more or less confirmed a miss once all the players were in range.

[ag3]

Tonight will show if models will go more north and faster track like NAM and GFS are depicting now.

Or if the southern, rely on perfect phase, is the right one.

That's what I am saying when I say tonights runs are big.

[Alpha5]

As the wave gets closer to the CA coast and eventually onshore the overall depictions are more accurate, once that thing is onshore I doubt we'll see any major changes, even the last event was more or less confirmed a miss once all the players were in range.

Comes ashore in T-48

Until then, let the (moderate) madness continue

[ARyan]

ok and now in english.

I don't think you can put something like that in "layman's terms." CCB is a result of differential advection, or airmass of different densities being advected over each other.

[Edge Weather]

Approximately what run will all the players be in place?

As the wave gets closer to the CA coast and eventually onshore the overall depictions are more accurate, once that thing is onshore I doubt we'll see any major changes, even the last event was more or less confirmed a miss once all the players were in range.

[IsentropicLift]

GFS says all the snow gets washed away in a flooding new years day rainstorm before frigid air returns

lots of potential with the new years storm...its something that even though its very far out their seems to be some form of consistency with it. Looks like repeat of late feb early march big snow followed by melting followed by heavy rain...bad combo...of course though its fantasy land

[ARyan]

Approximately what run will all the players be in place?

12z Wed and even more so 00z Thurs.

[Edge Weather]

Thank you.

12z Wed and even more so 00z Thurs.

[HSNN4]

The NOGAPS being more NW at 12 Z was an indication that this was going to come NW ...At least in my personal opinion!

I been hearing alot of this thread about the NOGAPS model, Can any point me to any paper where the NOGAPS has shown any skill in forecasting winter storms ? Thanks

[atownwxwatcher]

the 18 Z means are actually east of the operational run ...

http://raleighwx.americanwx.com/models/gfsensemble/18zgfsensemblep12132.gif

http://raleighwx.americanwx.com/models/gfsensemble/18zgfsensemblep12144.gif

[IsentropicLift]

let's not forget their is still quite a large model spread to this point. Even though several models have showed nice hits..even major hits last yesterday and today the GFS and EC seem to be in different camps with regards to how they achieve their respective soultons. I was pleased at 12z that the GFS had seemed to trend towards the 00z euro but now at 18z its changed its tune again. The 12z euro also changed from its 00z solution. Let's see some continuity out of the models before we give grab on to one particular solution.