00z Dec 8 Model Guidance

[earthlight]

It will be interesting to see the jumps and/or trends this evening considering some of the developments at 18z. Interestingly, the NAM is further south with the clipper shortwave energy. We will see where the rest of the suite goes from here. I included the 00z NAM link referenced above below:

http://www.meteo.psu.edu/~gadomski/WRF_0z/f72.gif

[LetItSnowInPhilly]

NAM actually looks similar to the further east GFS ensemble members from 18z.

I doubt it means much as its the NAM at 72, but I guess it could be noted.

[greg ralls]

I love these model threads, and look forward to reading this one. I thought they were all supposed to go in the main forum now, though?

[LVblizzard]

Two notable differences from the 18z GFS on the 0z NAM is that the ridge out west is slightly sharper and the PV is farther north. To my knowledge, the PV being farther north wouldn't cause the system to phase as quickly, therefore leading to a farther east solution.

[LVblizzard]

Here's the 18z GFS at 90 vs. the 0z NAM at 84. The s/w is farther south and more positively tilted, along with that PV being a little farther north. Ultimately this would lead to a better solution east of the Apps, maybe not necessarily in the cities, but it definitely looks better.

[Alpha5]

I wary of taking the NAM so far out but its interesting to see it has such a different solution.

Storm should be moving over better sampled waters so we'll see some defining trends the next few runs

[Sundog]

It looks like the 850's are also colder at the same hour when compared to the 18z gfs. Probably too early to tell if it means anything but any improvement should be noted.

[earthlight]

The NAM is definitely slightly encouraging, but if you ask me the window for this to produce snow on the coastal plain is very, very small. Inland areas definitely should keep an eye out for the eastward trend with this one, though. It's still amazing to me that people were declaring this threat over two days ago when the system was 160 hours out.

[earthlight]

I wary of taking the NAM so far out but its interesting to see it has such a different solution.

Storm should be moving over better sampled waters so we'll see some defining trends the next few runs

It's going to take another day or two to get the pieces in a good RAOB area, especially the Polar Vortex to the north which is interestingly one of the most important feature now as we watch the evolution of the trough and the phase.

[Sundog]

The NAM is definitely slightly encouraging, but if you ask me the window for this to produce snow on the coastal plain is very, very small. Inland areas definitely should keep an eye out for the eastward trend with this one, though. It's still amazing to me that people were declaring this threat over two days ago when the system was 160 hours out.

I think at this point most would be satisfied with even a minor snowfall accumulation.

[Chris L]

Anyway, the NAM is slighty cooler than the GFS at the same time frame; but hard to say if it means anything.

I will say this: PV is looking interesting on this situation.

[Alpha5]

It's going to take another day or two to get the pieces in a good RAOB area, especially the Polar Vortex to the north which is interestingly one of the most important feature now as we watch the evolution of the trough and the phase.

Yeah, the PV certainly can not be forgotten in this equation. Also the GFS and others have been hinting at possible secondary development off the east coast, thats something that needs to be watch as well

[Sundog]

Yeah, the PV certainly can not be forgotten in this equation. Also the GFS and others have been hinting at possible secondary development off the east coast, thats something that needs to be watch as well

Someone did mention that there was a second wave being depicted on some of the ensemble members on the 12z run; I'm not sure how prevalent this was in the 18z ensembles.

[wxman]

I posted about this earlier, but once you get into the 120hr plus range what looks for all the world like being a certain type of storm (coastal, apps ruuner, cutter, etc) could easily turn out the exact opposite. And just as often some really smart people (even mets) will chime in on the model agreement and explain why the synoptic setup shows why the modeled outcome is likely. Well of course, if the modeled features are similar the outcomes are similar. But the features turning out as modeled at that time range is really not that much more than a crap shoot. I have absolutely, definitely seen a depicted cutter at this range (as shown on the GFS/Euro/GGEM) turn out wide right in the end.

[ag3]

Someone did mention that there was a second wave being depicted on some of the ensemble members on the 12z run; I'm not sure how prevalent this was in the 18z ensembles.

It was there on the 18z GFS operational and on a lot of the ensemble members. Not that it means much, but Dgex also had this feature at 18z.

[NJwinter23]

It's going to take another day or two to get the pieces in a good RAOB area, especially the Polar Vortex to the north which is interestingly one of the most important feature now as we watch the evolution of the trough and the phase.

The cold air is just not in place though ahead of the storm. So while the track can definitely still shift significantly, I gave up on this storm being a snow producer in the big cities largely for that reason, and every model cutting it to the west of course.

[LVblizzard]

I posted about this earlier, but once you get into the 120hr plus range what looks for all the world like being a certain type of storm (coastal, apps ruuner, cutter, etc) could easily turn out the exact opposite. And just as often some really smart people (even mets) will chime in on the model agreement and explain why the synoptic setup shows why the modeled outcome is likely. Well of course, if the modeled features are similar the outcomes are similar. But the features turning out as modeled at that time range is really not that much more than a crap shoot. I have absolutely, definitely seen a depicted cutter at this range (as shown on the GFS/Euro/GGEM) turn out wide right in the end.

A good example is Feb. 2-4, 2009. 5 days out, most models progged it to be a Great Lakes bomb, but the storm ended up coming east and bringing a period of light-moderate snow to the cities. It turned out that the models were wrapping up the storm too early with those 100+ hour runs.

[Sundog]

The cold air is just not in place though ahead of the storm. So while the track can definitely still shift significantly, I gave up on this storm being a snow producer in the big cities largely for that reason, and every model cutting it to the west of course.

The only thing most of us are probably hoping for is a bit of snow at the tail end to just whiten the ground at least. I think most of us have probably given up on the idea of big snows on the coastal plain.

[SnoSki14]

For us, these slight changes won't mean much, it'll still rain here regardless. If you live in central PA, upstate NY, into Ohio, then these slight changes do make a difference. For us the only difference will be how warm the temperatures get before the storm swings through. Will we rise into the mid 50s with rain or into the mid 40s with rain? I'll take the colder rain solution though, at least it'll feel like I'm close to winter weather rather than light years away from it (10-12 degrees above freezing vs 20+ degrees above freezing).

[tombo82685]

The cold air is just not in place though ahead of the storm. So while the track can definitely still shift significantly, I gave up on this storm being a snow producer in the big cities largely for that reason, and every model cutting it to the west of course.

what i don't get is if you look at the 18z ens, the ones that have the snow tracks how does the cold air get involved? The clipper takes basically the same track north of us over the lakes or over canada. So is it from the plains storm diving so far south that the cold air can seep in? Or are they showing the clipper dragging a cold front with it and that gets there before the 2nd storm comes along? Because it can't be from the pv, once the pv dives south that storm is going to phase with it.

[tombo82685]

The only thing most of us are probably hoping for is a bit of snow at the tail end to just whiten the ground at least. I think most of us have probably given up on the idea of big snows on the coastal plain.

the only thing i can see where we can salvage a snow event is if the s/w energy coming into the plains does not phase with the pv and thus its just a low travelling east, then once hits the coast it can go up it or ots. Thats the only way i see a snowstorm for i95 corridor

[Analog96]

The cold air is just not in place though ahead of the storm. So while the track can definitely still shift significantly, I gave up on this storm being a snow producer in the big cities largely for that reason, and every model cutting it to the west of course.

There IS enough cold air for snow in a thread the needle type situation with this storm, although it is far from ideal.

[benfica356]

clipper stronger than 18z at 30 hr on 00z

[Sundog]

There IS enough cold air for snow in a thread the needle type situation with this storm, although it is far from ideal.

There is also plenty of cold air to tap if needed. The problem is getting the storm in a position that would allow it to tap the cold air and funnel it toward the coast. Not impossible but we need to definitely move a couple things around.

[SnoSki14]

I'm not contradicting myself, if it's dry, then I want it to be warm but if there's precipitation and it's def gonna be rain, I'll take the colder rain over the warmer rain.

[benfica356]

still stronger at 36

[Analog96]

There is also plenty of cold air to tap if needed. The problem is getting the storm in a position that would allow it to tap the cold air and funnel it toward the coast. Not impossible but we need to definitely move a couple things around.

This is even more true. There is PLENTY of cold air to tap.

[wxman]

A good example is Feb. 2-4, 2009. 5 days out, most models progged it to be a Great Lakes bomb, but the storm ended up coming east and bringing a period of light-moderate snow to the cities. It turned out that the models were wrapping up the storm too early with those 100+ hour runs.

I wish I could go back to eastern and pull out some of those threads....if I'm remembering correctly that Feb 2009 event (as modeled) changed dramatically during a 12z run.... I remember laughing as everyone was pulling for an east shift, but in the end it was too much!

[SnowGoose69]

the only thing i can see where we can salvage a snow event is if the s/w energy coming into the plains does not phase with the pv and thus its just a low travelling east, then once hits the coast it can go up it or ots. Thats the only way i see a snowstorm for i95 corridor

NYC could see wraparound snow, but the low would have to be positioned to their SE, E, or NE, if the low is to the north over ALB its almost impossible to see any significant wraparound since the NNW flow causes too much of a downslope.

[tombo82685]

through 48 hrs, clipper is sub 1000 compared to sub 1004 from 18z...the pv looks like its tad further east, and also the hgts along the east are lower