18Z Model Thread

[Ian]

It's the Nam at long range. I'm much more interested in the improvements through 48hrs than I am the end result at this point. Were not miles away from a ECS...just a day late and a dollar short.

nam is pretty far east with the low.. even further than the euro. but there's growing consensus at this point. maybe not a miracle is needed but close.

[mattinpa]

The precip shield does look closer to the coast at hrs. 78 and 84. But, as people have said, we need bigger steps than this.

[IsentropicLift]

anybody else notice how incredily broad the trough is at this point on the NAM? 18z hr 72

Now compare it to hr 78 on the 12z gfs

The trough on the GFS is much sharper and also has much more of a positive tilt. Also look at the differences on the west coast. The GFS has one s/w near AZ while the NAM has multiple pieces of energy diving southeastward. Looks as though it might even be phased. My point is...still big differences even between the various NCEP models.

[Ji]

HOW DOES THIS NOT PHASE?????

[Ian]

HOW DOES THIS NOT PHASE?????

is this your first winter here? welcome!

[rygar]

anybody else notice how incredily broad the trough is at this point on the NAM? 18z hr 72

Now compare it to hr 78 on the 12z gfs

The trough on the GFS is much sharper and also has much more of a positive tilt. Also look at the differences on the west coast. The GFS has one s/w near AZ while the NAM has has multiple pieces of energy diving southeastward. My point is...still big differences even between the various NCEP models.

Fairly large for certain. Another way to look at it is - either way OTS

[baroclinic_instability]

anybody else notice how incredily broad the trough is at this point on the NAM? 18z hr 72

Now compare it to hr 78 on the 12z gfs

The trough on the GFS is much sharper and also has much more of a positive tilt. Also look at the differences on the west coast. The GFS has one s/w near AZ while the NAM has has multiple pieces of energy diving southeastward. My point is...still big differences even between the various NCEP models.

Yes this will need a miracle. I spoke about this yesterday in the 0Z thread but was ripped to shreds when I suggested that the fast solution would result in the upstream jet digging through the plains would not develop in time for the ejecting s/w and the result would be a broad trough and an ots result. It goes to show how narrow of a window we have now. Too slow and the southern PV is too far W and has no influence because it is honestly too weak. Too fast and the ejecting wave over the gulf stream doesn't get the downstream support of the digging jet with the needed cold air reinforcing the GOM baroclinic zone.

[Ian]

Yes this will need a miracle. I spoke about this yesterday in the 0Z thread but was ripped to shreds when I suggested that the fast solution would result in the upstream jet digging through the plains would not develop in time for the ejecting s/w. It goes to show how narrow of a window we have now. Too slow and the southern PV is too far W and has no influence because it is honestly too weak. Too fast and the ejecting wave over the gulf stream doesn't get the downstream support of the digging jet with the needed cold air reinforcing the GOM baroclinic zone.

it's perhaps easier to remain clear headed when you have no backyard investment. pretty much everyone here is at least 1/2 snow weenie.

[baroclinic_instability]

it's perhaps easier to remain clear headed when you have no backyard investment. pretty much everyone here is at least 1/2 snow weenie.

True, but I wanted a big storm too, but I was trying to remain subjective given the small window I knew we had.

[WinterWxLuvr]

It all depends on perspective. If you want some improvement, you got it. Depends on where you are too. 500 is a little better, 700 is a little better. Total precip is a little better. Sim radars are a little better. If you look only below about 38 latitude, its a lot better at the surface. I'm mainly focused on Virginia here. If we were looking for one run to bring back the big storm, I guess we'll have to be disappointed. But this is a pretty big difference from the run just 6 hours earlier. I won't allow myself to believe this thing keeps changing this way with every model run. But what if does?

[Confuzzled]

It's the Nam at long range. I'm much more interested in the improvements through 48hrs than I am the end result at this point. Were not miles away from a ECS...just a day late and a dollar short.

Only focusing on the "improvements" isn't good, IMHO. The negatives are the 12z srefs, gefs, euro, gfs, ukie and ggem and the 18z nam all pretty much fishing with much a mildercoastal system. They have also been consistently fishing and the only model seriously supporting a big east coast I95 snow event is trending away from it with the last few runs.

[Ian]

True, but I wanted a big storm too, but I was trying to remain subjective given the small window I knew we had.

yeah, true. these situations are usually good ones to remain pessimistic about.. even with a euro hecs 3 runs in a row.

[baroclinic_instability]

It all depends on perspective. If you want some improvement, you got it. Depends on where you are too. 500 is a little better, 700 is a little better. Total precip is a little better. Sim radars are a little better. If you look only below about 38 latitude, its a lot better at the surface. I'm mainly focused on Virginia here. If we were looking for one run to bring back the big storm, I guess we'll have to be disappointed. But this is a pretty big difference from the run just 6 hours earlier. I won't allow myself to believe this thing keeps changing this way with every model run. But what if does?

I do agree, and this NAM run is actually quite close even though the solution is OTS. If it dug a little more and had more GOM influence, perhaps. Problem is the southern PV is now so weak it yields little GOM development and the needed latent heat release through condensation in the low levels, which supports rapid cyclogenesis, is not there. Given the overall orientation of the trough, we need rapid positive feedback cyclogenesis for this to hook even into SNE. In other words, unless the models are out to lunch on that southern PV, this seems unlikely.

[Ian]

It all depends on perspective. If you want some improvement, you got it. Depends on where you are too. 500 is a little better, 700 is a little better. Total precip is a little better. Sim radars are a little better. If you look only below about 38 latitude, its a lot better at the surface. I'm mainly focused on Virginia here. If we were looking for one run to bring back the big storm, I guess we'll have to be disappointed. But this is a pretty big difference from the run just 6 hours earlier. I won't allow myself to believe this thing keeps changing this way with every model run. But what if does?

i dont think it's really better at all. examining a panel individually as a model runs does not always give you a ton of insight into changes. i think you need to look at the evolution etc and then make a decision unless it's plainly obvious. to me if you want to hold out hope look for some light snow with the northern stream but it's not going to be a lot, maybe not even a coating.

[Yeoman]

it's perhaps easier to remain clear headed when you have no backyard investment. pretty much everyone here is at least 1/2 snow weenie.

Perhaps.. I know if I lived in Minnesota and a historic storm was modeled for somewhere outside my area I'd be a little biased on the side of it not happening. If I lived somewhere it didn't snow I would probably care less either way.

[WinterWxLuvr]

i dont think it's really better at all. examining a panel individually as a model runs does not always give you a ton of insight into changes. i think you need to look at the evolution etc and then make a decision unless it's plainly obvious. to me if you want to hold out hope look for some light snow with the northern stream but it's not going to be a lot, maybe not even a coating.

You have the ability to look at features and then project what they will lead to later. I don't. I will look at a 500 map and say, well that looks better than it did so the surface probably does also. Most of the time, when I then look at the surface, it does look better. That's about as far as I can go with it. When I look at the maps at 42 hr 18z vs. 48 hour 12z, they are better. If I lived south of a line from say Charlottesville to Lexington, Ky. I'd feel pretty good with the improvement from 12z to 18z. I didn't really care what it showed after that. I guess I've bought into this NAM after 48 hours stuff. My logic would be that if I keep going back to the same time, say Sat morning, and that time frame keeps getting better, then the later times should as well. Probably flawed logic. Will they keep getting better. If things keep going like they have, I doubt we'd seen anything even similar next run.

[Ian]

You have the ability to look at features and then project what they will lead to later. I don't. I will look at a 500 map and say, well that looks better than it did so the surface probably does also. Most of the time, when I then look at the surface, it does look better. That's about as far as I can go with it. When I look at the maps at 42 hr 18z vs. 48 hour 12z, they are better. If I lived south of a line from say Charlottesville to Lexington, Ky. I'd feel pretty good with the improvement from 12z to 18z. I didn't really care what it showed after that. I guess I've bought into this NAM after 48 hours stuff. My logic would be that if I keep going back to the same time, say Sat morning, and that time frame keeps getting better, then the later times should as well. Probably flawed logic. Will they keep getting better. If things keep going like they have, I doubt we'd seen anything even similar next run.

i think i agree in that sense there may be some hope. some snow on christmas is nice one way or another.

[Ian]

Perhaps.. I know if I lived in Minnesota and a historic storm was modeled for somewhere outside my area I'd be a little biased on the side of it not happening. If I lived somewhere it didn't snow I would probably care less either way.

right.. i mean we all do it. the euro was crap till it showed 1"+ qpf blizz three runs in a row and visions of last yr danced in our heads.

[Lee]

You have the ability to look at features and then project what they will lead to later. I don't. I will look at a 500 map and say, well that looks better than it did so the surface probably does also. Most of the time, when I then look at the surface, it does look better. That's about as far as I can go with it. When I look at the maps at 42 hr 18z vs. 48 hour 12z, they are better. If I lived south of a line from say Charlottesville to Lexington, Ky. I'd feel pretty good with the improvement from 12z to 18z. I didn't really care what it showed after that. I guess I've bought into this NAM after 48 hours stuff. My logic would be that if I keep going back to the same time, say Sat morning, and that time frame keeps getting better, then the later times should as well. Probably flawed logic. Will they keep getting better. If things keep going like they have, I doubt we'd seen anything even similar next run.

Good, well reasoned,positive post! Hopefully, will help encourage everyone that is so down over the recent turn of events. Need more of this. JI...Where are you?

[PhineasC]

It is a little better but not much. I have no doubt some random run over the next few days will give us hope. Big snow is off the table, though.

[CAPE]

yeah, true. these situations are usually good ones to remain pessimistic about.. even with a euro hecs 3 runs in a row.

not pessimistic....skeptical

and i might be 1/2 snow weenie, but after last winter, and a visit to San Diego, I think i could do without cold and snow for a long while.

[Riptide]

People were so eager to analyze the NAM and the GFS has some really significant changes at H5 on 18z.

Compare 18hr to 24hr - 12z

[PhineasC]

Just when I thought I was out, they pull me back in!

The NAM is still a complete miss. GFS likely to follow suit.

[Ian]

gfs a bit slower/diggier with the southern vort thru 30.. would probably lead to slightly better outcome with coastal in the end if continued but pretty early to say that with any real authority

[Riptide]

Too little too late? Sort of like scoring when you're down by a ton near the end of the game?

I mean that only a little facetiously!

Places along the coast and especially New England are very much in play at this point.

[Scarlet Pimpernel]

Places along the coast and especially New England are very much in play at this point.

Agreed...sorry, I was speaking from a strictly MA perspective there, but you're correct.

[Dalfy]

Just a question, can someone tell me what happens to the energy btwn the southern s/w and the northern energy btween hour 24 and hour 30 on the 18z GFS? Why does it just disappear?

[Ian]

by 42 that s/w is a good deal sw compared to 12z.. hmm-- west of euro at same time as well

[PhineasC]

by 42 that s/w is a good deal sw compared to 12z.. hmm-- west of euro at same time as well

Noticed the same. This run might actually be a little better if it can continue slow.

[baroclinic_instability]

Just a question, can someone tell me what happens to the energy btwn the southern s/w and the northern energy btween hour 24 and hour 30 on the 18z GFS? Why does it just disappear?

That southern PV anomaly has become so weak it really isn't even "phasing" anymore. The increasing flow aloft associated with the northern stream essentially "deforms" the flow field associated with the leftover southern PV/migratory circulation. It is basically almost a remnant circulation with little to no baroclinity associated with it in the upper levels.