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January 26-27 Snowstorm Disco V


Baroclinic Zone

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The NAM is fine just faster.

Weathafella, this is what I meant about a two part storm. Bastardi is talking about the same thing. There's a HUGE split in the precip even up here, we wait for the CCB to develop. That's the big difference between these models and the older Euro. Ultimately the idea of having to wait for the CCB I think is the right one as the s/w coming out of the Gulf etc causes a big dry slot/rift as the main precip shield gets east.

I'll wait for the 0z but I'm leaning pretty heavily to the idea that the meso/nam idea won't be terrible, there will be a sharp cuttoff.

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Slowly but surely it succumbs to the Euro..1st it took off it's shirt..then at 18z it bent over the table..At 00z it 'll drop it's pants

if not we followed a storm for 6 days.....for .50 qpf (not awful) but always nicer when they fatten up within 48 hours.

looks like the cape is now in the "game" for a big hit.

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Definitely an improvement on the upper low track vs 12z run. QPF went up too but that's not important right now...more important to look at the key features. NAM is still having a horrible convective low go well east initially.

I would imagine, the qpf would be better by a fair margin if it weren't for that low we described.

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Definitely an improvement on the upper low track vs 12z run. QPF went up too but that's not important right now...more important to look at the key features. NAM is still having a horrible convective low go well east initially.

Yeah, it's all dicomboobalated. Should be there by tonight, tomorrow morning.:thumbsup:

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H5 does look MUCH better though...

anyone having trouble with NCEP lately...not getting images to load, error messages, etc.

The 30 HR 500mb map wouldn't load when I made that post but now it loads and it looks pretty sweet.

yeah - some weird errors but it eventually worked.

500, 850, and 700 all close off south of SNE - despite the crazy surface depiction with the convection heavily displaced from the low and the poor orphaned comma head - I'd think that this thing would be a nice hit but who knows, only the GGEM, UK, Euro are all showing a ton of QPF for most of SNE - maybe the NAM is right...

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as usual...conflicting opinions on whether this is a good run or not.

NW cut off seems to have been nudged a bit farther NW...totals elsewhere look fairly similar to 12z.

At hour 30, the low center looks farther W and it looks like it shapes up for a monster hit...but then the surface low rockets E-NE along with the precip. Seems like a slightly faster solution which means no bump up in QPF for most from the 12z.

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The NAM is fine just faster.

Weathafella, this is what I meant about a two part storm. Bastardi is talking about the same thing. There's a HUGE split in the precip even up here, we wait for the CCB to develop. That's the big difference between these models and the older Euro. Ultimately the idea of having to wait for the CCB I think is the right one as the s/w coming out of the Gulf etc causes a big dry slot/rift as the main precip shield gets east.

I'll wait for the 0z but I'm leaning pretty heavily to the idea that the meso/nam idea won't be terrible, there will be a sharp cuttoff.

This might be true in that there could be a lull in qpf just off the Delmarva, but the NAM may have done that because of some convective feedback. It has nothing off the Delmarva during tomorrow aftn..like a 150 miles gap. I'm not sure about that.

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The NAM is fine just faster.

Weathafella, this is what I meant about a two part storm. Bastardi is talking about the same thing. There's a HUGE split in the precip even up here, we wait for the CCB to develop. That's the big difference between these models and the older Euro. Ultimately the idea of having to wait for the CCB I think is the right one as the s/w coming out of the Gulf etc causes a big dry slot/rift as the main precip shield gets east.

I'll wait for the 0z but I'm leaning pretty heavily to the idea that the meso/nam idea won't be terrible, there will be a sharp cuttoff.

that's what I was thinking as well. any idea for why it seem to speed things up a bit from 12z? how does the speed compare to the EC?

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Definitely an improvement on the upper low track vs 12z run. QPF went up too but that's not important right now...more important to look at the key features. NAM is still having a horrible convective low go well east initially.

It's been suffering convective nausea for at least 7 cycles now...

The difference here appears to be that the gradient is difused off the EC. If we recall the big guy 10 or whatever days ago it was, that was not the case. The gradient thermal ribbon was right where the low happened to be, and that is why the NAM nailed that. Here, it is constantly foresaking the mechanics of deep layer cyclogenesis in lieu of having the convective signal spread out over a larger storm-leading spatial medium.

There probably is greater convective potential with this seaward, but the NAM's initialization schemes are just too much of a good thing.

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as usual...conflicting opinions on whether this is a good run or not.

NW cut off seems to have been nudged a bit farther NW...totals elsewhere look fairly similar to 12z.

At hour 30, the low center looks farther W and it looks like it shapes up for a monster hit...but then the surface low rockets E-NE along with the precip. Seems like a slightly faster solution which means no bump up in QPF for most from the 12z.

Yeah, And some mind games being played in a place where there is a lot of unrest already..

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This might be true in that there could be a lull in qpf just off the Delmarva, but the NAM may have done that because of some convective feedback. It has nothing off the Delmarva during tomorrow aftn..like a 150 miles gap. I'm not sure about that.

I think this is overblown but it made for a good illustration of an earlier point that got muddied. There will be some type of "break" off NJ I'm pretty sure.

that's what I was thinking as well. any idea for why it seem to speed things up a bit from 12z? how does the speed compare to the EC?

I don't really take this run seriously....I won't until tonight. Between the missing obs and some of the other weirdness I'd assume get a fresh start tonight. I wouldn't be surprised to see the other models pull the same gap though. It's a legitimate feature that it's keying on, it may be overdoing it as Tip says, but it's not pure convective feedback that's spun out of the blue at least not per the NOAA writeups I've read.

It's been suffering convective nausea for at least 7 cycles now...

The difference here appears to be that the gradient is difused off the EC. If we recall the big guy 10 or whatever days ago it was, that was not the case. The gradient thermal ribbon was right where the low happened to be, and that is why the NAM nailed that. Here, it is constantly foresaking the mechanics of deep layer cyclogenesis in lieu of having the convective signal spread out over a larger storm-leading spatial medium.

There probably is greater convective potential with this seaward, but the NAM's initialization schemes are just too much of a good thing.

But what if it's not to the extreme that the NAM is showing but still a feature out over the water associated with an impulse at 5h that takes a lot of moisture with it. It's not like we haven't seen it before with southern systems.

--

The NCEP writeup on convective feedback:

"When specific thresholds in the mass fields are met, convective scheme is triggered and then dumps a large amount of QPF over a grid point - releasing so much latent heat over the grid point that the model is forced to adjust the mass fields by producing a local vertical motion max in the mid troposphere (~ 500mb), a corresponding upper level jet max over the vertical motion max - an intense and small scale vort max in the mid levels (MCV).

The model scales up the mesoscale circulation at mid levels and holds onto it as a real feature for as long as 3 days. The model can produce precipitation in association with the feature as it tracks along in the flow.

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But what if it's not to the extreme that the NAM is showing but still a feature out over the water associated with an impulse at 5h that takes a lot of moisture with it. It's not like we haven't seen it before with southern systems.

--

The NCEP writeup on convective feedback:

"When specific thresholds in the mass fields are met, convective scheme is triggered and then dumps a large amount of QPF over a grid point - releasing so much latent heat over the grid point that the model is forced to adjust the mass fields by producing a local vertical motion max in the mid troposphere (~ 500mb), a corresponding upper level jet max over the vertical motion max - an intense and small scale vort max in the mid levels (MCV).

The model scales up the mesoscale circulation at mid levels and holds onto it as a real feature for as long as 3 days. The model can produce precipitation in association with the feature as it tracks along in the flow.

Okay, your point being ....?

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Yes W. of CR. about .1 QPF for me on the NAM...

Don't sweat the NAM though I think we do a little better than that or at least your area does. I'm really not sweating anything until 6z tomorrow. With what's already on the ground I'll be happy w/ as little as 4" and that seems to be almost a lock even up here towards the VT border.

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