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Jan 23/24 Major Coastal Storm Discussion


Zelocita Weather

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gfs_6hr_snow_acc_nyc_17.png

 

I know this map may be completely wrong and not to look at snow totals yet, but why does there seem to be a "snow hole" in Somerset, Morris, and Western Bergen counties? I'm out in Somerset County and this seems to be a trend too in previous storms. Is there any scientific reason or just bad luck recently? Because to the west it looks great, south and east too...just seems weird...

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I know this map may be completely wrong and not to look at snow totals yet, but why does there seem to be a "snow hole" in Somerset, Morris, and Western Bergen counties? I'm out in Somerset County and this seems to be a trend too in previous storms. Is there any scientific reason or just bad luck recently? Because to the west it looks great, south and east too...just seems weird...

 

Could be resolution and resolving convective precipitation. Most models have a difficult time with convective precip because the parameterizations. And no one knows if this map is wrong or right yet.

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The Canadian has never wavered in at least 8 runs more than model noise

The Canadian seems to do well when there is a confluence issue over Canada. Although in this case the system closing off early is more the reason this doesn't reach into MA AND CT too well. It could be that a confluence setup to the north counteracts the GGEMs tendency to want to overamp things. Sometimes models can do well when a particular feature that counteracts its usual bias is pronounced in a given setup

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The Canadian seems to do well when there is a confluence issue over Canada. Although in this case the system closing off early is more the reason this doesn't reach into MA AND CT too well. It could be that a confluence setup to the north counteracts the GGEMs tendency to want to overamp things. Sometimes models can do well when a particular feature that counteracts its usual bias is pronounced in a given setup

Goose you like where we sit or fear confluence is too strong

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The Canadian seems to do well when there is a confluence issue over Canada. Although in this case the system closing off early is more the reason this doesn't reach into MA AND CT too well. It could be that a confluence setup to the north counteracts the GGEMs tendency to want to overamp things. Sometimes models can do well when a particular feature that counteracts its usual bias is pronounced in a given setup

I just found it sort of strange when the LPs on the GFS and CMC jumped east in between 78 and 84 hrs. Will low pressure form there, or are the models just placing them on top of the convection?

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I wouldn't worry about "snow holes" showing up on the clown maps or QPF. The mid level features matter a lot more at this point. Banding features are tough to resolve until last minute.

 

True, I'm not worrying about these maps yet because they change drastically run to run and model to model. But I have noticed totals in my area have been significantly less in a few storms the past few years. Wondering if the location is like a transition type area where banding tends to set up to the west, south, or east...this could be a question for a different thread, just trying to learn more...thanks for the feedback guys

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I just found it sort of strange when the LPs on the GFS and CMC jumped east in between 78 and 84 hrs. Will low pressure form there, or are the models just placing them on top of the convection?

 

From what I saw it reforms twice. Initally around Hr 70 then again after Hr 78. Its almost like it tries to go N then hits a wall and reforms E. 

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I don't buy anything right now. It's disconcerting when things look to be going in the right direction and then something happens that doesn't make much sense, and you just hope that whatever is going on gets sorted out quickly. 

That's because things don't "go" in any direction.  Remember, trends have no significance.  Just random walk.  Basic story - NYC is just south of the expected location of a very sharp gradient, with a significant possibility (but still less than 50%) of ending up on the wrong side of that gradient - is unchanged. 

 

Everything else is just noise.

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I don't think there's any physics based reason that the double barrel low feature should be discounted. We have a strong closed upper level low that will try to pin the surface low near the coast, and strong convection over the warmer waters that will drop pressures and make a case for a second surface low east of LI. Really I can imagine a double barrel setup of a gradual lobing as the upper level lows stack and decay and the eastern surface low wins out. The problem with all of this is it will foul up surface circulations needed for that sexy CCB over northern NJ into CT.

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That's because things don't "go" in any direction.  Remember, trends have no significance.  Just random walk.  Basic story - NYC is just south of the expected location of a very sharp gradient, with a significant possibility (but still less than 50%) of ending up on the wrong side of that gradient - is unchanged. 

 

Everything else is just noise.

NYC is likely fine in this setup, but that doesn't help people who live to the North and far Northwest. 

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I don't think there's any physics based reason that the double barrel low feature should be discounted. We have a strong closed upper level low that will try to pin the surface low near the coast, and strong convection over the warmer waters that will drop pressures and make a case for a second surface low east of LI. Really I can imagine a double barrel setup of a gradual lobing as the upper level lows stack and decay and the eastern surface low wins out. The problem with all of this is it will foul up surface circulations needed for that sexy CCB over northern NJ into CT.

That is an excellent post and said better than I could have said it. This is my biggest concern with current modeling

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The Canadian seems to do well when there is a confluence issue over Canada. Although in this case the system closing off early is more the reason this doesn't reach into MA AND CT too well. It could be that a confluence setup to the north counteracts the GGEMs tendency to want to overamp things. Sometimes models can do well when a particular feature that counteracts its usual bias is pronounced in a given setup

Well, it is the Canadian model, so it should handle Canadian confluence issues better, no?  :>)

 

On a serious note, I see many folks, pros included, like yourself talking about model biases.  Just wondering if these are well-supported by data from similar systems or if they're more of a general feeling, based on experience/observation.  If it's the former, it would be interesting to see what data any model biases are based on.  

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Not buying areas of LI getting 15" or better. I really think the track E of the bench (we're I think it ends up) and the SST are going to have a major influence. The wind is also going to seriously cut down on totals. At least as far as being able to be measured accurately.

Curious as to why you think a track east of the benchmark is relevant to a place that the benchmark doesn't apply to.  Benchmark is the, well,  benchmark for SNE, not NYC/LI.

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I don't think there's any physics based reason that the double barrel low feature should be discounted. We have a strong closed upper level low that will try to pin the surface low near the coast, and strong convection over the warmer waters that will drop pressures and make a case for a second surface low east of LI. Really I can imagine a double barrel setup of a gradual lobing as the upper level lows stack and decay and the eastern surface low wins out. The problem with all of this is it will foul up surface circulations needed for that sexy CCB over northern NJ into CT.

Well stated; I agree. This is not convective feedback IMO. I think the CMC is pretty spot on with the final evolution of the storm. That double barrel low is going to rob us of a lot of QPF.

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NYC is likely fine in this setup, but that doesn't help people who live to the North and far Northwest. 

 

No one is fine or not fine.  There will be a sharp gradient  and a ton (1-2') of snow south of that gradient, a very narrow zone  (could be 10-20 miles!) of moderate totals in the gradient, and then <3" to the north of that.

 

All you know right now is the probability of being in the good side of that gradient.  South parts of our area are probably, what, 80%?  Up by Poughkeepsie, probably what, 25%?  And NYC is probably what, 60%?

 

That fundamental truth hasn't changed since 1PM yesterday.  Literally, we've had probably a dozen runs, all in - GFS op runs, GFS paras, 0Z Euro, the 0Z and 12Z Canadian, the NAM, and the probabilities are basically unchanged.   The models have narrowed in on a very clear solution - frankly we could be 6 hours out from the storm and you still might have the same uncertainty - we had it in 2/2010.

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