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Jan 23/24 Major Coastal Storm Discussion


Zelocita Weather

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We're at the range where the OP's are becoming more useful than the ensembles. I'm not saying they should be ignored, but the mean is still 4-6" which really isn't bad at this range. Ensembles aren't going to pick up things like mesoscale banding.

^^^this. Think generally speaking ens long range, op models when in their wheelhouse. If used properly, guidance is a wonderful tool :-)
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This is 6 hour snow ending on 12z Saturday, so basically nothing has fallen up to this point which is near dawn

 

GFS-MAXRES_Snow6_ne_f78.png?v=1453283491

 

This is the core of deformation banding peaking Saturday night

 

GFS-MAXRES_Snow6_ne_f96.png?v=1453283833

 

And this is as everything begins to pull out on Sunday morning. Should be over by sunrise.

 

GFS-MAXRES_Snow6_ne_f105.png?v=145328399

 

 

You didn't show between 12z Sat and 00z Sunday...  u missed a 12 hour window!

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last year storm there was no doubt it would be 100% snow it was just a matter of where the heavier snow would set up.. with this storm there is some doubt if mixing happens...

We're not mixing in the city, rapidly deepening low pressure and the resulting ageosteophic flow will take care of that. If we mix, that means we've already gotten a ****ton of snow and we're (briefly) dry slotted. That happened in 1996. It's not a bad thing, it means the low is tucked in.

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You didn't show between 12z Sat and 00z Sunday...  u missed a 12 hour window!

All I was showing you was the timing of when things will start, when they peak and when they wrap up. 

 

Here is when Long Island gets hit the hardest

 

GFS-MAXRES_Snow6_ne_f84.png?v=1453283606

 

Then the band pivots to the north and then northwest

 

 

GFS-MAXRES_Snow6_ne_f87.png?v=1453283669

 

GFS-MAXRES_Snow6_ne_f90.png?v=1453283728

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It was similiar on the 0z run and then it continued on the 6z run. We have already been burned this winter by the ensembles.

I posted in the pa thread that for several runs the last few days the eps ggem and gfs ensembles have been south with a 40% camp being very south, even missing dc with most snow. There is obviously a trend of the higher res ops favoring a more amped solution then their ens because it's several runs on all 3. I wish someone with more knowledge then me on what that might mean would discuss. Weather the higher resolution ops are more likely on to this or going overboard.
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^^^this. Think generally speaking ens long range, op models when in their wheelhouse. If used properly, guidance is a wonderful tool :-)

Someone posted a forecast discussion in the NE forum that theorized the OP runs may be better at picking up higher SST's and baroclinicity along the coast than the ensembles due to their higher resolution. Certainly something to watch moving forward.

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We're not mixing in the city, rapidly deepening low pressure and the resulting ageosteophic flow will take care of that. If we mix, that means we've already gotten a ****ton of snow and we're (briefly) dry slotted. That happened in 1996. It's not a bad thing, it means the low is tucked in.

I mixed in 96' and had over 30" of snow.

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before the 96 storm hit you had a incredibly arctic air mass over the region it started snowing here in nyc with temps like 12 degrees and in some places in the single digits.  that won't be the case with this storm..

That's not particularly relevant. A strong storm with the wrong pattern will advect warm air into the coldest of air masses. It's more a question of wind direction, and a rapidly deepening storm off shore will cause the winds to back. Also, that touch of confluence up in eastern Canada is helping us because it is creating higher pressures in the source region for our cold. We need that.

If you mix, in the city, it is likely because you've gotten the full force of the WAA snow and the CCB is lurking just to your west waiting to crawl through as the storm stalls and inches off the to ENE. This isn't like 1/2000 where the storm is progressive so all you get is the WAA thump.

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I know the NWS does this, but I think it's stupid / patronizing. They assume the public can't understand the actual forecast so they make up a fake one with the least chance of verifying. IIRC the research on this shows that the public can understand a more accurate forecast. What they're doing is CYA - forecasting to avoid a fiasco - rather than presenting the public with the best information for people to make independent judgments about preparation.

Are you sure that they're just not factoring in the 0z Euro's scenario and weighting a bit heavier and combining it with the GFS's consistency (if you want to call it that)? I think given the fact that we're 48-72 hourse out and the whole idea of forecasting totals is not exactly completely objective to begin with ... it's not a bad call. You don't want to create panic by issuing a forecast of 12"-24" if you are not confident enough that it could verify yet ... and you don't want to assume the Euro is correct and the totals will be dramatically lower due to a more southern track or mixing either. At 48-72 hours, they HAVE to say SOMETHING. What would you have recommended if you were running NWS at Upton?

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All I was showing you was the timing of when things will start, when they peak and when they wrap up. 

 

Here is when Long Island gets hit the hardest

 

GFS-MAXRES_Snow6_ne_f84.png?v=1453283606

 

Then the band pivots to the north and then northwest

 

GFS-MAXRES_Snow6_ne_f90.png?v=1453283728

GFS-MAXRES_Snow6_ne_f87.png?v=1453283669

 

 

OK now I understand where you were coming from.... I thought you left it by mistake. Sorry about that... so basically it shows 12-18 on average throughout the entire area.  Correct??

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I don't care how cold it is. If the winds are SE, E or even ENE, eastern and southern sections of LI are in for some mixing for sure. I have see storms start at 5 - 10F and rain within a few hrs of the storm starting. The column can warm incredibly fast especially if you are dealing with warming SST. Keep an eye on the wind direction. Also (as it was pointed out by NWS) model forecasts usually underestimate the northerly backing winds for storms that are near the BM. 

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Here's the issue. There's a warm tongue somewhere around 850mb, and it's hard to decipher without looking at the entire sounding.

 

The good news is that the warm layer appears temporary so anyone that changes over should go back to snow.

gfs_T850_neus_14.png

The 850s crash when the mod-heavy precip begins. The bigger concern is when the low occludes, and how long it has to drag warm air in, and also whether Long Island has to deal with nonideal ENE winds. 

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If you want to know where the heaviest banding occurs, look at the darker reds that extend from Long Island, over the city and into NJ

gfs_z700_vort_neus_17.png

That then shifts to just NW of the city

gfs_z700_vort_neus_18.png

Everything then pulls East as the low departs

gfs_z700_vort_neus_19.png

Textbook 700mb CCB. There's going to be some awesome snow growth under those bands.

Sent from my iPhone using Tapatalk

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The 850s crash when the mod-heavy precip begins. The bigger concern is when the low occludes, and how long it has to drag warm air in, and also whether Long Island has to deal with nonideal ENE winds. 

Long Island has a very hard time keeping all snow when the winds aren't out of the North or the Northeast. With this storm, the winds could even be out of the Southeast for awhile, especially on the East end.

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