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1/23-24 Randytastic Snowstorm Part 2 STORM MODE THREAD


BxEngine

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I'll take it, brought the gradient further north - would still like it to gain more latitude before ejecting east, but there's room for that in later runs.

 

 

That is an improvement of AT LEAST 30-40 miles which is MAJOR for this type of storm.  Brings warning snowfall all the way to I-84 instead of I-87 in NY like the last run.... no reason why it shouldn't come north more. 

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The GFS is surely nothing like the NAM, however, it is a HUGE improvement compared to its last several runs. 20"+ even into parts of Hunterdon country NJ, not just southern NJ. As Issntropic said, move this 25 miles N, it's not too far off from the hi res NAM (assuming we discount the 12km NAM). Nice run!

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I'll take it, brought the gradient further north - would still like it to gain more latitude before ejecting east, but there's room for that in later runs.

 "I'll take it" might be the understatement of the year, lol.  Huge shift northward, relatively speaking.  Looking really good for NYC/LI and adjacent NJ at least not getting hosed and maybe getting a foot of snow.  

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My quibble with those ensembles is that they seem unrealistically tight.  Right now they have a 6" gradient in mean snowfall in 30 miles (BLM-JFK).  That seems improbably certain to me - isn't there more uncertainty than that  even if you knew almost precisely what the initial conditions were?

Yeah, they are compute limited and can only afford to run a 10 member ensemble.  However, there is decent variability if you look at the postage stamp simulated reflectivity (member 1 is pretty far north, and member 5 way south, and all others in between).

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The GFS is surely nothing like the NAM, however, it is a HUGE improvement compared to its last several runs. 20"+ even into parts of Hunterdon country NJ, not just southern NJ. As Issntropic said, move this 25 miles N, it's not too far off from the hi res NAM (assuming we discount the 12km NAM). Nice run!

Follow where the GFS is painting it's huge blob, there's clearly going to be a tremendous band oriented nearby and it's not going to look like that, almost a muffin like blob.

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I don't take the parent (12km) NAM seriously, especially when it differs from its nest (4km).  I also tend to ignore the SREFs in favor of the NCAR WRF ensemble system: http://ensemble.ucar.edu/

 

Having said that, I have only just started paying attention to the northern part of this forecast as I'm always fascinated by these aspects.  I haven't done enough digging to be able to say anything intelligent about the "why" with respect to the differences.

 

 

If you don't mind me asking, what is your reasoning for favoring the NCAR WRF over the upgraded SREFs? Better verification? Thanks.

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The Eastward adjustment isn't all bad for a few reasons:

 

- so long as you get engulfed in the overrunning, it will continue to snow as the low departs as you'll be under the CCB

- limits mixing potential, which is there with the wrapped up solutions

- minimizes dry slot issues (which were showing up to our south primarily but you get the idea)

- greatly limits the coastal flooding risk

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GFS actually looked a good amount better to me. Like the RGEM, it washes out the very heavy banding over SE PA before hitting NYC, but it's a decent step the right direction. It redevelops the far out to sea low a little too soon, which reduces the dynamics near NYC. It wouldn't have taken much for this to be 1.50"+ liquid for many more people.

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Pretty Much identical - locked in like last year's blizzard?

The RGEM actually didn't perform very well in that storm for areas outside of New Jersey and Far East Suffolk. The areas in between it was significantly too low. Overall it didn't have a great winter like it did in 13-14, this winter it has been markedly better so far

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If you don't mind me asking, what is your reasoning for favoring the NCAR WRF over the upgraded SREFs? Better verification? Thanks.

Higher resolution, single model, better design.  The SREF is flawed in its two-model design and mixing/matching of initial, boundary, and model perturbations.

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I'll take it, brought the gradient further north - would still like it to gain more latitude before ejecting east, but there's room for that in later runs.

 

Looks like the 12z GFS brings the 1.25"-1.50" line into Union County NJ as well southern areas of the city, I am just south of that in Northeastern Middlesex County. So certainly another shift north.

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