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March 7th 2018 Coastal Storm thread (not obs)


Rjay

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Why are we worried about off-hour NAM runs? We have a consensus between the two best models, the ECM and the UKMET, for a 8-12"+ snowstorm in NYC metro. This is supported by the RGEM, which has been excellent in short-range situations.

The NAM is NOT meant for synoptics; its use is more geared towards boundary layer temperatures, cold air damming, and banding in convective scenarios. Using it to determine where a low is going to track is not what it was designed for.

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7 minutes ago, nzucker said:

Why are we worried about off-hour NAM runs? We have a consensus between the two best models, the ECM and the UKMET, for a 8-12"+ snowstorm in NYC metro. This is supported by the RGEM, which has been excellent in short-range situations.

The NAM is NOT meant for synoptics; its use is more geared towards boundary layer temperatures, cold air damming, and banding in convective scenarios. Using it to determine where a low is going to track is not what it was designed for.

This is actually very interesting information.

Thanks for sharing

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4 minutes ago, mattinpa said:

It may be west, but it seems to be picking up on colder thermal profiles. That results in the increased snow amounts. 

Yes that was my first reaction when I saw the snow map (not buying what a snowmap shows, just for trends) and it  seemed higher for nyc metro than at 12z. I could be mistaken though.

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Being honest, imo, this run (18z nam) looks poor (snow wise) for long Island and NYC is fringed. Having the SLP just south of isp does not bode well for a large snow storm in this neck of the woods, it just doesn't. H5 shows that the western extent of the SLP will be along the NJ coast and then slowly creep along the south shore of LI essentially. This is verbatim.

 

As far as sensible weather for the area, what we seem to have is Americans VS globals. The NAM has been hot and synoptically it makes the most sense currently. The rgem and cmc still piund the area, and the rgem is pulling inside its deadly range. That being said, I would blend more towards the Rgem, while keeping in mind the NAM.. 65/35 Rgem favor. What this means is LI looks like it is in a poor place for snow, but it is also right on the edge. Any shift, either way, will have drastic consequences in terms of sensible weather. This storm will have surprises and the models are having a hard time figuring out exactly where this storm touches land and shoots ENE.

 

Furthermore, the NAO and AO being negative would give credence, imo, towards a slightly further S&E track with the storm, as well as (Cranky has repeatedly said) a bit of a colder solution.

 

All of this to say, Long Island and NYC are on the cusp of all forms of sensible weather (NYC is in a better spot for frozen precipitation).

 

Sent from my SM-N950U using Tapatalk

 

 

 

 

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1 minute ago, weatherlogix said:

At least its below 0C at 925

nam4km_2018030618_024_KJFK.png

That’s a sounding for rain with maybe some sleet mixed in. A small layer of around freezing air at 925 would create some sleet pellets but predominantly that would be cold rain. Again we need a further SE 850 low track. There’s a strong southerly flow at that level which is bringing warm air in. 

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5 minutes ago, jm1220 said:

That’s a sounding for rain with maybe some sleet mixed in. A small layer of around freezing air at 925 would create some sleet pellets but predominantly that would be cold rain. Again we need a further SE 850 low track. There’s a strong southerly flow at that level which is bringing warm air in. 

I know JM. I was being facetious....I hope the NAM is wrong...that would be utterly sickening

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1 minute ago, weatherlogix said:

I know JM. I was being facetious....I hope the NAM is wrong...that would be utterly sickening

At this point who knows. I wouldn’t be very quick to go against it when it’s been staying warm like this. I doubt it’s that much a torch given how the non-US models are, but we need that ENE bend after it hits south NJ. Even then we probably still go over for a time. The Euro didn’t get warm 850mb or 925mb air this far north but it was closer than 0z. 

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1 minute ago, SnowGoose69 said:

This may come down to real time ultimately.  Unless we see a substantial cave tonight from one suite it’ll be nearly impossible to know in the corridor near the metro what may occur 

you can make an argument for 15" or 3" in nyc. this is so annoying

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This could come down to where parts of the tri-state see prolific snowfall rates and accumulations while areas a few miles away are heavy rain. Times like these is where I'm glad I pursued a different career and not forecasting.

 

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5 minutes ago, weatherpruf said:

Then go with history. Secret sauce. The thing guys like Nate Silver use to make predictions; intangibles. What else have you got when the science is limited out? So if we went with history, what would be your guess? 

For historical perspective, the last March snowstorm to bring 6" or more snow to Central Park occurred on March 14, 2017 when 7.6" fell. The last snowstorm to bring 8" or more snow to New York City in March occurred on March 1-2, 2009 when 8.3" snow fell. The last 10" or greater March snowstorm occurred on March 13-14, 1993 when 10.6" fell. The last March snowstorm to dump a foot or more of snow was the March 3-4, 1960 blizzard when 14.5" fell. Both the 1960 and 1993 storms had colder air masses with which to work.

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