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January 19-20th Winter Storm Threat


Rjay

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3 minutes ago, HeadInTheClouds said:

I'm in HV a little north of Poughkeepsie. I have a question concerning above Nam maps. 1st Snow/sleet map gives me a foot, then next Kuchera map gives me 2.9 inches but I get zero accumulated freezing rain. What science goes into Kuchera map? Anybody know?

The nam is assuming everything that falls as snow or sleet is a 10:1 ratio. Kuchera is much lower due to the fact most will fall as sleet

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I mentioned this in the HV thread earlier and now there are some good discussions on Twitter about it, but it's worth bearing in mind that precip during a freezing rain event doesn't accrete at a perfect 1:1 ratio... in fact, the average is around 0.7:1, and it can be much lower in certain sitiations. The models are only printing out QPF while conditions favor ZR. In reality, the amount of ice that actually sticks to things will be significantly lower. 

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4 minutes ago, Brasiluvsnow said:

HV how far west are you thinking ? Because if that last Euro if verifies it would make me think it would be much farther west. Again this system could still be South and East of what we just saw on the Euro

I didn't see the entire run but agree with what was posted above people are exagerating how awful it is. It still even has 4-5 inches down to where I am at the border of Bronx and Westchester, it has a very sharp cutoff right across the city. The Euro is about 7-8 inches for Rockland County. 

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Please explain what you mean thanks!
This storm is moving along the temperature gradient. If the storm outruns the cold, the temperature gradient is displaced further NW. In turn, the storm rides the boundary further NW. Thus.. Less snow.

Sent from my SM-N960U using Tapatalk

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7 minutes ago, NJwx85 said:

The trolling is over the line.

The Euro is not an all out torch. This is the warmest panel. It might be warm on Long Island but this was never a snowstorm in that area.

Weather Model

Hey yanks wasn’t the euro showing 40’s for the city a couple of days ago or it was just the GFS showing that?

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Just now, NYCweatherNOW said:

Hey yanks wasn’t the euro showings 40’s a couple of days ago or it was just the GFS showing that?

The Euro had a few very warm runs with temps near 60.

The good news is that we're still roughly 48 hours out, and that even though the models have shifted back NW, they are still showing a track basically along the NJ TPK instead of an Apps runner like they did on Tuesday. I would be very cautious to declare that models are locked in at 48hrs.

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1 hour ago, Stormlover74 said:

The nam is assuming everything that falls as snow or sleet is a 10:1 ratio. Kuchera is much lower due to the fact most will fall as sleet

It has nothing to do with Kuchera, which is only a snow bulk density modulator, depending on the max temp the snow falls through in the column; there is no "Kuchera" for calculating sleet density.  The major difference between TT and Pivotal is that Pivotal simply does not count sleet at all, while TT counts the sleet as 10:1 ratio snow for depth calcs.  Both are flawed if only looking at one of them in a mixed precip event.  

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1 hour ago, Juliancolton said:

I mentioned this in the HV thread earlier and now there are some good discussions on Twitter about it, but it's worth bearing in mind that precip during a freezing rain event doesn't accrete at a perfect 1:1 ratio... in fact, the average is around 0.7:1, and it can be much lower in certain sitiations. The models are only printing out QPF while conditions favor ZR. In reality, the amount of ice that actually sticks to things will be significantly lower. 

Same is true for snowfall.  All snowfall maps assume that all the snow that falls accumulates, whereas we know that some melts, depending on surface temps, indirect sunlight, albedo, etc.  

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