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Tuesday over running event


Mitchel Volk

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The NAM BL of mid 30s in CNJ NYC and LI look suspect to me. .5 liquid thru minus 2 to 4 air. Yet the sounding do not suggest snow there .

 

Another case of models not resolving evaporative cooling, the MOS is 31/20 when snow starts, thats gonna be primarily snow til the end when it may end as some drizzle.

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The NAM BL of mid 30s in CNJ NYC and LI look suspect to me. .5 liquid thru minus 2 to 4 air. Yet the sounding do not suggest snow there .

The NAM has sometimes had issues with warm advection snows warming the column too aggressively. February 5 is a good recent example. The NAM's soundings indicated almost no snow would fall in the NYC Metro Area, yet NYC picked up 4.0" and EWR received 4.1".

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Another case of models not resolving evaporative cooling, the MOS is 31/20 when snow starts, thats gonna be primarily snow til the end when it may end as some drizzle.[/quot

I agree. If .5 liquid falls thru minus 4 air I just hav to believe thats snow.

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The NAM has sometimes had issues with warm advection snows warming the column too aggressively. February 5 is a good recent example. The NAM's soundings indicated almost no snow would fall in the NYC Metro Area, yet NYC picked up 4.0" and EWR received 4.1".

I'm wiling to take that look. .5 and minus 2 to minus 4 at knyc Think that would work out

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Another case of models not resolving evaporative cooling, the MOS is 31/20 when snow starts, thats gonna be primarily snow til the end when it may end as some drizzle.[/quot

I agree. If .5 liquid falls thru minus 4 air I just hav to believe thats snow.

Bufkit agrees. The 0z 4km NAM prints out 4.0" snow at LGA (Maximum Temperature in Profile algorithm) before the precipitation ends as rain.

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I don;t know whats worse, those snow maps or BUFKIT...BUFKIT is not bad if you look at soundings but its Ptype tends to run too cold, it will show snow with a 850mb layer of +2C or show sleet with a surface temps of 42. ...my guess is the NAM BUFKIT will show entirely snow although that too will be wrong.

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Bufkit agrees. The 0z 4km NAM prints out 4.0" snow at LGA (Maximum Temperature in Profile algorithm) before the precipitation ends as rain.

Ok , when I looked at Maue s snow maps i know he uses the soundings to approximate amounts and it didn't show anything

At KNYC

So wasn't sure if that's still an unresolved prob with there algo or the soundings didn't see the evaporative cooling .

Ok good. Think Upton and mt holly were early with this and may turn out to be a very good early call by both offices

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I don;t know whats worse, those snow maps or BUFKIT...BUFKIT is not bad if you look at soundings but its Ptype tends to run too cold, it will show snow with a 850mb layer of +2C or show sleet with a surface temps of 42. ...my guess is the NAM BUFKIT will show entirely snow although that too will be wrong.

I love those guys but the snow maps will make ur head spin.

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I don;t know whats worse, those snow maps or BUFKIT...BUFKIT is not bad if you look at soundings but its Ptype tends to run too cold, it will show snow with a 850mb layer of +2C or show sleet with a surface temps of 42. ...my guess is the NAM BUFKIT will show entirely snow although that too will be wrong.

I agree. My thoughts as per the NAM run would be that the run, taking into consideration the above and the NAM's not infrequent overly aggressive warming of the column, supported something in the 1"-3"/2"-4" range for the greater NYC area (lower figures at JFK and higher figures at NYC) and perhaps an inch or two higher in the immediate northern and western suburbs.

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Ok , when I looked at Maue s snow maps i know he uses the soundings to approximate amounts and it didn't show anything

At KNYC

So wasn't sure if that's still an unresolved prob with there algo or the soundings didn't see the evaporative cooling .

Ok good. Think Upton and mt holly were early with this and may turn out to be a very good early call by both offices

I'm not sure how his maps calculate the snowfall. It will be interesting to see the future model runs and then the event.

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I don;t know whats worse, those snow maps or BUFKIT...BUFKIT is not bad if you look at soundings but its Ptype tends to run too cold, it will show snow with a 850mb layer of +2C or show sleet with a surface temps of 42. ...my guess is the NAM BUFKIT will show entirely snow although that too will be wrong.

 

BL temps from the 4km NAM Bufkit is marginal for LGA. JFK is also mostly rain.

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The NAM has low-level SE flow of about 15-30kts.

Critical thicknesses on the front side of a significant mid level Ridge are also not great.

http://mag.ncep.noaa.gov/Image.php?fhr=039ℑ=data%2Fnam-hires%2F00%2Fnam-hires_namer_039_850_700_thick.gif&model=nam-hires&area=namer&param=850_700_thick&group=Model+Guidance&imageSize=

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Just not sure with minus 5 with .5 falling the BL doesn't cool. ( as long as the 925 sr ok)

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SSTs off the coast are in the lower to mid 30's, SE wind isnt going to hurt like in Dec

 

I've always assumed the fetch of moist air coming in with a storm off the coast includes air originating hundreds of miles away, like off the Gulf Stream, which is much warmer than the mid-30s. Not sure what the aggregate air temp coming in via SE winds is, but I imagine it's warmer than just the air right off the coast.

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