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NYC/PHL January 7-9 Potential Part Deux


NickD2011

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verbatim looks like 0.1" to 0.2" on the RGEM for Philly, and 0.2" to 0.5" for NYC

still good to see the norlun down this way and not up in SNE, that's what we need to take away from tonight's model runs rather than just the QPF

rgem is only through 48, so there would be more after especialy nyc and points north and east.

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GFS looks nothing like the NAM through 48 hrs

Very true...I'd go with a compromise, like you said, of the SREF and NAM QPF, with NAM trough placement.

If you look closely at 500mb between the 12z and 00z runs of the GFS, you'll see that the PV is actually digging more on the 00z. The improvements aloft are not very well depicted at the surface, but they are there albeit not too significant.

Ok, the GFS is wacky with this Norlun trough. It takes it from NJ to Boston? Is that even possible for a Norlun trough to do? I thought most of the time, Norluns stay put in one area with little or no shift.

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Very true...I'd go with a compromise, like you said, of the SREF and NAM QPF, with NAM trough placement.

If you look closely at 500mb between the 12z and 00z runs of the GFS, you'll see that the PV is actually digging more on the 00z. The improvements aloft are not very well depicted at the surface, but they are there albeit not too significant.

Ok, the GFS is wacky with this Norlun trough. It takes it from NJ to Boston? Is that even possible for a Norlun trough to do? I thought most of the time, Norluns stay put in one area with little or no shift.

I don't think it has the Norlun... it basically has a progressive spoke of vorticity rotating through the NYC-BOS corridor... there is no interaction with the Low offshore

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Looks to be realistic--- of course the snow hole lives on with this map and that is why it appears to be realistic

Okay I mostly troll and try to learn from this board, but I have to ask if the qpf output is maybe .5 or so for NYC and north and west how does it make sense for calls for a foot or more of snow with 10:1 ratio? Thanks.

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Np offense to DT but that map is absolutely ridiculous, and I don't need to be a meteorologist to realize that. Not one model besides the NAM is outputting numbers that even remotely support this 1st guess forecast.

If someone had posted his written thoughts to go along with that, he said that 1.) It's his 1st GUESS. 2.) the models always underforecast norlun setups.

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he shifted his band which was previously over Central LI back towards the west to include the NYC metro/Hudson Valley, Nassau and Western Suffolk. I think his original idea was for the heaviest band to be across Central LI and stretch into the hudson Valley, but leaving out NYC and Western LI (similar to the map Gregory posted at 1000pm).

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These big totals sound overdone to me; NAM always likes to exaggerate QPF in dynamic situations. I'm not saying someone won't see 6-10" but I think over a foot is going to be almost impossible to achieve with a Norlun. That being said, NYC has been lucky the past few winters, so how can we possibly know?

Probably not a Norlun exactly, but an inverted trough extending NW from a coastal low was the culprit that concentrated the bulk of the snow in the NYC area on 12/26/1947.

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Really? 6+ for NYC too?

I definitely don't envy the forecast down there. What a discrepancy between the NAM and some other guidance. I usually have to forecast 1 or 2 norlun type events per season up here and they are terrible from a forecasting perspective. Very difficult to handle...even 24h out, never mind 36-48h out.

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Hurricane said 1-3" for Philly, 2-4" for Bucks and Trenton on N&E. NYC is included in 2-4" but remember he's just a Philly forecaster.

He definitely nailed the big max up around the NYC area on the 12/26 storm. We all thought then that 20"+ was ludicrous, and that's exactly what many of us had.

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