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December 8-10, 2018 Winter Storm


Orangeburgwx
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Just now, pbrown85 said:

So I have seen people talk about the NAM at this range not being accurate, then some people saying that it does a great job with the temp profiles in these situations? Is the NAM to be believed with it showing the cold getting down to upstate SC or are people just hugging the NAM because it shows the temps we need?

I trust the NAM with thermal profiles in these situations, other details are much more iffy.

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15 minutes ago, griteater said:

12z NAM Surface Wet Bulb Temps on Friday - the white line is 32 deg

mcM5ivB.gif

Cool graphic, thanks for posting. It's retreating pretty  fast until that last frame, then appears to retrograde a bit. I would be interested to see the frames for Sat and Sun when they come out. The wetbulbs on this map are colder than the dps on the other map for Sat. That can only happen if the dps really plummet on Sat, or the wetbulbs really shoot up. Wetbulbs can't be colder than dps.

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I really doubt this storm ends up as 100% snow for anyone except the mountains, including the foothills. The ratio of sleet to snow obviously grows as you push further east but the question is how much sleet. I do feel pretty confident right now that it's either going to be sleet or snow at this juncture IMBY. If I was s&e of 85(Cary, Raleigh, Most of Wake and Johnston), I'd be really concerned about a massive ice storm. I also feel like we're going to see a colder surface reflection with the damming and heavy precip. 
What do u think for greenville/greer area

Sent from my SM-N950U using Tapatalk

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3 minutes ago, Cheers for Western Ears said:

I know that the NAM in the past has been relatively good with thermal profiles, but would you guys agree that the NAM has somewhat of a cold bias?

It's usually colder than the global models during cold air damming, and warmer than the global models with its handling of warm nosing moving in from the south - which tends to be correct.  It's higher resolution, so it should handle those situations better....but it has to get the big picture right first, and it may struggle to get that right out at its outer range of 72-84 hour.

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14 minutes ago, ryan1234 said:

It baffles me that people are already jumping off the cliff and are able to seriously call this storm a bust when we are still 4.days.out. 

Don't know if it'll bust or not but I stay at the bottom of the cliff. I like it down here. I leave a rope so I can pull myself up 24 hrs out if need be

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In my opinion NAM typically does pretty well with thermal profiles. GFS and EURO typically play catch up with CAD setups and trend cooler/colder as the event gets closer. Doesn't always work out that way but usually the NAM does better sniffing out the strength of the CAD before the others do. It has been said before and is a concern for me is the cold source to our northeast will be stale which will probably not lead to a super strong CAD in my opinion.

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7 minutes ago, griteater said:

It's usually colder than the global models during cold air damming, and warmer than the global models with its handling of warm nosing moving in from the south - which tends to be correct.  It's higher resolution, so it should handle those situations better....but it has to get the big picture right first, and it may struggle to get that right out at its outer range of 72-84 hour.

Thanks for the reply Griteater. So I guess that is why they say you should wait until within 48 hours until you really start trusting the NAM and not long range? 

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Just now, pbrown85 said:

So I have seen people talk about the NAM at this range not being accurate, then some people saying that it does a great job with the temp profiles in these situations? Is the NAM to be believed with it showing the cold getting down to upstate SC or are people just hugging the NAM because it shows the temps we need?

Surface wise I would not trust it with low pressure setup, etc.. that far out , however the Nam is able to see low level processes that relate directly to topography and ageostrophic events, I.e. CAD, damming of cold air and effective funneling processes that occur. I have seen it many times be correct in events such as these. NAM is probably the biggest tool you could use for CAD events in my opinion. Even when I lived in the northeast, the NAM would be more or less way ahead of the curve when it came to ice storm setups because of the tools it has built into it. So no it is not a farce in my opinion when it shows dewpoints the way it does right now. 

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17 minutes ago, Iceagewhereartthou said:

Yes. What the upstate and NEGA needs is for those upper teens in WNC to bleed our way. With dps in the mid to upper 20s our wetbulbs would likely be above freezing, so we'd get just cold rain or a melting slop that never accumulates.

That's still well before the event. Plenty of time for it to bleed in. Someone posted a wet bulb output earlier and the wet bulb was below freezing even Friday night.

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5 minutes ago, Cheers for Western Ears said:

Thanks for the reply Griteater. So I guess that is why they say you should wait until within 48 hours until you really start trusting the NAM and not long range? 

Sure.  We bang on the NAM a lot, but even at its outer ranges I swear it does as good as any of the other models...it handles southern stream waves well too

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