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December Medium/Long Range Discussion


WxUSAF

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Just now, stormtracker said:

When do we start extrapolating the NAM?

i started friday, didn't you? 

Just now, EastCoast NPZ said:

that's irrelevant to its trend. And it's likely to get more accurate every 6 hours.

what trend? you just said the thing shifted south. if there was a trend, it wouldn't have shifted at all. 

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2 minutes ago, psuhoffman said:

If you look at the FV3 over the last 48 hours its pretty much locked in with each run only jumping around a little bit well within a normal error at this range.  If you take the average of all those runs its obviously focusing its attention on southern into central VA.  A few runs get DC into the mix and a few miss south... but the bottom line is the FV3 is "right there" with a close miss to the south.  Its not suppressing the thing to oblivion.  The kind of adjustments it would take from day 6 to turn a southern VA hit into a DC hit are a fairly minor synoptically for that range.  

Maybe, but it's alarming that it took a step towards its brother's solution.

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45 minutes ago, WinterWxLuvr said:

It does seem logical to ask the question as to whether the Canadian could possibly be correct when you frame it with the "this is a northern stream issue, northern stream vorts originate in the main domain of the canadian model, so shouldn't it be able to resolve those better" thinking.

Is there any evidence to suggest that that model handles the northern stream better?

And how are 500 verification scores created for global models?  Can a model handle certain regions better, some worse and that affect its scores?  Or no?

I haven't seen any evidence that the Canadian does better with northern stream systems, but I've never really looked.  There's lots of evidence that it's not so good with tropical systems though.  :)

There do seem to be some regions that models handle better than others; for example, all of the globals seem to do better in the northern hemisphere than southern -- I suspect it's because we have better assimilation data in the northern hemisphere.  I usually look at the North American verification scores, as that appears to be the smallest region for which scores are widely available.  LWX has recently developed an in-house tool that allows them to quickly compare recent verification scores in our area.  They gave a presentation on it at AMS this year.

https://ams.confex.com/ams/29WAF25NWP/videogateway.cgi/id/47907?recordingid=47907&uniqueid=Paper345889&entry_password=580936

Unfortunately I don't think they plan on releasing it to the public.

 

 

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1 minute ago, Bob Chill said:

Ukie looks decent @ h5. Would prob allow enough northward trajectory to get our area into the precip shield. Good run imo. 

Just going off that precip SLP and h5 at 140 it looks like a central VA storm... but again that is kind of where I want it right now anyways.  Botton line is nothing else looks like the GFS.  There is a big difference between a close miss and a "not even close" look at this range.  

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1 minute ago, psuhoffman said:

Just going off that precip SLP and h5 at 140 it looks like a central VA storm... but again that is kind of where I want it right now anyways.  Botton line is nothing else looks like the GFS.  There is a big difference between a close miss and a "not even close" look at this range.  

but the southern trend! 

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4 minutes ago, EastCoast NPZ said:

Maybe I got 0z and 6z switched.  But the last FV3 run I saw was well north of 12z.

Pull up the FV3 at 140 and then go back over like the last 8 runs...they are just bouncing around a center point that indicates a southern/central VA hit.  Some are a little north, some a little south, but they are obviously all in the same general idea and basically saying the same thing for that range.  

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1 minute ago, psuhoffman said:

Pull up the FV3 at 140 and then go back over like the last 8 runs...they are just bouncing around a center point that indicates a southern/central VA hit.  Some are a little north, some a little south, but they are obviously all in the same general idea and basically saying the same thing for that range.  

Yeah, looking at that right now.  Seems  more consistent than other modeling and definitely very different than its brother.  Better than being on the south-side of the storm, but I find no comfort in a central / southern VA storm as currently modeled. That's been a recurring theme for the last 2 winters, and we've rolled snake-eyes at every turn.

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8 minutes ago, EastCoast NPZ said:

Yeah, looking at that right now.  Seems  more consistent than other modeling and definitely very different than its brother.  Better than being on the south-side of the storm, but I find no comfort in a central / southern VA storm as currently modeled. That's been a recurring theme for the last 2 winters, and we've rolled snake-eyes at every turn.

We will see but those storms were much weaker STJ systems first of all and second I remember around day 5-7 the consensus had shifted way south with most of them...south of where we are now with the majority of the guidance...assuming the Euro doesnt crap the bed soon.  We recovered in some of those cases from a weak wave off the southeast to a big snow for just southeast of our area...  if we are looking at a richmond hit at day 5 the same kind of correction would work for us.  

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