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December 26-27 Storm Threat

Baroclinic Zone

By Baroclinic Zone,
in New England

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weatherwiz

weatherwiz

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I lost my fooking post, but I was saying I would never throw anything out, but given the euro and ensembles...and also what happened at NCEP, these solutions give me pause, that's all. There will be explosive cyclogenesis, and gulf lows scare me, but man...something like the NAM?? I just don't know about that. I guess we'll see what 00z does. If that moves towards the 12z gfs and 18z nam, then we may have something. The gfs going to the BM is one thing, but the 12z gfs going south of BID and 18z NAM over Nauset Beach is something else. It just comes down to probability. You incorporate all the solutions and figure out the best approach. I'd lean to the euro end ensembles right now, but that doesn't mean it can't go west a little.

Yeah nothing can certainly be discounted at all given the spread we are seeing and some of the issues were dealing with, if the 0z models, and the Euro are anything like what we have just seen than that definitely would be an eye opener.

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CT Rain

CT Rain

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Posted

I lost my fooking post, but I was saying I would never throw anything out, but given the euro and ensembles...and also what happened at NCEP, these solutions give me pause, that's all. There will be explosive cyclogenesis, and gulf lows scare me, but man...something like the NAM?? I just don't know about that. I guess we'll see what 00z does. If that moves towards the 12z gfs and 18z nam, then we may have something. The gfs going to the BM is one thing, but the 12z gfs going south of BID and 18z NAM over Nauset Beach is something else. It just comes down to probability. You incorporate all the solutions and figure out the best approach. I'd lean to the euro end ensembles right now, but that doesn't mean it can't go west a little.

Nice post. My 5pm forecast is going to be "the most likely scenario is a low-impact event here in CT" but it's possible a more serious snowstorm impacts us. Just too early to say with any more confidence than that.

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Clinch Leatherwood

Clinch Leatherwood

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Seems to be back? lol

Was posting on the cell, seems like a server reboot.

Anyway back now, just talked for ten minutes with shall be a nameless weather pro that fully explained the situation to me re the diagnostic.

Long story short it does not appear to be bad data in the sense that a RAOB or whatever was bad. Instead either something slipped between stations and was poorly resolved or there's the issue of persistence - ie it was an error 18-24 hours ago that didn't get caught etc. That part I don't fully understand.

Regarding the 18z, it uses the 12z data but with some new input. So if the 12z was really bad as contended, it would be using some faulty data. What's interesting is it got more extreme with what should have been at least some muting of the errors. When I look at the water vapor and RUC for 18z init, I don't see an egregious errors on the 18z NAM or 12z GFS. Sure the first s/w coming south into the MS Valley (north of the GOM s/w) is coming in at a different trajectory but these are errors we see ALL the time at 6-12hrs. It's not earth shattering. Same goes up to the north in the Dakotas. To be totally honest - and all of you that were around in the ne.weather and #neweather days know there were some doozies back then were my grandmother could have spotted initialization errors if given the maps and a water vapor - it's just not that bad this time. Maybe it is really a matter of a few miles in this pattern that what is a normal error even at 6h is so critical that it effects the storm later, but boy.....can't say I see it. Doesn't mean the western outliers are right by any means, but it's just odd to me. This is one of the most strongly worded NCEP statements I've ever read on model error...and I just wish I could see it more easily in any of the obs. Usually there is a mention of specific stations, directions, knots whatever.....

Wary eye to the 0z, nothing is off the table and I would say a track near the BM is still a good bet.

How were the EC Ens? To be blunt they weren't so hot with that last system at 48-60 I don't think either....

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ORH_wxman

ORH_wxman

Posted
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I lost my fooking post, but I was saying I would never throw anything out, but given the euro and ensembles...and also what happened at NCEP, these solutions give me pause, that's all. There will be explosive cyclogenesis, and gulf lows scare me, but man...something like the NAM?? I just don't know about that. I guess we'll see what 00z does. If that moves towards the 12z gfs and 18z nam, then we may have something. The gfs going to the BM is one thing, but the 12z gfs going south of BID and 18z NAM over Nauset Beach is something else. It just comes down to probability. You incorporate all the solutions and figure out the best approach. I'd lean to the euro end ensembles right now, but that doesn't mean it can't go west a little.

Yeah I don't think these NCEP models do a ton for me except say that some western scenarios are still in the game...but I certainly wouldn't take what the GFS and NAM are showing at face value. All it might mean is the Euro (and the other guidance) went a shade too far east....but I still think the logical solution is something near or just east of the BM. That's where most ensembles are clustered...including the now further west GGEM ensembles (forget the OP run)

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CT Rain

CT Rain

Posted
Posted

Was posting on the cell, seems like a server reboot.

Anyway back now, just talked for ten minutes with shall be a nameless weather pro that fully explained the situation to me re the diagnostic.

Long story short it does not appear to be bad data in the sense that a RAOB or whatever was bad. Instead either something slipped between stations and was poorly resolved or there's the issue of persistence - ie it was an error 18-24 hours ago that didn't get caught etc. That part I don't fully understand.

Regarding the 18z, it uses the 12z data but with some new input. So if the 12z was really bad as contended, it would be using some faulty data. What's interesting is it got more extreme with what should have been at least some muting of the errors. When I look at the water vapor and RUC for 18z init, I don't see an egregious errors on the 18z NAM or 12z GFS. Sure the first s/w coming south into the MS Valley (north of the GOM s/w) is coming in at a different trajectory but these are errors we see ALL the time at 6-12hrs. It's not earth shattering. Same goes up to the north in the Dakotas. To be totally honest - and all of you that were around in the ne.weather and #neweather days know there were some doozies back then were my grandmother could have spotted initialization errors if given the maps and a water vapor - it's just not that bad this time. Maybe it is really a matter of a few miles in this pattern that what is a normal error even at 6h is so critical that it effects the storm later, but boy.....can't say I see it. Doesn't mean the western outliers are right by any means, but it's just odd to me. This is one of the most strongly worded NCEP statements I've ever read on model error...and I just wish I could see it more easily in any of the obs. Usually there is a mention of specific stations, directions, knots whatever.....

Wary eye to the 0z, nothing is off the table and I would say a track near the BM is still a good bet.

How were the EC Ens? To be blunt they weren't so hot with that last system at 48-60 I don't think either....

Yes, you are correct with all of this. It was not a data error the error was that the initialization (through data assimilation) looked wrong to the guys at NCEP. They thought the error was large enough that it drastically impacted the op runs and will likely influence at least the next run (18z GFS and 18z NAM).

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ORH_wxman

ORH_wxman

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And btw... thankfully Kevin is unable to post this afternoon. He would have added nothing to the discussion and just gotten on everyone's nerves. He'll be a great addition once the 00z models sort things out a bit more :)

We might not see him until the storm is nearly about to start, lol. 00z tonight will be past his bedtime and tomorrow is Christmas so he might be out all day. :snowman:

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Clinch Leatherwood

Clinch Leatherwood

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Posted

Yes, you are correct with all of this. It was not a data error the error was that the initialization (through data assimilation) looked wrong to the guys at NCEP. They thought the error was large enough that it drastically impacted the op runs and will likely influence at least the next run (18z GFS and 18z NAM).

Okay, good so I understood correctly.

Here's the question? After 20 years of playing around doing this I've looked at a lot of water vapor loops, 0h maps and in the last xx years the RUC.

I don't see a glaring error on the 18z inits of both the NAM and GFS vs the RUC or water vapor. the 18z ruc init is almost dead nuts on the GFS. I just don't see this big error, I see almost no error compared to normal day to day runs.

Is it more that the american models are having problems with the physics of the situation as much as it is the assimilation? I will tell you I don't often see this many changes at h6 which gives pause....only happens when a major model bust is about to happen. But again, it's not like it's trending the wrong way on the w/v Ruc, it keeps looking more extreme.

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HIPPYVALLEY

HIPPYVALLEY

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And btw... thankfully Kevin is unable to post this afternoon. He would have added nothing to the discussion and just gotten on everyone's nerves. He'll be a great addition once the 00z models sort things out a bit more :)

That's it! I couldn't quite place my finger on the strange sense of peacefulness permeating this thread.

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CT Rain

CT Rain

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Posted

Okay, good so I understood correctly.

Here's the question? After 20 years of playing around doing this I've looked at a lot of water vapor loops, 0h maps and in the last xx years the RUC.

I don't see a glaring error on the 18z inits of both the NAM and GFS vs the RUC or water vapor. the 18z ruc init is almost dead nuts on the GFS.

Is it more that the american models are having problems with the physics of the situation as much as it is the assimilation? I will tell you I don't often see this many changes at h6 which gives pause....only happens when a major model bust is about to happen. But again, it's not like it's trending the wrong way on the w/v Ruc, it keeps looking more extreme.

The Euro has superior data assimilation. The guys at NCEP will tell you that as well. If you compare the 12z GFS and Euro 500mb initializations the GFS was substantially stronger with the 3 main shortwaves. The location of the 3 was identical but the vorticity was quite a bit more impressive on the Euro.

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weathafella

weathafella

Posted
Posted

Nice post. My 5pm forecast is going to be "the most likely scenario is a low-impact event here in CT" but it's possible a more serious snowstorm impacts us. Just too early to say with any more confidence than that.

If I were forecasting, I'd simply put a WTF? on the map and tell viewers to check later tonight...lol..

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