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Mid January/Mid February Medium/Long Range Discussion


WinterWxLuvr
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It's most definitely going to be rain along I-95...the cold air is moving out.  But it's vastly different solution than the GFS for this period. 

 

ETA: Yup, goes to rain, but close.  I guess it's something to keep in mind.  But I'm like the man who the storm is named for...unless something sig changes, time to go dormant 

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3 minutes ago, stormtracker said:

It's most definitely going to be rain along I-95...the cold air is moving out.  But it's vastly different solution than the GFS for this period. 

 

ETA: Yup, goes to rain, but close.  I guess it's something to keep in mind.  But I'm like the man who the storm is named for...unless something sig changes, time to go dormant 

Of all the things that we haven't been able to get to trend our way in the medium range...I'd take my chances for a trend to a colder solution (and only needing small shifts for such). Here's hoping it's still there next Tuesday! :D

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4 minutes ago, ryanconway63 said:

Well the Euro likes the idea of a storm off the NC Coast Jan 31/Feb 1 also.....this kills me to see the lack of cold air around.....perhaps this will change.

image.png.1dc7be39081c7aaeda8273d6dbbfdc85.png

Man I hope so...otherwise that's gonna be a real knife in the heart after what we've been through with snow the last few years (especially to happen right at the end of what's supposed to be the coldest part of the year!)... C'mon...we oughta be due, lol

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9 minutes ago, PivotPoint said:

Lol at how different the cmc is to the gfs same time period. 
 

cmc

image.thumb.png.a6f9e99b5573a4ac780431f06216ad28.png

Gfs

image.thumb.png.bf26fc516ea93b3ef39753280cd18f07.png

That isn’t that different for 240 hours. The longwave pattern is actually somewhat similar. If your focusing on exact strength and location of storms at day 10....plus the fv3 gfs has a known over amplified bias so...

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7 minutes ago, MD Snow said:

GFS op on it's own for the chill storm. 12z CMC/JMA/EURO/ICON all have a more suppressed solution than the GFS' cutter solution. 

gfs is more of an apps runner than a cutter.  given the competing energy to the north i could see how that system ends up on the southern envelope.  that said, the first wave is a week away, so there's gonna be waffling.

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2 minutes ago, psuhoffman said:

All 3 major ops agree on a dual wave system on the east coast day 8-10. That’s amazing for that range. 

HM says this warm pattern can produce a lot of snow with active southern jet..just have to get lucky

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I knew someone would chime in! 
 

It is different...

And I’m not just talking about the surface. if you look at side by side comparison of 500mb heights for same time period GFS clearly builds stronger positive anomalies through Hudson’s Bay which provides much stronger blocking for our trough to turn negative.

Id agree they’re not worlds a part in terms of 60s and sunny vs. 30s and rain, but they are still very different and shows a larger spread. I know 240hrs seems like an eternity but in age of 2020 and super computers I still find it amusing that the differences can be as large as they are... even for 240hrs.
 

image.thumb.png.93ec644730bb2373a04091de85ffd22d.png

 

image.thumb.png.be23cd9d55b66b77b2a6eabb56d4df5d.png

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6 minutes ago, Ji said:

HM says this warm pattern can produce a lot of snow with active southern jet..just have to get lucky

Not this weekend. The airmass is just too putrid. Way too much ridging ahead of it. 

But the next couple “could”. I know not to ever rule anything completely out. I showed that Hudson Bay composite. The pattern is close enough. Get lower heights in front, maybe from this weekends system bombing, and it could work. It will be a struggle with the crappy air mass though. 

But we’ve snowed before in a similar pattern. We’ve also cold rained more often. Like HM said...need luck.  If we want a pattern that needs less luck we need that AK vortex to scram or the NAM to flip. 

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1 minute ago, PivotPoint said:

I knew someone would chime in! 
 

It is different...

And I’m not just talking about the surface. if you look at side by side comparison of 500mb heights for same time period GFS clearly builds stronger positive anomalies through Hudson’s Bay which provides much stronger blocking for our trough to turn negative.

Id agree they’re not worlds a part in terms of 60s and sunny vs. 30s and rain, but they are still very different and shows a larger spread. I know 240hrs seems like an eternity but in age of 2020 and super computers I still find it amusing that the differences can be as large as they are... even for 240hrs.
 

image.thumb.png.93ec644730bb2373a04091de85ffd22d.png

 

image.thumb.png.be23cd9d55b66b77b2a6eabb56d4df5d.png

The main difference is the depth of the system in the southeast. But all the guidance agrees on the main players. AK vortex. +AO. +NAO. Southwest ridge connected to a ridge across Eastern Canada. Trough in the southeast. That’s amazing agreement for that range. You’re stuck on specifics that should not be looked at day 8-10. Plus if you correct for the known bias of the gfs they look remarkably similar. 

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2 minutes ago, psuhoffman said:

The main difference is the depth of the system in the southeast. But all the guidance agrees on the main players. AK vortex. +AO. +NAO. Southwest ridge connected to a ridge across Eastern Canada. Trough in the southeast. That’s amazing agreement for that range. You’re stuck on specifics that should not be looked at day 8-10. Plus if you correct for the known bias of the gfs they look remarkably similar. 

You make good points but you’re using bias confirmation (known gfs bias) to explain the more amped solution of the gfs vs cmc. In reality, it could be an over amplification or it could be picking up the time period dynamics more accurately. Time will tell.

But I disagree that there is amazing agreement in the sense that, yes, the anomalies are similar in their relative positions but the strengths are fairly different (euro and cmc) vs gfs. 
 

You’ll probably end up being correct that the gfs has over amplified the shortwave, but we do  not know that,  and I would not automatically attribute it to a “known bias”. I think that is a bit premature to say, imo.

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4 minutes ago, PivotPoint said:

You make good points but you’re using bias confirmation (known gfs bias) to explain the more amped solution of the gfs vs cmc. In reality, it could be an over amplification or it could be picking up the time period dynamics more accurately. Time will tell.

But I disagree that there is amazing agreement in the sense that, yes, the anomalies are similar in their relative positions but the strengths are fairly different (euro and cmc) vs gfs. 
 

You’ll probably end up being correct that the gfs has over amplified the shortwave, but we do  not know that,  and I would not automatically attribute it to a “known bias”. I think that is a bit premature to say, imo.

I get where you’re coming from. But part of using the guidance effectively is correcting for biases. The guidance won’t be perfect from range.  It’s also incorporating climo and historical reference with the NWP guidance. The most logical correction right now is to assume the gfs is over amplified. But you are correct that could be a mistake. And that’s why forecasting long leads is low accuracy.  

But at day 8 we really shouldn’t expect that level of accuracy. Right now we can say with some confidence based on guidance that there is likely to be a system in the east day 8-10 with about seasonal temperatures that is likely a rain or maybe snow threat. That’s good enough. A day 8 forecast shouldn’t be more detailed. Exactly how strong isn’t necessary. 

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