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Pattern Fabulous February

Jessy89 said:
Is it ice snow or what?


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I don’t know until tropical tidbits comes out but it may be two separate storms back to back ... regardless it shows 24-36 inches across much of central and western NC and upstate SC with heavy amount surrounding ... but most certainly I would expect some to be ice and sleet and all that sort of stuff
 
Interesting development on the 18Z GEFS: the SER is MUCH weaker 2/12-15 and the SE is actually much colder than prior runs with near normal 2/12-14 (like the EPS has) even though the SER and SE warming later reappears. For now, I recommend we concentrate on 2/12-15 and see if future GEFS runs cool further then and not worry about later periods yet, which are less predictable anyway. This is how pattern changes often work into models. They often don't wait to near the end of the runs but instead start changing much earlier. This kind of thing happened one month ago. If 2/12-15 ends up drastically colder with much less SER, the later periods could very well follow suit and not be warm, themselves. Right now this is but one GEFS run...so not at all a trend yet. But let's see what the 0Z and later ones do.
 
Jon said:
It’s snow depth change, but it includes sleet and mixed Ptype...


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So far nothing showing up on tropical tidbits. Must be way off close to end of run


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Jessy89 said:
So far nothing showing up on tropical tidbits. Must be way off close to end of run


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Yeah, it’s day 13-16. Actually shows snow depth of 24”+ in the triad so it will be interesting to see this clown map. Looks like a southern slider too, not a miller A.


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I wouldn’t get any hopes up on the 17th threat. For several days the fv3 was showing ice on feb 10th. Just to back off of it.


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GaWx said:
Thanks. So, it sounds like you’re saying the very warm SW Atlantic SSTs are only at best a secondary influence vs planetary scale waves (PSWs). So, I’ll ask you about the PSWs. I’m assuming you’re largely talking about upper level winds. If not, please correct me. But if so, what is driving what in the upper atmosphere right now to allow for the predicted strong SER, —PNA, and -EPO ridge? Where in the N Hem is the upper atmosphere causing this combo to be predicted? Is there a crucial part of the N Hem? I noticed you referring to a trough over E Asia. Are the upper winds over that region about to be a major driver now? If so, why would it be the major driver and the SE ridge or some other region not be the major driver, for example? And I do know that tropical forcings like MJO and ENSO are often critical. Are they still the main driver? Regardless, I’d still like to know why you just emphasized the E Asia trough.
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Well on the timescales we care about the most, yes low-level wind stress forcing right near the surface of the ocean where it influences the Ekman layer imparted by planetary scale waves is more important than the contribution from SSTs, but that doesn't mean the latter isn't important particularly on longer timescales when this atmospheric white noise becomes washed out and the reddened (lower frequency/longer timescale) response overturning circulations, multidecadal variability, etc is more effectively expressed. There's no particular crucial part in the N hem upper atmosphere (I presume you're referring to the upper troposphere here) that's necessarily "driving" the pattern per say but it's important to look at the location, juxtaposition, and strength of the waveguide (jet stream) and wave "sources" altering the jet (like tropical convection, Rossby Waves propagating over a mountain range, etc.,).

The real reason I continually refer to northeast Asia is because this is a wellspring for observed downstream discrepancies over North America-NE Pacific between the GEFS & EPS suites after this week and how the aforementioned wave energy is dispersed into our part of the world, also altering the strength, placement, and duration of the SE US ridge for example.

The handling of the E Asia trough around day 7-9 is a very clear source of model error that propagates downstream and forward in time.

Columnar heating distribution changes attributed to tropical convection that's tied to the MJO & ENSO is what ultimately "drives" mid-high latitude waves. This convection is virtually always present in some, way, shape, or form somewhere in/around Indo-West Pacific warmpool where the sea surface is sufficiently warm/moist to regularly destabilize the boundary layer to trigger deep convection at any given time at preferred spectrum of frequencies, which means it's actually "forcing" the pattern virtually all the time. The question actually is where the convection is located, how strong, at what spatial/temporal frequency, how will this convection interact w/ "standing wave" modes like ENSO, and if we think there may be a signal, will be able to detect it and furthermore if we don't detect anything, does that really mean the tropics aren't "driving" the pattern in some way? (the answer to this last question is obviously no).

Here, I think it's a combination of many factors that are forcing the pattern, where subseasonal tropical forcing is located at this time of the winter obviously isn't favorable in its own right and it doesn't help when you have an expansive eastern Hemisphere Hadley Cell which is being hastened by long-term trends in our background climate state & the fact we don't have a significant +ENSO event to at least temporarily quell it. The expansive Hadley Cell pushes wave fluxes from rossby waves and the waves themselves (including the subtropical highs like the SE US ridge at the edge of the Hadley-Ferrell Cell) poleward, strengthening the mid-latitude jet, making it harder to acquire frequent high-latitude blocking, etc. I'm only scratching the surface here btw these concepts run so much deeper than what I'm alluding to above.
 
Jessy89 said:
I wouldn’t get any hopes up on the 17th threat. For several days the fv3 was showing ice on feb 10th. Just to back off of it.


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I agree! That model is horrible IMO It tries showing snow behind every cold front, which pretty much never happens.......................
 
Brick Tamland said:
This is the one.
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If there was any fantasy storm to even try and call "The one", I would never pick this. It's so unrealistic and it's also so far out. I'm certain it will be gone in 4 hours too. Also, not to point at NC, but y'all have had your fun already. We haven't. I'd rather see something that benefits more of us too that isn't an ice storm either. Unfortunately, I don't think we will have enough time to pull something off this year unless a freak storm comes up.
 
Pretty much all the globals agree on a in-Situ CAD, here we go again with maybe some front end icing, been pretty active this year when it comes to ice for the foothills
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GaWx said:
Interesting development on the 18Z GEFS: the SER is MUCH weaker 2/12-15 and the SE is actually much colder than prior runs with near normal 2/12-14 (like the EPS has) even though the SER and SE warming later reappears. For now, I recommend we concentrate on 2/12-15 and see if future GEFS runs cool further then and not worry about later periods yet, which are less predictable anyway. This is how pattern changes often work into models. They often don't wait to near the end of the runs but instead start changing much earlier. This kind of thing happened one month ago. If 2/12-15 ends up drastically colder with much less SER, the later periods could very well follow suit and not be warm, themselves. Right now this is but one GEFS run...so not at all a trend yet. But let's see what the 0Z and later ones do.
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The good news is that for the most part, the 0Z GEFS held onto the favorable changes in the SER for 2/12-13 that were on the 18Z GEFS. However, it largely backtracked to the prior runs for 2/14-5. I'd still watch this period for potential improvements on GEFS runs later today. Sometimes these occur in a zigzaggy way. Significant improvements followed by some backtracking followed by even better improvements then some backtracking, etc. We'll see.
 
GaWx said:
The good news is that for the most part, the 0Z GEFS held onto the favorable changes in the SER for 2/12-13 that were on the 18Z GEFS. However, it largely backtracked to the prior runs for 2/14-5. I'd still watch this period for potential improvements on GEFS runs later today. Sometimes these occur in a zigzaggy way. Significant improvements followed by some backtracking followed by even better improvements then some backtracking, etc. We'll see.
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Do you find that change off the west coast pretty significant ? Looks as if a ridge is trying to build around British Columbia 62477939-30AD-4631-ABC3-34A7A21E2574.gif
 
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