Carvers Gap

ICON, GFS, CMC vs AIGFS, UKMET...so far

Choose your own adventure at 0z. Welcome to the show!

At this point, I think we take a bit of a suppressed system at this point. Once those systems jog north of us on modeling, they are tough to get back south. I suspect those big highs will either verify too big OR they will produce a storm along the front, and significant at that. I definitely didn't expect a southward jog at 0z. Let's see where other modeling goes. Pretty huge run by the GEM.....

at 132...full blown winter storm on the GEM and similar to the GEFS. I think suppression w/ that big high is the concern so far. I can't decide what to be worried about...haha.

At 114, the GEM has a 1055 high over the top of the system.

Oh, wait......

0z GFS.....is trying hard.

I want my power, Jeff. LOL. I can't watch Tenn lose heartbreaking basketball games without it!

Slider w/ no warm nose. Need that storm a little to our south - I think.

0z Icon is on board!

No idea, but fun question about if/how their is a connection. Just spitballing, I would probably say the tendency for amplification is partially QBO related. When you dig back through years with strong amplifications during winters, the QBO is often negative during the heart of winter. As one poster noted in this thread, some big snows in Juneau and Russia.

Of note, the 18z EPS and EPS AIFS are super similar. The AI is a tick north, but not by much. I can't say I like the trend for E TN at 18z, but we have a ways to go before that gets nailed down. A big trend north or warm nose tomorrow, and I will politely hand this off to the middle and west guys(same for most recent Nina winters!).....again, probably need 3-4 more runs to really get a good handle on where that nose sets up shop. All great storms have the warm nose....need that high to build in. HOWEVER, I do worry a little about suppression w/ the 18z GEFS and EPS losing moisture transport northward....so let's worry about it all. Haha.

For sure, hopefully we will have a clearer picture by tomorrow evening. We battle the warm nose w/ nearly every big system over here. Will reset and head to 0z.

So w/ the AIFS EPS out of commission on WxBell...here are the 18z(left) and 12z(right) comparison of the EPS and GEFS runs. I prefer the EPS right now as it has been steady. Let's hope their algorithms are right! The 18z GEFS trended south. The EPS might by 20 miles north and a bit drier as well on the northern fringes.

Haha. Definitely a bias or algorithm issue there!

Eyes -> 18z GEFS and 18z AIFS EPS snow means for the entire run.

Better than tracking SLPs in the Lakes!!!

I am gonna ride w/ ensembles for about 24-36 more hours, and watch deterministic runs for trends. I don't use the AIGFS stuff. I barely use the GFS. Overall trends: 18z Euro(only to 144): trend north w/ ice over much of the forum, but...sure looks like the second wave would be snow. 18z EPS(only to 144): Looks super steady...maybe a tick north. Looks ready to deliver the goods. Looks remarkably similar to the AIFS Euro. I trended a hair colder. 18z AIFS: Slight trend north, and northernmost of all guidance. Looks a little overly aggressive w/ the warm nose, but that has precedent for sure. 18z AIFS EPS: Slight trend north but the accumulation map has barely changed at all. Temps barely budged. Steady. 18z GFS: Slight trend north, and southernmost of all guidance 18z GEFS: Accumulations are much higher than previous runs Things to watch....we need a true banana high over the top without a hp slipping eastward too quickly. I highly doubt models have this nailed at this range. IF(huge IF) the GFS is half right, then the followup waves will almost certainly be frozen for E TN. It does look like a multi day event. E TN for sure will have to watch the precip axis. I can just about guaranteed modeling will continue w/ its ebb and flow. NW TN looks favorable w/ this setup as it normally does. Middle looks good. E TN north of I40 probably is ice to snow. Crapshoot south of that...and maybe a crapshoot in NE TN. FWIW, one of those 93-94 or 95-96 events(maybe both!!!) started out as freezing rain during an over-running event and switched to snow. I think we see that setup. TBD on rain/snow/ice lines. I may try to do the late night suite tonight, but my tradition is to look at those in the AM along w/ 6z and then post at 12z.

I like the 18z Euro(non AI) and 18z Euro AIFS EPS. The look almost identical. Ice to snow over NE TN. May even start as some light run. The AIFS EPS pushes the cold front in quickly as soon as precip starts. That cold air just crashes into the system.

The AIFS has never really been snow for the eastern valley, but its ensemble has. I haven't looked at the 18z ensemble yet. The actual operational Euro look about right IMHO.

The BIG difference is how the AI models are handling hp. They are quicker to move it east which allows precip to nose northward. The deterministic runs hold much more hp behind the system. I will have to look at trends to see if one set is moving to another.

The 18z Euro(non AI) makes a lot of sense.

And that AIFS ensemble was honking for a winter storm at 12z. Let's see what 18z does. Looks to me like AIFS Euro, then EPS, then Euro??? The AIFS (at that time) deterministic looks a bit down there, but I can't really tell. I agree w/ the top 3 if so. Though the AIFS EPS is a bit to snowy as a bias.

I am gonna have to see some support from the AI ensembles before I buy the AI deterministic runs. The 18z AIGEFS is further south than its 12z AIGEFS run and south of the 18z deterministic run. The AIFS EPS was much colder than its 12z deterministic run. If the 18z AIFS EPS comes in south w more hp...I think the deterministic still has some room to move.

Both AI models have HP much further east than ensembles(including their own) and deterministic runs have had. Looks like an error to me, but I could be wrong. Not sure I want to argue w/ a robot. Usually turns out poorly in chess.