Carvers Gap

Haha. Same. I just don't even bother to strike it out anymore. I just assume folks see the error in my ways and politely move along!!!

This thought crossed my mind as I looked at the CMC this morning at 0z. That looks like an anafront hybrid(w/ over-running). This run wasn't necessarily more amped....it was surprisingly flatter.

Upwards of 3" of ZR in E TN on that CMC run per pivotalwx.

12z GEM definitely not suppressed. Big winter storm on that map at 126 on Pivotal - usually earlier than wxbell and I often forget that!

Don't want' to be bullseye w/ an over-running system at this range. Need some modeling south of us in my experience.

Of note the 12z ICON is a bit north of its 6z run but no significant change in its hp(mid 1040s). The 12z GEM and GFS are not budging w/ that hp.

Just watching the GEM roll. At 72 hours, its Yukon high is smidge stronger at 1050 when compared to 0z. I noticed the same minor change in increasing expansiveness of that hp early in the ongoing GFS run. At 81, the hp is at 1053. I have to think another suppressed solution is incoming. I don't know for sure, but I would guess that.

Chattanooga w/ 7" of snow on that run.

Man, that is a LONG fetch of frozen precip on the 12z GFS. At 129, snow stretches from southwest New Mexico to Wilmington, NC. Ice sits directly south of that line. Textbook over-running setup.

And where the GFS tries to send a slug of moisture up west of the Apps at the last minute....I don't play that game! That feature almost always trends east. But again, probably a good thing that this system doesn't boomerang trend into the mid-state.

At 120, the 12z GFS is south of its 6z run. Honestly, that is probably about where we want that model at this range. As a good friend noted, those over-running events tend to trend north. I agree.

We need the 12z GFS to get a lil' bit of AIFS in its veins.

Very suppressed solution incoming by the 12z GFS at 111...stepped away from the 6z AIFS. No idea if right, but that would be a massive shift to get that solution to cut. Heck, I just want it to come back north on that run. Haha.

Well, the 12z GFS just doubled down on that big high. That might end up in Cuba.

At 93, the GFS does not want to budge w/ weaning that big hp. 1051 sitting in North Dakota. Might come north a hair, but that maybe will yield yet another suppressed solution?

Precip and temp maps above are good though, right?

Maybe one of the worst head fakes(here) was snowmageddon. All those pretty 30" clown maps moved to DC. Well, the worst headfake was CLT area forecast to get 3-4' right up to and during the storm....not even sure the grass got covered. So yes, I want the synoptics right before jumping on board fully. I don't like that the Baja low has a different iteration w/ each run. I don't know which camp is gonna be right about the high which will likely roll into the northern Plains. Is it 1040-1042 or is it 1050+? Definitely important things still to sort out...

I just don't know at this point.

I mean when looking at the AI scenarios above...either looks plausible, right? We have seen both scenarios play out. I think we need to really watch trends w/ hp to our north and how the Baja slp evolution plays out. I do think we could see a truncation as the energy involved gets better sampled in the northern stream. No matter how good programming is...data input quality is just as important at the programming in the model.

The fun question is weather the AIFS will outperform its own ensemble at this range. The ensemble is quite different for our forum area. One thing that many models have missed over time is that when we have a hp funneling cold down west of the Apps, many models will often miss that the actual surface is below freezing. Depending on the sequence that this arrives, the scenario exists that cold air could get trapped in the eastern valley. That is why the model difference below is important. The AIFS has changed quite a bit since 18z w/ a more amped cutter while the AIFS EPS has remained fairly steady. The ensemble mean (rightly or wrongly) smooths out that amped look. If the mean is correct, then the heat transport northward(moisture) will be less and cold air at the surface could be trapped. If the AIFS is correct....liquid drops for almost everyone but NW TN.

So, I have been digging through lots of verification for the AIFS. The one thing I notice over and over is that the EPS scores equal or better than the AIFS at days 4-5. At days 4-5 all deterministic models and AI models are fallible...sometimes very fallible in regards to dew point, windspeed, and temp-C. I Most papers that I have read this morning strongly recommend using a blend of models - EPS, Euro IFS, and AIFS. I have provided a link to one paper below. If you favor ensembles, NWP, or AI...there is probably something in that article for you. This will be a good test, but by no means is it the final test. Modeling is only as good as its programming and quality/quantity of data input. All modeling is much better inside of d4. If I was going to rank models...it would still be pretty much the following at d5....EPS, Euro AIFS EPS, Euro or AIFS. I would feel much better about the AIFS if it wasn't in the same camp as the UKMET which has low verification scores at this range and also with the AIGFS. But again, this will be an interesting comparison for sure! Right now, the AIFS is on the north side of guidance w/ the GFS suspiciously on the south side. My guess would be the solution is somewhere in between. However, I am reminded that most folks were skeptical that a chess bot(not AI) could defeat a grand master. The chess bot is now better. But in this case...pretty much all numerical modeling is a chess bot. We are just trying to see which chess bot is better. Here is the article I found out of Australia in regards to comparing AIFS vs IFS from AMETSOC. https://journals.ametsoc.org/view/journals/aies/4/4/AIES-D-25-0037.1.pdf Interesting quote... However, as with NWP models, the autoregressive nature of AIFS means that small errors are amplified over the forecast period, which causes AIFS (and HRES) to fall behind ENS in accuracy as the lead time increases. It is well established that blending models generally im- proves the accuracy relative to the best individual forecast [see e.g., Vannitsem et al. (2021)], and therefore, it is a common approach in operational weather forecasts.

Found these 0z comparisons at Dacula Wx...stilll working to find the AI verification in comparison. They have data fo the last calendar year. Notice the UKMET verification at 5 days? It is almost as bad as the GFS. The EPS and Euro models score highest at d4-5. The WPC medium range desk(conveniently? lol) scores the highest. The closer to the 1 models get...the better they are.

The 6z AIFS Euro EPS is almost identical to the 6z Euro…looks like they may have fixed the algorithm for the ensemble at wxbell. General agreement right now between deterministic models and their ensembles and the AIFS ensemble. Either way, four days to go(five for some), this could change. Right now the 6z AIFS is an increasingly bonified cutter. The AIFS has change quite a bit overnight. The AI models handle hp over the top completely differently. Honestly, I don’t trust the AI models as they have each burned me this winter pretty badly…I will have to dig back through the Dec or Jan thread and find it. The AIFS Euro has been very warm d5-15 and badly so…but sometimes it swings very cold. I have found the Euro deterministic to be more dependable in my own experience as we have gotten deeper into winter. The AI models look over amped….but deterministic models seem to be inconsistently handling the Baja low. The AIFS models may or may not be mishandling hp over the GL area…deterministic models have been sometimes too aggressive with cold this winter. When looking at the model verification graph posted by Tellico last night….the AIFS was kind of mid. The best model was the AIFS Euro ensemble, then the EPS, and then the Euro. Now, admittedly maybe that was just for that moment in time. As for the AiGFS…it has been completely awful at all ranges. I give it no credence. The UKMET/AIFS is a formidable pair and cannot be discounted. As for now, neither is budging. I had fully expected the deterministic models and their ensembles to cave to the AI. They have not. In fact, they may have trended a hair south from 0z or only nudged a hair north.

AI models have almost a completely different alignment and evolution of hp over the top of this storm. Are they right? IDK. But deterministic modeling is almost uniformly placing more cold hp above or just to the NW of the system whereas the AI models quickly dissipate the hp over and behind the system. Are they right? IDK that either! The 12z Euro jogged south of its 18z run, and is a tick north of its 12z run. Pretty decent agreement w/ the three deterministic models. It is not surprising to see models jog north a bit. However, there remains a risk of suppression w/ this and even at the last minute if those big highs verify to the north and northwest of the storm and can persist longer than AI models depict. Important aspects still to be ironed out, but we are getting closer to a solution - maybe. As of now, we are potentially tracking a strong winter storm which could impact portions of the forum area. Nothing written in stone at this time, but we will see where this goes.

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