psuhoffman

This from MAG5035 in the central PA forum "Hmm, well at least on the WeatherBell products it appears the op data for the GFS and Euro is 0.25º and 0.1º respectively while their ensembles are both at 0.5º resolution. Without getting into a whole thing on GIS/mapping/degrees to meters conversion, the short answer would be yea the ensembles are run at a lower resolution (higher degree number). The high res Euro at 0.1º would be a bigger resolution difference vs it's ensemble. So I guess it could be implied that the lower resolution could flatten mesoscale features and thermal boundaries a bit and that difference could show with coastal low development, especially with how warm the water is off the eastern seaboard. Also, ensembles aren't going to see CAD as well as an op or especially a meso model for that same general reasoning. The higher resolution of the ops might be promoting a more explosive coastal response (and also closer to the coastline) just simply on the premise of modeling a sharper clash of warm vs cold. Given the +SST anomalies present on the eastern seaboard and a fairly respectable cold air air mass being supplied by the Canadian high, it may be wise to lean that direction with trying to blend guidance. Ultimately, I'm not sure how much the resolution difference actually plays in the grand scheme of things, as an ensemble is made of individual members that have their own specific conditionals to form a mean within a range of possible outcomes, which pretty much can have a similar effect as lower resolution flattening features out. Thing with ensembles is we're typically looking at them to get a handle on overall larger scale things with these events (QPF fields, pressure/height fields, accumulation probabilities, etc).. especially at this middle range where we don't have our short range or meso models in range quite yet. "

Thank you

We finally found some use for that thing The 2010 cutoff was crazy. Razor thin...cutoff even went south of due east as it hit the wall. Crazy blocking. This cutoff is more typical of big storms...1996, 2016...where there is a sharp northern cutoff somewhere as you hit the confluence but its not like going from over a foot to nothing in 30 miles like some places in 2010. yea...because for us to get crushed we need that confluence to our north...not just to stop the storm from cutting but to create the crazy lift and fgen you get from the WAA be resisting. If there is no resistance the warm air just pushes north and you don't get the same VV's. The more the cold resists the more lift. But that means there is likely a wall of confluence somewhere to your north and the northern edge will hit a brick wall somewhere. Add in the subsidence you will get outside that NW most banding and you can get a pretty sharp cutoff. It is definitely more Miller A then it was represented a few days ago. And I would agree with your assessment. But there are some that classify any system with a primary that initially gets up west of the apps as a hybrid. Some even argued that 96 was hybrid because there was a trough up west of the apps early in its development. I think that is going a bit far but...I am not one to argue over definitions much. Yea the guidance has been on a long range roll lately. It pegged this from super long range as a "window of opportunity" and there was about 36 hours where it became a bit murky there but for the most part this was a time to watch from weeks ago. Guidance is hinting at another period after xmas that bears watching now...lets see if they remain on a heater.

It's actually 2mb deeper this run at the critical moment for us...from 90-96 hours...it just lost that wonky due north jog that screwed us 18z. More in line with the ensembles. The SW associated with the primary was slightly less amplified originally and that helped. Don't want that to go negative too soon.

Before things get crazy with the 0z runs... the long range GEFS from last night really reloads a great looking -AO/NAO pattern in January. It's workable to favorable straight through actually.

Sorry I posted this in the wrong thread a min ago @dtk @WxUSAF @high risk do you know what resolution the GEFS and EPS members are run at compared to the operational? I have noticed that the ensemble members (of both the EPS and GEFS) have been running warmer even with similar or further east tracks then the operational runs. This has been a consistent correlation for several runs across both ensemble suits. The track of the operationals has changed but the presentation of the thermal structure of the storm has remained fairly consistent...meaning where you expect the thermal boundaries to be wrt to mslp is roughly the same places each run dependent on the MSLP. But those same thermal boundaries seem to be further NW given the same MSLP track on the individual ensemble members of both the EPS and GEFS. I am wondering if they are run at a lower resolution...they may be warmer due to not modeling the meso scale features as well. That may not be correct...just grasping at possible causality for the observation I noted. I know back in the day the NAM would pick up on CAD better due to its higher resolution...one of the few things it was good for at range with a winter synoptic event. You had to adjust for its over amplified bias...but you could get an idea what the thermal structure of the storm might look like.

@MAG5035 do you know what resolution the GEFS and EPS members are run at compared to the operational? I have noticed that the ensemble members (of both the EPS and GEFS) are often warmer even with similar or further east tracks then the operational runs. This has been a consistent correlation for several runs across both ensemble suits. The track of the operationals has changed but the presentation of the thermal structure of the storm has remained fairly consistent...meaning where you expect the thermal boundaries to be wrt to mslp. But that seems to be different on the ensembles. I am wondering if they are run at a lower resolution...they may be warmer due to not modeling the meso scale features as well. That may not be correct...just grasping at possible causality for the observation I noted. ETA: I know back in the day the NAM would pick up on CAD better due to its higher resolution...one of the few things it was good for at range with a winter synoptic event. You had to adjust for its over amplified bias...but you could get an idea what the thermal structure of the storm would look like.

Before the 0z starts..fwiw I think the 18z rgem looked great at 84 hours. High stronger and further SW then most other guidance. Faster wave. It looked like it was about to get good.

March 18 clipped his area pretty good

best run yet wrt mslp track 18z v 12z

Was comparing these wrt the colder profile on top of the primary in KY. Thermals did retreat SLIGHTLY in VA too.

I wasn’t picking on you. That was totally ok. Not your fault. That map did say what you said. Those multi plot precip type charts aren’t as precise with estimating pressure locations as the mslp plots.

Lol. Not your fault but that map has the high from the 12z run in the wrong spot. I think because the map cuts off just below the true center of the high. Here.. like I said maybe a few miles apart...

@WxUSAF one other minor different wrt 18z euro. The thermal boundary shifted north ever so slightly in southern VA by like 10-15 miles but the cold is still draining increasing the gradient so the entire profile didn’t retreat just along the edge. However, it’s colder west of the apps in KY on top of the primary. I don’t the primary would make it as far north on the 18z v 12z. That is provably a trade off I would take for the ever so slight changes in the temps and pressure among the coast. Thoughts?

By like 3 miles maybe

Other than the slightly weaker system the rest of the representation is remarkably similar for 84 hours. The pressure field up top is nearly perfectly identical. Wrt slightly weaker...if we lose a tiny bit of the mega banding qpf but get this to tuck just a little less that’s probably a winning trade off for most of us. We have dynamics to spare here, room to breath with the track not so much.

You’re right. I was comparing it to 12z op. The 18z is slightly slower so it’s not a perfect comp but they seem to be identical in track through 96h but then 18z jumps due north into the CAD wedge. It is definitely in response to SW going neg. But while the 18z SW is slightly more amplified then 12z I feel like that looks overdone wrt the surface tuck there v 12z. If course maybe 12z was underdone! Lol. Either way the op would be the second most inside track of all the ensembles so it’s an outlier. For the comments WRT the gefs being warmer. They are lower resulting I believe. So they might tend to be warmer by missing some of the dynamic cooling. But what I am more sure of is when you have a few inside runners in the mean they will skew the temps warm a little. I would worry more about the slp clusters and getting a good track more than the mean temps on those plots.

The jump due north between 96-102 is odd imo.

Well that gfs run looked like one of the inside eps members. Low gets to the mouth of the Potomac. That’s way inside where we want.

Honestly I don’t look at a lot of that crap other then for entertainment sometimes. At some point more info, if it’s likely not better info, is just distracting noise.

The NAM wouldn’t have ended well. But it’s NAM at 84. That’s like the Gfs at 240. If it wasn’t over amped at that range I’d be shocked.

Icon is slowly trending more towards the other globals every run imo. It wasn’t long ago (last night I think) the icon was a primary with almost no secondary and a rainstorm to upstage NY and central New England after a brief period of WAA snow.

@WxUSAF just quick visual evidence of what I said. The edges tightened some due to some outliers falling off. But look at the 50% prob of 6” line runs. Almost identical at 12z to 0z. The probabilities of the 2 camps hasn’t changed much. 0z 12z

There was a bit of a freak out in the mid atl forum over the EPS looking a bit “inside” at 108 hrs. This really only matters to the SE zones in here but for them I’ll post what I said in the mid atl thread. Since the Eps is based on the op and typically supports it it makes sense it would have the same bias but I can’t say for sure. But Imo the reaction to the 12z Eps is overblown. It’s not as bad as it looks. It’s sort of an illusion imo. There are several factors that make that 108 hr panel look awful. There was always a camp in the EPS going back 48 hours that has a too far inside track v the cluster of tracks that would support a decent amount of frozen. From my analysis I don’t think the % in each cluster changed that much. Several factors made that 108 panel look worse. First a few if the inside runners are way inside this run. But it matters not to us if the track is up the fall line vs up the bay. Both are rain. Matters for Harrisburg I guess. The inside runners are deeper too skewing the mean. Second the timing tightened up. There is way less timing differences on the 12z v 0z so now there is one panel where you can see all the inside runners at one time. Third the timing changed by 3 hours so now that 108 panel catches the storm at its closest inland pass in VA where before most of the lows we’re still down in NC then off the MD coast. We didn’t have one panel on the EPS that caught all the lows at their ugliest look before. By my count if you look at all the panels and estimate (hard to do with some but this is close) there were 21 members out of 50 that were inside of a “frozen supporting track” at 0z. That doesn’t mean the others were all huge hits but tracks that should support a decent bit of snow into 95. At 12z I count 23 inside runners. So maybe 2 more in the camp we don’t want. But that seems like noise to me. I’m not saying an inside runner isn’t a legit fear here. Even up here that’s my fear. I don’t see any way this gets suppressed south. The trough goes neutral and starts to lift pretty far west. The whole flow is amplified. The block/50-50 are anchored a little north of the examples where we see something squashed to our south. Imo this is going to be a hit or too far north and rain. I feel pretty good about this ATT but still a long ways to go. But you know me if there is an “oh no it’s all falling apart” moment I will be the first on here warning about it. The 12z EPS wasn’t that imo.

@WxUSAF I’m not saying an inside runner isn’t a legit fear here. Even up here that’s my fear. I don’t see any way this gets suppressed south. The trough goes neutral and starts to lift pretty far west. The whole flow is amplified. The block/50-50 are anchored a little north of the examples where we see something squashed to our south. Imo this is going to be a hit or too far north and rain. I feel pretty good about this ATT but still a long ways to go. But you know me if there is an “oh no it’s all falling apart” moment I will be the first on here warning about it. The 12z EPS wasn’t that imo.