psuhoffman

Omg it’s better than the Hrrr and RAp

Because we needed too much. They usually trend some, 30 miles maybe and more importantly they usually under do the qpf along the northern fringe so between a small shift north and a 25% increase in qpf suddenly a place expecting 3” gets 6” or 8”. But if we need some 75 mile shift the last 24 hours that’s unlikely. I don’t mind sitting around the .3 qpf area going into the final 24 hours. But being on the outside looking in or on the fringe of any precip at all usually isn’t good. Tonight’s euro is big. It’s been bouncing a bit. If it holds or improves on the 18z run I feel good about higher totals all the way to PA. If it looks like the icon or rgem I might start to worry some.

Didn’t Jan 2022 shift north enough to get DC good when it looked like it might fringe them?

No that storm in 2019 was one of the only examples that didn’t trend north and I got less than I expected.

I’m just using the hrrr and rgem here but you can sub the NAMs FV3 and GFS for the hrrr and the uk and somewhat euro (but it’s coming around some) and it’s the same. This is just 18 hours from now… The error is happening right now as the wave amplifies in the plains after ejecting from the Rockies. By 18 hours the camps have diverged and it’s just dominoes falling from there. The Hrrr, FV3, GFS, NAMs are amplifying the wave significantly more in the next 12-18 hours. That’s the difference.

By 18 hours it’s already diverged significantly from the “south” camp like the uk and rgem. Someone’s gonna cave very soon because the error is very early on.

The euro and gfs have been slowly converging and now aren’t really that far apart. My guess is they split what little difference there is in the next run or two. Then I don’t expect any appreciable change in where both locate the two main bands here but I do expect the typical adjustment where the h7 associated northern band over performs due to a combo of models typically under estimating qpf a bit and the high ratios with that band causing that small qpf error to be exacerbated wrt snow accumulations. My guess is the final 24 hours will be about pinning down those details. Exactly how much of any sleet mixes in the southern max, how much qpf beefs up in the northern one, and are there any unfortunate bust zones in between the two bands.

For those near the PA MD line that stuff south of DC associated with the h85 forcing isn’t ours. You can see the euro hinting at the duel banding also. It has the h7 associated band right over us. Exactly where I expect it given the synoptic setup. It’s just weak sauce as of now. But that almost always ends up producing and often ends up the better band for accumulations. Get that band over us and I’ll take my chances. We don’t really need the euro to shift north. We just need it to increase the qpf associated with that band some. Not a ton. Right now we’re around .3 qpf. Get that to like .45 and with the high ratios we get up here and under that type of banding and that’s 5-8”. A very slight adjustment and it’s what I’ve expected given the setup.

About all these “how are the models so far apart” posts. Just a reminder we do this EVERY time we have a wave that isn’t some wound up sub 990 hecs monster with a 250 mile wide jack zone. NWP has become absolutely amazing (imo) at picking up on the general synoptic ideas on a 10,000 foot view at ranges unfathomable 20 years ago. I was on a plane a week ago looking at this same threat and we already had the general idea of a wave into the TN or Ohio Valley with gulf moisture overrunning the cold. Look at this from 180 hours! By 150 hours even the hiccup runs were gone and all 3 major ensemble systems were showing the same general idea. We didn’t even discuss or look at anything past 100 hours when I used to attend some of the guidance discussions at Penn State 25 years ago! Most of the models didn’t even go past 120 or 144 and we didn’t take anything seriously until it was within NGM and ETA range which was 48. Now we’re having serious discussions about stuff 7 days away! But NWP cannot pin down the exact location of meso banding or the location of the edges of these bands to the mile. Guidance even at 24-36 hours will shift these things around 40-50 miles run to run and every storm we say the same things “omg how are they doing this” It’s just the limitations of our current science and it doesn’t matter if it’s a large expansive qpf field and you're in the center but in events with a smaller jack zone or for those near the edges this is still all standard procedure.

Wrt NAM, I often toss is, it’s way to jumpy and prone to wild tangents. But it does sometimes pick up on a mid level warm push that can lead to a north shift on this type of setup and it’s not often this locked in and when it is sometimes it’s onto something. But not always.

I’ll give the storm another “reminder” as I fly through in a few minutes. Whichever camp is going to cave (or more likely a compromise) it has to happen soon because the differences that lead to the south v north results occur in only about 24 hours and the rest is just the dominoes falling after that.

For the northern crew of course it’s possible we get fringed, yes it happens no matter how often the southerners think it doesn’t (in the grand scheme it doesn’t matter because we benefit way more than we lose over the long term) BUT…usually when we get fringed bad we were on the outside of the best lift and the qpf cutoff on guidance at this point. 80-90% trend north the final 24-36 hours. Actually what really happens is guidance struggles to depict the banding that happens near the h7 fgen that’s usually near the northern edge of the qpf field. They also tend to place that too far south by some amount until the very end. Almost every time I was the jack 48 hours out it ended up north of me. Yes I still did better than everyone south so it’s totally understandable that’s all they remember if I got 4” and they got nada but often I was supposed to get 8” 48 hrs out! And most of the times we got fringed we were outside the northern fringe of qpf completely at this point. Even the ones that missed us shifted the northern edge north some at the end just not enough to save us if the fringe area was down near DC or worse at 48 hrs. No it’s not universal. There was a storm in Jan 2019 that got squashed some at the last min and there was no north adjustment but that’s the only example I can remember and I can count like 10 off the top of my head recently to at did shift the north periphery of banding north. So I’ll play the odds this is one of the 90% not the 10. Synoptically I don’t see a compelling reason for the copious moisture transport from the gulf with a healthy wave getting onto KY to get shunted that badly. This is a storm type that we usually do well. If this is the rare exception oh well but I’m not gonna overly stress it unless we see signs it’s going off the rails like either another shift south this evening or we get to 24 hours and there is no north movement. Until then I feel ok where we are

EPS trend

Can this thing be right just once please

Euro was noise level changes. Pretty much copy of the 18z.

H5 looks almost identical at 45 hours. Upper low is slightly north. Surface low identical. Confluence identical in our area maybe slightly north to our west.

I did my part…

There are no goalposts. In March 2014 48 hours out they were expecting a foot up in PA and it ended up hitting DC with almost nothing to the PA line. The last couple years there were storms that 48 out the jack was south of me and ended up way north! If the models are miscalculating how that lobe up to our north interacts with the system it could still get squashed to our south. It could also end up shifting so far north you end up south if the good snow! I don’t expect that but I’ve seen it and there is no super crazy high to prevent it just that 50/50 And the lobe rotating around it and if that were to get out of the way… My point is you seem to be searching for a degree of certainty and there is none. Just have to accept that and hope for the best.

Ok I guess some didn’t know this. But we knew the gem was south when the rgem was. They are never that far off. The rgem might have some meso features the gem doesn’t see but the general idea will be the same 99% of the time.

welcome to an hour ago

We did but there was an area in between here and DC that got fringed by all 3 significant storms in 2022 and none were warning. The Baltimore area has had it the worst, within a region that’s been in their worst stretch ever. Im not justifying the freak outs but I get it.

What trend? We don’t even have the full 0z suite yet. If the euro goes significantly south I’ll worry. And there are still 5-6 model Cycles left before we get to the range the exact location of banding will be figured out. The last snow we got Feb last winter went from a MD bullseye 48 hours out to giving Allentown PA 12” and MD 1-3”. It won’t matter if it were way down south and we needed a 150 mile shift. But a 50-75 mile shift the last 24-36 hours is absolutely nothing and happens almost every storm one way or another. We do this every time. People act all “how can the models be this all over the place when it’s only 48 or 72 hours” when this is totally normal. We haven’t progressed as far as some think. 48-72 hours is still a long time.