psuhoffman

I can't look right now...but might want to take a look at the "median" or 50% map...to see if that snowfall closer to DC is the product of a few crazy outlier runs that have like 20" creating that mean of 2" in the area. We get a lot of false flags where people look at a mean on the EPS and think it's saying we should get some snow when really it's not saying that at all and the snow mean is just a product of big outlier solutions.

I said I’d reserve judgement until today. I don’t need to see everything lock in on a big hit today but I need to see it look close enough that the typical small bleed north we see the final 72 hours will be enough. What we need most at this point is some combo of 3 things. For the upper low to go negative slightly sooner, more separation up top so it can lift north sooner or for the whole thing to simply cut off further north.

I’d rather need a north trend than south.

It’s digging and cutting off too far south. Since once it cuts off it’s not going to lift north due to the flow over the top we need it to cut off and track across the NC/VA border not down near SC. We just need one thing, for that upper low to trend north.

Buy me a drink at the next HH. If it trends worse from 18z first rounds on me

Wait 2.5 hours

It was coming north, at least enough to get out area before turning ENE.

My best guess looping the h5 and mslp is the nam was going to pull that low right up off VA beach or Norfolk then slide ENE based on how the flow was backing and where the upper low was about to cut off.

I am not throwing in the towel until tomorrow. One observation before tonight's runs.... Need a north trend = good shape Need a west trend = next This is because of typical model bias errors. Models very commonly are too far south in the medium range with northern stream mid and upper level features. That H5 low is likely to adjust north some in the final 48 hours. So if things start to trend towards a solution closer to the GFS, again not necessarily that extreme, but with a miss somewhat to our SOUTH not EAST... we are in the game going into the final 48 because I expect the same bleed north we see 75% of the time. Models do NOT, however, have a bias of usually amplifying too slowly in phase situations. If anything it's the opposite. Miller b storms trend east more often than west. So if the guidance converges on the more east idea with a more positively tilted upper low that doesn't close off until 6-12 hours later and we need a west trend... this is dead going into the final 48 hours. Again, I will reserve judgement until tomorrow

It wasn’t, the track was almost identical to 12z but the storm was slightly more intense but also compact. Less broad precip shield. It was noise. The overall setup improved. But within each larger scale setup there is variability to the outcome based on small scale variables. IMO this run had a better chance of a good result but we saw a worse ground truth based on some noise level variables not going our way.

I am totally fine with where the ggem is. It actually trended better with the larger features. The fact the storm was slightly east was noise

Ggem trend

A thought. There is variability within the larger scale setup. So it’s possible to get a better setup in terms of the major long wave features but end up with a worse result due to minor factors causing a slower development or less amplification. However, if the larger scale trend of backing both the NS wave and the western ridge continues at some point a better outcome becomes much more likely regardless of the small scale variables. In other words get the whole thing to back another 150 miles and it would take a much less perfect progression to get a hit. Right now we could win but it would take damn near perfect phase and amplification which is what the runs showing a hit have. Keep improving the ridge/trough axis and even a less perfect result can end up good.

I like everything about the ggem at 90 except it’s weaker and slightly easy with the southern wave. But its more amplified and detached and west with the NS and as expected the western ridge continues to bleed slightly west every run.

GFS is trending west a little with the western ridge BUT it's also flatter which is probably offsetting any gains in longitude

That is THE storm...NAM is just 12 hours faster getting it going...which I am not sure is a good thing...it opens the door to a minor snowfall v all or nothing...but it has the surface wave running out ahead of the NS upper feature such that the timing for a bigger event is probably off.

HOLY… I honestly hadn’t looked at the analogs. I was just looking at the whole H5 setup and going off memory. But DAMN

@Bob Chill 1980 was decent in DC but a fringe north of there. 2011 was a MD bullseye. But again hard to really worry about analogs when the whole setup is shifting still.

It wouldn’t show up because the CIPS are using the gfs day 5 and currently the GFS is way off. So is the euro frankly. But if they continue to adjust the whole long wave pattern west at the same rate they have been lately the next few days, 1996 might pop up. lol

You must be fun at parties jk

So you know what I’m talking about visually and not just talking out my ass. This is the trend on the eps since 0z. This is just 18 hours. Look at the position of the eastern trough and western ridge. Now imagine if this same trend continues for another 1-2 days. Or god forbid this same slow bleed were to continue for the whole next 5 days like it did the 5 days leading up to the last storm and frankly has been happening for weeks. This doesn’t mean every run. You get the hiccup run like 12z or the 0z runs last Friday night that buck the overall trend. But imagine if this overall trend continues what this would look like by the weekend!

The way the math really works…that .4 qpf mean is the product of different outcomes averages. The truth is the median snowfall for IAD is nothing! Thats because about 60% of the eps members have absolutely no snow and are too far east. The mean among the other 40% that have a more amplified solution isn’t .4 it’s closer to .8 at IAD. And if the most amplified 20% are correct it’s closer to 1” Qpf. So the math says the most likely outcome is we get nothing. But there is about a 40% chance is a storm and in that case a good chance it will be a significant one with some members already looking like a 1996 type event.

Who am I to stop a good ratio argument, but the argument assumes something about the EPS mean that isn't true. That .3-.5 qpf mean is from various clusters of permutation outcomes. There is a camp of EPS members that tuck the low into the Delmarva, and those solutions likely have 1"+ QPF. Then there are the OTS solutions which mostly have nothing. So arguing over what the ratios would be on a mean that is the compromise of two different permutations is really....well I'll be nice and say "not the best use of your time".