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Weekend Storm Discussion Part II, 2/18-2/19


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Looks like the GFS ensemble members are generally a little south of the op with the precip shield.

Being ~48 hours out, we're within the time where the Op is superior (in statistics) to the ensemble mean and the members. Perhaps dtk can comment on how true that still is since the GEFS has been updated, but until told otherwise, I'd trust the Op more than the ensembles at this junction.

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I may be delusional, but I feel like we have seen this same scenario many times over the years. The models clearly want to give us precip, so to me the massive suppression risk is low now. I am very confident in the next 24 hours we'll see the whole area get painted with .50" of precip.

I wouldn't be surprised if that didn't happen until 00z Sunday.

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09z SREF 24 hr tot precip has 0.5 QPF line right over top of DCA at 72... which basically is a hold when you compare it to the 03z SREF 24 hr tot precip at 78. Perhaps a few miles further south on 09z SREF, but basically same

Please let us know exactly how many miles farther south on the 72 hour SREF using older data. Is it 5 miles Yoda? 10? 3 blocks?

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The 0.5" line moved very little but the nrn edge shrunk considerably to the south. Either way, for the DC proper, it wasn't that noticeable of a change. it also gives rise to the notion of heavier precip just south of the nrn edge of the cutoff.

As far as the euro looking funny, it looks like at 500mb, the confluence to the north prevented the s/w trough from amplifying at hr 66 and shoved it east. You can see a weak disturbance moving into New England which actually reinforces the confluence at this time. Part of me believes the whole nrn tick in the final 48 hrs, but there has been an overall subtle trend south. It's a delicate balance between this wanting to come north and the confluence over NNE. A 50 miles shift here or there is huge. Even 30 miles.

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Being ~48 hours out, we're within the time where the Op is superior (in statistics) to the ensemble mean and the members. Perhaps dtk can comment on how true that still is since the GEFS has been updated, but until told otherwise, I'd trust the Op more than the ensembles at this junction.

Yeah and within 72 hours, on average, it's not even really close. The ensembles can still have some utility in the 48/72 hour lead time range for particularly volatile situations (where error growth is much larger than normal)....but really only to express possible outcomes and uncertainty (I wouldn't use the ensemble mean for any lead time < 3, maybe 4 days).

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Being ~48 hours out, we're within the time where the Op is superior (in statistics) to the ensemble mean and the members. Perhaps dtk can comment on how true that still is since the GEFS has been updated, but until told otherwise, I'd trust the Op more than the ensembles at this junction.

This close in I am basically just looking for a red flag with a bunch of members diverging rapidly from the op.

Don't think I have ever seen the statistics on that though. You wouldn't have a link handy by any chance?

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What are you talking about? First of all, it's an ensemble (with perturbed ICs). Secondly, the IC for 9z SREF comes from the 6z cycle of the NAM....and by the way, we do have observations at 6z.

I know, but im saying if the 12z nam wants to come north, a new complete set of upper air data and observations is there that would maybe also trend rhe 15z SREF

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I know, but im saying if the 12z nam wants to come north, a new complete set of upper air data and observations is there that would maybe also trend rhe 15z SREF

That wasn't your original post. Also, considering the fact that the SREF system is a multi-model ensemble (non of the members are the operational NAM-NMMB model), I wouldn't expect the operational NAM to "trend" toward the SREF necessarily (it can happen, to be sure). It's a completely different animal than the GEFS/GFS or ECMWF and its ensembles.

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This storm reminds me alot of Jan. 30, 2010. Maybe the setup isn't the same, it certainly is nowhere near as cold, but in that storm it was the low heights in the NE that was squashing the precip from coming north. I remember at that time, mets saying that that feature was often overmodeled. Going on memory here, so might be fuzzy. Anyway, in that storm, we didn't start seeing the north movement of the precip until within 24 hours of the event. And that movement was huge when it happened. Not saying the same thing happens here, but I can tell you that I'll be watching all the way through tomorrows runs before I jump for joy or off the bridge.

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That wasn't your original post. Also, considering the fact that the SREF system is a multi-model ensemble (non of the members are the operational NAM-NMMB model), I wouldn't expect the operational NAM to "trend" toward the SREF necessarily (it can happen, to be sure). It's a completely different animal than the GEFS/GFS or ECMWF and its ensembles.

I know dtk, i mean like many have stated it can be a trend starter, but im not sure that makes sense either now that i think about it because the data is old and 09z srefs shouldnt indicate 12z nam

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