February 12-13 Storm, Part III: Trilogy ends and then Obs thread soon!

[BryanInMd]

x1000.

 

The one thing that really bothers me about the whole sampling argument is people completely ignore lead time/error growth for a specific event.  Of course a model is going to hone in on a solution when there is less lead time....there is a shorter time window for small perturbations (initial condition errors) to grow and for model error to exacerbate the problems.  Error growth is not even close to linear.

 

As a corollary, more recent data is always better data.  

 

It has been particularly noticeable this past couple of weeks watching the american models try to resolve that mess at 500 off the NW coast.  Small differences in how the model resolved the strength, focus or trajectory of the energy as early as 24 hours into a given model run has caused big downstream changes.   Once the energy actually ejected, the models did not change much.

 

I always try to keep in mind that the circumference of the earth is 24901 miles and we predict that weather in that 3d space with multiple variables driven by chaos and differential equations. 100 miles is not a big error - 0.4% to be exact.  Snowstorms are often no more that a a couple hundred miles wide.  It is amazing to me that we can talk about 25-50 mile shifts having meaning.  

[MDstorm]

Looks like it could be a hit.  I want to see more.

 

MDstorm

[Interstate]

Looks like it could be a hit.  I want to see more.

 

MDstorm

 

Could be a hit... that panel is 4 inches of snow alone in the Balt/DC area

[EasternUSWX]

The boom

 

[WxUSAF]

Looks like RIC goes over to rain on the RGEM around 7z Thursday.  Snow arrives in DC-Balt around 0-1z Thursday.  

[Ji]

that looks really Amped(Euro style). 995 South of OBX?

[WxUSAF]

Yikes…RGEM is really warm.  Rain knocking on the door of I-95 by 48hrs.  

[k94]

12z GGEM precip maps show mixing @48 

[EasternUSWX]

Looks like RIC goes over to rain on the RGEM around 7z Thursday.  Snow arrives in DC-Balt around 0-1z Thursday.  

 

Ya 48 is warm and the precip shield is choppy.

 

[Ian]

Not all obs are weighted the same.  Raobs are pretty heavily weighted...dtk can confirm.

I think they already chimed in that changes won't be because of "better sampling."

 

I'm a data analyst by day so I'm never going to argue more data isn't better than less data. That said, I'd love some examples of when better sampling had a huge impact.  I'm sure it's happened at least once or twice.. but usually there are no differences a regular viewer could tell apart from closing in.  

 

I've chatted with a few model makers on the side so "myth" might be a little strong but probably not crazy strong.  To me a lot of the extra obs etc is for future research and bettering of the models etc.  If extra sampling is so super critical we'd be flying recon in the WPAC still. 

[high risk]

    4 km NAM nest is an impressive 0.80" at DCA between 6 and 12z Thursday

 

    The parent NAM is no slouch either at 0.55".

 

    Should be one heck of a 6-hr period.

[clskinsfan]

Gem still west of the NAM with its track. I expected it to shift east a little after the other guidance this morning. Interesting to say the least.

[Ian]

GEM sucks.. ignore the conversations last night.  

[Bob Chill]

GGEM has similar slp track as the euro. I'm not ignoring it. 

[ravensrule]

GEM sucks.. ignore the conversations last night.  

I don't know it has been stellar this year, this is cause for a little  .

[Scarlet Pimpernel]

What happens after that 48-h panel?

[Bob Chill]

Little more amp and stronger ns shortwave on 12z gfs vs 6z. 

[vinylfreak89]

last nights discussion was about GGEM... this is RGEM lol

[ravensrule]

What happens after that 48-h panel?

RGEM only goes to 48HR.

[Interstate]

Little more amp and stronger ns shortwave on 12z gfs vs 6z. 

 

I was just going to post that... the 21 panel vs the 27 panel

[high risk]

    The parallel NAM which will be implemented in May or June has been consistently showing a

 warmer solution with a risk of mixing along the I-95 corridor, so other guidance this morning

 showing something similar may be a legitimate concern.

[Ian]

last nights discussion was about GGEM... this is RGEM lol

that solidifies it. 

[cgillesp]

Probably because that's a myth.

But what about the weather balloons? IIRC they run at 0&12z. Don't know whether that gets in in time for the 0&12z runs though.

[Scarlet Pimpernel]

RGEM only goes to 48HR.

 

Ah, OK...d'oh!  I got confused since people refered to it as the GGEM and others as the RGEM.  Thought it seemed early for the GGEM to be out.  Anyhow, I don't know how similar the Canadian regional vs. global are, i.e., if they tend to show the same thing.

[wxdude64]

Little more amp and stronger ns shortwave on 12z gfs vs 6z. 

Yes. 'Mix issues' comments forthcoming....

[ravensrule]

Ah, OK...d'oh!  I got confused since people refered to it as the GGEM and others as the RGEM.  Thought it seemed early for the GGEM to be out.  Anyhow, I don't know how similar the Canadian regional vs. global are, i.e., if they tend to show the same thing.

They are like the GFS and NAM, plenty of times they show different solutions. The RGEM is much better than the NAM of course.

[Scarlet Pimpernel]

Yes. 'Mix issues' comments forthcoming....

 

That's been a concern in and around the DC area all along for this event.

[mappy]

GFS has light precip in the DC area by 03z

[needbiggerboat]

Yes. 'Mix issues' comments forthcoming....

 

Mixing was always a potential part of this set-up.  A system this strong will always bring that into the picture.

[WxUSAF]

GFS closes off at 500mb by 45hr.